Genotypic background of the recipient plant is crucial for conferring RB gene mediated late blight resistance in potato

Background: Late blight, caused by oomycetes pathogen Phytophthora infestans (Mont.) de Bary, is the most devastating potato disease in the world. RB gene from Solanum bulbocastanum has been shown to impart broad spectrum resistance against P. infestans races. In this study Katahdin transgenic event SP951 was used as male parent to cross with the popular Indian potato cultivars viz., Kufri Bahar (KB) and Kufri Jyoti (KJ) to enhance the late blight resistance. Results: Populations of 271 F1seedlings from the crosses KB x SP951 (87) and KJ x SP951 (184) were screened for inheritance of RB transgene through PCR and bioassay. Disease response based on AUDPC of different hybrid lines varied from immunity to complete susceptibility. High degree of resistance (< 25% infection) was observed in KJ x SP951 derived seedlings (85.2%), whereas level of resistance in KB x SP951 (36.4% infection) derived seedlings was of low order. Conclusion: This study provides valuable genetic materials for development of potentially durable late blight resistant potato varieties. Besides, it also corroborates the fact that efficacy of R gene is not solely dependent on its presence in the variety but largely depends on the genetic background of the recipient genotype.