An analysis of groat-weight variation in irradiation-derived populations of oats

Abstract

Primary and secondary caryopses (groats) of oat lines derived from irradiated and non-irradiated Clintland and Beedee varieties were subjected to component analysis according to the formula; groat weight = L ( W 2 ) 2 π DS , where L and W represent groat length and width, and π, D, and S are the constants, 3·14, density and shape. In the Clintland-derived materials, the mean weights of both groat classes (primary and secondary) were significantly greater in the irradiation-derived population than in the controls. Although the means of each component in the irradiation-derived materials were slightly higher than their counterparts in the control populations, only width of the primary groats was significantly increased. The greater groat length and width in the irradiation-derived population accounted for the total increase in primary groat weight, but for only a portion of the increase in secondary groat weight. Correlated variation of secondary groat length and width was responsible for secondary groat weight being greater than expected. The genetic correlations between groat length and width were +0·14 and +0·73 for primary and secondary groats, respectively. In the Beedee-derived materials, the mean groat weights of the irradiation-derived and check populations were not significantly different, but the mean groat widths were significantly decreased, and the mean groat lengths were significantly increased. The changes in length and width tended to nullify the effects of one another when contributing to groat weight. The actual groat weights were smaller than expected for both primary and secondary groats. This resulted from the negative associations between groat length and width covariation. The genetic correlations between groat length and width were −0·56 and −0·29 for primary and secondary groats, respectively.