Expression of Arabidopsis NPR1 (AtNPR1) in Brassica juncea var Varuna confers significant resistance against Sclerotinia sclerotiorum and Alternaria brassicae

The productivity of Brassica juncea, a major oilseed crop grown widely in South Asia, is limited by two major fungal pathogens: Sclerotinia sclerotiorum, and Alternaria brassicae. Currently, no effective resistance against these pathogens has been identified in the B. juncea germplasm. To improve the resistance against these fungal pathogens, Non-expressor of PR1 (NPR1) from Arabidopsis was expressed in the mega variety Varuna via Agrobacterium-mediated transformation. A total of 129, independent transgenic events were generated. Segregation analysis for Basta resistance and subsequent Southern hybridization identified six single-copy transgenic lines (PN23, 42, 60, 72, HN30, and HN32) which were taken forward for disease assays over two generations. Transgenic lines challenged with S. sclerotiorum exhibited a significant reduction in stem lesions ranging from 13 to 42% in the T3 generation and 4 to 31% in the T4 generation. We also observed a reduced infection against A. brassicae in the transgenic lines which developed smaller and fewer necrotic lesions as compared to untransformed lines. A correlation between the upregulation of defense marker genes and enhanced tolerance was observed in the transgenic lines upon S. sclerotiorum infection.