POSTHARVEST PHYSIOLOGY OF FRESH HAWAIIAN COMMODITIES

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1020617
• Project Start Date: Oct 1, 2019
• Project End Date: Sep 30, 2024
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIV OF HAWAII
3190 MAILE WAY
HONOLULU,HI 96822

Performing Department
Tropical Plant & Soil Science

Non Technical Summary
In the marketing of fresh horticultural commodities from Hawaii, postharvest physiological problems impose three major limitations. Economic loss is associated with chilling damage due to improper storage temperature. This limitation leads to reduced storage life, failure to ripen and predisposes the commodity to pathogens. Secondly, there is a lack of information on the physiology and optimum handling procedure for many tropical fruits and ornamentals. Thirdly, the presence in the islands of at least three species of fruit flies and other quarantine insects, which means special postharvest treatments are necessary to achieve disinfestation prior to export.The most important requirements for fresh horticultural commodity marketing are consistency in supply and quality. This means that postharvest physiology must be considered from preharvest factors that influence supply and quality to postharvest maintenance of quality and assuring maximum storage life. In the evaluation fresh commodity quality, food safety andnutritional value have become more important as consumers age and, nutritional deficiencies and other health related issue increase. The study of the preharvest-postharvest handling continuum involves a multidisciplinary approach. This approach needs to include extension and stakeholders to cooperatively develop the needed research data and to integrate into Hawaii commodity production and handling practices.

Animal Health Component

30%

Research Effort Categories

Basic

20%

Applied

30%

Developmental

50%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
201	1099	1020	25%
204	1099	1020	25%
503	1099	1020	30%
712	1099	1020	20%

Knowledge Area
204 - Plant Product Quality and Utility (Preharvest); 712 - Protect Food from Contamination by Pathogenic Microorganisms, Parasites, and Naturally Occurring Toxins; 201 - Plant Genome, Genetics, and Genetic Mechanisms; 503 - Quality Maintenance in Storing and Marketing Food Products;

Subject Of Investigation
1099 - Tropical/subtropical fruit, general/other;

Field Of Science
1020 - Physiology;

Keywords

postharvest

quality

preharvest

storage

delay ripening

Goals / Objectives
Pineapple1. Using biotechnology and management strategies to minimize precocious flowering.2. Determine the factors that control the sugar/acid ratio in the new low acid varieties.3. Determine the importance of different preharvest factors that influence postharvest fruit quality especially translucency.4. Assist industry to find solutions to new problems as they arise.Papaya1. Develop, via backcrossing and selection, varieties that possess slow ripening traits and have commercial potential.2. Determine the role and regulation of cell wall degrading enzymes in ripening related fruit softening.3. Determine the relationship between the physiological effects of the insect disinfestation irradiation treatment on fruit ripening and ethylene.4. Assist industry to find solutions to new postharvest problems as they arise.Tropical Fruit1. Develop, in conjunction with industry, suitable postharvest handling protocols for fruit export.2. Prepare and distribute extension publications on the postharvest handling and physiology of tropical fruit.3. Assist industry to find solutions to new problems as they arise.Vegetables1. Develop an assay for taro acridity.2. Assist agents and industry in finding solutions to postharvest handling problems.3. Determine the influence of preharvest and postharvest environment and production methods on postharvest quality, food safety and nutritional value.Ornamentals1. Assist industry in developing new handling practices to assure Hawaii exports a high quality product.2. Determine the factors that reduce quality and evaluate practices that maintain product quality.

Project Methods
A. PineapplePineapple Objective 1 -Flowering: Natural flowering (NDF) of pineapple occurs sporadically, usually in the November-February period and the fruit produced from NDF ripen six to seven months after its occurrence.Another management approach to addressing natural flowering is to provide concise data on the incidence and timing of flowering in a field. Initial data fromflights with a drone (UAV) has been encouraging with a clear signature that a plant has flowered been detected. The UAV has also given some data on disease andweed incidence and development, plant establishment and fruit harvest efficiency. We have secured outside funded to expand this effort.We have generated transcriptome data from the apex and leaf bases of plants treated and not treated to induce flowering. We are currently analyzing this mass of data and expected that during this project we will need to confirm our most significant finding with quantitative PCR.Pineapple Objective 2. - Low Acid Fruit - Translucency & Microbial Disease ControlFruit acid/sugar balance is crucial to fruit flavor quality. The ability to provide year around fruit having consistent flavor is critical to fruit marketing. This project will provide research data that will enable the industry to select agronomic practices to modify fruit acid levels. In addition, the potential for genetic approaches to fruit acid adjustment will be evaluated.We have also generated transcriptome data from developing pineapple fruit. As with the flowering transcriptome data, we are currently analyzing this mass of data and expected that during this project we will need to confirm our most significant finding with quantitative PCR.B. PapayaPapaya Objective 1 - Develop, via natural mutant and genetic engineering, varieties that possess slow ripening traits and have commercial potential.No tomato germplasm altered in ripening has been described (Giovannoni, 2001; Moore et al., 2002) that has a similar functional change to that shown by our papaya fruit ripening lines.We have found a single QTL for this slow ripening trait and are now using papaya transcriptome data to determine the expression of the possible transcription factors present in this QTL region. The microarray analysis will be confirmed with RT-qPCR.Papaya Objective 2 - Determine the regulation of cell wall degrading enzymes in ripening related fruit softening.The papaya genome has been sequenced (Ming et al., 2008) and we have survey those genes that could potentially be involved in fruit ripening (Paull et al., 2008). This analysis has given us leads as to the transcription factors potentially involved in regulating fruit ripening and endoxylanase expression.During the last project, we generated transcriptome data from developing and ripening papaya fruit. Initial analysis data has been published with our current focus being on a more detailed look at genes potentially involved in fruit quality. We will need to confirm our most significant finding with quantitative PCR.We are following up on earlier work that showed jasmonic acid when applied to color break papaya fruit significant delayed ripening. However, this delay in ripening was less pronounced when applied when the fruit were more than 25% yellow. The literature shows that jasmonic acid is a stress plant growth regulation that interact with ethylene though how it suppresses ethylene production during ripen as recent shown in our laboratory is unclear.Papaya Objective 3 - Determine the relationship between the physiological effects of the insect disinfestation irradiation treatment on fruit ripening and ethylene.Nondestructive measurements for skin color will be made before and after irradiation treatment and throughout the ripening period. Destructive measurements for texture, internal color and soluble solids content will be made on a subsample of fruit at the beginning of the experiment and after full ripening. Total RNA will be isolated from fruit mesocarp with special attention paid to RNA purity and integrity (Chen & Paull, 2003). Primer probe pairs for each of the three papaya ethylene receptor genes (CpETRs) (Paull et al., 2008) will be designed and tested for their specificity. Levels of CpETR RNAs will be quantified using RNAs synthesized by in vitro transcription from plasmids containing the coding region of each CpERT gene and the total quantity (μg) of in vitro-transcribed RNA will be determined, and the in vitro transcription product used to generate a standard curve in real-time RT-qPCR analysis.C. Tropical FruitsThe general and specific fruit evaluation criteria used in tropical fruit studies include: 1. Fruit color and appearance (scald) - % skin coloration and appearance 1 to 5 scale; 2. Fruit shrivel subjective 0 to 3, none to obvious; 3. Fruit injury - mechanical damage 0 to 5, none to severe; 4. Disease incidence (# fruit/10); 5. Disease severity - 0 to 5, no disease to complete; 6. Fruit internal condition - color; 7. Internal defects; 8. Total soluble solids; 9. Shelf life. The tropical fruit that most commonly have postharvest problems aside from papaya and pineapple are litchi, rambutan, avocado and banana. We have just finished a project with USDA-ARS-Hilo on maturity standards for Sharwil avocado. The amount of research and fruit crop will depend upon availability of funds and most likely will be done in a cooperative project.E. VegetablesObjective 1. Develop an assay for taro acridity.We have shown that the acridity is most likely due to a protein on the surface of the raphides. The raphide-associated proteins will be separated using 2D gel electrophoresis and selected proteins sequenced (Paull et al., 1999). The amino acid sequences will be used to isolate full-length cDNA clones. Selected cDNAs will be expressed in E. coli to obtain sufficient protein to test the selected protein's acridity and produce antibodies. The assays will be evaluated on samples from taro that differ in acridity grown under different conditions and during commercial corm processing stages.Objectives 2 Assist agents and industry in finding solutions to postharvest handling problems.Procedures will be developed as needed when specific problems are referred.Objective 3. Determine the influence of preharvest and postharvest environment and production methods on postharvest quality, food safety and nutritional value.The World Vegetable Centre in Taiwan has 83 accessions of Kong Xin Cai (Ipomoea aquatica) also known as ung choi and kang kong. In conjunction with a colleague in Taiwan, we have published a harvesting and quality guide for this vegetable (https://www.ctahr.hawaii.edu/oc/freepubs/pdf/VC-6.pdf). This vegetable was more widely grown in Hawaii when it could be exported to the mainland until a sweet potato larvae was found in a shipment. This semi-aquatic vegetables has nearly 2% protein and is high in iron, vitamin C, vitamin A, phenolics and flavonoids (Huang et al., 2005; Igwenyi, et al., 2011; Du and Hwang, 2015). However, little is known about the nutritional changes postharvest that limitation also occurs in most leafy vegetables. Using five of the most morphological accession we will evaluate the changes postharvest. We will sample kang kong accession at three day interval when held at the recommended storage temperature of 12oC. Leaf tissue will be analyzed for ascorbic acid, phenolics, and antioxidants (ORAC).F. OrnamentalsWe will also determine the impact on vase life and quality when Hawaii's floral and foliage products are displayed in different environments that maybe warmer or cooler or with higher or lower relative humidity, and evaluate new postharvest treatment to maintain quality and extend the vase life of Hawaii's cut flowers and foliage. The data from this comparison can be used to expand Hawaii's competitive advantages and develop newer competitive niches.

Progress 10/01/19 to 09/30/20

Outputs
Target Audience:Growers, shippers, packer, wholesaler, retailers and consumers of Hawaii's fresh fruits, vegetables and ornamentals. Also impacts will be other scientists and extension personnel that work in these research areas. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?Trained visiting graduate student from Kyoto University on tropical fruit production. How have the results been disseminated to communities of interest?Yes to both growers, packers, wholesaler and other researchers worldwide. What do you plan to do during the next reporting period to accomplish the goals?The intent in the next reporting cycle is to focus on the following: 1. Complete the transcriptome analysis of how ethylene induces the change from a vegetative to floral apex. 2. Evaluate preharvest application of methyl jasmonate and melatonin on reduce pineapple fruit translucency. 3. Continue our studies in pineapple fruit size by evaluating optimum application practices for gibberellin and relationship throughout the year of plant weight at forcing and final fruit size. 4. Complete the transcriptome analysis of papaya fruit ripening and how this is modified in the slow ripening line. 5. Continue our evaluation of melatonin on fruit ripening and chilling injury develop 6. Collaborate with other faculty and a private company on coffee disease development using unmanned aerial vehicles (drones) to detect severity and incidence. 7. Complete a brochure on current knowledge of breadfruit postharvest practices and start a project maturity indexes and storage treatments. 8. Evaluate some new lines of the widely consumed leafy vegetable Kang Kong in collaboration with extension.

Impacts
What was accomplished under these goals? Pineapple The sugar/acid ratio of pineapple (Ananas comosus L.) contributes towards giving the fruit its unique flavor. This ratio is an important indicator of both commercial and organoleptic ripeness, and useful in determining harvest date. Citric acid is the major acid in pineapple and usually determined by titration to a specific pH endpoint while sugars are determined as total soluble solids by refractometry. Both acid and sugar levels vary with season in the year-round production cycle. Acid titration is slow and difficulty to perform in the field. A digital acidity meter based upon diluted juice conductivity was evaluated for potential field use. The readings obtained from the meter varied with clone and fruit potassium concentration. The meter evaluated had utility for field use to evaluated fruit quality and harvest date. Since fruit potassium levels can vary between harvests, the meter needs to be re-calibrated on a regular schedule to adjust for potential crop management and seasonal effects. Natural flowering affects fruit development and quality, and impacts the harvest of specialty plants like pineapple. Pineapple growers use chemicals to induce flowering so that most plants within a field produce fruit of high quality that is ready to harvest at the same time. Since pineapple is hand-harvested, the ability to harvest all of the fruit of a field in a single pass is critical to reduce field losses, costs, and waste, and to maximize efficiency. Traditionally, due to high planting densities, pineapple growers have been limited to gathering crop intelligence through manual inspection around the edges of the field, giving them only a limited view of their crop's status. Through the advances in remote sensing and computer vision, we can enable the regular inspection of the field and automated inflorescence counting thus enabling growers to optimize their management practices. Our work uses deep learning-based density-estimation approaches to count the number of flowering pineapple plants in a field. Notably, the computational complexity of this method does not depend on the number of plants present and therefore efficiently scale to easily detect over a 1.6million flowering plants in a field. We further embed this approach in a weakly supervised framework for continual learning and model improvement. Melatonin (MT) is found in different plant organs and tissues and is described as an endogenous elicitor with a signaling role that alleviates fruit chilling symptoms during postharvest storage. Melatonin effects on the overall quality of pineapple was investigated in fruit dipped in a 0.1 mM solution for 10 minutes and then stored at 9°C for 21 days. MT application delayed the deterioration process in pineapple during storage. The respiration rate was reduced, and skin color and flesh firmness changes were delayed. Internal flesh translucency and internal browning of pineapples were higher in control fruit. Immersion of pineapple in MT has commercial potential to alleviating internal browning symptoms and maintain the external quality of pineapple during cold storage followed by 4 days at room temperature. Papaya Papaya (Carica papaya L.) leaves are large, up to 70 cm wide, and frequently deeply lobed, with seven to 13 major veins. The scan width of current handheld digital leaf area instruments is generally less than 15 cm. A rapid method is needed to estimate the total leaf area of a plant in the field with leaves at different stages of growth from the apex. The length of the main and side veins of papaya leaves can be used to estimate the area of a single leaf and the total leaf area of the plant. The relationship between main vein lengths and total leaf area was determined for mature leaves from the cultivars Sunset, Line-8, and Kapoho. A simple relationship exists between leaf area and the length of the two main side midribs (L3 and L4): Leaf area (cm2) = L2280 + 87.7*L3 + 55.6*L4 (P > F = 0.0001; r2 = 0.969), explaining 94% of the variation between estimated leaf area and leaf area. The most recently matured leaf is the third or fourth discernable leaf from the apex, with a positive net photosynthetic CO2 assimilation rate and an average area of 2,331 cm2 that could fix up to 1.6 g carbon per 10-hour day under full sun. The rate of photosynthesis declined with leaf age, and the overall net photosynthetic CO2 assimilation rate of the plant can be predicted. Following 80% leaf defoliation of the plant, the net photosynthetic CO2 assimilation rate of the most recently matured leaf increased 30% to 50% on days 11 and 19 after treatment when the photosynthetic active radiation (PAR) is approximately half of that on day 15 under full sun when no difference in net photosynthetic CO2 assimilation rate was seen. Fruit removal did not affect the net photosynthetic CO2 assimilation rate. Papaya adjusts its single-leaf net photosynthetic CO2 assimilation rate under lower light levels to meet plant growth and fruit sink demand. Tropical Fruit Two extension brochure were produced in collaboration with the Hawaii Tropical Fruit Growers Association. Both brochures dealt with native fruit from Australia that have potential crops for Hawaii. Finger lime fruit are usually yellow-green but can vary widely from yellow and green to pale pink and crimson, with similar variation range in the flesh and seediness. The small translucent vesicles, or "citrus pearls," like caviar, inside the fruit are spherical and almost free, unlike the long, narrow vesicles in other citrus species. These pearls are used as a garnish or added to various recipes. When chewed, the vesicles have an effervescent tangy flavor. In another publication we highlighted four plants from Australia that have potential in Hawai'i as niche crops. The focus is on fruit crops with unique flavors, textures, and nutrient composition. The crops were "Ooray" (Davidsonia pruriens), Midyim (Austromyrtus dulcis), Lemon Aspen (Acronychia acidula) and Magenta Lilly Pilly (Syzygium paniculatum). Vegetables The pot herb drumstick or horseradish leaves (Moringa oleifera Lam) requires an irradiation treatment for insect disinfestation before shipping to the West Coast from Hawai`i. This irradiation treatment as well as packing and air shipment leads to leaflet abscission. To minimize this abscission the shipper had been including frozen gel packs in the shipping carton. However, these packs are heavy and lead to chilling injury on the leaflets and the development of mold on the leaves adjacent to the gel pack. Holding and shipping the product at 12oC negated the need for the frozen gel packs. Inclusion of a sachet of 1-methylcyclopropene (1-MCP) in the carton significantly reduced leaflet abscission, further reduction was obtained by inclusion of an ethylene absorption sachet and thus helped maintain overall product quality and marketability. Ornamentals No activity

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Paull, R.E. 2020. Dragon Fruit Improved Production. 30th Hawaii Tropical Fruit Growers Association Annual Conference. 2020 September 21 Q&A October 2 Online. https://davedoucette.wixsite.com/htfg/2020-conference
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Paull, R.E., Uruu, G., and Chen, N.J. 2020. Rapid Field Assay for Pineapple Fruit Acidity. HortTechnology 30, 593-596. https://doi.org/10.21273/HORTTECH04664-20
• Type: Journal Articles Status: Accepted Year Published: 2020 Citation: Hobbs, J., Prakash, P., Paull, R., Hovhannisyan, H., Markowicz, B., and Rose, G. 2020. Large-Scale Pineapple Flower Counting through Deep Density-Estimation. Frontiers in Plant Science. 11, 599705. Special Research Topic "Artificial Intelligence Applications in Specialty Crops" https://doi.org/10.3389/fpls.2020.599705
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Zhou, L., Reyes, M.E.Q., and Paull, R.E. 2020. Papaya (Carica papaya L.) leaf area estimation and single-leaf net photosynthetic CO2 assimilation rate following leaf defoliation and fruit thinning. HortScience 55, 1861-1864. https://doi.org/10.21273/HORTSCI15345-20
• Type: Journal Articles Status: Published Year Published: 2020 Citation: Paull, R.E. and Chen, N.J. 2020. Tropical fruit genomes and postharvest technologies. Acta Hortic. 1299, 113-122 DOI: 10.17660/ActaHortic.2020.1299.18 https://doi.org/10.17660/ActaHortic.2020.1299.18
• Type: Other Status: Published Year Published: 2020 Citation: Love, K., and Paull, R.E. 2020. Finger Limes. University of Hawaii at Manoa, College of Tropical Agriculture and Human Resources. Fruit, Nut, and Beverage Crops, FN-56 https://www.ctahr.hawaii.edu/oc/freepubs/pdf/FN%2056.pdf
• Type: Other Status: Published Year Published: 2020 Citation: Love, K. and Paull, R.E. 2020. Bush Tucker in Hawaii. University of Hawaii at Manoa, College of Tropical Agriculture and Human Resources. Fruit, Nut, and Beverage Crops, FN-57. https://www.ctahr.hawaii.edu/oc/freepubs/pdf/FN-57.pdf
• Type: Book Chapters Status: Published Year Published: 2019 Citation: Paull, R.E. and Chen, N.J. 2019. Pineapple. In. Freitas, S.T., and Pareek, S. (Eds) Postharvest physiology disorders of fruits and vegetables. Pp. 513-527. Taylor and Francis, Boca Raton, Florida, USA.
• Type: Book Chapters Status: Published Year Published: 2019 Citation: Oliveira, J.G., Morales, L.M.M., Silva, W.B., Gomes Filho, A. and Paull, R.E. 2019. Papaya. In. Freitas, S.T., and Pareek, S. (Eds) Postharvest physiology disorders of fruits and vegetables. Pp. 467-493. Taylor and Francis, Boca Raton, Florida, USA.
• Type: Book Chapters Status: Published Year Published: 2020 Citation: Paull, R.E. and Oliveira, J.G. 2020. Chapter 17.3 Tropical Fruits: Papaya. Pp 373-379. In: Maria Isabel Gil and Randolph Beaudry (Eds). Controlled and Modified Atmospheres for Fresh and Fresh-Cut Produce, Academic Press. https://doi.org/10.1016/B978-0-12-804599-2.00024-7
• Type: Book Chapters Status: Published Year Published: 2020 Citation: Paull, R.E. and Chen, N.J. 2020. Tropical Fruits: Pineapple. Pp 381-388. In: Maria Isabel Gil and Randolph Beaudry (Eds). Controlled and Modified Atmospheres for Fresh and Fresh-Cut Produce, Academic Press. https://doi.org/10.1016/B978-0-12-804599-2.00025-9
• Type: Book Chapters Status: Published Year Published: 2020 Citation: Muda, P., Chen, N.J., and Paull, R.E. 2020. Postharvest Handling, Storage and Quality. In. The Papaya: Botany, Production and Uses. Edited by S. Mitra. Chapter 16. Pp 237-251 CAB International.
• Type: Conference Papers and Presentations Status: Published Year Published: 2020 Citation: Hobbs, J., Paull, R.E., Markowicz, B., and Rose, G. 2020. Use of aerial imagery for automated pineapple flower counting. 2020. (Blog-Post) Harvard Center for Research on Computation and Society (CRCS) Workshop on AI for Social Good. In conjunction with the International Joint Conferences on Artificial Intelligence (IJCAI). July 20-21. https://crcs.seas.harvard.edu/publications/flowering-density-estimation-aerial-imagery-automated-pineapple-flower-counting (Accessed 2020 August 26)