AbstractsBiology & Animal Science

Evaluation of early generation testing in a diallel cross involving four winter wheat cultivars (Triticum aestivum Vill., host)

by Abderrazak Daaloul




Institution: Oregon State University
Department: Agronomic Crop Science
Degree: MS
Year: 1972
Keywords: Wheat  – Breeding
Record ID: 1583043
Full text PDF: http://hdl.handle.net/1957/45196


Abstract

Factors which influence the effectiveness of making early generation selections within bulk populations were investigated. Material utilized included the parents, F₁, and F₂ through F₅ bulk populations resulting from a diallel cross. Information concerning the response of two traits, plant height and grain yield, was obtained for these populations at three diverse experimental sites. Estimates of gene action were determined by calculating heterosis, inbreeding depression, narrow-sense heritability, and combining ability values. Results obtained suggested that selections for plant height could be effectively made as early as the F₂ generation since this trait was largely controlled by additive gene action. Grain yield was found to be influenced significantly by non-additive gene action; however most populations were stabilized by the F₃ generations where high yielding populations could be identified and effective selection practiced. Results from this study suggested that genotype x environment interaction could influence early generation selection by masking the additive genetic effects. Under very favorable growing conditions the non-additive gene action x environment interaction dominated the additive effects for grain yield and to a lesser degree plant height. However, under dry land conditions both non-additive and additive genetic effects were masked by the environment and could not be expressed fully for grain yield. It is evident that for simply inherited traits like plant height, selection in the F₂ generation must be practiced under an environment where there is full expression for that trait, while selection for grain yield must be conducted under the same environments where the potential varieties are to be grown. The use of Average Combining Ability as an indirect method to evaluate the contribution of parents to performance of the progency was found to be valid by the predicted results obtained for the simply inherited trait plant height. This method could be used with some confidence to estimate contribution of parents for a complex trait like grain yield. Two parents were identified as the best combiners for grain yield. This confirms what was learned about them after fifteen years of actual experience indicating the importance of a technique whereby the breeder can determine in a very short period of time which parents to cross and then concentrate his efforts within the more promising segregating populations.