Progress 10/01/13 to 07/01/14
Outputs
Target Audience:The target audience reached for this reporting period are local, national and international scientists working on fruit growth and development in blueberry as well as other fruit crops. Changes/Problems:One of the results of this research was the identification that fruit detachment by abscission occurs such that a pedicel is left attached to the fruit. This occurs in response to the application of the growth regulators as well. Hence, any application of abscission agents is likely to require subsequent pedicel detachment from the fruit. What opportunities for training and professional development has the project provided?A doctoral student conducted here dissertation research on this project. How have the results been disseminated to communities of interest?Multiple publications in reputed horticulture journals were developed from this research to disseminate relevant information to the scientific community. Additional manuscrips are under preparation and will be submitted within the next year to horticulture and plant biology related journals. What do you plan to do during the next reporting period to accomplish the goals?Additional research will be performed to specifically characterize the roles of some of the genes that were identified through the extensive RNA-Seq analysis. Further, physiological regulation of abscission will be further evaluated. The growth regulators identified in this study as potent fruit detachment agents will be evaluated for their potential applicability either alone or in combination with other agents as harvest aids.
Impacts
What was accomplished under these goals?
In the current reporting period, multiple goals associated with the project have been addressed and significant progress has been made in terms of the achieving the goals. The clear points of fruit detachment in blueberry were identified including the specific point of abscisison. Effects of wounding and organ removal on abscission at this location have benn characterized. Differential fruit detachment across two southern highbush blueberry genotypes has been characterized. It was identified that these genotypes do not differ in the establishment of the abscission zone but may have altered timing of activation of the abscission program. An extensive RNA-Seq analysis was performed to identify genes associated with the progression of abscission in response to the application of abscission agents. Biochemical analysis of changes in cell wall components was also performed to develop a deeper understanding of the changes associated with the progression of abscission in blueberry.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Two journal articles were published and one more has been submitted for publication. The citations are provided below:
Dash, M., L.K. Johnson, and A. Malladi. 2013. Reduction of fruit load affects early fruit growth in apple by enhancing carbohydrate availability, altering the expression of cell production-related genes, and increasing cell production. Journal of the American Society for Horticultural Science. 138: 253-262.
Vashisth, T., and A. Malladi. 2014. Fruit abscission in rabbiteye blueberry in response to organ removal and mechanical wounding. HortScience. 49: 1403-1407.
Vashisth, T., S. NeSmith, and A. Malladi. Anatomical and gene expression analyses of two blueberry genotypes displaying differential fruit detachment. (Submitted to the Journal of ASHS)
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Progress 07/01/08 to 07/01/14
Outputs
Target Audience:
Nothing Reported
Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
See last Progress report.
Publications
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Progress 01/01/13 to 09/30/13
Outputs
Target Audience: Professional fruit workers, Fruit growers in the southeast Changes/Problems: None What opportunities for training and professional development has the project provided? The project resulted in the training of a graduate student in the field of molecular fruit physiology. The Ph.D student has obtained training in fundamental principles of physiology and molecular biology. How have the results been disseminated to communities of interest? The results have been presented at tqo national meeting of professional societies (ASHS and ASPB). Some of the data have been published in peer reviewed journal articles. What do you plan to do during the next reporting period to accomplish the goals? The mode and site of action of the growth regulators used for fruit detachment will be further studied. Data on genotypes differing in fruit detachment potential will be obtained to better understand abscission.
Impacts
What was accomplished under these goals?
The point of natural fruit detachment in mature blueberry fruit has been clearly identified. Transcriptomics apporaches have led to a better understanding of the changes in gene expression during fruit abscission in blueberry. A gene associated with cell wall metabolism has been found to increase in expression in response to the application of two different growth regulators that induce mature fruit detachment. Biochemical approaches have been used to identify the specific changes in cell wall carbohydrates during fruit abscission in blueberry.
Publications
- Type:
Journal Articles
Status:
Accepted
Year Published:
2013
Citation:
Vashisth, T., and A. Malladi. 2013. Fruit detachment in blueberry: abscission and physical separation. Journal of the American Society for Horticultural Science. 138: 95-101.
- Type:
Journal Articles
Status:
Accepted
Year Published:
2013
Citation:
Malladi, A., T. Vashisth, and S. NeSmith. 2013. Development and evaluation of a portable, hand-held mechanical shaker to study fruit detachment in blueberry. HortScience. 48: 394-397.
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Progress 01/01/12 to 12/31/12
Outputs
OUTPUTS: A Ph.D. student is being mentored to conduct research on the physiology and molecular biology of abscission in rabbiteye blueberry. Research findings were disseminated through presentations at two venues in 2012: 1. The International Society for Horticultural Science: International symposium on mechanical harvesting and handling systems of fruits and nuts in Lake Alfred, FL. 2. The American Society for Horticultural Science annual meeting in Miami, FL. PARTICIPANTS: Ph.D. Candidate: Tripti Vashisth Collaborator: Dr. Scott NeSmith TARGET AUDIENCES: The target audience are the blueberry growers and blueberry breeders in the United states. PROJECT MODIFICATIONS: None
Impacts
New knowledge was generated from this research in 2012: It was determined that fruit detachment in blueberry occurs through one of two processes: Abscission or physical separation. The physiological process of abscission results in fruit detachment at the point of attachment of the fruit stalk to the stem resulting in stemmy fruit. Fruit detachment between the stalk and berry is through physical separation and tearing of the tissue. Natural and abscission-agent induced detachment occur through abscission while mechanical harvesting methods result in detachment through physical separation. This new knowledge has implications for the use of abscission agents and for the breeding and selection of genotypes better suited for mechanical harvesting. Profiling of the changes in the cell wall glycome during fruit abscission resulted in the identification of specific changes associated with the progression of this process. These data enhance our understanding of the process of fruit detachment and allow for the development of tools to manipulate it.
Publications
- Three publications were developed from the above research in 2012: (2 published in early 2013). 1. Vashisth, T., and A. Malladi. 2013. Fruit detachment in blueberry: abscission and physical separation. Journal of the American Society for Horticultural Science. 138: 95-101.
- 2. Malladi, A., T. Vashisth, and S. NeSmith. 2013. Development and evaluation of a portable, hand-held mechanical shaker to study fruit detachment in blueberry. HortScience. 48: 394-397.
- 3. Malladi, A., T. Vashisth, and L.K. Johnson. 2012. Ethephon and methyl Jasmonate affect fruit detachment in rabbiteye and southern highbush blueberry. HortScience. 47: 1745-1749.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Further research on abscission in rabbiteye blueberry was performed this year. Experiments were conducted at the University of Georgia, Horticulture farm in Watkinsville, GA. Three sets of experiments were performed. 1. Two potential abscission agents and other growth regulators associated with fruit detachment were applied to 'Climax', 'Briteblue' and 'Powderblue' blueberry genotypes. Fruit drop data was collected at regular intervals following application of the abscission agents. Additionally, abscission zone samples were collected at regular intervals for analyzing the expression of genes associated with abscission. 2. Natural fruit drop was recorded in two rabbiteye blueberry cultivars, 'Briteblue' and 'Premier'. This experiment was performed to determine the position from where the fruit normally detach in blueberry. 3. Fruit detachment in response to mechanical shaking. A hand-held mechanical shaker was designed and used to determine the point of fruit detachment in response to mechanical shaking in the rabbiteye cultivars 'Briteblue'. The point of detachment studies were designed to determine the applicability of growth regulators as harvest-aids in blueberry. PARTICIPANTS: One graduate student, Tripti Vashisth, and one technician, Lisa Klima Johnson were actively involved with the research reported this year. Additionally, Dr. Scott NeSmith has been closely associated with the research. A publication with him as the co-author was reported earlier. TARGET AUDIENCES: The main target audience for this research are the blueberry growers in Georgia. Presentation will be made at a grower conference to disseminate the knowledge gained from this research. PROJECT MODIFICATIONS: One change in the project is to shift the focus towards the mechanisms involved in fruit detachment at the branch abscission zone. This change is required as the data strongly indicate that this is the main point of fruit detachment.
Impacts
One of the major outcomes of research conducted in 2011 was the change in our knowledge that fruit detachment in blueberry normally occurs from the branch abscission zone. This information was derived from studies on growth regulator applications, and those on natural fruit detachment.This information impacts the use of mechanical harvesting in a very important manner. This change in knowledge indicates that fruit detachment in blueberry using harvest-aids will require further post-harvest processing using de-stemmers.
Publications
- No publications reported this period
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Progress 04/01/10 to 03/31/11
Outputs
OUTPUTS: Fruit size regulation is being studied in blueberry. Contribution of cell number and cell size to fruit size variation was evaluated across 20 rabbiteye blueberry genotypes. This research led to a publication in January 2011 (Journal of the American Society for Horticultural Science). Potential abscission agents capable of inducing fruit detachment and thereby enhancing mechanical harvesting efficiency in blueberry are being studied. In addition, genes specifically expressed in the fruit detachment zones are being identified. A high throughput, next generation sequencing approach (454 sequencing) was employed for this purpose. A research project has been initiated to profile changes in the cell wall polysaccharides during abscission induction in blueberry. Additionally, research on the effects of drought on fruit abscission responses has been initiated. Together, these studies are expected to lead to a better understanding of the process of fruit abscission in blueberry. An effective method for the isolation of high quality RNA from multiple tissues of blueberry was developed. Over 12 potential reference genes were evaluated and a set of 4 genes suitable for normalization of gene expression using qRT-PCR was identified. These studies led to a publication in July 2011 (Plant Cell Reports). These data are expected to be of interest to the academic community. PARTICIPANTS: Tripti Vashisth (Ph. D student), Lisa Klima Johnson (Research Technician) TARGET AUDIENCES: Scientific research community within the field of Horticulture. PROJECT MODIFICATIONS: A significant finding of research on blueberry abscission is that majority of fruit detachment in response to growth regulators occurs at the branch abscission zone. Hence, research on differences in the anatomy, physiology and biochemistry of the fruit and branch abscission zones is being initiated.
Impacts
Data on fruit size regulation revealed the role of cell number as a critical factor regulating final fruit size in blueberry. Additionally, cell number in blueberry was found to be controlled by cell production prior to bloom as well as during early fruit growth. These fundamental changes in knowledge may allow for crop improvement in the future. Several growth regulators capable of inducing abscission in blueberry fruit have been identified. Most agents appear to induce abscission at the branch abscission zone. A hand-held mechanical shaker has been developed. This tool is expected to enable the simulation of mechanical harvesting in blueberry. Evaluation of cultivars for their suitability for mechanical harvesting will be performed with this instrument. Over 150,000 expressed gene fragments from blueberry abscission zones were identified using a high throughput sequencing approach. These data were mined using bioinformatics tools to identify critical genes associated with fruit abscission. Over 50 genes associated with hormone biosynthesis and signaling, and cell wall maintenance have been identified from this research. These genes are being further studied to determine their roles in abscission.
Publications
- Vashisth, T., L. K. Johnson and A. Malladi. 2011. An efficient RNA isolation procedure and identification of reference genes for normalization of gene expression in blueberry. Plant Cell Reports. DOI: 10.1007/s00299-011-1121-z.
- Johnson, L. K., A. Malladi and S. NeSmith. 2011. Differences in cell number facilitate fruit size variation in rabbiteye blueberry. Journal of the American Society for Horticultural Science. 136: 10-15.
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Progress 04/01/09 to 03/31/10
Outputs
OUTPUTS: Research has been conducted on 2 aspects of the project during the reporting period. Fruit size regulation in blueberries has been closely studied using different cultivars/advanced selections of rabbiteye blueberry. Results obtained from this research are being disseminated in several ways. Data from this research will be presented at the annual meeting of the American Society for Horticultural Science in August 2010. A poster describibng progress in this research will be presented at the meeting. Additionally, a publication is currently under preparation to help disseminate results to the horticultural industry. Research on abscission in blueberries has lead to significant results. These results were shared with growers and professional fruit workers at several venues. An oral presentation on abscission agents for blueberries was made at the Southeastern Professional Fruit Workers meeting in Clemson, SC in October 2009. Additionally, some of this research was presented at the Georgia Fruit and Vegetable Grower's conference in January, 2010. In addition, results from the above research have been shared with blueberry growers on different occassions including field visits to grower farms. PARTICIPANTS: Anish Malladi; Assistant Professor, Department of Horticulture, University of Georgia was the Principal Investigator of this project. Lisa K. Johnson, Research Technician III. Department of Horticulture, University of Georgia worked extensively on these research projects. Tranining on microscopy was provided to two Horticulture undergraduate students: Sarina Barich and Lucas O'Meara. Dr. Scott NeSmith was a collaborator on the fruit size research project. TARGET AUDIENCES: Targest audience for this research were blueberry growers in the state of Georgia as well as growers across the country. Additional target audience were professional fruit workers from Southeastern US as well as blueberry researchers across the US. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
One of the major findings of research on fruit size regulation in blueberry is that fruit size variability across blueberry genotypes is dependent on cell number and not on cell size. These results were achieved through a thorough study of cell number and cell size across several established cultivars and advanced selections from the blueberry breeding program at the University of Georgia. Additionally, results indicate that final cell number is not related to cell number at bloom suggesting that the period of early fruit development is critical for determining final fruit size potential. This is a significant advancement in our understanding of size regulation in blueberries. These results are of importance to production practices particularly during early fruit growth. Manipulation of fruit size may be effectively achieved through such practices during early fruit growth. In addition, some of these results are of importance to blueberry breeders. These results provide a physiological basis for selection for large size berries in blueberry breeding programs. Research on abscission agents in blueberries has led to the identification and characterization of several compounds with the potential to alter fruit detachment. One of these compounds induces rapid and effective fruit detachment. However, a major issue identified through this research is that blueberries respond to abscission agents by inducing fruit detachment at a region not conducive for post-harvest handling. These data indicate that while the abscission agents have the potential for improving fruit detachment and mechanical harvesting efficiency, more work is essential to fine-tune the application of these growth regulators to achieve fruit detachment at the desired location.
Publications
- Johnson, L. K., and Malladi, A. 2010. Analysis of cellular basis of fruit size variation in rabbiteye blueberries (Vaccinium ashei Reade). Annual meeting of the American Society for Horticultural Science. August, HortScience (In press)
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Progress 07/01/08 to 03/31/09
Outputs
OUTPUTS: Several studies were initiated in 2008 to understand regulation of fruit size and abscission in rabbiteye blueberries. A research plot has been established at the Horticulture Farm in Watkinsville, GA. The plot currently has 4 different rabbiteye blueberry varieties (30-60 plants each) varying in fruit size and time to maturity. Recently, an additional southern highbush blueberry cultivar has been added to the plot (60 plants). Studies have been initiated to understand the contribution of cell number and cell size to fruit size variation across rabbiteye blueberry varieties. Twenty selections differing widely in their fruit size potential were selected. Analysis of fruit diameter and fruit weight was performed, and varieties were classified according to final fruit size characteristics. Microscopy studies have been initiated to understand the contribution of cell number and cell size to fruit size variation across these cultivars. In the following years, the effect of several environmental factors and pollination on fruit size will be studied. Research on blueberry fruit abscission was initiated in 2008. The plant growth regulator, ethephon was evaluated as a potential abscission agent. A force gauge was retro-fitted with help from the machine shop to specifically measure fruit detachment force in blueberries following PGR application. Current data suggest that ethephon (1000 ppm) initiates fruit drop across several rabbiteye blueberry cultivars. Fruit detachment force appears to be decreased by ethephon treatment. Fruit drop, however, appears to occur at the branch abscission zone more readily than at the calyx abscission zone. Hence, further evaluation is essential to prevent `stemminess' in these berries. Additionally, a naturally produced plant volatile was evaluated and found to be highly effective as an abscission agent. Further studies will be performed in 2009 to verify these results and to determine its applicability across a wide range of varieties. Also, evaluation of fruit detachment force across many rabbiteye selections will be performed in the following years to understand the genetics of fruit detachment. Tools are being developed in the laboratory for future research on molecular aspects on abscission signaling. Data generated from the above studies will be presented to growers at the southeastern fruit and vegetable growers conference in the following years. PARTICIPANTS: Dr. Anish Malladi is the principal investigator (PI) on this project. Collaborations have been developed between the PI and other researchers at the University of Georgia. A primary collaborator with some of the above research is Dr. Scott NeSmith, Department of Horticulture, University of Georgia, Griffin, GA. TARGET AUDIENCES: The target audience for this research are the blueberry growers of GA. Data from the above studies will be presented to the growers at grower meetings in a timely manner. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
During the first year of this project, several interesting results were obtained. Fruit size measurements across multiple cultivars allowed the identification of extremes in natural variation in fruit size. Greater than a 2-fold variation was observed in terms of fruit diameter across these varieties. Extremes from these cultivars were thus identified from this study. These extremes are currently being utilized to further understand the contribution of cell division rates and duration to fruit size regulation. These data will enable efficient breeding of blueberry varieties with large fruit size in the future. A primary output of abscission research in the previous year has been the evaluation and identification of PGRs with potential for enhancing fruit detachment. A plant volatile compound was found to be effective in achieving the above response, although abscission occured along with an attached stem. Application of this compound at lower rates or in combination with other compounds may be an effective strategy which will be further evaluated in the following years. An additional output from abscission research during the past year was the development of an instrument that can accurately measure fruit detachment force on blueberries. A pull force guage was retro-fitted with an attachment to enable this objective. Additional modifications will be made in 2009 to measure detachment at the branch abscission zones in blueberry fruits.
Publications
- No publications reported this period
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