We've worked with a number of prolific sources over the years and wished to learn something about their inheritance. We grew two sets of six generations each at Mankato in 1970 that involved inbred lines where Ladyfinger pop (LP) and Southern dent (SD) were sources of prolificacy; the single eared parent was an early derivative of C103. In addition we have taken Duvick's data (1974 Crop. Sci. 14:69-71, Table 1) that involves Argentine pop (AP) and C103 grown at Johnston, Iowa, in 1965. The means were fitted by regression to Hayman's generation means analysis (Table 1).
Additive gene effects explain nearly all the genetic differences in the LP data. Additive and dominance effects explain most of the variation in the SD and AP data. A model for mean, additive, and additive x additive epistatic effects was also fitted to the SD and AP data, and it accounted for 99.5% of the variation. Addition of dominance to this model did not account for significant additional sums of squares.
Though additive and dominance effects account for 98.6 percent of the variance for the SD data, the P2 value observed at 1.62 appears too low compared with its genetic potency. If the P2 value for SD is omitted, the remaining five generations increase the fit to 99.8 percent, and indicate P2 should have had an observed value of near 2.8. P2 for SD is much later flowering (P1 - 1404 gdu, P2 - 1596 gdu) than the other materials grown at Mankato. The season during flowering and ear formation was hot and dry; later flowering of P2 was probably disadvantageous and reduced its phenotypic value.
Based on the present data inheritance of prolificacy for three sources appears to be mostly additive with some dominance effects.
Robert E. Stucker* and A. Forrest Troyer
*University of Minnesota
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