Molecular Characterization of Sclerotinia sclerotiorum Sacc. Initiating White Mold Disease in French Bean (Phaseolus vulgaris L.) and its Biological Management

Abstract

Background: White mold disease caused by S. sclerotiorum is a serious peril to the cultivation of french bean in India. The disease primarily spreads by spores and normally in forms of sclerotia, which can remain viable in soil for several years and under appropriate environmental conditions, germinate to form mycelium, leading to infectious hyphae or producing apothecia. Methods: In the present study, antagonistic activity of locally isolated bio-inoculants including four fungi and three bacteria were evaluated against white mold disease of french bean. In vitro efficacy of bio-inoculants was tested by dual culture method against S. sclerotiorum. Result: The molecular characterization of isolated pathogen was performed using ITS sequencing. The sequence length of the pathogen was 516 bp and approximately identical to publicly available S. sclerotiorum sequences on NCBI data base. In vitro study showed that, P. fluorescens isolate Pf008 was best causing 95.55 per cent mycelium growth reduction. In field experiment, the bio-inoculants were tested by various inoculation methods. Sclerotinia sclerotiorum infested soil treated with bio-inoculants as seed treatment and soil application. Results revealed that, seed treatment with formulation of T. harzianum isolate TS004 was best and enhance the growth promotion and increase the grain yield i.e. 13.93 q/ha and 12.10 q/ha during the year 2018-19 and 2019-20 respectively. Soil application with formulation of T. viride isolate TS006 was the utmost effective in reducing disease incidence by 83.91% during the year 2018-19 and seed treatment with formulation of T. viride isolate TS006 reducing disease incidence by 74.83% in the year 2019-20.