Genetic dissection of developmental behavior of crop growth rate and its relationships with yield and yield related traits in rice

Crop growth rate is a dynamic character that determines the final yield in cereal crops. The objective of the current study is to reveal its genetic basis and to genetically understand its relationships with grain yield and yield related traits like heading date, grain-filling duration, 1000-grain weight and plant height in rice (Oryza sativa L.). With 258 recombinant inbred lines (RILs) derived from a cross between cv. Lemont and cv. Teqing, time-related QTL mapping was conducted. Eight QTL for crop growth rate were identified at four consecutive growth periods. These QTL individually explained 5-29% of the trait variation. The Teqing alleles increased the trait values at all the four QTL detected before heading, while Lemont contributed alleles to increase the trait values at three of the other four QTL mapped after heading, which was in agreement with the observation that Teqing was the high-value parent before heading, while Lemont became the high-value parent after heading. No common QTL was observed at different growth periods. These results implied that crop growth rate of rice might be controlled by different genes (QTL) during different time intervals. A total of 22 QTL were identified for the other five traits, and the amount of variation explained by individual QTL ranged from 3% to 26%. The interval RM25-CSU754 on chromosome 8 was identified to produce a major effect on multiple traits such as crop growth rate IV, grain yield, heading date, grain-filling duration, plant heights II and IV, which provided a genetic explanation for the close correlations among the traits. The implications of the results for further improvement in rice yield potential were discussed.