Abstract
The present study focuses on bioprospecting of halotolerant bacteria from a hypersaline environment for antifungal agents against major mushroom pathogens. A total of 20 morphologically different fungi were isolated from composts and infected fruiting bodies of Agaricus bisporus; belonging to the genera Trichoderma, Penicillium, Aspergillus, Mucor and Rhizopus. In addition, 131 halotolerant bacteria out of 280 exhibited antifungal activity against phytopathogens, Trichoderma sp., and Penicillium sp. The isolates (80) showing maximum and consistent activity were screened against the isolated mushroom pathogens, Trichoderma harzianum MTCC 3178 and Lecanicillium fungicola MTCC 2016. About 33.8% halotolerant bacteria produced an antifungal metabolite that inhibited the mycelial growth of Trichoderma harzianum MTCC 3178, 20% inhibited mycelium growth of Lecanicillium fungicola MTCC 2016, 48.8% other Trichoderma spp., 26.3% Penicillium spp. and 2.5% inhibited Aspergillus spp. The bacterial isolate BGUMS93 showed highest broad spectrum activity against these pathogens. Carbohydrate utilization profile, biochemical characteristics and 16S rRNA gene sequencing revealed BGUMS93 as Bacillus sp. (KC991034.1) with 97% similarity to Bacillus subtilis. BGUMS93 produced extracellular antifungal metabolites in butanol extract showing maximum activity against Trichoderma harzianum MTCC 3178 and in chloroform extract against Lecanicillium fungicola MTCC 2016. Thus, Bacillus spp. from Goa’s salterns could be a way to provide natural fungicide as an alternative to synthetic fungicides used in mushroom cultivation.
Highlights
IntroductionKnown as white button mushroom is one of the most common, globally grown edible mushrooms
Agaricus bisporus, known as white button mushroom is one of the most common, globally grown edible mushrooms
The present study focuses on bioprospecting of halotolerant bacteria from a hypersaline environment for antifungal agents against major mushroom pathogens
Summary
Known as white button mushroom is one of the most common, globally grown edible mushrooms. Mushrooms are susceptible to microbial diseases at various stages including compost, casing, spawn run and even mushroom fruiting body These diseases further propagate through various sources such as air, water, machines and workers causing secondary infections, thereby reducing its yield and marketability. Lecanicillium fungicola (previously known as Verticillium fungicola), the causal agent of dry bubble disease is the most common fungal disease of Agaricus bisporus (Berendsen et al, 2010) This soil-borne pathogen, at an early stage of mushroom growth results in typical onion shaped mushrooms whereas late infection shows traces of grey mouldy fuzz on the mushrooms. Trichoderma spp. cause major losses as they spread quickly and on a massive scale They occur in all stages of mushroom growth; soil, organic matter and air, being sources of infection. The present work was aimed to investigate the potential of hypersaline bacteria from salt pans to suppress mushroom pathogens Trichoderma harzianum and Lecanicillium fungicola
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