Genetic variability and relationships for seed yield and its components in Chinese Cynodon accessions

Cynodon dactylon (L.) Pers. is indigenous to and widely distributed in China but no information is available on the genetic variation of the native germplasm for seed yield and related traits. Accordingly, we conducted a field experiment in 2002 and 2003 at Stillwater, OK, to characterize the genetic variability among 114 C. dactylon accessions from China for seed yield, its components, and their interrelationships. The field plot design for the experiment was a randomized complete block with three replications. Significant differences (P < 0.01) existed for seed yield, inflorescence prolificacy, seed set percentage, seed number inflorescence−1, raceme number inflorescence−1, and raceme length inflorescence−1 among the accessions. Genetic variation for seed yield and its components was large in tetraploid (104) and low in pentaploid (3) and hexaploid (7) accessions. Significant (P < 0.01) year and accession × year interaction effects for seed yield, inflorescence prolificacy, seed set percentage, and seed number inflorescence−1, and large magnitudes of variances for year and accession × year interactions indicated substantial environmental influences on those traits. Phenotypic correlations of seed yield with inflorescence prolificacy, seed set percentage, and seed number inflorescence−1 were substantial and positive (P < 0.01), while correlations of seed yield with raceme number and raceme length inflorescence−1 were negligible. Path coefficient analyses indicated that inflorescence prolificacy and seed set percentage had the highest direct effects on seed yield. Accordingly, indirect selection for these traits should increase seed yield. The enormous amount of genetic variability among the 114 accessions for seed yield and related components indicated that C. dactylon germplasm from China should be a valuable resource for the breeding of seed-propagated bermudagrass cultivars.