NE1018: Postharvest Biology of Fruit
Statement of Issues and Justification
Consumption of fruit contributes significantly to human health, and yet Americans fall far short of consuming the recommended servings. US consumers have access to moderately priced fruits of apparent good quality, the result of many years of effort by fruit breeders and postharvest specialists. Yet, consumers limit purchases with the primary complaint of insufficient quality and lack of flavor. Fruit producers often market fruit from cultivars with poor quality and flavor to maintain market share. The key to increasing consumer consumption of fresh fruits, without loss of grower income, lies in providing fruit with both superior flavor and shelf life.Storage protocols of temperate fruits are cultivar- and sometimes region-specific, and must be optimized to reduce postharvest losses. Protocols are needed for each replacement cultivar on a regional level. The geographical composition of the team in this project provides a unique situation where responses of cultivars to a wide range of growing conditions can be studied. Such studies provide essential postharvest linkages to studies on productivity and other horticultural factors carried out in the NE183 Regional Project. New apple cultivars such as Honeycrisp have been widely planted in the US and a number of physiological and pathological disorders are limiting continued expansion and threatening the viability of the industry.
While the introduction of agrichemicals has contributed to considerable gains by fruit producers, negative effects of some chemicals on the environment and/or human health have caused increased concern (NAS, 1993). Globally, increased emphasis is being placed on production of high-quality food and fiber at low cost and with minimal deleterious effects on humans or the environment. The National Academy of Sciences has recommended that the U.S. Make research investments and policy changes that emphasize development of pesticides and application technologies that pose reduced health risks and are compatible with ecologically based pest management (NAS, 2000). The Academy further specified that the development and incorporation of new, safer chemistries into agriculture to maintain productivity while protecting human and environmental health must be based on sound fundamental and applied research, and decisions must be based on science. and they recommended expansion of the research effort in government, industry, and university laboratories.
The fruit industries are heavily reliant on postharvest chemicals to control decays, insects, and physiological disorders during storage. Kuchler et al. (1997) reported that 47 percent of detectable pesticide residues on apples were attributable to products such as diphenylamine (DPA), thiabendazole, and captan that are applied after harvest. Non-toxic alternatives are needed to better position our domestic producers for maintaining their global market share. New approaches are needed to minimize losses of fruit during storage and transport. A better understanding of relationships between postharvest physiology of fruits and their susceptibility to decay is essential for developing improved control measures.
Recent progress in understanding the biology and genetics of ethylene formation and its role in fruit softening will enable us to interfere with fruit softening at the genetic level. Recent developments of transformation vectors and protocols will permit the tailoring of ethylene suppression to individual apple cultivars for extended storage life and aroma formation. One of the targets for extended storage life is McIntosh, an apple cultivar that is produced in the largest quantities in the US, has appealing characteristics, but softens rapidly.
The presence of insects after harvest can interfere with international and domestic marketing of US fruit crops. Phytosanitary treatments must control the pests without damaging the fruit and be safe for the environment. Postharvest insect control often involves fumigation with methyl bromide or other fumigants. There is great interest to develop sustainable alternatives that are economically feasible. Alternative strategies are essential to maintain important export markets for US fruit crops and to compete effectively with foreign producers.
The discovery and commercialization of 1-methylcyclopropene (1-MCP) as a means of controlling fruit ripening, maintaining fruit quality in storage and reducing storage disorders has developed a critical area of research for this project. 1-MCP was approved for food use in July 2002 and used commercially on apples in several states. It has low toxicity, has negligible residues, and is effective at low concentrations. However, as with many new technologies, there are still many questions left to be answered on how it can best be used to ensure high fruit quality.
Thus the focus of our project is to evaluate the storage potential of new cultivars, make better use of existing storage technologies, and develop new, safer technologies, with a minimum use of chemicals. Underpinning this research, we have an active group that is investigating the metabolism of ripening and the biological causes of physiological disorders. Our emphasis has also shifted towards investigating the effects of postharvest handling on the nutritional and flavor quality of fruit because of their importance to consumers. Specialist skills within this multistate project will allow collaborative activity among regions, allowing greater advances in a shorter period of time. As in the past, the group will develop experimental protocols on various research topics that will be carried out in diverse geographical regions to explore the effects of environment on fruit response to various factors. In addition, members with more fundamental research skills will team with those with more applied knowledge to allow a greater understanding of the issues. Participation in this multistate project facilitates these important types of interactions that may not be available within the individuals institution. In some cases, storage facilities and equipment will be shared among members to increase efficiency and efficacy.
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