PATTERN-ANALYSIS OF THE DIVERSITY OF MORPHOLOGICAL PLANT ATTRIBUTES AND HERBAGE YIELD IN A WORLD COLLECTION OF WHITE CLOVER (TRIFOLIUM-REPENS L) GERMPLASM CHARACTERIZED IN A SUMMER MOISTURE STRESS ENVIRONMENT OF AUSTRALIA

Information on the variation available for different plant attributes has enabled germplasm collections to be effectively utilised in plant breeding. A world sourced collection of white clover germplasm has bee n developed at the White Clover Resource Centre at Glen Innes, New Sou th Wales. This collection of 439 accessions was characterised under fi eld conditions as a preliminary study of the genotypic variation for m orphological attributes; stolen density, stolen branching, number of n odes, number of rooted nodes, stolen thickness, internode length, leaf length, plant height and plant spread, together with seasonal herbage yield. Characterisation was conducted on different batches of germpla sm (subsets of accessions taken from the complete collection) over a p eriod of five years. Inclusion of two check cultivars, Haifa and Huia, in each batch enabled adjustment of the characterisation data for yea r effects and attribute-by-year interaction effects. The component of variance for seasonal herbage yield among batches was large relative t o that for accessions. Accession-by-experiment and accession-by-season interactions for herbage yield were not detected. Accession mean repe atability for herbage yield across seasons was intermediate (0.453). T he components of genotypic variance among accessions for all attribute s, except plant height, were larger than their respective standard err ors. The estimates of accession mean repeatability for the attributes ranged from low (0.277 for plant height) to intermediate (0.544 for in ternode length). Multivariate techniques of clustering and ordination were used to investigate the diversity present among the accessions in the co;lection. Both cluster analysis and principal component analysi s suggested that seven groups of accessions existed. It was also propo sed from the pattern analysis results that accessions from a group cha racterised by large leaves, tall plants and thick stolons could be cro ssed with accessions from a group that had above average stolen densit y and stolen branching. This material could produce breeding populatio ns to be used in recurrent selection for the development of white clov er cultivars for dryland summer moisture stress environments in Austra lia. The germplasm collection was also found to be deficient in genoty pes with high stolen density, high number of branches, high number of rooted nodes and large leaves. This warrants addition of new germplasm accessions possessing these characteristics to the present germplasm collection.