Occurrence of grain chalkiness in upland rice genotypes grown with and without irrigation

Among physiological disorders, chalkiness is one of the main problems in rice breeding since it directly affects grain quality and rice price in the market. Chalkiness can occur due both genotypic and environmental effects, including malformed grains, moisture content, pest attack, and water stress. Therefore, the study of mechanisms influencing the expression of chalkiness can greatly help breeders to deal with this problem. The objective of this study was to access the influence of water supply on the occurrence of chalkiness in rice grains of twenty elite inbred lines from the Upland Rice Breeding Program from the Brazilian public research institutions UFLA, EMBRAPA and EPAMIG. Lines were evaluated for grain chalkiness in two irrigated environments and in a non-irrigated one. The experiments were carried out in the 2013/2014 growing season following a randomized block design with three replications. The proportion of chalkiness was accounted of the number of chalky grains of a random sample of 100 grains taken from 10 random panicles of each plot. Genotype x environment interaction was significant in the combined analysis of variance of all environments, so progenies performance varied across environments. Lines showed variability for chalkiness on the non-irrigated environment and on the mean of all environments, but they did not differed on the irrigated environments separately, indicating that the expression of chalkiness in this study occurred mostly due to the environment rather than to genotypes. Lines evaluated in the non-irrigated environment showed a significant large proportion of chalky grains compared to the proportion found in the irrigated environments, suggesting that water supply influenced the expression of grain chalkiness. Lines CMG 1987 and CMG 1698 showed significant tolerance of chalkiness in the non-irrigated condition.