On-farm assessment of effect of low temperature at seedling stage on early-season rice quality

Low temperature often occurs at seedling stage in early rice-growing season in southern provinces of China. However, it is not clear whether the low temperature at seedling stage has an impact on early-season rice quality. This on-farm study was conducted to compare quality and growth traits of an early-season rice cultivar between two contrasting years with respect to temperature at seedling stage, 2009 (normal temperature) and 2010 (low temperature). The results showed that brown rice percentage, milled rice percentage, gelatinization temperature and gel consistency were significantly lower in 2010 than 2009, whereas 2010 had significantly higher percentage of chalky rice grains, degree of chalkiness and protein content than 2009. The yearly difference in rice quality was attributed to variation in rice structure. In 2010, a marked decrease of grain weight was observed, which was not accompanied by a decrease in rice length or width. Source capacity (aboveground biomass accumulation) did not explain the difference in grain weight between 2009 and 2010, because grain-filling rate was comparable in the two years. Shortened grain-filling duration, indirectly caused by the low temperature at seedling stage, was responsible for the decreased grain weight in 2010. These results suggest that low temperature at seeding stage can affect early-season rice quality through its indirect effect on grain-filling duration. (c) 2012 Elsevier B.V. All rights reserved.