Accelerating hybrid rice breeding through the adoption of doubled haploid technology for R-line development

Hybrid rice holds significant yield advantage over inbred lines, but its adoption rate is very slow in India. Development of cytoplasmic male sterile line (CMS) and fertility restorer line with superior grain quality is the prerequisite in three line hybrid rice breeding programme. Minimum of three to four years are required for development of useful R-line which severely delays the pace of hybrid breeding. Application of doubled haploid (DH) technology will be very useful to develop elite R-lines within short period of time. An elite inbred line LAXMI was crossed with the R-line RPR158 and anthers from the resulting F1 population was used for development of DH plants. Eight hormonal combinations and four different cold pre-treatment conditions were tried in tissue culture. Maximum callusing frequency was observed in N6 medium supplemented with 2.0 mg L−1 2, 4-diclorophenoxyacetic acid (2,4-D), 0.5 mg L−1 napthalene acetic acid (NAA), 0.5 mg L−1 benzyl amino purine(BAP) and 6% maltose with 3 days cold pre-treatment. Highest green plant regeneration frequency was found with Murashige and Skoog medium supplemented with 0.5 mg L−1 NAA, 0.5 mg L−1 kinetin, 2 mg L−1 BAP. A total of 280 DH plants were generated and evaluated under field conditions for agronomic characters and fertility restoration capacity in CMS system. Two distinct DH lines were identified as improved R-lines based on high restoration ability (94%), superior grain quality and medium slender grain type. This study successfully demonstrated that superior R-lines can be developed within two crop seasons through the application of DH technology.