Heat shock enhanced Agrobacterium tumefaciens mediated T-DNA delivery to potato (Solanum tuberosum L.)

The genetic transformation is a genotype specific phenomena in potato, which complicates the trait specific genetic manipulations and mandates optimisation of protocol for each cultivar. In the present study, heat shock treatment was used to develop genotype independent Agrobacterium-mediated genetic transformation protocol of potato. Initially six cultivars of potato namely, ‘Kufri Chipsona 1’ (CS-1), ‘Kufri Chipsona 2’ (CS-2), ‘Kufri Pukhraj’ (KP), ‘Kufri Khyati’ (KK), ‘Kufri Jyoti’ (KJ) and ‘Kufri Chandramukhi’ (KCM), were tested for genetic transformation efficiencies using previously optimised Agrobacterium mediated T-DNA delivery protocol and the outcome was highly genotype dependent. Based on the response, cultivars were grouped as ‘high’ (CS-1, CS-2, KK) and ‘low’ (KP, KCM, KJ) genetic transformation efficiency cultivars. Further, the attempts were made to understand the biochemical basis of variation in genetic transformation efficiencies of these cultivars. It was noteworthy that in ‘low genetic transformation efficiency’ cultivars, the level of antioxidant enzymes and phenols was significantly higher than ‘high genetic transformation efficiency’ cultivars. In order to optimise a genotype independent protocol, explants from all the cultivars (both groups) were subjected to heat shock treatment (30–50 °C; 15–45 min) immediately before infection. The heat shock treatment at 40 °C for 15 min resulted in a significant increase in transient GUS expression, callogenesis and regeneration of transgenic shoots. Using this approach, transgenic shoots were recovered from all the cultivars. Following the heat shock treatment, levels of antioxidant enzymes and phenols were significantly affected, thus it seems that cultivars with stronger defense system are likely to be more difficult for A. tumefaciens-mediated genetic transformation.