In vitro antifungal activities of endophytic bacterial isolates against postharvest heart rot disease agent Alternaria alternata in pomegranate fruits

Pomegranate (Punica granatum L.) is one of the most commonly consumed fruit which suffers from postharvest decay giving rise to large economic losses. Alternaria alternata (Fr.) Keissl. is an important postharvest fungal pathogen causing loss of fruit during transportation and storage. Chemical applications are primarily made to control them. However, the recent trend is to convert toward safer and more friendly alternatives for the control of postharvest decays. In this study, we investigated the biological control of pomegranate postharvest heart rot disease agent using endophytic bacterial isolates obtained from healthy pomegranate fruits. A proteomic analysis through MALDI-TOF MS (matrix assisted laser desorption ionization time of flight mass spectrometry) was performed to identify these bacterial isolates. The antifungal activities of 12 putative endophytic bacterial isolates of Bacillus pumilus, Bacillus subtilis ssp. subtilis, Bacillus amyloliquefaciens, Bacillus vallismortis, Bacillus mojavensis, Bacillus megaterium, Solibacillus silvestris, Erwinia herbicola, Corynebacterium glutamicum, Bacillus cereus, Pantoea dispersa and Bacillus endophyticus were tested against A. alternata in dual culture assays. Bacillus mojavensis PEB39 was the most effective isolate against pathogenic fungi in vitro (80% inhibition of mycelial growth) followed by Bacillus amyloliquefaciens PEB46 (78.9%) Bacillus vallismortis PEB40 (76.7%) and Bacillus subtilis ssp. subtilis PEB43 (75.6%). Our findings suggest that as an alternative and promising biological control agent B. mojavensis can suppress postharvest diseases caused by A. alternata and may effectively control postharvest physiological changes caused by fungal pathogens.