Mapping quantitative trait loci for plant height, heading time, growth duration and grain yield in two advanced back cross populations of rice

Two BC2F4 populations of rice, Hashemi/IR67418-110-3222 (Hashemi/IR-22) and Hashemi/Neda, Hashemi was as recurrent parent, were studied during two years (2009 and 2010) for QTLs detection for plant height, days to 50% heading, growth duration and yield. The role of epistasis and QTL-environment interaction on these traits was also studied. Hashemi/IR-22 and Hashemi/Neda lines were tested with 61 and 65 polymorph SSR primer pairs, respectively, which were distributed on all chromosomes. The total genetic maps lengths of Hashemi/IR- 22 and Hashemi/Neda were 1103.45cM and 1260.53cM, respectively. Four to five QTLs were detected for each trait in Hashmi/IR-22 population with at least two QTLs repeated for each trait during two years. These QTLs explained 5.6% to 37% of the traits phenotypic variation. In Hashemi/Neda population three to four QTLs were detected for each trait, with at least one QTL repeated for each trait during two years. These QTLs explained 5.1% to 43.2% of the traits phenotypic variation. From detected QTLs, only a plant height QTL flanked by RM234 marker on chromosome 7 and a yield QTL flanked by RM3337 and were the same in the two populations. This indicated the important role of genetic background effect on controlling these traits. In each population there were QTLs that simultaneously affected two or more of the studied traits, e. g. plant height, days to 50% heading, growth duration and yield, which suggested pleiotropic or linkage gene effects for these traits. Two QTLs on chromosomes 6 and 8 for growth duration and QTL on chromosome 8 for yield in Hashemi/IR-22 population and one QTL on chromosome 6 for days to 50% heading and growth duration and one QTL on chromosome 3 for yield in Hashemi/Neda showed interaction with environment. Also in each population a pair of QTLs was recognized with significant epistatic effect.