Studies on Predominant Epiphytic Micro-flora as Antagonists to Postharvest Pathogens of Apple

Apple (Malus domestica Borkh) is an important horticultural crop that is affected by the number of diseases round the year. The fruit is particularly susceptible to a number of pathogens both pre- and post-harvest. Management of these diseases is based mostly on the application of synthetic fungicides with obvious disadvantages of environmental pollution, health hazards, pathogen resistance, etc. In the present study, eleven epiphytes were isolated using potato dextrose agar, nutrient agar and yeast maltose agar media. Amongst them, five fungal isolates viz., Aspergillus sp. (I1), Penicillium sp. (I2), Fusarium sp. (I3), Rhizopus sp. (I4) and Alternaria sp. (I5) and six bacterial isolates viz., Pseudomonas sp. (I6), Pseudomonas sp. (I7), Bacillus sp. (I8), Bacillus sp. (I9), Staphylococcus sp. (I10) and Micrococcus sp. (I11) were predominantly noticed under all the three methods (leaf impression, serial dilution and fruit washing) and were hence, used for further studies. The highest average colony count of 3.62 colonies/cm2 was recorded in fruit washing method followed by leaf impression (3.17) and lowest in serial dilution method (2.12). The in vitro screening of various bacterial and fungal epiphytes revealed that isolates of Pseudomonas sp. (I6) and Bacillus (I8 and I9) were the only bacterial strains capable of inhibiting the growth of all the test pathogens using dual culture method. Assays on wounded apples revealed that Pseudomonas sp. I6 at 107 cfu/ml was effective antagonist against Penicillium sp. and Fusarium sp., Bacillus sp. I9 at 107 cfu/ml was effective antagonist against Alternaria sp., whereas, Bacillus sp. I8 at 107 cfu/ml was most effective antagonist against Diplodia sp. The present study revealed that the antagonists were more or less efficient towards each pathogen and can be utilized for the management of post-harvest diseases of apple.