CHARACTERIZATION OF NATURALIZED STRAINS OF TRIFOLIUM-SUBTERRANEUM VARBRACHYCALYCINUM CV CLARE IN NORTHERN NEW-SOUTH-WALES

Burrs were collected from paddocks on 3 properties in northern New Sou th Wales where the age of the Trifolium subterraneum var. brachycalyci num cv. Clare swards varied from 19 to 28 years. At 1 site burrs were also sampled from swards sown 2 and 10 years previously. Twenty seedli ngs from these burrs and 20 plants of certified cv. Clare were grown a s spaced plants in a nursery. These were assessed for vegetative and f loral characters, flowering time, number of seeds per burr, seed weigh t, and percentage hardseed after storage at 25/25-degrees-C for 6 mont hs and 25/45-degrees-C for a further 6 months. For most plants the mea n number of days from sowing to first flower was similar to that of Cl are. Compared with the naturalised strains, Clare had the lowest (P<0. 05) mean number of seeds per burr: about 25% below the mean of the str ains (2.7 seeds per burr). While the lowest mean seed weights of the s trains were not significantly different from those of Clare, the seed weights of plants from 3 sites were higher (P<0.05) than those of Clar e. After storage for either 6 or 12 months, hardseed levels were also lowest (P<0.05) for Clare. Plants from the 2-year-old sward had the sa me median number of seeds per burr (2.0) as Clare. As sward age increa sed, the median number of seeds per burr increased to 2.8. Hardseed pe rcentages were lowest for plants of Clare and for those from the 2-yea r-old sward after 6 months, and for Clare after 12 months. These studi es indicated the presence of divergent strains in old swards of Clare in a summer rainfall environment. Natural selection among variability within Clare is the most likely reason for the development of these st rains in an environment marginal for the long-term persistence of this soft-seeded cultivar. Although strains had the same vegetative and fl oral markings as Clare, differences in ecologically important characte rs such as number of seeds per burr, seed weight, and hardseededness m ay result in plants that are better adapted to the environment in whic h they evolved. From these studies 23 plants of T. subterraneum var. b rachycalycinum were selected for further evaluation.