| New rice varieties,which have high yield,broad adaption and high grain quality,play an important role in practical application and plant breeding.In rice breeding,it is a very important topic that germplasm resources with genetic diversity are used for genetic analysis and germplasm enhancement.In this study,a compound population consisted of 8 BC1F5 introgression line(IL)populations was used as materials.The 8 IL populations,derived from the crosses between an excellent conventional rice variety Huanghuazhan(HHZ)as recurrent parent and eight varieties from different countries or regions(IR64,Teqing,PSBRC66,CDR22,PSBRC28,OM1723,Phalguna and IR50)as donor parents,were previously developed after two rounds cross-screening of drought,salt and submergence tolerance and high yield.Total of 497 ILs of the compound population were tested through three years of repeated experiments in six environments,for 14 yield and its related phenotypic traits.In the mean time,all ILs are crossed with four photoperiod-temperature sensitive genic male sterile(PTSGMS)lines(Y58S,C815 S,1892S and Xin'an S)to construct four sets of corresponding F1 testcross populations,respectively.These four sets of test-crosses plus all ILs(male)and four two-line sterile parents(female),were tested in 2013 winter in Hainan and 2014 early season in Shenzhen for measurement of 12 yield and yield related traits.Based on high-throughput sequencing genotypic data,genome-wide association analysis methods was used to detect QTLs affecting yield and its related traits for IL and their test-cross populations,mining stably expressed favorable alleles for target traits from different sources across different environments,and disscet genetic basis of heterosis.The main results are as follows:(1)When the populations were constructed,the positive effects due to moderate stress genetic screening,improved selection efficiency of the favorable alleles responsive to relevant ecological environment so that the ILs had a higher genetic background of the recurrent parent and lower frequency of introgression of donor genome,thus improving the utilization efficiency of germplasm favorable genes under the condition.(2)For the experiments through three years in six environments,192 QTLs were detected for 14 yield and its related traits among the 12 chromosomes;and favorable alleles at many QTLs were from different parents,indicating that these 8 donor parents occupy rich genetic diversity.(3)Total of 26 genetic overlapping loci underlying different traits were identified and distributed on chromosomes 1-3,5-8,11 and 12.The alleles for different traits from various donors had different quantities of additive gene effect with same or opposite directions of gene effect.The pleiotropic effects may be genetic mechanisms for relationships among these traits.(4)Total of 429 QTLs were detected for yield and its related traits for the four test-cross F1 populations and their corresponding parent lines in the two ecological conditions and distributed 12 chromosomes.Among them,88 QTLs were detected for the ILs and 390 for the four test-cross populations,and 49 QTLs(12.6%)are simultaneously detected for both of them.The lesser degree of genetic overlap suggests the fact that genetic mechanisms controlling inbred and hybrid yield are quite different.(5)For yield and its related traits of the four sets of test-cross populations,76(19.5%)and 100(25.6%)QTLs were identified on chromosomes 2 and 3,respectively.It was suggested that chromosomes 2 and 3 are important genomic regions controlling heterosis for yield and its related traits.(6)Among 390 QTLs mapped in the four test-cross populations for yield and its component traits,38 were simultaneously detected in the three populations and 6 detected in all four populations,having the same or opposite directions but similar quantities of gene effect in different test-cross populations,suggesting that those loci contributing to heterosis in different backgrounds are valuable for molecular improvement of rice heterosis in future. |
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