| Hybrid rice has made considerable contributions to achieve the ambitious goal of food security for the world population.However,a majority of the hybrids are indica subspecies varieties,and yield had reached the bottleneck.Hybrid rice from indica/xian and japonica/geng subspecies showed much higher heterosis,which is an important approach to increase rice yield per area.However,hybrid sterility is a major obstacle to the breeding of xian-geng hybrid rice.The discovery of wide-compatibility variety provides an opportunity to overcome the sterility of xian-geng hybrid.Study on this subject was divided into two parts.In the first part,two three-cross genetic populations were developed from wide-compatibility restorer line Hua53,xian restorer line 9311 and geng variety Balilla.The genotype of three-cross populations was determined by RAD-seq(Restriction Associated DNA Sequencing)technology,and the spikelet fertility,pollen fertility and embryo sac fertility of individual plants were assessed.The genetic basis of wide-compatibility of Hua53 was analyzed.The second part based on the two wide-compatibility pyramided lines9311(S5-n+f5-n+pf12-j)and 9311(S5-n+f5-n+Sc-j),four compatibility alleles S5-n,f5-n,pf12-j,and Sc-j were incorporated into an indica restorer line 9311 via crossing and molecular marker-assisted selection.The genetic effects of four compatibility alleles will be clarified and the breeding value of S5-n+f5-n+pf12-j+Sc-j were assessed for the utilization of xian-geng heterosis.The main research results are as follows:1.In this study,a total of 25,921 SNPs of Hua53/9311//Balilla and 26,758 SNPs of Balilla//Hua53/9311 were identified by using RAD-seq technology.Combining the recombination breakpoint of individual plants in the two three-cross populations,a total of 1,720 bins of Hua53/9311//Balilla and 1,791 bins of Balilla//Hua53/9311 were obtained.Two high-density Binmap genetic map were established with 1,779.99 c M and 1,587.52 c M in total length,respectively.A total of 13 segregation distortion loci were mapped in the two three-cross genetic populations by chisquare test,of which three segregation distortion loci(q SD9,q SD10.2 and q SD11)were detected in both three-cross populations.2.A total of 47 QTL(10 for pollen fertility,15 for embryo-sac fertility and 22 for spikelet fertility)in the two three-cross populations were detected.Among these loci,two QTL controlled pollen and embryo-sac fertility,nine QTL controlled embryo-sac and spikelet fertility,and four QTL controlled pollen and spikelet fertility.Seven QTL were detected in both two three-cross populations,including pollen fertility loci q Pf5 and q Pf12.1,embryo sac loci q Ef6 and q Ef9.2,and spikelet fertility loci q Sf5.1,q Sf6.1,and q Sf12.1.3.A four-gene pyramiding line 9311(S5-n+f5-n+pf12-j+Sc-j)was obtained with98.51% genome recovery of the recurrent parent.The results of chip analysis showed that the size of the introgression fragment was 74,389 bp for S5-n,1,069,308 bp for f5-n,4,192,047 bp for Sc-j and 2,885,730 bp for pf12-j.4.The major agronomic traits of the six developed lines were evaluated.No significant difference was observed among the six developed lines 9311(Sc-j),9311(pf12-j),9311(S5-n+f5-n),9311(S5-n+f5-n+pf12-j),9311(S5-n+f5-n+Sc-j),and9311(S5-n+f5-n+pf12-j+Sc-j)compared with the control 9311 in terms of number of panicles per plant,day to heading,spikelet per panicle,yield of per plant and so on.In addition,the plant height and spiket length of 9311 was decreased by introducing of Sc-j.5.We further evaluated the genetic effect of four compatibility alleles on hybrid pollen,embryo-sac and spikelet fertility.In the xian-geng hybrids,Sc-j increased pollen fertility by 13.25%,pf12-j increased pollen fertility,embryo sac fertility and spikelet fertility by 20.94%,6.57% and 11.09%,and the double compatibility gene S5-n+f5-n increased pollen fertility,embryo sac fertility and spikelet fertility by37.81%,26.40 and 33.83%.The average pollen fertility,embryo sac fertility,and spikelet fertility of hybrids derived from 9311(S5-n+f5-n+pf12-j+Sc-j)and japonica testers were 92.02%,90.87% and 84.75%,respectively.Meanwhile,the average pollen fertility,embryo sac fertility,and spikelet fertility of hybrids derived from9311(S5-n+f5-n+pf12-j+Sc-j)and indica testers were 96.12%,92.04% and 92.27%,respectively.Taken together,the genetic analysis of the wide compatibility line Hua 53 was performed in this study,and we further improved the wide compatibility of 9311 by using four compatibility gens S5-n,f5-n,pf12-j,Sc-j,successfully developed the new wide compatibility line 9311(S5-n+f5-n+pf12-j+Sc-j).These results provide theoretical guidance and germplasm resources for the utilization of hybrid hetersosis in xian-geng subspecies. |
PDF Full Text Request