| Grain appearance and milling quality are the key elements for rice market value.The improvement of grain quality and yield are the main objects of rice breeding program globally.The identification of QTLs controlling grain quality traits through Marker-assisted selection(MAS)has become essential for increasing efficiency of breeding program.Rice grain appearance and yield are the vital traits in any rice breeding program.Moreover,the global human population is increasing substantially.Therefore,it is of paramount importance to design studies for the identification of quantitative traits loci(QTLs)controlling quality and yield related traits under different environmental conditions.The present research work was designed to identify QTLs of rice grain quality by utilizing double haploid(DH)population of YK17/D50.The main focus of this study was to identify novel and important QTLs that could be stable under different environmental conditions and influence rice grain quality.Moreover,to identify the rice grain appearance and milling properties,a genetic linkage map using DH population was constructed from cross between Zhongjiazao 17(YK17,a super rice cultivar)and a tropical japonica variety D50 to analyze the QTLs of quality of grain appearance and milling traits such as grain length(GL),grain width(GW),length-width ratio(LWR),grain thickness(GT),Thousand grain weight(TGW),Percentage of grain with chalkiness(PGC),Chalkiness score(CS),Brown rice recovery(BRR),Milling rice recovery(MRR),Head rice recovery(HRR).The research was performed under 3 differentrice growing seasons including Hangzhou,(Zhejiang province)2017 and 2018 and in Lingshui(Hainan province)during the winter of 2018.The genetic linkage map contains length of 1215.2 cm with 170 SSR markers.The adjacent markers had genetic distance ranged between 0.5 cm to 26.9 cm,and with average of 7.1 cm.To determine QTLs,Windows QTL Cartographer Version 2.5(Win QTLCart 2.5)with Composite Interval Mapping(CIM)parameter was used,and with LOD value of 2.5 as its threshold level,whereas,an epistatic effect of QTL-by-environment interaction(QEs)was explored utilizing QTL Network-2.1,with mixed-model-based composite interval mapping(MCIM).Some significant findings in this study were as follow:1.The genetic basis of appearance quality traits of rice grain was determined in current study.Totally,73 QTLs were located on 11 chromosomes,however,four QTLs including GL3,GW3,LWR3,and TGW3 were found in the pericentromeric region of chromosomes 3.2.QTLs responsible for grain width and length were also identified.GL3 a major gene along with q GS3 were repeated detected under all three environments,located between markers interval RM6929-RM15490 on chromosome 3 with phenotypic variations of 34.97%,21.32%,and 33.0%,respectively.In addition,for digenic interaction,8 QTLs controlling five traits associated with grain quality were identified with additive environment interaction.The epistatic interaction was also explored in PGC.3.QTLs associated with milling quality traits,Brown rice recovery(BRR),Milled rice recovery(MRR),and Head rice recovery(HRR)were studied under three different rice growing seasons,and total of 23 QTLs were identified.The identified QTLs for BRR,MRR,and HRR were detected on all chromosomes except chromosome 10 and 12,with single QTL containing 8.06% to 22.47% of phenotypic variations.Among these detected QTLs,four QTLs were repeated under two environmental conditions.Among the detected QTLs,most of the QTLs for BRR and MRR were located between marker intervals of RM73769-RM23946 on chromosomes 9.In summary,identified and validated QTLs that were stable and consistent under three different environmental conditions associated with rice grain quality and yield.Along with these QTLs associated with milling quality traits,stable QTLs in two environments were also indentified.These results,particularly the identified stable QTLs,will be valuable in future breeding programs to improve rice grain quality and yield. |
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