Studies on early backcross generation inbred lines of Rice (Oryza sativa L.) for yield under stress evaluated under different moisture regimes

Rice under rainfed condition faces frequent moisture stress. Recent studies at IRRI have shown moderate to high heritability of grain yield under stress. QTLs were introgressed through backcrossing of Apo (donor) and IR 64 (recipient) lines. Evaluation was done for reproductive stage moisture stress tolerance in severe moisture stress and well irrigated condition to study the effect of the introgressed QTLs in BILs. Set of 85 backcross inbred lines (BILs) at BC1F3 (81) and BC2F3(4) generations developed through MAS (Marker Assisted Selection) bearing one at a time, two and three DTY (yield under drought) QTLs (Quantitative Trait Loci) for yield under stress donated by Apo. High heritability for yield and predominant association was seen between spikelet fertility, harvest index and grain yield per plant. Single QTLs DTY2.2 performed best for grain yield and also showed least drought susceptibility index (DSI). DTY (2.2 + 8.1) performed better in traits like grain yield, plot yield and spikelet fertility and harvest index than expected three QTL line. QTLs bearing BILs were advantageous over IR 64 under severe moisture stress with respect to higher 1000 grain weight and spikelet fertility %.