Abstract:

To reveal the role and genetic mechanism of leaf water potential (LWP) to japonica rice under various water status, 120 recombinant inbred lines (RILs) derived from a cross between IRAT109, an upland japonica rice, and Yuefu, a lowland japonica rice, were planted under both upland and lowland environments for mapping QTL associated with high LWP. LWP was measured at pre-dawn and mid-day. Drought resistance was evaluated with index of drought resistance (IDR), which was the ratio of grain yield of upland treatment to that of lowland treatment at maturity. Significant variations of LWP were observed in RILs in both upland and lowland treatments. Correlation analysis indicated that LWP at mid-day in upland (WPU) was positively correlated (r = 0.256**; r = 0.259**) with IDR and yield per plant (YPU), and water potential variation in upland (WDU) negatively correlated (r = -0.280**; r = -0.260**) with IDR and YPU. For LWP, 6 additive QTLs including 2 for LWP at pre-dawn in upland (WPIU), 1 for WPU, 2 for WDU, and 1 for LWP variation in lowland (WDL) and 5 pairs of epistatic QTLs including 1 for WPU, 1 for WPIU, 1 for LWP at pre-dawn in lowland (WPIL), and 2 for WPL were detected, respectively. Among the 6 additive QTLs, the 2 for WPIU (wpiu1 and wpiu4) and 1 for WPU (wpu6), all donated by IRAT109, can explain 5.4%, 7.9%, and 10.0% of the phenotypic variances, respectively; the 2 for WDU, wdu6 from IRAT109 and wdy12 from Yuefu, can explain 11.6% and 9.5% of phenotypic variances, respectively. For IDR, 3 additive and 2 pairs of epistatic QTLs were identified. The broad heritability of LWP was low for direct selection in the field, but may be effective via marker-assisted selection.

Key words: Index of drought resistance, Leaf water potential, drought resistance, QTL, Rice (O. sativa L.)