Inter specific hybridization (Brassica carinata x Brassica oleracea) for introgression of black rot resistance genes into Indian cauliflower (B-oleracea var. botrytis L.).

Indian cauliflower (Brassica oleracea var. botrytis L.; C genome) is highly susceptible to black rot caused by Xanthomonas campestris pv. campestris (Pam.) Dowson. Till now no durable resistance genes have been identified in C genome of Brassica. Two B. carinata genotypes, NPC-9 and HCA-6 were found highly resistant to Xcc race 1 and 4, most prevalent throughout the world. Inter-specific hybridization was attempted for introgression of resistance genes from B. carinata into Indian cauliflower using three different embryo rescue approaches. Reciprocal crosses were made between two B. carinata and 7 lines of Indian cauliflower. Very low rate of success was observed when B. oleracea lines were used as female parents. Among the three different approaches, direct embryo culture was the most successful for development of F-1 and BC1 population. Through ovule culture and direct embryo culture 58 F-1 hybrids were developed. Success rates for hybrid plant development through ovule culture and direct embryo culture were 1.04 and 11.33 %, respectively. All the F-1 hybrids were found to be highly resistant to Xcc race 1 and 4. Eleven NPC-9 based F-1 hybrids were used for development of BC1 population through direct embryo culture with a success rate of 30.76 %. Direct embryo culture can be used as an effective tool for introgression of desirable genes across Brassica species. Among 29 BC1 plants, 26 and 25 plants were highly resistant to Xcc race 4 and race 1, respectively. The population developed through inter-specific hybridization would open several avenues to develop durable black rot resistant lines in B. oleracea.