Source: UNIVERSITY OF GEORGIA submitted to NRP
ADVANCING BLUEBERRY PRODUCTION EFFICIENCY BY ENABLING MECHANICAL HARVEST, IMPROVING FRUIT QUALITY AND SAFETY, AND MANAGING EMERGING DISEASES
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
OTHER EXTENSION GRANT
Reporting Frequency
Annual
Accession No.
0216040
Grant No.
2008-51180-19579
Cumulative Award Amt.
(N/A)
Proposal No.
2009-01228
Multistate No.
(N/A)
Project Start Date
Sep 1, 2008
Project End Date
Aug 31, 2013
Grant Year
2014
Program Code
[SCRI]- Specialty Crop Research Initiative
Recipient Organization
UNIVERSITY OF GEORGIA
200 D.W. BROOKS DR
ATHENS,GA 30602-5016
Performing Department
PLANT PATHOLOGY
Non Technical Summary
The exponential expansion of the southern blueberry industry during the past three decades has been a remarkable success story within the U.S. specialty crops sector. Nearly one-third of the cultivated blueberry acreage is located in the South, and within the next 5 years the region is projected to become the largest blueberry-producing area in the nation. Growth in acreage and production has been especially rapid for the early-maturing southern highbush blueberries, which ripen during a favorable market window and provide an important source of income for small and medium-sized farms and a lifeline for the surrounding rural communities. However, in the face of increasing domestic supply, rapidly strengthening international competition, increased pressure on producer prices, and looming shortages in labor, blueberry growers will have to elevate their overall production efficiency considerably to remain profitable. This Coordinated Agricultural Project will enable an unprecedented leap in efficiency through a comprehensive, multi-disciplinary effort integrating three major themes: 1) overcoming the genetic, horticultural, and engineering barriers that stand in the way of machine-harvesting highbush blueberries for the fresh market; 2) improving overall fruit quality and safety; and 3) addressing emerging systemic diseases that threaten the viability of the industry. An economic re-evaluation of the production chain together with comprehensive efforts in outreach and technology transfer ensures that new knowledge and technologies will be put into practice.
Animal Health Component
60%
Research Effort Categories
Basic
15%
Applied
60%
Developmental
25%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2051120106040%
2051120108025%
2121120116025%
6011120301010%
Knowledge Area
601 - Economics of Agricultural Production and Farm Management; 212 - Pathogens and Nematodes Affecting Plants; 205 - Plant Management Systems;

Subject Of Investigation
1120 - Blueberry;

Field Of Science
1060 - Biology (whole systems); 1160 - Pathology; 1080 - Genetics; 3010 - Economics;
Goals / Objectives
The exponential growth of the southern blueberry industry during the past three decades has been a remarkable success story within the U.S. specialty crops sector. Nearly one-third of the U.S. cultivated blueberry acreage is located in the South, and within the next 5 years the region is projected to become the largest blueberry-producing area in the nation. Growth in acreage and production has been especially impressive for the early-maturing southern highbush blueberries, which ripen during a favorable market window and provide an important source of income for small and medium-sized farms and a lifeline for the surrounding rural communities. However, in the face of increasing domestic supply, rapidly strengthening international competition, increased pressure on producer prices, and looming shortages in labor, blueberry growers will have to elevate their overall production efficiency considerably to remain profitable and sustainable. The long-term goal of this Coordinated Agricultural Project is to enable an unprecedented leap in efficiency through a comprehensive, interdisciplinary research and extension effort integrating three major themes: (i) overcoming the genetic, horticultural, and engineering barriers that stand in the way of mechanical harvesting highbush blueberries for the fresh market; (ii) improving overall fruit quality and safety; and (iii) addressing emerging systemic diseases that threaten the viability of the industry. Specific objectives are to: 1) Develop superior southern highbush blueberry cultivars with enhanced mechanical harvest capability and understand the genetic basis for improved fruit detachment; 2) Evaluate and demonstrate horticultural and engineering principles with the potential to improve mechanical harvest capability of fresh-market blueberries; 3) Develop strategies to improve overall quality, shelf life, and microbial safety of harvested blueberries; 4) Understand the etiology and develop management strategies for emerging systemic blueberry diseases; and 5) Conduct economic assessments and engage in outreach and technology transfer with growers, packers/ shippers, and consumers. An economic re-evaluation of the production chain together with comprehensive efforts in outreach and technology transfer ensures that new knowledge and technologies will be put into practice. This project addresses all five focus areas of the SCRI as well as the strategic goals formulated by the Berry Crop Production Committee of the National Berry Crops Initiative.
Project Methods
Objective 1: A comprehensive evaluation of recent releases and advanced selections from the NC and FL breeding programs for mechanical harvest capability will be conducted at research and grower sites. Fruit will be hand- vs. machine-harvested, subjected to a packinghouse run, cold-stored, and assessed for key quality parameters. New southern highbush blueberry cultivars with superior mechanical harvest qualities will be developed utilizing recent locally adapted releases in crosses with new sources of the crisp texture trait from the cultivated blueberry genepool and exotic sources. The molecular physiology and genetics of the ease of fruit detachment will be studied on cultivars having different fruit detachment force with or without growth regulator application to facilitate fruit detachment. Early changes in gene expression upon induction by the abscission treatment will be assayed. Objective 2: Trellis and crown restriction treatments will be applied to facilitate fruit removal by mechanical harvest and reduce ground losses, respectively. Growth regulators that facilitate fruit abscission will be selected based on previous knowledge from other fruit crops and screened for reductions in fruit detachment force on blueberry. Field trials will determine the effect of the most promising abscission agents on ground loss, yield, and fruit quality. Sources of bruising will be identified and bruise reduction systems optimized for commonly used mechanical harvesters. A small-size instrumented sphere will be developed to measure impacts at different stages of the harvesting process. Objective 3: The postharvest physiology of the new "crispy flesh" berry type will be studied in detail. Various plant and fungus-derived volatiles will be assessed for their effect on reducing fungal decay, increasing antioxidant capacity, and improving microbial safety following postharvest treatment. Objective 4: The susceptibility of cultivars and advanced selections to X. fastidiosa and their attractiveness to the glassy-winged sharpshooter will be assessed in greenhouses and in the field. The Botryosphaeria species complex on blueberry will be characterized using phylogenetically relevant sequences. A seedling screen to identify host resistance early in the selection process will be developed. The potential to control of blueberry leaf scorch by cross-protection with benign strains of X. fastidiosa will be examined. Pathogen transmission and plant survival for different propagation systems (softwood cuttings vs. tissue culture) will be quantified. Objective 5: The innovations resulting from this project will have potentially profound impacts on costs and returns, warranting an economic re-evaluation of the production system. Outreach and program evaluation plans will be developed and implemented using both traditional and novel vehicles. A survey of blueberry growers will be conducted about their decision to participate in the learning process as a result of message format and accessibility, production preferences, and information requirements will be carried out to guide outreach projects related to adoption of alternative specialty crop production technologies.

Progress 09/01/08 to 08/31/13

Outputs
Target Audience: Blueberry producers throughout the southeastern U.S. Blueberry packers and shippers, as well as harvest equipment manufacturers. Changes/Problems: PI changes: At the University of Florida, Dr. Paul Lyrene retired in 2010 and was replaced with Dr. James Olmstead as a PI. Dr. Dan MacLean left the University of Georgia in 2011, and his part of the project was assumed by Dr. Anish Malladi, another University of Georgia PI.During 2013, Drs. Gerard Krewer and Robert Shewfelt retired from the University of Georgia but remained active in the project. What opportunities for training and professional development has the project provided? Students: one MS student in Agricultural Economics, two MS students in Food Science & Technology, three MS students in Plant Pathology, one PhD student in Plant Pathology, one PhD student in Horticultural Sciences. Postdocs: two postdocs in plant pathology, one postdoc in Entomology. County extension agents: two comprehensive agent trainings focused on mechanical harvest conducted in conjunction with the Southern Region Small Fruit Consortium (SRSFC) in 2011 and 2012. Also participated in an agent training conducted by a complementary SCRI project (Darnell et al.) in California in 2013. How have the results been disseminated to communities of interest? Dissemination of project findings and products occurred via the Extension county delivery mechanism (see county agent trainings described above), through the SRSFC, and through numerous one-on-one, county, statewide, and regional meetings to extend results and recommendations directly to blueberry producers. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Objective 1: In NC alone we now have >100 advanced mechanical harvest (MH) selections in replicated trials. Cultivar trials are used to evaluate and demonstrate new cultivars and establish their local utility. Significant new, elite accessions from breeding programs at UF and UGA have tripled the size of field trials. Elite seedling populations produce fruit at grower locations, both to demonstrate characteristics and to accelerate selection. New plantings in 2013 included 26 new selections and five new named cultivars. In FL, >7,000 seedlings from hybridization between crisp fruit parents have been planted for evaluation. Selection for MH ability and disease resistance (stem blight and necrotic ring blotch) is ongoing. Work on the physiology of fruit detachment has shown that natural fruit detachment occurs at the branch abscission zone, leaving the pedicel attached to the fruit. Fruit detachment without the pedicel is associated with tissue tearing and physical separation. Thus, if chemical abscission agents are to be used as harvest aids, de-stemming will be necessary. Transcriptomics experiments showed that detachment in response to methyl jasmonate and Ethephon involves changes in xylan and xyloglucan composition in the cell walls of the abscission zone. The results have led to a better understanding of the process of fruit detachment in blueberry, critical for developing more efficient MH methods for blueberry culture. Objective 2: A miniature and low-cost berry impact recording sensor (BIRD) was developed for the evaluation of the blueberry MH and postharvest handling processes. The size of the BIRD sensor is <1/2 of the current smallest instrumented sphere, and only 8% of the cost. The sensor provides an unprecedented approximation of a berry fruit and enables researchers to better understand how the berry interacts with different machine parts within the harvester. BIRD sensor readings were also correlated with biologically determined bruising rates in blueberry fruit. Drop tests onto different types of surfaces confirmed that the conventional-flesh genotype was more susceptible to bruising than the semi-crisp or crisp-flesh genotypes. Objective 3: Field research clearly documented that MH of crisp-textured southern highbush blueberry cultivars is feasible from a fruit quality perspective. Most importantly, MH fruit of crispy flesh genotypes developed levels of natural postharvest decay lower or similar to those of hand-harvested fruit of conventional genotypes. Results of artificial inoculations with postharvest fungal pathogens supported this fact. There was a negative association between postharvest disease incidence and fruit firmness across genotypes and harvest methods, indicating that fruit firmness is a good predictor for postharvest decay risk. This relationship also suggests that the lower level of postharvest disease in crispy flesh genotypes is mostly due to their greater firmness, and not some other form of genetic resistance. In separate studies, nine southern highbush blueberry cultivars were evaluated for sensory attributes and consumer acceptability. The significant differences in sensory quality between the crisp and conventional berry types were in crispness and firmness. In contrast, differences in flavor and color were not significant. Consumers found the crisp-flesh berries superior to the non-crisp flesh cultivars. Baking tests showed that consumers were unable to detect differences in pies made from the crisp and non-crisp selections, but the lack of juice release from the crisp fruit would confuse most home bakers. The most important finding is that although concerns were raised initially that crisp berries would be found unacceptable to consumers, they are actually preferred when consumed fresh. Objective 4: A survey of fungi causing stem blight identified Neofusicoccum ribis as the most common pathogen. Plants sourced from outside the Southeast and propagated through tissue culture were compared with plant material sourced in FL propagated by rooted cuttings. Plants from rooted cuttings died more frequently, and their stem blight incidence was higher. Thus, plant mortality due to stem blight could be reduced through changes to the propagation methods. Additional work on emerging diseases focused on bacterial leaf scorch (BLS) and Blueberry necrotic ringblotch virus (BNRBV). We showed that transmission of BLS through softwood cuttings was low but non- negligible; in contrast, there was no evidence for transmission of BNRBV via vegetative propagation. Strains of Xylella fastidiosa from blueberry, elderberry, lupine, almond, and blackberry produced blueberry BLS symptoms after artificial inoculation. Strains that caused BLS were primarily recombinant X. fastidiosa subsp. multiplex. Southern highbush cultivar Emerald is resistant to BLS in the field, but was highly susceptible to a strain from elderberry and two blueberry strains after artificial inoculation. The fact that BLS can be spread via vegetative propagation, albeit at low incidence, highlights the need for clean propagation practices. This is particularly important since visual symptoms are not generally apparent during the propagation process. Our strain analyses showed that blueberry BLS strains could have originated from phony peach or plum leaf scorch strains. Greenhouse screening for BLS resistance could be effective if attention is given to the strain of X. fastidiosa. BNRBV was reported as a new pathogen in southern highbush blueberries. The movement pattern of the disease suggest a slow-moving arthropod vector, and the local-lesion, non-systemic nature of the virus implies a limited ability to overwinter in the plant. In FL, two distinct virus symptoms were associated with variants of BNRBV. The most likely vector is an undescribed vagrant foliar eriophyid mite. Objective 5: Several key outreach events during this project are highlighted in previous sections of this report. Across the southern region, thousands of acres of new crisp or semi-crisp cultivars have been planted to facilitate MH as a result of the Blueberry SCRI project. Acquisition of quantitative bruising data through the BIRD technology and the ability to transform them into simple, grower-friendly outputs has identified high-impact points due to surface composition and drop heights in their packing-lines and field operations and has allowed them to modify their fruit handling procedures that will help to increase fruit quality. Management recommendations for BNRBV were developed and delivered to producers. Growers have indicated that insecticide use has reduced BNRBV-associated defoliation on their farms. Grower awareness of the disease was increased, and our management recommendations have helped reduce losses and prevented unnecessary fungicide applications due to confusion of the virus symptom with those caused by fungal leaf spots. In an economic assessment of hand- vs. MH for crisp or semi-crisp cultivars, total fruit yield per bush was higher but pack-out was lower for MH relative to hand-harvest. Ceteris paribus and assuming harvest costs of $0.72/lb for hand-harvest and $0.18/lb for MH, net return was better for MH. Economic cost comparisons of hand- vs. MH were finalized and presented at producer and scientific meetings. We updated Fruit and Nut Planning Budgets online and as interactive Excel spreadsheet versions. Compilation and preliminary qualitative review of the mail survey of blueberry growers in FL, GA, MS and NC were completed. Econometric analysis was conducted in and the resulting publication will be submitted in mid-2014.

Publications

  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Quito-Avila, D.F, P.M. Brannen, W.O. Cline, P.F. Harmon, and R.R. Martin. 2013. Genetic characterization of Blueberry necrotic ring blotch virus, a novel RNA virus with unique genetic features. Journal of General Virology 94:1426-1434.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: De La Fuente, L., J.K. Parker, J.E. Oliver, S. Granger, P.M. Brannen, E. van Santan, and P.A. Cobine. 2013. The bacterial pathogen Xylella fastidiosa affects the leaf ionome of plant hosts during infection. PLos ONE 8(5): e62945, doi:10.1371/journal.pone.0062945.
  • Type: Book Chapters Status: Awaiting Publication Year Published: 2014 Citation: Brannen, P.M., H. Scherm, and R. Martin. 2013. Blueberry Necrotic Ring Blotch Disorder. In: Compendium of Blueberry and Cranberry Diseases. Eds. F. Caruso and J. Polashock. (accepted for publication). APS Press, St. Paul, MN.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Yu, P., C. Li, F. Takeda, G. Krewer, G. Rains, and T. Hamrita. 2014. Evaluation of rotary, slapper, and sway blueberry mechanical harvesters for potential fruit impact points using a miniature instrumented sphere. Comput. Electron. Agr. 101:8492.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Li, C., P. Yu, F. Takeda, and G. Krewer. 2013. A Miniature Instrumented Sphere to Understand Impacts Created by Mechanical Blueberry Harvesters. HORTTECHNOLOGY 23:425-429.
  • Type: Journal Articles Status: Awaiting Publication Year Published: 2014 Citation: Yu, P., C. Li, F. Takeda and G. Krewer. 2014. Visual bruise assessment and analysis of mechanical impact measurement in southern highbush blueberry. Applied Engineering in Agriculture In Press (formally accepted in December 2013).
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Williamson, J. G., Cline, W. O. 2013. Mechanized harvest of blueberries for the fresh market: An introduction and overview of the workshop proceedings. HortTechnology 23:416-418.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Cantu-Iris, M., Harmon, P.F., Londono, A., and Polston, J.E. 2013. A variant of blueberry necrotic ring blotch virus associated with red lesions in blueberry. Archives of Virology 159 2197-2200.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Srivastava, P., Andersen, P.C., Marois, J.J., Wright, D.L., Srivastava, M., and Harmon, P.F. 2013. Effect of phenolic compounds on growth and ligninolytic enzyme production in Botryosphaeria isolates. Crop Protection 43:146-156.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Malladi, A., T. Vashisth, and S. NeSmith. 2013. Development and evaluation of a portable, handheld mechanical shaker to study fruit detachment in blueberry. HortScience. 48: 394-397.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Vashisth, T., and A. Malladi. 2013. Fruit detachment in rabbiteye blueberry: Abscission and physical separation. Journal of the American Society for Horticultural Science. 138: 95-101.
  • Type: Theses/Dissertations Status: Published Year Published: 2013 Citation: Gianella, C.L. 2013. Sensory quality and consumer acceptability of southern highbush blueberry cultivars. MS thesis. University of Georgia. 57 pp.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Takeda, F., Krewer, G., Li, C. MacLean, D. and Olmstead, J.W. 2013. Techniques for increasing machine-harvest efficiency in blueberries. HortTechnology 23:430-436.
  • Type: Theses/Dissertations Status: Published Year Published: 2013 Citation: Holland, R.M. 2013. Location, transmission, and impact of Xylella fastidiosa in southern highbush blueberries. M.S. thesis, Department of Plant Pathology, University of Georgia, Athens.
  • Type: Theses/Dissertations Status: Published Year Published: 2010 Citation: Mehra, L. K. 2010. Fungal infection and postharvest quality of blueberry fruit in relation to berry flesh type, harvest method, and postharvest biofumigation. M.S. thesis, Department of Plant Pathology, University of Georgia, Athens. 95 pp.
  • Type: Theses/Dissertations Status: Published Year Published: 2009 Citation: Haralson, J.C. 2009. Pathogens associated with blueberry cutting failure in south Georgia nurseries and their control. M.S. thesis, Department of Plant Pathology, University of Georgia, Athens.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Takeda, F. 2013. Challenges with mechanical harvesting of blueberries for the fresh market. 2013 Proc. Lower Mainland Horticulture Improvement Association annual meeting, C. Kempler, T. Kabluk, and L. Frey, eds., (Abbotsford, BC, Canada, Jan. 2013), p. 169-171.
  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Holland, R. M., Christiano, R. S. C., Gamliel-Atinsky, E., and Scherm, H. 2014. Distribution of Xylella fastidiosa in blueberry stem and root sections in relation to disease severity in the field. Plant Dis. doi:10.1094/PDIS-06-13-0680-RE
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Mehra, L.K., MacLean, D.D., Shewfelt, R.L., Smith, K.C., and Scherm, H. 2013. Effect of postharvest biofumigation on fungal decay, sensory quality, and antioxidant levels of blueberry fruit. Postharvest Biology and Technology 85:109-115.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Mehra, L. K., MacLean, D. D., and Scherm, H. 2013. Postharvest disease development on southern highbush blueberry fruit in relation to berry flesh type and harvest method. Plant Dis. 97:213-221.
  • Type: Journal Articles Status: Published Year Published: 2013 Citation: Haralson, J.C., Brannen, P.M., Scherm, H., and NeSmith, S.D. 2013. Chemical control of Cylindrocladium and Rhizoctonia root rots in blueberry propagation. Crop Protection 44:1-5.
  • Type: Other Status: Published Year Published: 2013 Citation: Brannen, P.M., Scherm, H., and Holland, R. 2013. UGA Department of Plant Pathology research results in additional cultural management recommendations for bacterial leaf scorch (Xylella fastidiosa). Dixie Blueberry News 13(2):10-12.
  • Type: Theses/Dissertations Status: Published Year Published: 2013 Citation: Robinson, T.S. 2013. Epidemiology of Blueberry necrotic ring blotch virus of southern highbush blueberry in Georgia. MS Thesis, Department of Plant Pathology, University of Georgia, Athens.
  • Type: Theses/Dissertations Status: Other Year Published: 2014 Citation: Rodgers, A. 2014. Determining willingness to adopt mechanical harvesters among southeastern blueberry producers. MS thesis, Mississippi State University (to be submitted in May 2014).


Progress 09/01/11 to 08/31/12

Outputs
OUTPUTS: Objective 1: Seventy-one recent selections established in duplicate three-plant plots in NC at the Castle Hayne Station, plus a backup plot at the Sandhills Station. More than 8,500 seedlings established in two locations, and 203 new seedling selections identified at three test sites. Twenty-six successful crosses among elite parents made. Flowering and ripening dates recorded for 35 named cultivars and selections, selected clones further evaluated for yield and fruit quality, and 25 advanced selections from UGA planted for comprehensive testing. Objective 2: Continued studies on fruit detachment in blueberry showed that fruit detachment in response to chemical abscission agents to facilitate mechanical harvest occurs at the branch abscission zone resulting in stemmy fruit. Work is in progress to understand changes in the transcriptomes of the fruit and the abscission zone in response to abscission agent application to better understand the mechanisms behind fruit detachment. Objective 3: Southern highbush blueberries from GA, FL, and NC were cold-stored for up to 2 weeks and subjected to sensory analysis using a trained panel who rated crisp and non-crisp blueberry varieties using nine descriptors. Consumer acceptability tests performed using a three-point scale of acceptability. Results showed a significant difference in firmness and crispness among crisp vs. non crisp cultivars, whereby 'Sweetcrisp' had the highest superior plus acceptable rating among consumers (94.4%) and 'Rebel', a non-crisp selection, had the lowest acceptability rating (52.5%). Objective 4: Work on emerging diseases of blueberry focused on bacterial leaf scorch (BLS), caused by Xylella fastidiosa, and Blueberry necrotic ringblotch-associated virus (BNRBaV). Studies between 2010 and 2012 showed that transmission of BLS through softwood cuttings was low but non- negligible (~5% as determined by PCR); in contrast, there was no evidence for transmission of BNRBaV via vegetative propagation. Strains of X. fastidiosa from blueberry, elderberry, lupine, almond, and blackberry produced blueberry BLS symptoms after artificial inoculation. Strains that caused BLS were primarily recombinant X. fastidiosa subsp. multiplex. Southern highbush Emerald is resistant to BLS in the field, but was highly susceptible to a strain from elderberry and two blueberry strains, and resistant to three other blueberry strains. Objective 5: An advanced mechanical harvest workshop for county agents was held in Gainesville, FL, on 25-26 April 2012, covering all aspects from cultivar selection and cultural practices to harvest technology, postharvest handling for machine-harvested fruit, and economics. Economic cost comparisons of hand vs. machine-harvest finalized and presented at producer meetings and the Food Distribution Research Society annual meetings. An existing blueberry production and cost database was revised to include Advisory Panel feedback. Connected, coordinated, attended and presented grant-related outreach activities with other funded projects related to southeastern blueberry markets, including the SCRI-funded All About Blueberries Community of Practice. PARTICIPANTS: PROJECT PIs: University of Georgia: Harald Scherm (Plant Pathology, overall project PD), Phil Brannen (Plant Pathology, extension), Changying Li (Engineering), Anish Malladi (Horticulture), Rob Shewfelt (Food Science & Technology, sensory evaluation); University of Florida: Phil Harmon (Plant Pathology, FL lead-PI), Don Hopkins (Plant Pathology); Paul Lyrene (Horticulture, blueberry breeding), Jim Olmstead (Horticulture, blueberry breeding); North Carolina State Univ.: Bill Cline (Plant Pathology, NC lead-PI), Jim Ballington (Horticulture, blueberry breeding); Mississippi State Univ.: Kim Morgan (Agricultural Economics, extension); USDA-ARS: Fumi Takeda (Horticulture, mechanical harvest). TRAINING/ PROFESSIONAL DEVELOPMENT: Kristin Abney (PhD student, UGA), Rock Christiano (postdoc, UGA), Lisa Johnson (MS student, UGA), Renee Holland (MS student, UGA), Laura Williford (MS student, UGA), Tripti Vashisth (PhD student, UGA), Tanisha Robinson (MS student, UGA), Amanda Wright (PhD student, UF) TARGET AUDIENCES: The primary target audience for this project consists of commercial blueberry growers in the southeastern and mid-South regions of the United States. Knowledge transfer has occurred in numerous educational sessions at regional (e.g., Southeast Regional Fruit and Vegetable Conference, Gulf South Blueberry Growers Association), statewide (e.g., North Carolina Blueberry Open House; Georgia Blueberry Growers Disease Update), and local (e.g., annual Bacon County Blueberry Meeting) scales. The multi-state Mechanical Harvest Workshop for county extension agents in Gainesville, FL, in April 2012 was organized in conjunction with the Southern Region Small Fruit Consortium. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Objective 1: We are increasing numbers of advanced selections for potential release. In NC alone we now have >100 advanced mechanical harvest selections that have been established in replicated trials 2010-2012. Cultivar trials are being used to evaluate and (during field days) demonstrate new cultivars and establish their local utility. Significant new, elite plant accessions under MTAs from breeding programs at UF and UGA have tripled the size of field trials, and greatly increased chances of discovering new machine-harvestable clones. Elite seedling populations are now producing fruit at grower locations, both to demonstrate desirable characteristics and to accelerate the selection process. Objective 2: Our miniature and low-cost berry impact recording sensor (BIRD) has now been fully developed and validated. The size of the BIRD sensor is less than half of the current smallest instrumented sphere commercially available, and the cost is only 8% of a typical commercial sensor. BIRD has drawn the attention of commodity funding agencies and commercial packers/shippers to improve harvest and postharvest processes and fruit quality. Our work on the physiology of fruit detachment in blueberry has documented that natural fruit abscission and fruit detachment occur at the branch abscission zone, leaving the pedicel attached to the fruit. Fruit detachment without the pedicel appears to be associated with tissue tearing and physical separation. Thus, if abscission agents are to be used as harvest-aids, then de-stemming would be a key postharvest step to ensure optimal fruit quality. Objective 3: Our sensory studies have demonstrated qualitative and quantitative differences in textural properties between crisp and non-crisp cultivars. These results, when combined with those of previous years, show that consumers prefer the crisp southern highbush cultivars over their non-crisp counterparts. Objective 4: The fact that BLS can be spread via vegetative propagation, albeit at low incidence, highlights the need for establishment and monitoring of clean propagation practices throughout the southeastern blueberry industry. This is particularly important since visual symptoms are not generally apparent during the propagation process. Our strain analyses showed that blueberry BLS strains could have originated from phony peach or plum leaf scorch strains which occur in the southeastern U.S. Greenhouse screening for BLS resistance could be effective if careful attention is given to the strain of X. fastidiosa utilized. Objective 5: At the regional workshop in Gainesville, 26 county extension agents from across the Southeast received advanced training in the area of mechanical harvesting of blueberries. Participants rated "Potential for Impact" at 3.63 on a 1-4 scale (where 4 is excellent). We updated Fruit and Nut Planning Budgets in pdf form online (http://www.agecon.msstate.edu/what/farm/budget/); interactive Excel spreadsheet versions of these budgets are in draft format.

Publications

  • Brannen, P.M., Cline, B., Scherm, H., and Brewer, M. 2013. Exobasidium leaf and fruit spot development in southeastern environments and initial management strategies with fungicides. Pages 5-14 in: Proc. 47th Annual Open House & Trade Show, NC Blueberry Council, Clinton, NC.
  • Haralson, J.C., Brannen, P.M., Scherm, H., and NeSmith, S.D. 2013. Chemical control of Cylindrocladium and Rhizoctonia root rots in blueberry propagation. Crop Protection 44:1-5.
  • Lyrene, P.M., and Olmstead, J.W. 2012. The use of inter-sectional hybrids in blueberry breeding. International Journal of fruit Science 12:269-275.
  • Malladi, A., Vashisth, T., and Johnson, L.K. 2012. Ethephon and methyl jasmonate affect fruit detachment in rabbiteye and southern highbush blueberry. HortScience 47:1745-1749.
  • McCallum, S., Woodhead, M., Jorgensen, L., Gordon, S., Brennan, R., Graham, J., Hackett, C.A., Rowland, L.J., Hancock, J.F., Olmstead, J.W., and Bassil, N.V. 2012. Developing tools for long-term breeding of blueberry germplasm for UK production. International Journal of Fruit Science 12:294-303.
  • Mehra, L. K., MacLean, D. D., and Scherm, H. 2013. Postharvest disease development on southern highbush blueberry fruit in relation to berry flesh type and harvest method. Plant Dis. 97:213-221.
  • Rowland, L.J., Bell, D.J., Alkharouf, N., Bassil, N.V., Drummond, F.A., Beers, L., Buck, E.J., Finn, C.E., Graham, J., McCallum, S., Hancock, J.F., Polashock, J.J., Olmstead, J.W., and Main, D. 2012. Generating genomic tools for blueberry improvement. International Journal of Fruit Science 12:276-287.
  • Yu, P., Li, C., Takeda, F., Krewer, G., Rains, G., and Hamrita, T. 2012. Quantitative evaluation of a rotary blueberry mechanical harvester using a miniature instrumented sphere. Computers and Electronics in Agriculture 88:25-31.


Progress 09/01/10 to 08/31/11

Outputs
OUTPUTS: Objective 1: In NC, 68 new selections established in first-round mechanical harvest (MH) trials. Fifteen selections added to second-round MH trials. Three-thousand seedlings established in the field, with 4,000 awaiting planting. Another 7,000 seedlings germinated to be planted in 2012 and 2013. Fourteen crosses made. In FL, >7,000 seedlings from hybridization between crisp fruit parents planted for evaluation. A higher percentage of seedlings evaluated as crisp generated from cross between Sweetcrisp and FL 98-325 than all other crosses. Seventy-five selections identified as MH candidates based on architecture, vigor, fruit firmness, fruit detachment force, and maturity period. Objective 2: Evaluated seven southern highbush genotypes (Farthing, Primadonna, Scintilla, and Sweetcrisp, FL 05-528, FL 06-556, and Meadowlark) in stimulation studies to determine effects of drop height (50 or 100 cm) and contact surfaces (hard or padded with No-Bruze) on fruit firmness and bruise development. High-throughput sequencing identified >150,000 sequences from genes expressed in the branch and fruit abscission zones (AZs). Sequences mined and genes associated with hormone biosynthesis, signaling, and cell separation identified. Glycome profiling used to identify changes in the abscission zone cell wall carbohydrates during the process of abscission agent-induced fruit detachment. Objective 3: A total of 300 consumers evaluated three cultivars at least one classified as crispy and at least one as non-crispy. More crisp-flesh blueberries (45.5%) rated superior than non-crisp-flesh (26.4%), whereas a higher percentage of non-crisp-flesh samples (17.2%) judged unacceptable than crisp-flesh berries (10.6%). A descriptive panel judged samples from the same batches and found crispy selections to be sweeter, less sour, firmer and crispier than non-crispy ones. Objective 4: A survey of fungi causing stem blight confirmed species in the Botryosphaeriaceae that affect southern highbush blueberry in the Southeast. Specifically, Neofusicoccum ribis found to be the most common pathogen. In a separate study, plants sourced from outside the Southeast and propagated from tissue culture compared with plant material sourced in FL propagated by rooted cuttings. Plants sourced from FL died more frequently, and their stem blight incidence was higher. Strains of Xylella fastidiosa evaluated for pathogenicity to blueberry. X. fastidiosa subsp. fastidiosa strains from elderberry and lupine, as well as subsp. multiplex strains almond and blackberry, produced blueberry leaf scorch (BLS) symptoms. Other strains of X. fastidiosa from elderberry, blackberry, grapevine, sycamore, and mulberry evaluated in the greenhouse for biological control of blueberry leaf scorch, and two strains effective. Field trials established with these two strains. Objective 5: Revision of existing blueberry production database from Fruit Budget Committee (MS) members to include grower Advisory Panel feedback. From April-June 2011 conducted mail survey of blueberry growers in FL, GA, MS and NC. Results entered into a database and initial analysis began in fall 2011. PARTICIPANTS: PROJECT PIs: University of Georgia: Harald Scherm (Plant Pathology, overall project PD), Phil Brannen (Plant Pathology, extension), Changying Li (Biological and Agricultural Engineering), Anish Malladi (Horticulture), Rob Shewfelt (Food Science & Technology, sensory evaluation); Moukaram Tertuliano (Entomology); University of Florida: Phil Harmon (Plant Pathology, FL lead-PI), Don Hopkins (Plant Pathology); Paul Lyrene (Horticulture, blueberry breeding), Jim Olmstead (Horticulture, blueberry breeding); North Carolina State Univ.: Bill Cline (Plant Pathology, NC lead-PI), Jim Ballington (Horticulture, blueberry breeding); Mississippi State Univ.: Kim Morgan (Agricultural Economics, extension); USDA-ARS: Fumi Takeda (Horticulture, mechanical harvest). TRAINING/ PROFESSIONAL DEVELOPMENT: Kristin Abney (MS student, UGA), Rock Christiano (postdoc, UGA), Lisa Klima (MS student, UGA), Lucky Mehra (MS student, UGA), Kylah Smith (MS student, UGA), Tripti Vashisth (PhD student, UGA), Pengcheng Yu (MS student, UGA), Amanda Wright (PhD student, UF). TARGET AUDIENCES: The primary target audience for this project consists of commercial blueberry growers in the southeastern and mid-South regions of the United States. Knowledge transfer has occurred in educational sessions at the Southeast Fruit and Vegetable Conference; the North Carolina Blueberry Open House; the Gulf South Blueberry Growers Association annual field day; the annual Bacon County Blueberry Meeting; the Georgia Blueberry Growers Disease Update; and the Georgia Blueberry Production Short Course. Utilization of crisp texture in breeding, advantages for production, and current and future cultivar availability presented to >1000 producers in spring and fall 2011. Article "Banking on Berries With Bite" published in Florida Grower magazine, which reaches 12,000 producers in the southeastern US. These venues provided the opportunity to increase grower knowledge of this trait and how it can be used in production. Disease trainings for producers conducted in FL (2), Georgia (4), and NJ (1), and approximately 1,000 producers attended. Two county agent training sessions held in collaboration with the SRSFC, and 30 county agents from seven states trained as a result. Blueberry necrotic ring blotch formally noted as a new virus (BNRBV) in a published abstract. Producers and agents are now more fully aware of the symptoms and causes of several new or emerging diseases, to include BLS, BNRBV, and Exobasidium fruit and leaf spot. For example, many producers have previously applied fungicides for management of BNRBV, a wasted application that has resulted in both a negative financial and environmental impact. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Objective 1: Advanced selection NC 4131 increased for release as a new midseason, MH cultivar. We now have 29 advanced MH selections established in replicated trials. New crosses emphasize later bloom to avoid frost, improved quality, fruit size, crisp texture, superior firmness and adaptation to MH for the fresh market. Objective 2: Miniature, low-cost berry impact recording sensor (BIRD) developed for evaluation of the blueberry MH process. Size of sensor <50% of the current smallest instrumented sphere available commercially. Cost only 8% of a typical commercial instrument, which enables deployment of multiple sensors for field application. Simulated drop tests showed significant effects and interactions of cultivar, contact surface, and drop height on fruit firmness and the extent of bruising. Fruit firmness was highest in Farthing, Meadowlark, Sweetcrip, and FL05-528. The least bruising developed in Farthing, Meadowlark, FL05-528, and FL06-556. Data from fruit abscission studies have led to the understanding that fruit detachment in blueberry, either naturally or by abscission agents, occurs primarily at the branch AZ. Thus, de-stemming may be essential if abscission agents are used in conjunction with MH. Genes associated with abscission being studied and their characterization may lead to better understanding of the process of fruit detachment. Objective 3: Our sensory tests clearly establish that consumers will accept crisp-flesh blueberries. However, due to differences in sweetness and sourness in the cultivars evaluated, it is premature to conclude that crisp-flesh berries are superior to non-crispy counterparts. Objective 4: Stem blight survey results will be used to guide future research into management including selection for host plant resistance. The comparison of tissue culture vs. rooted cutting propagation suggests that plant mortality specifically due to stem blight could be reduced through changes to the propagation methods. The development of the greenhouse screen for resistance to BLS will lead to more rapid identification of resistant breeding lines. Differences observed between the greenhouse screen and field survey rankings for the first time indicated cultivar specificity among strains. Objective 5: Initial examination of survey data indicates that attendance and participation at numerous field days, grower conferences and workshops has resulted in meaningful survey research. Released Fruit and Nut Planning Budgets in pdf form online. These documents will be updated in 2012 and released as interactive Excel spreadsheets, and will include MH costs for both rabbiteye and highbush.

Publications

  • Brannen, P., Scherm, H., Deom, M., Srinivasan, R., and Harmon, P. 2011. Blueberry necrotic ring blotch disorder widespread and severe in 2011. Dixie Blueberry News 11(6):21-25.
  • Brannen, P., Scherm, H., Cline, B., and Ingram, D. 2011. Exobasidium fruit and leaf spot: A newly developing issue on Georgia blueberries. Dixie Blueberry News 11(4):4-8.
  • Brannen, P., Scherm, H., Cline, B., and Ingram, D. 2011. Exobasidium fruit and leaf spot: An emerging concern on blueberries in the Southeast. Small Fruit News 11(4):1-3.
  • Tertuliano, M., Srinivasan, R., and Scherm, H. 2012. Settling behavior of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), vector of Xylella fastidiosa, on different southern highbush blueberry cultivars. Entomologia Experimentalis et Applicata, DOI: 10.1111/j.1570-7458.2012.01228.x.
  • Vashisth, T., Johnson, L.K., and Malladi, A. 2011. An efficient RNA isolation procedure and identification of reference genes for normalization of gene expression in blueberry. Plant Cell Reports 30:2167-2176.
  • Yu, P., Li, C., Rains, G., and Hamrita, T. 2011. Development of the berry impact recording device sensing system: hardware design and calibration. Computers and Electronics in Agriculture 79(1):103-111.
  • Yu, P., Li, C., Rains, G., and Hamrita, T. 2011. Development of the berry impact recording device sensing system: software. Computers and Electronics in Agriculture 77(2):195-203.


Progress 09/01/09 to 08/31/10

Outputs
OUTPUTS: As in the previous year, the comprehensive mechanical harvest trial in north-central Florida in early May was the major focal point of the project, bringing together the PIs across disciplines and institutions. The novel crisp or semi-crisp textured cultivars Sweetcrisp, Farthing, and Meadowlark were compared with the conventional-flesh genotypes Star (industry standard), Scintilla, and FL 01-248. Following one or more hand-harvests to ensure that ripe fruit from the different cultivars or selections were at similar maturity levels, experimental hand- and machine-harvest was conducted in four replicate row sections per genotype. The experimental design was a split-plot with genotype as the main-plot and harvest method as the sub-plot. The soil beneath plots was raked prior to mechanical harvest, and ground losses were determined by counting the total number of fruit on the soil after passage of the harvester. A miniaturized, custom-built impact recording sensor was placed in selected machine-harvested plots to document and analyze the impacts experienced by blueberries during the various phases of the harvesting process. Hand- and machine-harvested fruit from all plots were collected in standard blueberry lugs, weighed, assessed visually for quality (percent US no. 1 fruit), and maintained temporarily in a mobile field cooler (15C) before being subjected to standard packinghouse sorting and grading procedures. Clamshells containing fruit were placed into cold storage (2C) and assessed for firmness and postharvest decay after 0, 7, and 14 days. Fungal pathogens associated with diseased fruit were identified microscopically. Separately, the effect of biofumigation with four plant essential oils (cinnamon oil, linalool, p-cymene, and peppermint leaf oil) and the plant oil-derived biofungicides Sporan and Sporatec on postharvest fungal decay during cold storage was investigated. Hand-harvested berries were inoculated with Alternaria alternata, Botrytis cinerea, Colletotrichum gloeosporioides, or sterile deionized water and subjected to biofumigation treatments at 7C for 1 week, followed by assessment of disease incidence. Non-inoculated, biofumigated fruit were assessed for sensory attributes (sweetness, sourness, bitterness, astringency, blueberry-like flavor, firmness, crispness, color, and juiciness) utilizing a trained sensory panel. Furthermore, the effect of biofumigation on antioxidant content of treated fruit was determined by measuring the total oxyradical scavenging capacity in berry extracts. PARTICIPANTS: PROJECT PIs: University of Georgia: Harald Scherm (Plant Pathology, overall project PD), Phil Brannen (Plant Pathology, extension), Gerard Krewer (Horticulture), Changying Li (Biological and Agricultural Engineering), Dan MacLean (Horticulture, postharvest physiology), Anish Malladi (Horticulture), Rob Shewfelt (Food Science & Technology, sensory evaluation); Moukaram Tertuliano (Entomology); University of Florida: Phil Harmon (Plant Pathology, FL lead-PI), Don Hopkins (Plant Pathology); Paul Lyrene (Horticulture, blueberry breeding), Jim Olmstead (Horticulture, blueberry breeding); North Carolina State Univ.: Bill Cline (Plant Pathology, NC lead-PI), Jim Ballington (Horticulture, blueberry breeding); Mississippi State Univ.: Kim Morgan (Agricultural Economics, extension); USDA-ARS: Fumi Takeda (Horticulture, mechanical harvest). TRAINING/ PROFESSIONAL DEVELOPMENT: Kristin Abney (MS student, UGA), Rock Christiano (postdoc, UGA), Lisa Klima (MS student, UGA), Lucky Mehra (MS student, UGA), Kylah Smith (MS student, UGA), Tripti Vashisth (PhD student, UGA), Pengcheng Yu (MS student, UGA), Amanda Wright (PhD student, UF) TARGET AUDIENCES: The primary target audience for this project consists of commercial blueberry growers in the southeastern and mid-South regions of the United States. Knowledge transfer has occurred in educational sessions at the Southeast Fruit and Vegetable Conference; the North Carolina Blueberry Open House; the Gulf South Blueberry Growers Association annual field day; the annual Bacon County Blueberry Meeting; the Georgia Blueberry Growers Disease Update; and the Georgia Blueberry Production Short Course. We estimate that these outreach activities have reached more than 300 commercial growers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Studies with the blueberry impact sensor showed that impact forces were greatest (>300 g) when fruit were detached by the beater rods and fell onto the catch pans of the harvester. Relatively high forces were also recorded when berries fell into the harvester's fruit collection lug. In an economic assessment of hand- vs. machine-harvest for the three crisp or semi-crisp cultivars Sweetcrisp, Farthing and Meadowlark, total fruit yield per bush (across three harvests) was higher but pack-out was lower for machine-harvest relative to hand-harvest. Ceteris paribus and assuming harvest costs of $0.72/lb for hand-harvest and $0.18/lb for mechanical harvest, net return was better for machine-harvest than for hand-harvest. We documented that mechanical harvesting of crisp-textured cultivars is feasible from a postharvest quality perspective. Machine-harvested fruit of crispy flesh genotypes developed levels of natural postharvest decay lower or similar to those of hand-harvested fruit of conventional genotypes. Artificial inoculations with A. alternata, B. cinerea, and C. gloeosporioides supported the fact that crispy berries develop less postharvest decay than their conventional counterparts, regardless of harvest method. There was a negative association between postharvest disease incidence and fruit firmness across genotypes and harvest methods, indicating that fruit firmness is a good predictor for postharvest decay risk. Fruit firmness values >220 g/mm were associated with consistently low decay levels. This relationship also suggests that the lower level of postharvest disease in crispy flesh genotypes is mostly due to their greater firmness, and not some other form of genetic resistance. Although the two fruit firmness groups and harvest methods differed in postharvest disease incidence, the pathogen complex responsible was similar. Aureobasidium pullulans, Cladosporium spp. and Alternaria spp. were observed most commonly. Out of the six essential oils evaluated for managing postharvest fungal decay during cold storage, only one (the plant oil-derived biofungicide Sporatec) resulted in significant and relatively consistent disease suppression. However, even for Sporatec the final disease incidence after artificial inoculation was still relatively high. Furthermore, biofumigation had a negative impact on the sensory quality of treated berries, leaving a strong flavor which detracted from blueberry-like flavor and changing other characteristics such as sweetness and juiciness negatively. Finally, the finding of increased antioxidant levels following biofumigation reported previously for northern highbush blueberry fruit could not be confirmed in our study, where antioxidant activity, total phenolics levels, and the types and concentrations of anthocyanins remained largely unchanged. Taken together, the results suggest that the potential for postharvest cold-storage biofumigation in harvested blueberries is limited. At the Univ. of Georgia, four MS students (two in Plant Pathology and one each in Food Science & Technology and in Biological & Agricultural Engineering) funded through the project have completed and defended their theses in 2010.

Publications

  • Wright, A. F., and Harmon, P. F. 2010. Identification of species in the Botryosphaeriaceae family causing stem blight on southern highbush blueberry in Florida. Plant Dis. 94:966-971.
  • Yu, P. 2010. Development of the Blueberry Impact Recording Device (BIRD) to Evaluate Blueberry Bruising in the Mechanical Harvest Process. M.S. thesis, Department of Biological and Agricultural Engineering, University of Georgia, Athens.
  • Yu, P., Li, C., Rains, G., and Hamrita, T. 2010. Develop a miniature sensor to record impacts during blueberry mechanical harvest. ASABE Paper No. 1009272. ASABE, St. Joseph, MI. 13 pp.
  • Nissen, L.D. 2010. Characterization of Xylella fastidiosa Strains That Cause Bacterial Leaf Scorch of Southern Highbush Blueberry (Vaccinium corymbosum Interspecific Hybrids), and Detection of the Pathogen in Plants and Glassy-Winged Sharpshooters [Homalodisca vitripennis (Germar)] (Hemiptera: Cicadellidae) in South Georgia. M.S. thesis, Department of Plant Pathology, University of Georgia, Athens. 152 pp.
  • Scherm, H. 2010. The spring 2010 mummy berry epidemic: What happened, and what can you do now Dixie Blueberry News 10(2):5-9.
  • Smith, K.C. 2010. The Sensory Evaluation and the Effect of Radio Frequency Application on Southern Highbush Blueberry. M.S. thesis, Department of Food Science and Technology, University of Georgia, Athens. 59 pp.
  • Wright, A.F., and Harmon, P.F. 2010. First report of Lasiodiplodia theobromae associated with stem blight of southern highbush blueberries in Florida. Plant Dis. 93:962.
  • Brannen, P.M., and Scherm, H. 2010. Recap of the 2010 mummy berry epidemic, or the "perfect storm" revisited. Dixie Blueberry News 10(3):4-6.
  • Lyrene, P.M. 2009. Southern highbush blueberry plant named 'Primadonna'. United States Patent PP20181, Patent Genius, USPT Office, Alexandria, VA.
  • Lyrene, P.M. 2009. 'Sweetcrisp' southern highbush blueberry plant. United States Patent PP20027, Patent Genius, USPT Office, Alexandria, VA.
  • Mehra, L.K. 2010. Fungal Infection and Postharvest Quality of Blueberry Fruit in Relation to Berry Flesh Type, Harvest Method, and Postharvest Biofumigation. M.S. thesis, Department of Plant Pathology, University of Georgia, Athens. 95 pp.


Progress 09/01/08 to 08/31/09

Outputs
OUTPUTS: Objective 1: Harvested and germinated >30,000 hybrid blueberry seedlings for field evaluation for adaptation to mechanical harvest for the fresh market. Made numerous successful parental combinations with emphasis on crispy flesh and mechanical harvestability. Evaluated clonal plots propagated from selected seedlings with crisp fruit texture and found that the crisp genotype can be fully recovered in certain seedlings. Assessed 24 southern highbush cultivars/ selections from the GA breeding program for variation in the ease of mature fruit detachment. Objective 2: Cultivars and advanced selections from the GA breeding program were evaluated for mechanical harvestability on research stations and grower sites. A large cooperative mechanical harvesting trial with four crispy-textured and four conventional cultivars/ selections from the FL breeding program was conducted at a grower site in northern FL and assessed comprehensively for mechanical harvestability, fruit quality, and postharvest quality and shelf life. Two abscission agents, ethephon and methyl jasmonate (MeJA), were tested at different rates relative to their ability to improve abscission characteristics on two cultivars differing in relative fruit crispiness. Objective 3: Fruit from the cooperative mechanical harvest trial in northern FL were assessed for microbial safety (surface populations of total aerobic bacteria, yeasts and molds, coliforms, and E. coli) and decay during postharvest storage. Panelists were trained to score nine descriptors (color, blueberry-like flavor, sweetness, sourness, bitterness, astringency, crispness, firmness, and moisture release) for sensory evaluation of fruit from the mechanical harvest trial. Several plant volatiles (anethole, carvacrol, linalool, MeJa, perillaldehyde, p-cymene, and the plant-derived fungicide Sporatec) were evaluated as potential biofumigants for reducing postharvest decay on artificially inoculated fruit during cold storage. Objective 4: Dynamics of necrotic ringblotch, bacterial leaf scorch, and sharpshooter leafhoppers (the vectors of bacterial leaf scorch) was monitored in commercial fields and on research stations. Potted trap plants were exposed at intervals at a site with high disease pressure to identify X. fastidiosa infection periods. Greenhouse experiments examined the settling/ feeding preference of glassy-winged sharpshooters on blueberry cultivars. Artificial inoculations were carried out in the greenhouse to develop a cultivar resistance screening protocol and to identify benign strains of X. fastidiosa to be used as biological controls. Transmission of Botryosphaeria stem blight through propagation was compared on plants derived from cuttings vs. tissue culture. Objective 5: Collected grower, supplier, and equipment manufacturer contact information for interviews and mail surveys to update production cost data base and determine factors affecting producer willingness to adopt new technologies (such as mechanical harvest machine investments). PARTICIPANTS: PROJECT PIs: University of Georgia: Harald Scherm (Plant Pathology, overall project PD), Phil Brannen (Plant Pathology, extension), Gerard Krewer (Horticulture), Changying Li (Biological and Agricultural Engineering), Dan MacLean (Horticulture, postharvest physiology), Anish Malladi (Horticulture), Rob Shewfelt (Food Science & Technology, sensory evaluation); Moukaram Tertuliano (Entomology); University of Florida: Phil Harmon (Plant Pathology, FL lead-PI), Don Hopkins (Plant Pathology); Paul Lyrene (Horticulture, blueberry breeding), Jim Olmstead (Horticulture, blueberry breeding); North Carolina State Univ.: Bill Cline (Plant Pathology, NC lead-PI), Jim Ballington (Horticulture, blueberry breeding); Mississippi State Univ.: Kim Morgan (Agricultural Economics, extension); USDA-ARS: Fumi Takeda (Horticulture, mechanical harvest). TRAINING/ PROFESSIONAL DEVELOPMENT: Kristin Abney (MS student, UGA), Efrat Atinsky (postdoc, UGA), Lisa Klima (MS student, UGA), Lucky Mehra (MS student, UGA), Kylah Smith (MS student, UGA), Pengcheng Yu (MS student, UGA), Amanda Wright (PhD student, UF) TARGET AUDIENCES: The primary target audience for this project consists of commercial blueberry growers in the southeastern and mid-South regions of the United States. Knowledge transfer has occurred in educational sessions at the Southeast Fruit and Vegetable Conference; the North Carolina Blueberry Open House; the Gulf South Blueberry Growers Association annual field day; the annual Bacon County Blueberry Meeting; the Georgia Blueberry Growers Disease Update; and the Georgia Blueberry Production Short Course. We estimate that these outreach activities have reached more than 300 commercial growers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.

Impacts
Objective 1: Identified and propagated additional new selections with the crispy flesh trait derived from parents such as Reveille, Sweetcrisp, FL 98-325, and others. Patented four new blueberry cultivars in NC. Analysis of fruit detachment force in southern highbush germplasm indicated a 2-3-fold variation in the force required for detaching pedicels from fruit. Objective 2: A prototype instrumented sphere for evaluating impacts associated with the mechanical harvesting, sorting, and packing process was constructed. In NC, a new 1-acre blueberry field was established with both replicated and solid rows of 13 cultivars for evaluation of mechanical harvestability. In the cooperative field trial in northern FL, Farthing, Sweetcrisp, and FL 98-325 harvested well mechanically. The selections with the crispy berry type, as a group, had higher fruit firmness that declined more slowly during postharvest storage. The two abscission agents evaluated had relatively little effect on fruit abscission characteristics and will be evaluated at higher rates in 2010. Objective 3: There was no difference in microbial fruit surface contaminants between hand- and machine-harvested fruit or between crispy and conventional cultivars/ selections. Postharvest decay was greater for machine-harvested than for hand-harvested fruit, but decay incidence for machine-harvested crispy selections was very similar to that of hand-harvested conventional cultivars. In the sensory evaluations, crispy flesh types were significantly more intense in color, firmer and crispier than their conventional counterparts. Hand-harvested fruit were less intense in color, firmer, crispier and released more moisture (related to juiciness) than the mechanically harvested fruit. Sporatec, when used as a biofumigant during cold storage, significantly reduced fruit decay incidence following artificial inoculation. Objective 4: Evidence is mounting to suggest that necrotic ringblotch is caused by a novel virus. The glassy-winged sharpshooter was the dominating leafhopper species on blueberry bushes with bacterial leaf scorch. Feeding preference of leafhoppers on different cultivars in the field and greenhouse did not correlate with observed field resistance of these cultivars to bacterial leaf scorch. Inoculation with X. fastidiosa resulted in moderate symptom development in cultivars deemed to be field-resistant. Identified benign isolates of X. fastidiosa suppressing bacterial leaf scorch development after challenge with a pathogenic isolate. The fungi Neofusicoccum ribis and Lasiodiplodia theobromae were recovered most frequently from southeastern stem blight samples. Plants propagated from tissue culture were more vigorous and uniform and had less mortality from stem blight than those propagated from cuttings. Objective 5: Identified and recruited grower participants from each state for interviews. Developed, pre-tested and obtained institutional approval for interview script. Began to optimize online, interactive blueberry budget database development process. Connected and coordinating outreach activities with other funded projects related to southeastern blueberry production and markets.

Publications

  • Ballington, J. R., and Rooks, S. D. 2009. Blueberry named Beaufort. USPP 19,764P3. United states Patent and Trademark Office. Feb. 24, 2009.
  • Ballington, J. R., and Rooks, S. D. 2009. Blueberry named Carteret. USPP 19,903P3. United States Patent and Trademark Office. Apr. 14, 2009.
  • Ballington, J. R., and Rooks, S. D. 2009. Blueberry named New Hanover. USPP 19,990P3. United States Patent and Trademark Office. May 12, 2009.
  • Ballington, J. R. 2009. The role of interspecific hybridization in blueberry improvement. Acta Hort. 810:49-59.
  • Brannen, P., Scherm, H., and Chang, C. J. 2008. Survey of cultivar differences in bacterial leaf scorch incidence among southern highbush blueberries. Dixie Blueberry News 8(6):6-7.
  • Brannen, P., Scherm, H., and Chang, C. J. 2009. Update on bacterial leaf scorch (Xylella) in southern highbush blueberries and cultivar field resistance. Pages 72-77 in: Proc. Southeast Blueberry Conf., Savannah, GA, 9-11 Jan. 2009.
  • Brannen, P. M., and Scherm, H. 2009. Blueberry necrotic ringblotch disorder. Small Fruit News 9(2):3-6. http://www.smallfruits.org/Newsletter/Vol9-Issue2.pdf
  • Brannen, P.M., and Scherm, H. 2009. Necrotic ringspot disorder. Dixie Blueberry News 9(2):4-8.
  • Chang, C. J., Donalson, R., Brannen, P. M., Krewer, G., and Boland, R. 2009. Bacterial leaf scorch, a new blueberry disease caused by Xylella fastidiosa. HortScience 44(2):413-417.
  • Cline, W. O. 2009. Disease identification: Is it a fungal leaf spot or a virus Small Fruit News 9(4). http://www.smallfruits.org/Newsletter/Vol9-Issue4.pdf
  • Cline, W. O. 2009. New information on the prevalence and control of emerging blueberry diseases in NC and GA. Small Fruit News 9(2). http://www.smallfruits.org/Newsletter/Vol9-Issue2.pdf
  • Cline, W. O., Ballington, J. R., and Polashock, J. J. 2009. Blueberry red ringspot observations and findings in North Carolina. Acta Hort. 810:305-312.
  • Harmon, P. F., and Hopkins, D. L. 2009 First report of blueberry leaf scorch caused by Xylella fastidiosa on southern highbush blueberry in Florida. Plant Disease 93:1220.
  • Li, C., Krewer, G. W., Ji, P., Scherm, H., Kays, S. J. 2010. Gas sensor array for blueberry fruit disease detection and classification. Postharvest Biology and Technology 55:144-149.
  • Scherm, H., Brannen, P.M., and Krewer, G. 2008. Grant awarded by USDA Specialty Crop Research Initiative to focus on improving production efficiency and managing emerging diseases in southern highbush blueberries. Dixie Blueberry News 8(6):8-11.
  • Scherm, H., Mehra, L., and MacLean, D. 2009. Observations on fruit rots in a southern highbush harvesting experiment, 2009. Dixie Blueberry News 9(5):7-11.
  • Ballington, J. R., and Rooks, S. D. 2009. Blueberry named Robeson. USPP 19,756P3. United States Patent and Trademark Office. Feb. 24, 2009.