Persistence and productivity of Trifolium ambiguum M. Bieb. (Caucasian clover) in a high altitude region of south-eastern Australia

Abstract

The persistence and productivity of 12 lines of Trifolium ambiguum M. Bieb., encompassing three ploidy groups, and one line of T. montanum subsp. hurnboldtianum were compared in an elevated environment (1150 m) over a 4-year period with one cultivar each of T. repens L. and T. pratense L. Trifolium ambiguum was found to be well adapted to the cold winters and dry summers, all lines persisting throughout the experimental period, whereas the T. repens and T. pratense cultivars disappeared by the fourth year. The T. arnbiguum lines 'Monaro' and 'Kirovakan' (both hexaploid) and 'Alpine' and Forest (diploids) had the highest dry matter production. The control cultivars of T. repens and T. pratense outyielded T. ambiguum in the first year but were substantially less productive in later years as their density declined. T. montanum persisted but produced less dry matter than T. ambiguum and did not produce rhizomes or daughter plants. Ploidy of T. ambiguum was found to affect the date of flowering, persistence, leaflet shape and leaflet area. Productivity was not closely related to ploidy; however, the two most productive lines were hexaploids. All the T. ambiguum lines remained well nodulated over the 4 years, but the diploids had higher leaf nitrogen contents than the other two groups (3.4% vs. 2.5 and 2.4% N). The number of daughter plants produced was positively correlated (r=0.84) with rhizome length, which varied between lines but was not influenced by ploidy. Two bred lines, 'Alpine' (diploid) and 'Monaro' (hexaploid) exhibited superior vigour and spreading ability and warrant further evaluation as possible pasture legumes.