Genetic variation in arctic populations of timothy( Phleum pratense L.): I. Seed production characters

R ognli , O. A. 1987. Genetic variation in Arctic populations of timothy ( Phleum prafense L.). I. Seed production characters. — Hereditus 107: 27–54. Lund, Sweden. ISSN 0018–0661. Received October 10, 1986 Genotypic variation for seed production characters within four North Norwegian timothy populations (69–70°N) was assessed over two years in replicated clonal experiments at 60°N. 63.5°N and 69°N latitude in Norway. Seed yield range was 1.2–147.6 gramlplot of 4 clonal ramets. Genotypic and genotype × environment (GE) interacticn variances were highly significant for seed yield. plant height, culm score, and plant size, while variation in earliness was essentially genotypic. Genotypic variances were homogeneous among populations for all characters, while GE‐interactions were highly heterogeneous. Besides genotypic and error variances, genotype × location interactions were most important. Seed yield heritability (h 2 b ) was 0.64. Genotypic variability and expected selection response were largest for seed yield. Genotypic and environmental correlations between seed yield and other characters, except ear emergence, were consistently positive, indicating pleiotropy. Correlations involving ear emergence varied substantially among populations and locations, indicating linkage and/or coadaptation. Population differences in correlation pattern are discussed in the context of genetic origin, local adaptation, and agricultural management. Genotypic and environmental variances were largest at the intermediate, high yielding location. Genotypic coefficients of variation (GCV%) were highest at the southern and arctic location. Genotypic correlations showed that the arctic and intermediate location gave the most similar genotypic expressions of the character seed yield. Seed production at 60“N was low, indicating physiological constraints. Adaptation to hay‐production at higher latitudes results in high seed production potential. Possible effects for breeding high latitude timothy are discussed.