Improvement Of Drought Tolerance And Identification Of QTLs Conferring Drought Tolerance Using Selected Introgression Lines In Rice

Drought has become one of the main restrictive factors of rice production,the research of rice drought tolerance genetic and breeding now become one of the hot research topics.In this paper,Minghui 63,the widely used elite three-line restorer lines was used as the recurrent parent,ANR228,the new variety with big panicle and high combining ability as the donor parent for developing BC₂F₄ backcrossing introgression line?IL?population which includes 234 lines.Plant height?PH?,panicle number per plant?PN?,spiklet number per panicle?SNP?,spikelet fertility?SF?,thousand-grain weight?TGW?,grain yield?GY?and other six productive traits under the normal irrigation?control?and drought stress?stress?two level conditions were analyzed using phenotypic characterization and QTL mapping analysis.The results are as follows:1.Under the normal irrigation and drought stress two conditions,the SNP and TGW of the ILs are superior to the recurrent parent.In hainan under drought stress condition,the TGW and GY of the ILs are obviously higher than the recurrent parent,Minghui 63.Among Yield components,SF and SN are greatly influenced by drought stress,this is the main reason leading to loss of production.2.162 QTLs of the ILs which control productive and related traits were detected in two growing seasons,two kinds of cotrol conditions,the contribution rate rank is from 2.90%to 16.95%.25 QTLs control PH,6 QTLs control PN,37QTLs control SNP,14 QTLs control SF,24 QTLs control TGW,21 QTLs control GY.Among those QTLs there is 40 QTLs which can be detected in two moisture conditions can be stably expressed,most synergistic alleles are from the donor parent ANR228,such sites can be used as the main effective QTLs of improving GY.Such as site qGY12.9 controlling GY,the contribution rate rank is from 8.01%to 6.81%,site qPH4.5 controlling PH,contribution rate rank is from 11.55%to 7.31%,and sites qTGW1.3 qTGW10.2,qTGW12.3 and qTGW12 controlling TGW,contribution rate rank is from 12.85%to 4.10%.3.Totally 35 QTLs were detected in this ILs related to drought tolerance of rice,including 2,12,6,14 and 1QTLs controlling GY?SNP?SF?TGW and PH.This kind of QTLs increased the traits expression under drought stress,so this kind of QTLs have a direct contribution to rice drought tolerance.4.29 pleiotropic QTLs of the ILS were identified under two planting environments,and under the normal irrigation and drought stress conditions,among them 26synergistic alleles are from the donor parent ANR228,contribution rate rank is from16.95%to 16.95%.Such as QTLs which were detected in Hainan planting condition in 82.4 section of the loci on chromosome 9^th,qGY9.5 yield,qPH9.5 and qSNP9.5can control GY?SNP and PH at the same time,and those three QTLs additive effect value are positive,so in this site insert the genes from the donor parent ANR228 can effectively improve the GY?SNP and PH.Taking advantage of the MAS technology in such sites for the offspring of donor genotype individuals of different growth environment improvement and selection of offspring has important research significance.But there are some pleiotropic QTLs which can not be used to improve many traits at the same time,such as in Hainan planting environment,the site of qSF8.2 and qSNP8.2 located on chromosome 8^th sites on the 52.2 section,qSF8.2,controlling SF,synergistic allele is from the donor parent ANR228,qSNP8.2,controlling SNP,synergistic allele is from recurrent parent Minghui63,such sites should be used according to the different breeding goals.