Genetic Analysis Of QTLs Controlling Grain Yield In Rice Elite Cultivar Guichao 2

Rice is one of the most important staple crops feeding more than one third of the world population.The crop yield from shrinking arable land can not meet the requirements of the growing population.Increasing attention has been paid to the very significance of how to increase crop yield per unit area.In recent years,the continuous development of molecular markers,genetic map and bioinformatics methods allows a faster and efficient cultivation of new elite cultivars with high yield and quality with molecular marker-assisted breeding technique.Therefore,identification and application of QTLs(quantitative trait loci)by molecular marker-assisted breeding to increase crop yields has become one of the main focuses of the international rice breeding projects.Guichao 2 is a famous rice elite cultivar with high-yield and good stress resistance.It was cultivated by Guandong Academy of Agricutural Sciences and was selected from the progenitors of the Zhaoyangzao 18 and Guiyangai 49 crossing population in the 1980 s.However,the major QTLs controlling the high-yield traits of Guichao 2 are still not clear.In this study,we have developed a RIL population using single seed descent method by crossing Guiyangai 49 and Guichao 2.We have observed 9 typical yield-related traits,including plant height,heading date,grain length,grain width,thousand-grain weight,panicle length,primary branch number,secondary branch number and grain number per panicle.We did RAD-seq using 349 plants from the RIL population.17783 high-quality SNPs were obtained and integrated into 1688 recombination bins.Finally a linkage map with 721.40 cM genetic distance was constructed,of which the average genetic spacing of the bin marker was 0.43 cM.29 QTLs controlling rice yield-related traits were detected by using the QTL Cartographer software,including 3 heading date related QTLs,3 plant height related QTLs,5 grain legth related QTLs,6 grain width related QTLs,6 thousand-grain weight related QTLs,1 panicle length related QTLs,1 primary branch number related QTLs,5 secondary branch number related QTLs and 3 grian number per panicle related QTLs.At the same time,RNA-seq analyses were carried out with young inflorescence meristems of Guichao 2,Guiyangai 49 and Zhaoyangzao 18 respectively.This study sheds insights into the genetic structure of chromosome regions that correlate with the high yield potential of Guichao 2,which provides basis for identification key genes controlling yield potentials and their application in MAS(molecular marker-assisted selection)-based breeding technology in the future.