Mapping of QTLs Controlling Rice Grain Size

Purpose Grain size controlled by QTLs dispersed in rice genome is a quantitative trait that influence both the quality and yield of rice, and locating those QTLs is the first steps for further research, such as QTL clone and function analysis.Method A lager grain size rice variety, ZD05321 was crossed with a very small grain size variety Suwandel to produce a F2 population containing 246 lines. And the QTLs involving 4 grain size related traits, including grain length (GL), grain width (GW), thousand grain weight (TGW) and length-width ratio (L/W) were mapped with 48 SSR molecular markers in this F2 population.Results Genetic analysis showed that the GL, GW and TGW in the F2 population present continuous distribution as the typical quantitative traits. The phenotype of most plants in the F2 population is in favor of the lager grain size rice variety, ZD05321. There is an extremely remarkable positive correlation among GL, GW and TGW. And with the increase of grain weight, the grain length makes less contribution to grain weight. A total of 15 QTLs relevant to grain size were detected, in the 1st, 4th, 6th, 7th, 8th and 9th chromosomes in the rice, the number of QTLs detected for each trait are 3 to 5, and with the contribution of 1.02% to 16.52% to the corresponding characters. There are 4 QTLs relevant to grain length, grain width, thousand grain weight and length-width ratio were detected on the 9th chromosome, and these QTLs are located in the segment of RM3609-RM7586 and RM6543-RM566.Conclusion There may exist major QTLs which control the grain size within the larger grain size variety ZD05321. A chromosome region which control several grain size traits was discovered in the 9th chromosome, and this is the basis for fine mapping the related QTLs in this region in the future study.