Vol. 15 No. 3
Evaluation of synthetic antimicrobial peptides for the control of mulberry brown leaf spot disease incited by Myrothecium roridum
Brown leaf spot of mulberry is caused by necrotrophic pathogen Myrothecium roridum (ascomycete) and results in the foliage loss (12-15%) during June-September in West Bengal. The management practice for brown leaf spot (BLS) includes application of dithio-carbamate fungicides; which are combative for user-health and the environment. The current study evaluates application of synthetic antimicrobial peptides (AMPs) as an alternative for BLS suppression. Eight AMPs (cecropin-mellitin derivatives) were screened initially for anti-M. roridum activity in vitro (0-72hrs at 24h interval). Four AMPs (<50μM) inhibited significant conidial growth suppression and the minimum inhibitory concentration (MIC50) recorded for most effective AMP (PRE-2) was ~23μM after 24h. LDH (lactate dehydrogenase) activity of Bombyx mori haemocytes treated with PRE-2 (50 to 175μM showed negligible cytotoxicity post-4h treatment: 0.68% at 50μM and 9.4% at 175μM. The effectiveness of PRE-2 (100μM) was assessed by spraying on BLS inflicted mulberry leaves ex vivo. Around 42% BLS suppression was recorded 20 days posttreatment. DNA isolated from PRE-2 treated and untreated samples infected with BLS were profiled with 7 SSRS and 5 ITS primers. ITS 1&4 and ITS 3&4 primer pairs revealed significant variation in band intensities between control and AMP treated samples.
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