Genetic and Environmental Effects on Grain Size Uniformity in Winter Wheat

Abstract

Grain size is an important yield component and also influences flour yield, seed vigor and early plantlet development. It is usually described by the weight (or mass) of thousand grains or average of dimensions of a sample, without paying attention to the variability of individual grains. However, variation in individual grain size is economically important for milling industry, because many small grains are lost during the cleaning process prior to milling and a high proportion of small grains is indicative of a poor flour yield. Also, when grains are sown for a new crop, grain mass variability increases the heterogeneity of germination and leads to non-uniform seedling emergence and crop establishment, often leading to decreased yield. We analyzed using the software ImageJ (http://imagej.nih.gov/ij/) individual grain size distributions of samples 80 to 120 individual grains each, harvested from yield trials at NARDI Fundulea Romania with 13 cultivars grown on four management variants, during two years. Individual grain projected area, as a proxy of grain size, ranged from 8.18 to 29.06 mm2, and for most cultivars minimum values of individual grain projected area were less than half of maximum values. On average over all management variants and years, coefficients of variation (s%) varied from less than 14% in cultivars Bezostaya 1, Glosa and Pajura to more than 15.5% in cultivars Adelina and Litera. ANOVA for the coefficients of variation of grain projection areas showed that the main source of variation was the effect of cultivars, which was significant when tested both against the Error and the interaction Cultivars*Years. The effect of the four studied managements was significant when tested against the Error, but not when tested against the interaction with Years, suggesting that the managements did not have the same effect in the two years of study. The large differences between cultivars found in our study provide opportunities in breeding for higher grain uniformity.