Marker-assisted improvement of a stable restorer line, KMR-3R and its derived hybrid KRH2 for bacterial blight resistance and grain quality.

With 3 figures and 4 tables Abstract KMR-3R is a stable restorer line with medium-bold grain type and is the male parent of the popular public-bred Indian rice hybrid, KRH2. As both KMR-3R and KRH2 are highly susceptible to bacterial blight (BB) and possess undesirable bold-grain type, we crossed KMR-3R with a high-yielding, BB resistant, fine-grain-type variety, Improved Samba Mahsuri, possessing the major BB resistant gene, Xa21. The F₁s were backcrossed to KMR-3R, and the BC₁F₁ plants were subjected to marker-assisted selection (MAS) for Xa21 and two major fertility restorer genes, Rf3 and Rf4. 'Triple' positive BC₁F₁ plants were selfed and their progeny were subjected to MAS for Xa21 coupled with phenotype-based visual selection for agromorphological and grain-quality traits. At BC₁F₅ generation, three backcross derived lines (BK9, BK49 and BK61) possessing higher yield than KMR-3R, tall plant stature along with fine-grain type were identified and crossed with IR598025A, the female parent of KRH2. The hybrids were completely fertile, possessed long-slender grain type, exhibited resistance to BB and displayed a yield advantage of 24% over KRH2 under BB infection. [ABSTRACT FROM AUTHOR]