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Effectiveness of Early-Generation Selection for Tillering Capacity in Spring Wheat

Crop Development Ctr.
Dep. of Crop Science and Plant Ecology, Univ. of Saskatchewan, Saskatoon, SK S7N OWO

^* Corresponding author.

The tillering process is one of the major determinants of grain yield in wheat (Triticum aestimm L.). A restricted tillering (oligoculm) ideotype has been proposed for maximizing grain yield. This study was conducted to estimate the heritability and effectiveness of selection for tillering capacity in oligoculm and nonoligoculm spring wheat crosses. Eight populations derived from crosses among high tillering ('Neepawa', ‘Ingal’), low tillering (‘Ko Fong’, ‘Siete Cerros’), and oligoculm (M1417) parents were evaluated at Saskatoon, SK. The F₁, F₂, and the F₂-derived F₃, F₄, F₅, and F₆ lines were tested under dryland conditions. The 10 highest- and 10 lowesttillering F₇ lines from each of the oligoculm crosses were grown under irrigation at Saskatoon and Outlook, SK. Tiller production of F₁ hybrids did not differ significantly (P = 0.05) from their midparent values in 16 of 18 hybrid-environment combinations. Heritability estimates for tillers per plant were, on average, much higher for the oligoculm crosses. At commercial seeding rates, high- and low-tillering F₄ lines differed significantly in spikes per square meter in eight out of nine populations. High- and low-tillering selections in oligoculm F₄ populations differed, on average, by 19% for spikes per square meter, compared with 12% in nonoligoculm crosses. Limited May and June precipitation during the evaluation of the F, and F₆ generations resulted in few (4 of 16) significant differences in spikes per square meter between high- and low-tillering groups. Averaged across 2 yr (1987,1989), the low-tillering selection group in oligoculm crosses yielded 7% less than the high-tillering group. Early- generation divergent selection for tillering capacity was more effective in oligoculm than in nonoligoculm crosses.

Received for publication July 5, 1990.