Agronomic variation in Centrosema virginianum in relation to its use as a sub-tropical pasture plant

Abstract

Nineteen accessions of Centrosema virginianum were grown in replicated short rows at four sites in south-eastern Queensland and one site on the wet tropical north coast, and some of their agronomic characteristics were observed and compared with those of Macroptilium atropurpureum cv. Siratro. Three sites were abandoned when the accessions grew poorly or died during the winter, although Siratro survived and grew vigorously. At the remaining sub-tropical sites the accessions persisted under weed-free conditions where seedling regeneration more than compensated for plant losses during the winter. In the second season at these sites, rows were cut for herbage yield assessment either every six weeks during the growing season or once at the end of the season. Treatments were continued for a third season at one site. In most respects Siratro was superior to all C. virginianum accessions. The accessions differed considerably in herbage yield, winter survival, seed production, seedling regeneration and leafiness, and differed slightly in leaf and stem digestibility. Many accessions flowered for very long periods in south-eastern Queensland, in contrast to the markedly bimodal flowering pattern of Siratro, but peak flowering dates of the accessions in the autumn differed by up to three months. Both C. virginianum and Siratro showed a reduction in percentage pod set during the middle of the growing season. Variation between accessions is discussed in relation to potential improvement of C. virginianum by plant breeding.