Genetic Diversity Studies Based on Morphological Variability, Pathogenicity and Molecular Phylogeny of the Sclerotinia sclerotiorum Population From Indian Mustard (Brassica juncea)

Abstract

White mold or stem rot disease are ubiquitously distributed throughout the world and the causal organism of this disease Sclerotinia sclerotiorum (Lib.) de Bary, is known to infect over 400 plant species. Sclerotinia stem rot is one of the most devastating fungal diseases and poses a serious threat to the worldwide cultivation of oilseed Brassica including India. S. sclerotiorum pathogen usually infects the stem but in severe cases leaves and pods also affected at different developmental stages that deteriorate not only the oil quality but also causing the seed and oil yield losses up to 90% depending on the severity of the disease infestation. This study investigated the morphological and molecular characterization of pathogenic S. sclerotiorum (Lib) de Bary geographical isolates from oilseed Brassica including Brassica juncea (Indian mustard). The aim of this study was to compare isolates of S. sclerotiorum originated from different agro-climatic conditions and to analyse similarity or differences between them as well as to examine the virulence of this pathogen specifically in Brassica for the first time. The collection of S. sclerotiorum isolates from symptomatic Brassica plants was done and analyzed for morphological features, and molecular characterization. The virulence evaluation test of 65 isolates on four Brassica cultivars has shown 5 of them were highly virulent, 46 were virulent and 14 were moderately virulent. Phylogenetic analysis encompassing all the morphological features, SSR polymorphism, and ITS sequencing has shown the existence of high genetic diversity among the isolates that categorized all the isolates in three evolutionary lineages in the derived dendrogram. Further, genetic variability analysis based on sequences variation in ITS region of all the isolates has shown the existence of either insertions or deletions of the nucleotides in the ITS region has led to the interspecies variability and observed the variation were in a clade-specific manner. Together this analysis observed the existence of higher heterogeneity and genetic variability in S. sclerotiorum isolates collection and indicates the presence of clonal and sexual progenies of the pathogen in the mustard growing regions of India surveyed in this study. With a higher level of genetic variability and diversity among the S. sclerotiorum population needs robust screening approaches to identify the donor parent and utilize them in resistance breeding program for effectively counter the menace of stem rot disease in Brassica.

UPLC-QTOF-MS-Based Untargeted Study of Metabolites Secreted by Sclerotinia Sclerotiorum Pathogen Under Axenic Condition

“…This signi ed the role of the metabolites in determining the virulence and pathogenicity of the isolates over the susceptible hosts. No in uence of geographical location, as well as the source of origin of the isolates on their aggressiveness, has also been evident from earlier studies (Atallah et al, 2004;Sharma et al, 2018).…”

“…The pathogenicity grouping of S. sclerotiorum isolates including ESR-01, ESR-04, ESR-05, ESR-18, ESR-25, and ESR-42 (Fig. 1) as described by Sharma et al, (2018). The virulence grading was done for the individual isolates in terms of mean lesion length which is the function of individual isolates i.e., how fast the pathogen 1).…”

Sclerotinia sclerotiorum Thioredoxin1 (SsTrx1) is required for pathogenicity and oxidative stress tolerance

“…However, few sources of quantitative resistance have been reported (Atri et al, 2019;Boudhrioua et al, 2020;Rana et al, 2017Rana et al, , 2019Sun et al, 2020;Taylor et al, 2015;Wei et al, 2014Wei et al, , 2016. The majority of these sources provide partial resistance and are isolate-specific (Garg et al, 2010;Sharma et al, 2018;Taylor et al, 2015). Diversity of pathogen isolates can be an issue for the wide applicability of a resistance source if it is isolatespecific.…”

“…Diversity of pathogen isolates can be an issue for the wide applicability of a resistance source if it is isolatespecific. Population structure, haplotype diversity, and variation for aggressiveness have been widely reported for S. sclerotiorum isolates (Clarkson et al, 2017;Leyronas et al, 2018;Sharma et al, 2018;Yu et al, 2020). Canola hybrids with the Pioneer Protector Trx system in maintaining redox balance in the pathogen has been emphasized earlier (Zhang et al, 2019).…”

Extra‐large G‐proteins influence plant response to Sclerotinia sclerotiorum by regulating glucosinolate metabolism in Brassica juncea

“…The inherent susceptibility of Brassica species to biotic stresses is a major factor that has limited their productivity in recent decades. Sclerotinia sclerotiorum, the causal agent of sclerotinia stem rot in Brassica crops, causes extensive (40%–80%) yield losses worldwide (Sharma et al, 2018 ) and has proved hard to control, with host resistance being insufficient. The persistence of this fungus is due to its sclerotia, which remain viable under adverse conditions and can be retained in soil for many years (Brustolin et al, 2016 ).…”