Heritability of selected forage quality characters in Panicum coloratum L. under varying environmental conditions

Abstract

Eighteen half-sib families of kleingrass, Panicum coloratum L., were evaluated in each of three environmental periods (May, July, and September) in 1982. These families were evaluated within each period for tiller height, percent leaves, number of leaves per tiller, yield per tiller, and tiller in vitro digestible organic matter (IVDOM). In addition, estimates of broad and narrow sense heritability were obtained for each of the preceding characters. Evaluation of family means indicated definite seasonal trends for all characteristics. Tiller height, number of leaves per tiller and yield per tiller all declined with season, having their maximal values in May and minimal values in September. These reductions were apparently the result of soil moisture stress in July and September. Percent leaves and tiller IVDOM had maximal values in May and September and minimal values in July. The decline in digestibility of tillers in July was not due to an increased stage of ontogenetic development since tillers harvested at early head emergence also showed the same decline in IVDOM during July. The July decline in digestibility was apparently due to a decreased digestibility of cell wall components. Heritability estimates for the measured characters were greatly affected by season, and more importantly by environmental covariances within a season. When environmental covariances were reduced through the regression of progeny from one replication on parental plants from another replication, all characteristics had maximal heritabilities at the July harvest.Significant replication x family interactions for all characteristics measured indicated real problems in the evaluation of vegetative characteristics in forage breeding nurseries. These significant interactions probably resulted from the small family size utilized in this study. Future selection programs with warm season grasses should return to the use of larger families to reduce replication x family interactions or rely on more sophisticated experimental designs. The potential to make progress in selecting for improved in vitro digestibility, increased tiller height and number of leaves per tiller in this population appears small. However, previous selection for improved seed weight has not negatively altered the in vitro digestibility within this population.