Polycross Genetic Analysis of Forage Yield and Related Traits in Dactylis glomerata

Orchardgrass (Dactylis glomerata L.) is a long‐lived perennial forage grass and one of the main perennial grasses that naturally grow in temperate pasture and rangelands in northern and western Iran. This study was conducted to increase knowledge about the genetic basis of agro‐morphological traits in orchardgrass, which may help further improvement of this species. Half‐sib families derived from a polycross of 25 parental genotypes were evaluated during 2 yr, and 11 agro‐morphological traits together with two quality traits were measured. Families were significantly different for all the traits measured. Significant differences were also observed between the 2 yr of evaluation for all the traits except for mean percent of dry matter and panicle length. Narrow‐sense heritability ranged from 0.12 (number of fertile shoot) to 0.79 (mean percent of dry matter). The estimate of narrow‐sense heritability for the most economically important trait (total dry matter yield) was relatively low (0.17 to 0.30), showing that both additive and non‐additive gene effects played a role in the genetic control of this trait. In addition to a weak phenotypic correlation, total dry matter yield had a high genetic correlation with plant height and number of fertile shoots. No significant phenotypic correlation was observed between forage yield and crude protein, though a negative genetic correlation was evident. According to the results of heritability estimations and correlation between the traits, indirect selection for dry matter yield would be possible through selection for plant height.