Efficacy of sowing date adjustment as a management strategy to cope with rice (Oryza sativa L.) seed quality deterioration due to elevated temperature

The objective of this study was to evaluate the effect of high temperature on rice grain quality, and determine the existence of genotypic variation plus efficacy of sowing time adjustment as a management strategy to avoid heat stress. A field trial was conducted during 2009on a set of nine rice genotypes collected from various parts of China, and which represent both indica and japonicaeco types. Different temperatures were imposed by sowing at three different dates; with earlier sowing (SD1) resulting in comparatively greater temperature followed by mid (SD2) and late sowing (SD3), respectively. Milling degree, recovery and dimensions of milled kernel such as grain length (GL), and width (GW) were negatively affected by SD1 for most of the genotypes, followed by SD2 when compared with SD3. Moreover, SD1increased the protein content, percentage of grains with chalkiness (PGWC),percent area of chalky endosperm (PACE)and percent degree of endosperm chalkiness (PDEC) than the mid and late sowing. SD2showed intermediate results between SD1 and SD3for most of the traits. In terms of genotypes, the effect of temperature treatments on these traits was cultivar dependant. Although, the results of this trial confirm the deleterious effects of high temperature on rice grain quality, the findings also prove the existence of genotypic variation and efficacy of sowing time adjustment as a useful management strategy to cope with temperature stress in warmer ecosystems.