Analysis of Pyramiding Effect of the Rf3 and Rf4 Genes on Fertility Restoration in Rice (Oryza sativa) with Wild Abortive and Dwarf Wild Abortive Cytoplasmic Male Sterility
Abstract：Wild-abortive (WA) and dwarf wild abortive (DA) are two important cytoplasmic male sterility (CMS) types in rice(Oryza sativa). CMS can be restored by nuclear restorer gene (Rf). One or two dominant restorer alleles (Rf3 and/or Rf4) are usually suggested be responsible for the fertility of WA-CMS and DA-CMS. To develop the strong restorer lines for WA-CMS and DA-CMS and analyse the pyramiding effect of the Rf3 and Rf4 genes, seven indica chromosome double segments pyramiding lines (DSPLs), carrying the genotype Rf3Rf3/Rf4Rf4, and five second single segment substitution lines (SSSSLs) with the Rf3 on chromosomes 1 (or Rf4 on chromosomes 10) gene were selected by marker-assisted selection (MAS) in the F2 and F3 populations generated from the ten crosses among the seven SSSLs which possess the Rf3 (or Rf4) gene on fertility restoration in rice with WA-CMS and DA-CMS in this study. There were wide differences in restoring abilities for WA-CMS and DA-CMS among the six DSPLs. Of which the restoration ability of the DSPL11-01/14-10P with the genotype Rf3-4Rf3-4/Rf4-4Rf4-4 was the strongest, the DSPL07-01/14-10P carrying the genotype Rf3-1Rf3-1/Rf4-1Rf4-1 appeared to be weakest restoring ability, and the restoration abilities of the other DSPLs ranged from DSPL11-01/14-10P to DSPL07-01/14-10P. The length of substituted chromosome segments in the five SSSSLs ranged from 0.1 cM to 45.5 cM with an average of 18.7 cM, and the total length of substituted chromosome segments from them was 93.5 cM. To reveal the pyramiding effect of the Rf genes, the DSPL11-01/14-10P and its corresponding SSSLs were crossed with a typical WA-CMS lines of Bobai A (BBA) and a typical DA-CMS line of XieqingzaoA (XQA), respectively. In the F1 populations, the plants carrying the Rf3rf3/Rf4rf4 genotype were selected and their phenotyping for pollen was evaluated. The result showed that even if the restoration ability of the DSPL11-01/14-10P showed stronger than that of corresponding SSSLs, the difference between them was not significant, which indicated that there was not interaction effect between Rf3 and Rf4 genes in the DSPL11-01/14-10P. These studies have led to the development of three-line in rice and the transfer of Rf3 and Rf4 genes into adapted cultivars through backcrossing in an active hybrid rice breeding program.
