Genetic variation in arctic populations of timothy (Phleum pratense L.): II. Phenotypic stability of seed production

Abstract

Rognli, O.A. 1987. Genetic variation in arctic populations of timothy (Phleum pratense L.). II. Phenotypic stability of seed production. —Hereditas 207: 75–94. Lund, Sweden. ISSN 0018–0661. Received November 10, 1986 The present paper is concerned with phenotypic stability of seed production of four North Norwegian timothy populations. In clonal experiments conducted at 69°N. 63.S°N, and 60°N latitude in Norway. the genotype × location interaction was the most important interaction effect. Individual genotypic stability reactions were studied by ecovalence (or stability variance), and mean rank difference. Pattern analysis was used to investigate the form of the individual genotypic reactions. Large differences in stability were found among genotypes. Only 11.5% of the genotypes contributed significantly to the interaction sum of squares. Elimination of very unstable genotypes could therefore be a strategy of population improvement. rather than selecting stable genotypes. Correlation between ecovalence and mean rank difference depended upon the yield level, being low for high yielding genotypes. Ecovalence and average seed yield were positively correlated, but high yielding and stable genotypes could be found. Stability rankings were sufficiently consistent over years to justify a single year test of stability. Pattern analysis (FASTCLUS) was performed on the individual genotypic within-location residuals. Structure of cluster groups revealed specific genotypic and population adaptations, assessed according to the ecovalence concept. Canonical discriminant analysis (CANDISC) was used to aid visual interpretation of group differences.