Diallel Analysis of Grain Yield and Some Important Agronomic Traits in Bread Wheat

Wheat is one of the most important crops in the world that plays a key role in ensuring food security. In wheat breeding programs, selection of genotypes with desirable agronomic traits and high yield potential have always been the goal of plant breeders. Increasing the selection efficiency for grain yield depends on genetic knowledge from morphological traits and the effect of these traits on grain yield.

In order to estimate genetic parameters and general and specific combining abilities, six bread wheat cultivars including Falat, Tajan, Bolani, Ehsan, Morvarid and Catbird were planted in a crossing block and direct and reciprocal crosses were performed among the six cultivars to produce F1 generation. The progenies of the crosses with their parents were evaluated based on randomized complete block design (RCBD) with three replications in Gorgan agricultural research station in 2020-2021 cropping season.

Analysis of variance of Griffing's diallel method showed a statistically significant difference between genotypes in all studied traits. Mean squares of general and specific combining abilities were statistically significant in most traits. Reciprocal, maternal and non-maternal effects were significant for the number of days to heading, grain yield, and biological yield. In grain yield and biological yield, Ehsan cultivar had the highest general combining ability and was identified as a suitable parent for the genetic improvement of these traits. The Catbird×Bolani hybrid had the highest specific combining ability in plant height, peduncle length, biological yield, grain yield and harvest index, it was determined as the best hybrid in genetic improvement of desirable agronomic traits with high specific combining ability in yield and yield components. The ratio of additive variance from genetic variance for plant height, number of days to heading and peduncle length was greater than dominance variance. The highest degree of dominance was related to the number of spikelets per spike, 100-seed weight, grain yield and biological yield, respectively.

The results of this study showed that in the progenies of the crosses, genetic improvement can be done in plant height, number of days to heading and peduncle length in the initial generations, but for other traits including grain yield and its components, selection should be postponed to more advanced generations.