QTL Mapping And QTL×Environment Interaction Analysis Of Rice Milling Quality And Appearance Quality Under Water-and Dry–Stress Conditions

Rice is one of the important food sources of mankind,which plays a vital role in ensuring food security.However,due to the influences of the population increase,climate conditions,measurements for agricultural management and other factors,the phenomenon of drought often occurs in China,which results in a terrible threat in rice production.At the same time,with the improvement of living standard,higher requests are raised to the quality of rice.Therefore,identifying the QTLs which control the quality traits of rice under drought conditions is very important to accelerate the molecular improvement of rice quality traits.It has been proved that related traits in multiple environments to analysis simultaneously is an effective way to improve the accuracy of QTL mapping,to detect stable QTLs and to analyze the interaction effects between QTLs and environments.This study used a set of recombinant inbred lines(RILs)derived from the cross between female parent upland cultivar Xiaobaijingzi and male parent rice cultivar Kongyu131 as experimental materials.Experiments were conducted in both normal irrigation and drought stress in two years,union locating analysis of rice milling quality and appearance quality was estimated under both single environment and multiple environments,to explore the change regulation of related traits and identify the QTLs controlling rice quality traits stably under drought stress.The interaction effect between environment and QTLs was also analyzed simultaneously.To provide evidences for the genetic improvement of rice quality under drought stress.The results were as follows:1.The milling quality and the appearance quality showed a distinct difference between female parent Xiaobaijingzi and male parent Kongyu131 under drought stress condition.BRR,MRR,HMRR,GL,GT,LWR and CG showed significant or extreme significant differences between the two parents except GW.To compare with the normal irrigation condition,the values of BRR,MRR,GL,GW,GT,LWR and CG all declined except HMRR under drought stress in the tested RIL population.There are a certain number of transgressive segregations for each trait and all traits obey the normal distribution under different environments.Therefore,all traits showed the genetic characteristics of quantitative trait.2.Significant positive correlations between milling quality traits were observed in each environment.Significant positive correlation between grain length and length width ratio was observed under drought stress.Grain width showed significant positive correlations with grain thickness and chalky grain rate,however,it showed a significant negative correlation with length width ratio.Grain thickness showed a significant negative correlation with length width ratio,but a significant positive correlation with chalky grain rate.Length width ratio showed a significant negative correlation with chalky grain rate.3.Based on the F8 recombinant inbred lines,genetic linkage map was constructed with 142 pairs of SSR molecular markers which distributing the 12 chromosomes of rice,covering 1295.03 c M of rice genome,and the average distance between each marker was about 9.12 c M.4.A total of 47 additive effect QTLs were detected using QTL Network 2.1 software.In the test results,20 QTLs could be detected simultaneously in multiple environments,and 9 QTLs could express stably under drought stress.In addition,1 QTL for CG,GW,GT and LWR were detected respectively which could express in all environments simultaneously.5.The pleiotropic QTL intervals were found to exist between the milling quality and appearance quality traits widely by comparing the results of the identified loci.Among them,q BRR11 a and q MRR11 a with high contribution rate could be detected repeatedly in the RM229~RM287 interval of the 11 th chromosome under 2 years' drought stress.At the same time,q GW6 d and q CG6 d with high contribution rate could also be detected repeatedly in the RM402~RM162 interval of the 6th chromosome under 2 years' drought stress.Research indicates that q GL6 b,q GW6 c,q GT6 b,q LWR6 e and q CG6 c could be detected on the RM589~RM20261 interval of chromosome 6 simultaneously.In addition,the contribution rates of q GW6 c,q GT6 b and q LWR6 e were higher and can be detected repeatedly in 2 years' drought stress environment.Therefore,the results of the study are important QTLs for controlling traits of rice milling quality and appearance quality under drought stress.6.A total of 41 pairs of epistatic QTL interactions were detected and the presence of epistatic effects was detected in each trait in the process of epistatic effect locating analysis.This indicates that epistatic QTL interactions are widely existed between milling quality traits and appearance quality traits.7.A total of 5 additive effect QTLs and 20 pairs of epistatic effect QTLs were detected significant interaction effect between QTLs and the environment in the process of QTLs mapping analysis of environmental interaction effects.Except for GT,the remaining traits were all detected a significant interaction effect between the epistatic effect QTLs and the environment.The significant interaction effects between additive effect QTLs and the environment were detected on HMRR,CG,GL and LWR.But the contribution rate of environment interaction effect QTL of each trait is much smaller than that of additive effect QTL.