Analysis of variability, heritability, and genetic advance in seed yield and related traits of orchardgrass (Dactylis glomerata L.) populations

Orchardgrass (Dactylis glomerata L.) genotypes from different natural sources in the Eastern Anatolian Region of Turkey were clonally evaluated to study genetic variation and the relationships between seed yield and its components using a randomized complete block design. Results showed very significant genotypic variances among genotypes for all traits, including agronomic (seed, dry matter, and biological yields), morphological (plant height; panicle length; crown diameter; numbers of fertile, sterile, and total stems; and stem intensity), physiological (percent fertile stems, harvest and fertility indexes), and phenological (heading and anthesis dates) traits, as well as genotype x year interaction variances. Genotypic components were the main contributor to phenotypic variation of all traits (except physiologic traits, stem intensity, and number of sterile stems), resulting in high broad-sense heritability (>50%). Agromorphological and physiological traits had greater phenotypic (PCV), genotypic (GCV), and environmental coefficients of variation, while these were lower for phenological traits. After the phenological traits, plant height, crown diameter, and panicle length were the least variable traits, while stem intensity and fertility index were highly variable. Heritability estimates increased as GCV values approached PCV values. Expected genetic gain greatly increased as heritability estimates and PCV both increased, rather than heritability values alone. The first 5 principle components accounted for 84.90% of total variance. All agromorphological traits (except number of sterile stems) and fertile stem percentage were primary sources of variation of the PCI axis, while harvest and fertility indexes were for PC2. Out of the 4 clusters, genotypes in cluster 4 of higher seed yield were faster in aboveground biomass accumulation. They also had the best agromorphological traits coupled with early maturity. Seed yield greatly increased as aerial biomass increased without any change in harvest index, but there was a significant decrease in fertility index. It was concluded that selection for dry matter yield could result in a simultaneous increase in seed yield.