Abstract:

Drought tolerance (DT) in rice is a complicated trait. Recent genetic research has focused on yield under stress instead of physiological traits. Due to the limits from the huge labors required for both phenotyping and genotyping in traditional mapping work, progress in DT-QTL mapping is relatively slow. An attempt to identify DT-QTL based on genetic hitch-hiking theory in breeding population was described in this paper. With the combination of advanced backcrossing and artificial directional selection for yield under drought stresses of both rain-fed lowland (stress at the reproductive stage) and upland (stress through the whole life time), four sets of 43 introgression lines (ILs) with two relatively uniform genetic backgrounds (IR64 and Teqing) and the same donor of relatively good drought tolerances (BG300) were developed. Introgression of donor alleles in the DT ILs were characterized with 214 well distributed SSR markers representing 98 bins throughout the whole genome. A total of twenty-four significant loci (DT-QTL) were found, of which 20 belonged to allelic-frequency-deviation loci detected by chi-square test at the significant level of P<0.005 and 8 were detected by analysis of variances (ANOVA) with data from progeny test in replicated experiments at the significant level of P<0.01, respectively. Of the 20 loci detected by chi-square test, four (about 20%) were verified by ANOVA and supposed to be directly associated with yield under drought stress. The analysis for yield under irrigation for the same populations was also carried out; few overlap with the DT-QTL was found. The above DT-QTL as well as the DT ILs supposed to offer useful information and materials for the further rice DT molecular breeding. The genetic overlaps between the different selections and the effects of genetic backgrounds were discussed.

Key words: Rice (Oryza sativa L.), Drought, Yield, Genetic hitch-hiking, ANOVA