Study on heterosis of intersubspecies between indica and japonica rice （Oryza sativa L.） using chromosome segment substitution lines

Great heterosis exists in the inter-subspecific crossesbetween indica and japonica rice cultivars[1,2] and the ex-ploitation of this heterosis has long been considered as apromising method to further increase rice yield potential[3].Previous studies indicated that there were large differencesbetween the two subspecies with respect to morphology,isozyme, polymorphism of molecular markers and DNAstructure due to long time genetic differentiation[4,5]. Thosedifferences were identified to be clos…

Study on heterosis of inter-subspecies between indica and japonica rice (Oryza sativa L.) using chromosome segment substitution lines

Heterosis for yield and its component traits between chromosome segments from IR24, anindica variety, and the counterparts from 02428, ajaponica rice, was investigated by using a hybrid F₁ population composed of 63 combinations between 02428 and IR24 chromosome segment substitution lines (CSSLs) with the genetic background of Asominori,a japonica variety. Significant differences in heterosis for yield and yield-component traits were observed among the crosses. Analysis of graphical genotyping showed that 14 substituted segments were responsible for yield heterosis. All of them were from all the 12 chromosomes of IR24 except chromosomes 8 and 10. Six segments at the intervals of RFLP markers, such as X132-G1340-R459, X48-C393A, R288-R1854, R2918-X52, X257-C1350 and R367-X189-2-X24-2 on chromosomes 2, 3, 4, 11 and 12 respectively, had very significant heterosis for yield at the level ofP ⩽ 0.005 based ont-test, individually increasing the hybrid yield by more than 35% compared with the control cross “Asominori×02428”. Most of IR24 chromosome segments were found to have no significant hybrid effect for yield and yield-component traits, and one segment located at R2171 on chromosome 6 possessed significant negative effect with 27% of yield decrease. Advantages of using CSSLs in the heterosis studies were discussed and approaches of the partial and genome-wide exploitation of rice heterosis betweenindica andjaponica by molecular marker-assisted selection were then proposed.