Abstract
The major constraints in hybrid rice breeding are availability of limited number of parental lines with specific desirable traits and lower frequency of restorers among elite breeding lines. The popular, high-yielding mega-rice variety Swarna, has been identified to be a partial restorer (as it has only one of major fertility restorer genes, Rf4) and hence cannot be utilized directly in the hybrid rice breeding. To convert the partial restorer to complete restorer, a cross was made between Swarna and a stable restorer KMR3R possessing Rf3 and Rf4 genes and developed BC1F5 and BC2F4 populations by marker-assisted back cross breeding (MABB). The SSR marker DRRM-RF3-10 linked to Rf3 gene located on chromosome 1, clearly distinguished restorers from partial restorers. All the improved lines of Swarna possessing Rf3 and Rf4 genes showed complete fertility restoration in test crosses with higher grain yield heterosis. Few rice hybrids developed by using converted restorers were evaluated in multi location testing under the All India Co-ordinated Rice Improvement Project (AICRIP). The results indicated that new rice hybrids expressed higher heterosis with matching grain quality attributes like Swarna. This study provides significantly novel and relevant restorers to enhance and economize future hybrid rice breeding programs.
Highlights
Rice (O. sativa L.) is the most important staple food crop for more than half of the world’s population and it is cultivated in an area of 44.5 million hectare in India with the production of 106.5 million tonnes during the year 20161
To study the fertility restoration status of donor and recurrent parents, F1 hybrids were produced by crossing Swarna and KMR3R with four CMS lines viz., APMS 6A, IR79156A, IR68897A and IR58025A
The average pollen and spikelet fertility percentage of partial restorer Swarna was observed to be less than 80%, whereas KMR3R showed more than 90% fertility restoration when crossed with different A lines (Fig. 1)
Summary
Rice (O. sativa L.) is the most important staple food crop for more than half of the world’s population and it is cultivated in an area of 44.5 million hectare in India with the production of 106.5 million tonnes during the year 20161. The success of hybrid rice technology has been very well demonstrated in China, which produces 146.5 million tonnes of rice from 30.32 million hectares[1]. Hybrid rice seed production using CGMS/three line system involves a CMS (A) line, a maintainer (B) line and a restorer (R) line carrying the fertility restorer genes. Fertility restorer gene linked to RM6100 was mapped at a distance of 6–7 cM on chromosome 10 in the restorer lines viz., PRR 78 R, IR 40750 and MTU 999216. The candidate gene based marker, DRRM-RF3-10 associated with Rf3 locus showed maximum selection accuracy in identifying restores in comparison with other reported markers viz., RM10305, RM10318, DRRM-RF3-5 and DRRM-RF3-617
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