There are a myriad of post-harvest applications for fungal antagonistic agents however there are several challenges during the commercialization of these biocontrol strains. At present only two commercial products available as postharvest antagonistic agents with a small market share. Biosave (based on the bacterium Pseudomonas syringae) has been used in the USA to control diseases of sweet potato and potato diseases. “Shemer” (based on the yeast Metschnikowia fructicola) has been applied in Israel commercially to control post-harvest rots of sweet potato and carrot (Droby et al. 2009). Large-scale feasibility tests are warranted before the antagonistic strains are to be applied to fresh commodities. For the successful implementation of biocontrol strategies, the combination of commercial settings, industrial support, and quality control mechanisms to build up the confidence of farmers are all critical factors in the field. Some examples of potential fungi that can be used in post-harvest applications are provided below.
Saccharomycetes: Candida is a genus that comprises some commonly used antagonistic yeasts that can reduce post-harvest decay of several fresh commodities. For example, Candida guilliermondii has been used to control gray mold caused by Botrytis cinerea in nectarines and peach (Tian et al. 2002) and C. incommunis is effective against Aspergillus carbonarius and A. niger (which produce ochratoxin A) in grape berries (Bleve et al. 2006). The volatile organic compounds of C. intermedia reduce Botrytis fruit rot in strawberries (Huang et al. 2011). Candida oleophila has controlled banana crown rot caused by Colletotrichum musae, Fusarium moniliforme and fungal complexes (Lassois et al. 2008). Droby et al. (2009) applied Candida saitoana solely against Penicillium digitatum and Botrytis cinerea on the post-harvest rots affecting pome and citrus fruits. Candida membranifaciens has reduced post-harvest anthracnose disease caused by Colletotrichum gloeosporioides in mangos (Kefialew and Ayalew 2008). In vitro application of Pichia anomala (also known as Wickerhamomyces anomalus) has controlled post-harvest decay of apples (Santos et al. 2004) and bunch rot of table grapes (Parafati et al. 2015). In addition, the in vivo application of Pichia anomala has reduced crown rot disease in banana (Lassois et al. 2008). Saccharomyces boulardii can induce phytoalexin formation on sorghum and soybean (Stangarlin et al. 2010). Saccharomyces cerevisiae inhibited the activity of Botrytis cinerea (in grapes) by producing volatile compounds (Parafati et al. 2015). In vitro application of Metschnikowia pulcherrima against post-harvest rot of grapes (Bleve et al. 2006, Parafati et al. 2015) was also notably successful.
Other Ascomycota: Aureobasidium pullulans has been used to control bunch rot in table grapes caused by Botrytis cinerea (Parafati et al. 2015). In addition, post-harvest rot of table grapes caused by Monilinia laxa (Schena et al. 2003) were also controlled successfully by this fungus. Penicillium frequentans has been shown to effectively inhibit the growth of Monilinia sp., which causes brown rot in peaches (Guijarro et al. 2007).
Basidiomycota: Cryptococcus magnus can inhibit the mycelial growth of Colletotrichum gloeosporioides in vitro, and controlled post-harvest anthracnose in papaya (de Capdeville et al. 2007). An aqueous extracts from the basidiomes of Lentinula edodes has controlled the growth of Puccinia recondita f. sp. tritici (Fiori-Tutida et al. 2007). In addition, the in vivo application of Pycnoporus sanguineus has controlled the angular leaf spot in beans caused by Pseudocercospora griseola (Viecelli et al. 2009). Aqueous extracts of the basidiomes of Agaricus subrufescens have also shown an antagonism against Puccinia recondita f. sp. tritici. (Fiori-Tutida et al. 2007). However, these basidiomycetes and their extracts have not been proven to be effective in field trials, and the development of methods for effective mass production to attain favorable costs of goods will constitute a serious problem.