QTL Mapping of Yield under Irrigation and Rainfed Field Conditions for Advanced Backcrossing Introgression Lines in Rice

In rice breeding community,drought tolerance(DT) is becoming one of the most important target traits for variety improvement under ever-increasing severe drought situation all over the world.Yield is the most important target focused by breeders,so identification of favorable alleles related to yield and yield components for introgression into rice varieties that suit the specific environments is an efficient practice in plant MAS breeding.In the present study, the QTL conditioning the grain yield per plant(GY) and its component traits including 1000-grain weight(GW) and filled grain number per panicle(GN) in irrigation(control) and rainfed(drought stress) fields were investigated using 254 advanced backcrossing introgression lines(IL) of Lemont with Teqing genetic background and the two parents.Total of 32 main-effect QTLs for GY,GW,and GN were identified in the two conditions which can be grouped into three types based on their behaviors.TypeⅠincluded 10 QTLs which were detected both in the two conditions,type Ⅱ consisted of 14 QTLs which were mapped only in control condition,and type Ⅲ comprised 8 QTLs which were induced by drought and detected only under stress.In addition,nine QTLs affecting trait differences between stress and control were identified(QGn5,QGn6,QGn11a,QGw2,QGw8,QGw11a,QGw11b,QGy1,and QGy11).There were three QTLs(QGn11b,QGn12,and QGn11b) which expressed both in the two conditions with same direction and magnitude of gene effect.Therefore the three GN-QTLs and nine QTLs affecting trait differences were considered to directly contribute to drought tolerance(DT).Teqing alleles at the 12 DT-QTLs except QGn5 and QGy1 were associated with DT.As compared with the results from different mapping populations derived from the same parent,Lemont and Teqing,in different environments,seven QTLs including QGn3b,QGw1,QGw5,QGy1,QGy5,QGy8,and QGy10 which stably expressed across different genetic backgrounds and environments were identified.The strategy of applying QTL mapping results in rice improvement for DT by marker-assisted selection was discussed.