Expression of barley oxalate oxidase confers resistance against Sclerotinia sclerotiorum in transgenic Brassica juncea cv Varuna.

Abstract

Sclerotinia Stem Rot (SSR) caused by the oxalic acid (OA)-secreting necrotrophic fungal pathogen Sclerotinia sclerotiorum, causes significant yields losses in the crop Brassica sps. Oxalate oxidase (OxO) can metabolize OA to CO2 and H2O2. Degradation of OA during the early phase of fungal-host interaction can interfere with the fungal infection and establishment processes. The present study demonstrates the potential of barley oxalate oxidase (BOxO) gene in conferring stable resistance against stem rot in a productive and highly susceptible Brassica juncea cv Varuna under field conditions. Four stable, independent, single-copy transgenic lines (B16, B17, B18, and B53) exhibited a significant reduction in the rate of lesion expansion i.e. 11-26%, 39-47%, and 24-35% reproducibly over the three-generation i.e. T2, T3, and T4 respectively. The enhanced resistance in the transgenic lines correlated with high OxO activity, accumulation of higher levels of H2O2, and robust activation of defense responsive genes upon infection by S. sclerotiorum.