Jasmonate mediated inducible accumulation of indole glucosinolates confers resistance against Alternaria blight disease in cruciferous wild species Diplotaxis erucoides

The productivity of Indian mustard Brassica juncea is heavily constrained due to damage inflicted by Alternaria blight disease. Genetic resistance against this disease is obscure among the cultivated germplasms. Crop wild relatives (CWR) offer potential source of resistance genes against pathogen and insect-pests. A cruciferous wild relative Diplotaxis erucoides demonstrated high level of resistance against A. brassicae, the causative agent of Alternaria blight. In plants of the Brassicaceae family, sulfur containing secondary metabolites glucosinolates (GSL) play a significant role in plant immunity and inducible defense against pathogens. Here, we have studied the transcriptional activation of the GSL biosynthetic genes by qRT-PCR and analysed the metabolite profile based on LC-MS in Alternaria resistant D. erucoides and susceptible species B. juncea. A comparative assessment of the gene-expression data demonstrated more efficient transcriptional activation of the key GSL biosynthetic genes by jasmonate mediated defense signaling in D. erucoides compared to B. juncea. The LC-MS analysis empirically established concomitant, inducible and higher accumulation of the defense related GSL compounds in D. erucoides compared to B. juncea when challenged with the A. brassicae pathogen. The study also highlighted the two probable candidate genes for engineering resistance to Alternaria blight disease in susceptible genotypes of B. juncea. •Source of resistance for Alternaria blight disease caused by the fungal pathogen Alternaria brassicae is obscure in cultivated Indian mustard Brassica juncea.•A Cruciferous Crop Wild Relative (CWR) Diplotaxis erucoides demonstrated high level of resistance to A. brassicae.•In this CWR, the key genes of glucosinolate (GSL) biosynthesis including CYP83B1 and IGMT have been found to be highly activated in response to methyl jasmonate and pathogen challenge by A. brassicae.•LC-MS analysis of healthy and pathogen challenged leaves demonstrated more accumulation of indole glucosinolates in resistant CWR D. erucoides compared to the susceptible B. juncea.•CYP83B1 and IGMT of D. erucoides can be the potential candidate genes for augmenting indole glucosinolate mediated defense against Alternaria blight disease in susceptible Brassicaspp.