Yield gains
in rainfed rice that constitutes more than 45% of the world rice
area (IRRI, 2002) have not kept pace with those of irrigated
systems. Rainfed rice systems are often highly variable in terms
of soil characteristics and water availability, and they
experience much higher levels of abiotic stress because of
water shortage or crop submergence than do irrigated
ecosystems. Drought is the most important abiotic constraint
that reduces yield in rainfed areas (Bernier et al., 2008).
Drought stress can develop at any stage of the crop in unbunded
or bunded upper fields upon the cessation of rainfall for a few
consecutive days, often resulting in a severe yield reduction.
Bunded lower fields can also be affected by drought stress