Research On QTL Mapping Of Traits Related To Submergence Tolerant Seedlings Of Rice Seeds

In the production of direct seeding rice,seeds often subjected to submergence stress during germination and seedling stage,which results in yield reduction.Therefore,it is important to explore the submergence-resistant germination and seedling traits of rice seeds under the submergence stress to increase yield of direct seeding rice.In this study,6 materials were used to analyze the traits of hypoxic germination from physiological and biochemical perspectives,and the QTL mapping of submergence tolerance traits of rice seeds was conducted in combination with the high-density genetic map for the RIL population containing 275 lines of CHA-1/H335.The main research results are as follows:（1）The soluble protein,SOD,POD,CAT and AMS enzyme of 6 materials were measured at germination stage.The results showed that these enzyme responsable to hypoxia conditions.The activities measured in the six materials at the submergence germination stage showed different trends with the increase of hypoxia time,and there was no obvious rule,but the trend of SOD and POD enzyme activities was roughly the same.（2）In the condition of 10cm submergence,33 QTLs were identified in the RIL population of CHA-1/H335 in F₆ and F₇ generation,including 21 in the submergence germination stage and 12 in the submergence bud stage.They were distributed on chromosomes 2,3,4,6,7,8,and 10.A total of 19 QTL loci were found through comparison of physical locations.Among them,6 were overlapped the known loci,and the remaining 13 were not reported.（3）q SSD-2,q CD-4-1,q CSA-8 and q CV-8 can be located in both environments.Among them,the phenotypic contribution rates of q CSA-8 and q CV-8 were4.41～4.80%and 4.09～4.97%separately,and the two QTLs were located at the same locus,which controls both the surface area and volume of the coleoptile,which is of great research value.The expression of these QTLs is stable and insensitive to environmental impact,which has important reference value for direct seeding rice breeding.（4）A total of 9 loci showed pleiotropic of QTL loci,and 4 of them were not reported as new QTL loci.On the second chromosome,both Block3943-3970 and Block3988-3998 were localized to the QTL controlling the submergence germination and budding stage（Block3943-3970 was localized to q CD2-1 and q SSD-2,while Block3988-3998 was localized to q CD-2-2 and q SFW-2）.The phenotypic contribution rates were 6.77～10.89%and 7.46～11.28%,separately.Both loci had effects on the submergence germination and budding stages.On chromosome 10,the QTL locus of Block16658-16661 controls both bud length（q SH-10）and root surface area（q RSA-10）.The phenotypic contribution rates were 5.68%and 4.05%,separately.This locus controls both aboveground and underground parts,which is of great research value and can be further studied.Overall,this study dissected the genetic performance of seedling traits of rice seeds under the submergence stress;constructed the high-density genetic linkage map based on GBS technology,and identified important QTL loci firstly reported in this study.Late for cultivating submergence tolerance in rice varieties provides the basis for breeding practice,to improve direct seeding rice breeding has strong theoretical and practical significance.