75 Strategy for identifying genes and QTLs underlying grain quality characteristics in rice.

Susan McCouch (1), Jiming Li (1), Jinhua Xiao (1), Silvana Grandillo (1), Sang Nag Ahn (3), Steven D. Tanksley (1), Longying Jiang, and Longping Yuan (2).

To study the genetic basis of quality traits in Oryza sativa L. and to investigate the possibility of improving grain quality by introgressing genes from wild or unadapted species, the following three populations were developed during 1991–1996, i.e. two backcross-testcross populations using O. glaberrima and O. rufipogon as donors and V20/Ce64 (a Chinese hybrid variety) as the recurrent parent, and two recombinant inbred populations (BC1F7 and F8) derived from the same crosses. A total of 1190 families were evaluated for 20 grain quality traits during 1996–1999 at the China National Hybrid Rice Research & Development Center. One hundred and fifty RFLP and thirty microsatellite markers, well distributed on the rice genome, were used for segregation analysis on these populations at Cornell University. The morphological data from these populations showed that some alleles from the unadapted species contribute to enhanced quality characteristics in the cultivars. For example, favorable QTLs from O. glaberrima that significantly enhance rice cooked kernel elongation were identified on rice chromosomes 1, 3 and 4. The genetic basis for these and other quality traits will be discussed based on this comparative genomic analysis. This study suggested that favorable grain-quality QTL can be identified in interspecific crosses and used for marker-assisted improvement in breeding for better rice grain quality.