Heritability estimates of spaced-plant traits in three perennial ryegrass (Lolium perenne L.) cultivars

Abstract

Seed yield in perennial ryegrass is low and unpredictable. Spaced-plant traits suitable for indirect selection for total seed yield in drilled plots would be very useful. The objectives of this investigation were to evaluate genetic variation for seed yield components and other traits among clones from three perennial ryegrass cultivars differing in seed yield and their open-pollinated progenies. Per cultivar, a random set of 50 genotypes was cloned and on each genotype seed was generated by open pollination. Clonal ramets of the parents were observed for 17 traits in 1986 at two locations. In 1987 and 1988, parents and progenies were observed as single plants in a randomized complete block design with two replications. There was little cultivar-environment interaction for most traits. The parents differed significantly for almost all traits. Half-sib (HS) families differed for only three to five traits. Broad-sense heritabilities (h2b), based on variance components of the parents, were moderate to high; earliness had the highest hb2. Narrow-sense heritabilities (h2n), based on variance components among HS-families, were low to moderate and mostly not significant; for most traits h2n estimates varied between years and cultivars. Flag leaf width and date of first anthesis showed the highest h2n. Narrow-sense heritability estimates from parent-offspring regressions (h2nPO) ranged from non-significant to high, depending on year and cultivar; they were generally higher than the corresponding h2n estimates. Generally, h2nPO was highest for earliness, flag leaf width, ear length and the number of spikelets per ear. Breeding methods that capitalize on additive genetic variance, such as mass selection, should result in improvement for these traits.