- مبلغ: ۸۶,۰۰۰ تومان
- مبلغ: ۹۱,۰۰۰ تومان
Reliable selection of families with increased grain yield is difficult in breeding programs targeting water-limited environments. Carbon isotope discrimination () is negatively correlated with transpiration efficiency, and low is being used for indirect selection of high wheat yield in rainfed environments. Yet little is known of genetic control and opportunities for improving selection efficiency of in wheat. Half-diallel and generation means mating designs were undertaken to provide estimates of the size and nature of gene action for in a range of wheat genotypes varying for this trait. Significant (P < 0.01) differences were observed for leaf tissue among parents (19.3 to 20.7‰) and F1 progeny (19.4 to 20.9‰) in the half-diallel. General (GCA) and specific combining ability (SCA) effects were significant (P < 0.05), while Baker’s GCA/SCA variance ratio of 0.89 was close to unity, indicating largely additive gene effects. GCA effects varied from −0.38 to + 0.34‰ for low and high genotypes ‘Quarrion’ and ‘Gutha’, respectively. GCA effects and parental means were strongly correlated (r = 0.95, P < 0.01) while directional dominance and epistasis contributed to small, non-additive gene action for . Smaller in F1 progeny was associated with accumulation of recessive alleles from the low parent. Narrow-sense heritability was high (0.86) on a single-plant basis. Generation means analysis was undertaken on crosses between low genotype Quarrion and two higher genotypes ‘Genaro M81’ and ‘Hartog’. The F1, F2 and midparent means were not statistically (P > 0.05) different, whereas backcrossing significantly changed toward the mean of the recurrent parent. Gene action was largely additive with evidence for additive × additive epistasis in one cross. Narrow-sense heritabilities were moderate in size (0.29 to 0.43) on a single-plant basis. Genetic gain for in wheat should be readily achieved in selection among inbred or partially inbred families during the later stages of population development.