Identification of molecular markers linked to root penetration ability in rice (Oryza sativa L.)

The main objective of this study is to identify molecular marker like restriction fragment length polymorphism (RFLP) associated with penetrated root number, penetrated root thickness and root penetration ability of indica rice through wax-petrolatum layer simulated as compacted soil layer. Mapping population of this study composed of 166 recombinant inbred lines (RILs) developed from two indica genotypes was evaluated in the greenhouse twice with five replications. Data were collected for total root number (TRN), penetrated root number (PRN), root penetration index (RPI), and penetrated root thickness (PRT). The TRN varied from 71-328 with a mean of 161 and 45-213 with a mean of 98 in summer and fall experiments, respectively. The PRN varied from 14-122 with a mean of 40 and 6-57 with a mean of 21 in summer and fall experiments, respectively. The RPI varied from 0.08-0.56 with a mean of 0.26 in summer and 0.06-0.55 with a mean of 0.23 in fall experiment. The PRT varied from 0.40-1.18 mm with a mean of 0.82 mm and 0.40-1.10 mm with a mean of 0.78 mm in summer and fall experiments, respectively. A total of 16 QTLs were detected by single-point and interval mapping analysis in two experiments; three QTLs for TRN, four QTLs for PRN, four QTLs for RPI and five QTLs for PRT. Seven QTLs were found common in both the experiments, of which three QTLs for PRN explained total phenotypic variation of 43%, one QTL for RPI explained 22% phenotypic variation, and three QTLs for PRT explained together 26% of the phenotypic variation. One QTL detected in the interval between markers RG151 and RG256 was found to influence penetrated root number, root penetration index and penetrated root thickness. Another QTL flanked by the markers AA7-2a and AA7-2b influenced both penetrated root number and root penetration index. These two QTLs were found to be located in the same chromosomal regions of other populations with different genetic backgrounds. Markers which are tightly linked with the detected QTLs for root penetration ability and penetrated root thickness will facilitate the transfer of these QTLs to susceptible indica cultivars to improve drought resistance employing the marker-aided selection approach. (Abstract shortened by UMI.).