Genetic variation for seed yield in Caucasian clover

Abstract

Caucasian clover (Trifolium ambiguum M.Bieb) representing a range of 2x (diploid), 4x (tetraploid) and 6x (hexaploid) material together with ecotypes from the Caucasus region were established in a trial at Lincoln, Canterbury (43"38'S) in October 1993. Measurements were made from individual plants during summer 1994-95. The diploids were earliest to flower followed by the tetraploids and finally the hexaploids, which reached peak flowering in mid December. The hexaploids produced the most florets per inflorescence (115, 101, 96 from 6x, 4x, 2x respectively), the most inflorescences per plant (162, 101, 129 from 6x, 4x, 2x) and the highest seed yield(g) per plant (26, 9, 11 from 6x, 4x, 2x). There was large variation for all the seed production components within the three ploidy levels. For example, the hexaploid cultivar Endura consisted of plants that varied from 25-510 inflorescences per plant. The seed yield components of plants were associated with active spring growth. There was evidence of wide spreading plants producing lower numbers of -inflorescences-per-m2-andseed-yield-per-unit-area; The hexaploid material produced the greatest potential seed yields (1330,685, 1000 kg/ha from 6x, 4x, 2x respectively). There was a 5-fold difference between the lowest-yielding 6x cultivar, Prairie (570 kg/ha), and the highest-yielding KZ2 (2720 kg/ha), a selection from Monaro. Major gains are possible through selection but it is important to select for improved seed yield per plant (not just flowers) and to maintain a wide genetic base. Commercial crops yield approximately half that attained from research plots, whtch suggests a commercial yield of 900 kg/ha is possible from Endura. This compares favourably with other legumes but requires development of crop management practices that ensure consistently high seed yields. Keywords: Caucasian clover, genetic variation, Kura clover, seed components, seed yield, TrifIium ambiguum