Patterns of Seed Softening in Subterranean Clover in a Cool, Temperate Environment

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AsbtractsEnvironmental conditions affect seed softening patterns of annual legumes. These patterns have not been well established for cool, temperate environments. This work examines the effect of genotype and of growing and softening environments on the short‐term loss of dormancy in subterranean clover (Trifolium subterraneum L.) during the summer and early autumn. Burrs of six cultivars and one accession of subterranean clover that varied widely in maturity and hardseed level were placed to soften on the soil surface, over the summerautumn period, under two contrasting environments in western Victoria, Australia: Hamilton and Telopea Downs. There were significant differences (P < 0.05) in the rate of hardseed breakdown both among cultivars and at the two locations. At the cooler site, Hamilton, the levels of residual hardseed after the summer averaged 75% (over all cultivars and growing sites), compared with 66% at Telopea Downs. There was no interaction between cultivar and location of softening. At the end of the period of field exposure the ranking from lowest to highest residual hardseed was ‘Enfield’ < ‘Leura’ = ‘Gosse’ < ‘Dalkeith’ < ‘York’ = SE008 = ‘Nungarin’. High levels of embryo dormancy in Leura indicate that this cultivar has the capacity for delayed germination via embryo dormancy. The results suggest that in cool temperate environments high seed banks of subterranean clover can be achieved due to a lower percentage of seed softening, which in turn means a potentially greater long‐term persistence of subterranean clover and the possibility of conducting 1:1 pasture‐crop rotations in a rainfall zone where consistently high grain yields may be expected.