Proline Accumulation and Rooting Patterns in Rice in Response to Water Deficit under Rainfed Lowlands

ABSTRACT: Drought is a major impediment to a rainfed lowland rice system. Drought tolerance has been associated with proline accumulation in roots and leaves. However, genetic linkage was uncertain. To determine if there is a genetic correlation between proline accumulation and drought tolerance; a total of 220 double haploid lines, their parents (CT9993 and IR62266), and three standard checks (IR20, NSG19 and KDML105) were used in experiments to determine the extent of genetic variation in root characters, proline accumulation, relative water content, visual leaf rolling and drought injury under different intensities of water deficit. Genotypes with high proline content in leaf tissues were more dehydration tolerant, a relatively high water content was maintained, and leaf rolling and senescence were delayed under severe water deficit. However, the ability of rice roots to penetrate deep into the soil was negatively correlated with proline accumulation in leaf tissue. Rice roots are mostly distributed at 0-30 cm soil depth under lowland conditions. Therefore, the ultimate goal to combine high dehydration tolerance with strong root penetration may not be realized in the existing germplasm