An insight into the downstream analysis of RB gene in F1 RB potato lines imparting field resistance to late blight.

Earlier studies have shown that level of late blight resistance conferred by the classical R gene (RB Rpi-blb1) is dependent on genetic background of the recipient genotype. This was revealed in the analysis of late blight response that belonged to a group of F1 progeny obtained from the cross between Kufri Jyoti and SP951, which showed wide variation in late blight resistance response in spite of possessing the same RB gene. The global gene expression pattern in the RB potato lines was studied in response to late blight infection using cDNA microarray analysis to reveal the background effect. Leaf samples were collected at 0, 24, 72 and 120h post inoculation (hpi) with Phytophthora infestans for gene expression analysis using 61031 gene sequences. Significantly upregulated (1477) and downregulated (4245) genes common in the RB-transgenic F1 lines at 24 and 72 hpi were classified into several categories based on GO identifiers and majority of genes were assigned putative biological functions. Highest expression of an NBS-LRR along with protease, pectin esterase inhibitors, chaperones and reactive oxygen species genes were observed which affirmed a significant role of these categories in the defence response of RB-KJ lines. Results suggest that the immune priming of plant receptors are likely to be involved in stability and functionality of RB to induce resistance against P. infestans. This study is important for effective deployment of RB gene in the host background and contributes immensely to scientific understanding of R gene interaction with host protein complexes to regulate defence system in plants.