QTL Mapping Of Cold Tolerance In The Germination Period And Bud Bursting Period Of Super Hybrid Rice Y Liangyou 2

Super hybrid rice Y Liangyou 2 belongs to the subspecies of Oryza sativa subsp.Indica of a common cultivated rice,which has the potential of super high yield and the character of high cold-tolerance.It is of great importance to identify genes controlling rice cold tolerance thus to increase rice cold tolerance for stable and high productivity under changing climate.In this study,using the 276 RIL(Recombinant Inbred Line)of a super hybrid rice "Y Liangyou 2",which is a cross of Y58 S and Yuanhui 2,as the mapping population,QTL(Quantitative Trait Locus)for rice cold-tolerance at germinating and bud bursting stage were identified.Results are as follows:Firstly,the cold-tolerant phenotypic identification system of the ‘Y Liangyou 2’RIL population: This is the identification method at the germination stage.60 fully filled rice seeds of 100 seeds were selected by water.After routine disinfection and soaking,they were placed in a step-in artificial climate chamber and treated at 15 ° C for 7 days.The germination rate was calculated,and then recovered at 30 ℃ for 7days,and the germination rate was also counted.Then,it is the identification method at the bud bursting stage.120 seeds were taken,and after conventional disinfection,soaking and germination,60 rice buds with a bud length of 0.5-1cm were taken and placed in a step-in artificial climate chamber,treated at 5℃ for 7days,resumed growth for 7days and the germination rate was counted.Secondly,a continuous distribution of rice cold tolerance at germinating stage in the ‘Y Liangyou 2’ RIL population was observed,which indicated that rice cold tolerance at germinating stage is a quantitative trait controlled by multiple genes.Concurrently,two QTLs,qCTGP7 and qCTGP2,related to cold tolerance traits were located on chromosomes 2 and 7 of the RIL population.The LOD values were 6.1 and3.6,respectively.PVE were 10.16% and 5.13%,respectively.Further analysis showed that these two QTLs were positive for cold tolerance during the germination period.Thirdly,the cold tolerance of Y Liangyou 2 RIL population in the bud bursting stage is continuous in the rice population and is a quantitative trait controlled by multiple genes.At the same time,three QTLs qCTBP9,qCTBP7 and qCTBP12 related to cold tolerance traits were located on chromosomes 9,7 and 12 of the RIL population.The LOD values were 6.5,4.8 and 2.5,respectively,and the PVE were10.10%,6.73% and 3.53%,respectively.Among them,qCTBP9 and qCTBP12 were negatively dominant in cold tolerance at the germination stage,and qCTBP7 was positive dominant in cold tolerance at the bud bursting stage.Fourthly,the QTL of cold tolerance in the germination stage of Y Liangyou 2RIL population overlapped with the previous findings,but the QTL qCTBP9 at the bud bursting stage did not overlap or approximate the results of previous QTL identification of cold tolerance.And the genes in this QTL is not connected to all known genes of cold tolerance.It is speculated that the cold-tolerant mechanism of ‘Y Liangyou 2’ is special,which is different from the other rice.