Inheritance, generation prediction, and interrelationships among quantitative characteristics in four Triticum aestivum L. em Thell cultivars

The soft red winter wheat cultivars 'Arthur', 'Sullivan', 'Blueboy', and 'Pioneer S76', and their F₁, reciprocal F₁, F₂, reciprocal F₂, and backcrosses of the F₁ to the parents were grown in a randomized complete block design at three locations. A genetic model was developed to estimate additive, dominance, first-order epistatic, and reciprocal effects for grain yield, primary yield components, and several morphological characteristics. For all characteristics the gene action was not all additive, and dominance and/or epistatic types of gene action were also detected.

Prediction equations were developed to use the genetic parameters to estimate parental, F₁, reciprocal F₁, F_∞, reciprocal _∞, and backcross selfed to homozygosity (BCS_∞) values of all characteristics.

Compared to the midparent values, the F₁ hybrids tended to have a higher grain yield, weight per seed, spikes per square meter, test weight, plant height, seedling and spring vigor; a later maturity date, and a longer grain filling period.

Grain yield was positively correlated with a longer grain filling period, an increased resistance to powdery mildew, larger spike and top internode surface area, and increased seedling and spring vigor.

Compensation between the primary yield components, seeds per square meter and weight per seed, was observed. The most favorable compensation pattern in terras of high grain yield was the one that produced the highest number of seeds per square meter. This type of pattern was exhibited by the highest yielding F₁ crosses Blueboy x Pioneer S76 and reciprocal.

Such a favorable compensation pattern indicates that sink size during grain filling as measured by the number of seeds per square meter may be a favorable selection criteria.

Results indicate that selection for the improvement of wheat grain yield should be based on increasing the sink size to ensure full utilization of available assimilate sources and on increasing the source capacity especially during the grain filling period.

Using the predicted values of the F_∞ and BCS_∞ generation and on the basis of sink size and source capacity, the advanced generations of the Arthur x Pioneer S76 or reciprocal F₁ crosses, or the Arthur x Pioneer S76 or reciprocal backcrosses to either parent were selected as potentially favorable populations for the development of new cultivars.