RESPONSE TO SELECTION FOR STEM LENGTH IN RED CLOVER EVALUATED AT WIDE AND NARROW SPACINGS

Abstract

Six cycles of phenotypic recurrent selection for stem length were conducted in a 91-cm-spaced planted population of red clover (Trifolium pratense L.) as a means of increasing herbage yield. The objectives of this investigation were (1) to compare the effectiveness of selection for stem length tested in transplants at wide (91 cm) and narrow (7 cm) spacings, and in row seedings and (2) to determine the effect of selection for stem length on herbage yield. Response to selection for stem length was obtained under all plantings; however, greater gains were observed at the wide transplant spacing (3.3 cm∙cycle−1) compared to the narrow transplant spacing (0.7 cm∙cycle−1) and row seeding (0.8 cm∙cycle−1). Densely spaced transplants gave performance similar to row seedings and may be of value to forage crop breeders in situations where yield or quality assessment is desired but seed supplies are insufficient for the establishment of seeded plots, such as in the early stages of breeding programs. Selection for stem length was effective in increasing herbage yield at first harvest but was associated with reduced persistance, decreased regrowth yields, and increased partitioning of dry matter towards the shoot rather than the root during seedling development. Selection for stem length in the regrowth or in the second year, rather than in the primary (seedling) growth, might have avoided the declines in persistence and regrowth yields.Key words: Trifolium pratense L., red clover, recurrent selection, stem length, density, herbage yield