Genetic analysis in the pasture grass Setaria sphacelata. I. Dry matter yield and flowering

Abstract

The progeny of a 7 x 7 diallel cross between plants randomly selected from a segregating tetraploid setaria population (S. sphacelata var. sevicea and var. splendida) was studied at Lawes, south-east Queensland, over a two year period in two spaced plant replicates. Plants were harvested at 6-week intervals (9-10 week in winter), and dry weight and flower head number were recorded. Two additional replicates were allowed to grow uninterrupted, and date of flowering and flower head number were recorded. Damage caused by the fungus Pyricularia gvisea was scored on all four replicates. Genetic analysis indicated a high order of general combining ability variance for yield in the population and strong positive genetic correlation between seasons for yield (rg = 0.72-1.26). Variance estimates derived from analysis of variance and parent offspring regression were comparable. Genetic variance was strongly and consistently additive for days to flower and flower head number. Positive genetic correlations between seasons and years for days to flower (rg = 0.31-1.09) indicated that genetic differences in flowering were not strongly confounded by environmental effects. Dry matter yield was genetically correlated with flower head number and hence earliness to flower (rg = 0.79-1.16). Days to flower was genetically correlated with flower head length (rg = 0.71-0.91). Resistance to the pathogen Pyricularia grisea was shown to be under genetic control. The data suggested that resistance may be controlled by a gene exhibiting tetrasomic inheritance with two alleles necessary for expression of a high order of resistance.