QTL Analysis Of Cold Tolerance And Submergence Tolerance During Germinating Period,Budding Period,Seedling Period In Rice

Rice is one of the important food crops in China.In order to explore quantitative trait loci(QTL)conferring cold and submergence tolerance at the seedling stage,and lay a foundation to elucidate the molecular regulation mechanism in rice,a CSSL population derived from a backcross between indica variety Changhui 121(as recurrent parent)and japonica variety Koshihikari(as donor parent)was used.Test seeds of two parents and CSSL population were harvested in Nanchang 2015,Sanya 2016,Nanchang 2016,Sanya2017,respectively.The main results were as follows:1.Under the same treatment,the cold and submergence tolerance during early growth period of Koshihikari were significantly stronger than that of Changhui 121.In addition,the cold tolerance trait and submergence tolerance trait of the CSSL population showed a continuous distribution and two-way submergence tolerance trait in the early growth period,indicating that cold tolerance trait and submergence tolerance trait in early growth period of rice were quantitative traits and controlled by multiple genes.2.There is no significantly correlation among cold tolerance during germinating stage,budding stage,seedling stage.However,the survival rate,the withered grade and the proline content change rate in seedling stage were significantly correlated,indicating that these three indicators can be used together to test the cold tolerance of seedling stage.The germination rate under submergence was significantly correlated with the coleoptile leng under submergence;however,the plant height relative change rate and plant height after submergence and damage index of chlorophyll in rice were extremely negatively correlated;the plant height relative change rate and damage index of chlorophyll were has a very significant negative correlation3.A total of 40 QTL related to cold tolerance and submergence were identified in early growth period.6 QTL were related to germination chilling tolerance;8 QTL were related to cold tolerance during budding;2 QTL were related to survival rate of seeding,4QTL were related to withered grade,and 4 QTL were related to proline content relative change rate;3 QTL were related to germination rate under submergence.10 QTL were related to coleoptile length under submergence and 4 QTL were related to plant height relative change rate.These QTL were distributed on all 12 chromosomes of rice,which explained 5.0%～42.06% of the observed phenotypic variance.4.There are 13 QTL can be repeatedly detected in 2 or more environments.Among them,qGRS9-1 can be detected in 4 environments.qCTB6,qCLS1-2,qGRS8 can be detected in 3 environments,qCTG3,qCTG4-2,qCTG6,qCTG8,qCTB5-1,qWG12,qPCCR11,qPCCR12,qCLS4-2 can be detected in 2 environments,indicates that these QTL are less affected by the environment.5.A QTL(RM6296～RM27686)on chromosome 12 can simultaneously control seedling cold-tolerance survival rate and withering grade in rice,a QTL(RM7492～RM8201)on the chromosome 10 can simultaneously control submergence germination rate and plant height after submergence.In addition,other QTL can only control one trait.