2023 Volume 25 Issue 1 Pages 1-8
For the genetic analysis of tillering behavior in the late-bolting bunching onion ‘Okunegi’, a correlation analysis was performed at first between tiller number and various traits in ten bunching onion cultivars and four breeding lines. There were no significant correlations between the tiller number and bolting time, suggesting that it is possible to select independently for tillers and late bolting. Next, 6 × 6 half-diallel analysis was performed using five bunching onion cultivars and a single breeding line with various tiller numbers and bolting times picked up by the above correlation analysis. The tiller number was counted at three growth stages. The analysis of variance for tiller number in this half-diallel table showed that the additive variance of tiller number was much larger than the dominance variance and that its average degree of dominance was less than one at all stages. This suggests that the number of tillers was an incomplete dominant trait with a large additive effect, and that the dominant genes for tiller number act to increase tillers. In addition, the tiller number of the materials at three stages and their diallel analysis showed that the dominance order and the proportion of dominant and/or recessive genes in the parental lines varied as they grew, suggesting that the type and mechanism of the genes controlling tiller number are different among the parental lines. Furthermore, the high heritability in the narrow sense (>0.78 in each growth stage) and the results of the analysis of variance also suggested that selection in the early segregating generation is very important for the breeding of a monoculm late-bolting line from ‘Okunegi’.
