Detecting alleles conferring improved reproductive-stage drought tolerance in rainfed rice

Abstract

This study was aimed to identify the QTLs related to drought tolerance in rice. The 174 lines of RIL population derived from a cross between KDML105 and IR57514-PMI-5-B-1-1 were used for this study. These RILs were grown for phenotypic evaluation in wet season 2004 and 2005. Grain yields under drought condition were collected. Young leaf samples from these lines were collected for DNA extraction using CTAB method. Two hundred and seventy-seven SSR markers were used for parental survey. The PCR products were obtained from 226 markers (81.6 percent) but only 93 markers showed polymorphism (41.2 percent). Those polymorphic markers were used to conduct a progeny screening. The results, so far, indicate that 64 loci of SSR markers have been mapped onto rice chromosomes of the RILs from the cross between KDML105 and IR57514-PMI-5-B-1-1 with an average map distance of 24.6 cM between 2 markers. Grain yields under drought condition were used for conducting a QTL analysis using a MAPMAKER/EXP and a MAPMAKER/QTL program. It is found that the only QTL conferring grain yield under drought condition is located between the marker RM1106 and RM2634 on chromosome 2. The distance of this QTL is 49.6 cm with a LOD score of 2.46 and this QTL can explain 41.2 percent of phenotypic variation. For future work, it is necessary to map more markers on to the region of interest in order to identify the location of targeted QTL more precisely. However, the problem of this study is that the drought tolerant line IR57514-PMI-5-B-1-1 also contains some degree of KDML105's background, leading to very low polymorphism.