Abstract
A study was executed in a direction to attenuate Sclerotinia stalk rot (SSR) disease through biocontrol agent and also to enhance crop productivity. Culture filtrate of bacterial strain YSPMK11 inhibited growth of Sclerotinia sclerotiorum in vitro which also exhibited higher plant growth promoting attributes. Interaction studies revealed maximum (81.50%) growth inhibition at 35 °C and pH 7.0 after 72 h incubation period with 15% culture filtrate. Based upon 16S rRNA gene sequence strain, YSPMK11 was identified as Bacillus pumilus. Furthermore, the genome of this isolate was searched for antimicrobial lipopeptide, i.e., ItuD and SrfC genes. The PCR amplification results showed the presence of both these lipopeptide genes in isolate YSPMK11. Iturin A as antifungal compound was identified as major components of fraction through GC/MS. In field experiments, the application of strain YSPMK11 cell suspension (108 CFU/ml) suppressed disease severity by 93% and increased curd yield by 36% which was more that of commercially used fungicide in farmer practices under mid-hills of Himachal Pradesh. Conclusively, our study is first to demonstrate the effect of B. pumilus strain YSPMK11 in suppression of SSR under field conditions and would be employed as an efficient biocontrol agent to replace commercial fungicides in cauliflower cropping system. In addition, the presence of both lipopeptide genes (ItuD and SrfC) and iturin A in this isolate makes him potent strain for biological control application in agriculture.
Highlights
Sclerotinia stalk rot (SSR) caused by S. sclerotiorum (Ss) is a major disease of cauliflower (Brassica oleracea var. botrytis L.) under mid-hills conditions of Himachal Pradesh
When subjected to test antagonism against S. sclerotiorum, zone formation was observed by isolate YSPMK11 which may be due to secretion of antifungal substance that strongly inhibited radial growth of phytopathogenic fungi on agar
Isolate YSPMK11 was further subjected to molecular analysis. 16S rRNA sequence was highly homologous to B. pumilus
Summary
Sclerotinia stalk rot (SSR) caused by S. sclerotiorum (Ss) is a major disease of cauliflower (Brassica oleracea var. botrytis L.) under mid-hills conditions of Himachal Pradesh. Sclerotinia stalk rot (SSR) caused by S. sclerotiorum (Ss) is a major disease of cauliflower Botrytis L.) under mid-hills conditions of Himachal Pradesh. S. sclerotiorum known as white mold is a necrotrophic pathogen having wide host range including important vegetable and oil yielding crops (Bolton et al 2006) causing substantial yield losses. Disease first appears as wet soft lesion on curd which enlarges into a watery rotten mass of tissues covered by a white silvery appearance. Affected curds causes another plant parts to wilt and later die. Cool temperature and high humidity conditions in mid-hills of Himachal Pradesh are favourable for epidemics of SSR. The standard strategies employed to overcome SSR include crop management practices such as use of clean seeds, early planting date, soil tillage, and adjustment of row width and density of plant population; effectiveness of these measures is very limited (Yexin et al 2011) due to sclerotia survival in soil and high potential
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