Test of the Additive-Dominance Model of grain weight and grain uniformity of oat, Avena sativa L, genotypes
An investigation of the genetic mechanisms controlling grain weights for the primary and secondary grains uniformity expressed in primary: secondary individual grain weight (P: S IGW) ratio and % tertiary grains produced was conducted using a backcross experiment'. Two oat, parental genotypes, I.L82-1657 (pistillate) and 10589 Cn (staminate) with different grain weight characteristics were hybridized to obtain 6 backcross generations viz. P1, P2, F1, B1, B2 and F2. The scaling test indicated that overall average, primary and secondary individual grain weights and % tertiary grain weight produced failed to satisfy the additive - dominance model and digenic interactions were detected except for the secondary individual grain weight. Grain weight uniformity expressed as P:S IGW ratio satisfied the additive - dominance model and was highly heritable (h2 narrow sense >98%). However, additive gene effect was important in the control of all the grain weight variables except the primary: secondary grain yield ratio. Dominance effect was important only for the overall average grain weight and the proportion of tertiary grains produced. Attainment of uniformity of oat grains looks promising through genetically improving the P:S IGW ratio but is challenged by the presence of non-allelic interactions in the control of % tertiary grain weight.