Breeding of R8012,a Rice Restorer Line Resistant to Blast and Bacterial Blight Through Marker-Assisted Selection

Genetic improvement is one of the most effective strategies to prevent rice from blast and bacterial blight （BB） diseases, the two most prevalent diseases jeopardizing rice production. Rice hybrids with dural resistance to blast and BB are needed for sustainable production of food. An incomplete diallele design resulted in 25 crosses between five blast and five BB resistant germplasm accessions. Only one pair of parents, DH146 ×TM487, showed polymorphism for all the markers to identify one blast resistance gene Pi25 and three BB resistance genes, Xa21, xa13 and xa5, thus it was used in the marker-assisted selection （MAS）. F2 individuals of DH146× TM487 were genotyped using flanking markers of RM3330 and sequence tagged site （STS） marker SA7 for Pi25. The resistant F2 plants with Pi25 were used for pyramiding BB resistance genes Xa21, xa13 and xa5 identified by the markers pTA248, RM264 and RM153, respectively in subsequent generations. Finally, after selection for agronomic traits and restoration ability among 12 pyramided lines, we acquired an elite restorer line, R8012 including all four target genes （Pi25＋Xa21＋xa13＋xa5）. Hybrid Zhong 9NR8012 derived from the selected line showed stronger resistance to blast and BB, and higher grain yield than the commercial checks uniformally in experimental plots, 2007 state-wide yield trial and 2008 nation-wide yield trial. This study provides a paradigmatic example to show that MAS is a practically feasible tool in effectively pyramiding multiple resistance genes. The resultant restoring line and its hybrid would play an important role in securing rice production in China.

Selection of wide compatible restorer lines and their application in hybrid rice breeding

Since the middle of 1980’s, wide compatibility(WC) rice lines have been screened by ricebreeders in China and applied in hybrid ricebreeding program. Several WC lines such asPecos, T984, Lunhui 422, and 02428 withideal agronomic characters were identified. Weincorporated the WC gene into restorer linesby crossing these japonica WC lines with ob-tained indica lines. Some WC restorer lineswith indica-japonica medium type were ob-tained and their application value in intersub-specific hybrid rice breeding were evaluated. 1. Effect of crossing methods on selectionefficiencies of WC restorer lines

Inducing fertility restoration in the genic male sterile line of rice with chemical regulators

For the first time, the fertility of rice genic male sterile line was partially restored with the application of chemical regulators at Hainan Rice Breeding Nursery on Mar 1993. A single panicle of the rice plant could bear as many as 27 grains. The chemical agent that could modulate the growth of the rice plants of genic male sterile line was developed by Prof ZHOU Guangqia and his colleagues at the Biology Institute, Hunan Teachers University, China.

Construction of SSR Linkage Map and Analysis of QTLs for Rolled Leaf in Japonica Rice

Genetic analysis of rolled leaf is important to rice ideotype breeding. To detect loci controlling rolled leaf of japonica restorer lines, SSR marker genotypes and phenotypes of flag leaf rolling index （LRI） were investigated in Xiushui 79 （P1, a japonica rice variety）, C Bao （P2, a japonica restorer line） and 254 recombinant inbred lines derived from the cross between P1 and P2 , and in two environments. A genetic map of this cross was constructed, QTLs for LRI were detected and their interactions with environments were analyzed. Among 818 pairs of SSR primers, 90 primers showed polymorphism between P1 and P2, and 12 markers showed highly significant correlation with LRI in both environments based on single marker regression analysis. The genetic map containing 74 information loci has a total distance of 744.6 cM, with an average of 10.1 cM between two adjacent loci. Three QTLs （qRL-1, qRL-7 and qRL-8-1） were detected with two softwares： WinQTLCart 2.5 and QTLNetwork2.0. qRL-8-1 was a new locus, accounting for 15.5% and 12.8% of phenotypic variations in the two environments, respectively. The phenotypic variation explained by additive effect was 6.6%. No interaction was found between qRL-8-1 genotype and environments.