Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: January 5, 2011
Publication Date: January 23, 2011
Citation: Janisiewicz, W.J. 2011. Biological control of postharvest diseases of fruits: from wound to latent infection. Full-Bright Specialist Program workshop. University of Pretoria. p.32. Technical Abstract: Research on biological control of postharvest diseases (BCPD) on fruits is in its third decade. For the past 15 years, BCPD has been used in packinghouses to control various postharvest diseases of temperate, subtropical and tropical fruits, and vegetables. The use of individual products has been expanding as applications for controlling new diseases on new commodities are being developed. However, the use of these products is still very limited in comparison to fungicides. This is largely due to limitations of current biocontrol products, some of which are inherent to a biocontrol approach, but others have roots in their original development. During the past decade, much research has been focused on addressing these limitations. Existing products and those under development have been used in combinations with physical treatments such as high temperature, UV-C illumination, microwaves, ozone and controlled or modified atmosphere, GRAS substances such as bicarbonate and carbonate salts, calcium, ethanol, silicone and bacteriocin. These products have also been combined with elicitors of host defenses and retardants of senescence such as chitosan, harpin, methyl jasmonite, and salicylic acid, growth regulators, nutrients and nutrient analogs, and low doses of fungicides. The levels of decay control obtained by several of these combinations often matched the effectiveness of fungicide treatments and sometimes exceeded them, especially when resistance to fungicides occurred. The development of BCPD has been directed toward controlling decays originating from wound infections, but BCPD originating from latent infections occurring in the orchard remains largely unexplored. However, controlling latent infections would add new dimension to BCPD that is necessary to make this approach relevant on many important commodities. This is the next big challenge to BCPD that must be addressed. Fruit microflora has been an excellent source of biocontrol agents, and microbial ecology has been the driving force in developing BCPD originating from wound infections. Thus, the biocontrol potential of these microflora for controlling latent infections should also be explored. We characterized bacterial and yeast microflora of nectarines and plums. We also developed an in vitro screening procedure utilizing wax membranes to select antagonists colonizing mycelium, conidia and appressoria of Monilinia fructicola and Colletotrichum spp. causing brown rot, and various decays of subtropical and tropical fruits, respectively. Both pathogens can cause latent infections of fruits. An in situ inoculation procedure was developed for the production of M. fructicola appressoria on nectarines and plums, and to test potential antagonists for reducing decay originating from these infections. Several antagonists were found that effectively control latent infections on fruits under controlled laboratory conditions. Although still in the initial developmental stage, this approach appears to be very promising. If it can be successfully moved from the laboratory to a typical postharvest environment, it may result in the development of the next generation of biocontrol products.