The contribution of seed survival to yield in new Australian cultivars of oil-seed rape (Brassica napus)

Abstract
SUMMARY: A series of experiments in Tasmania examined the growth, development, yield and components of yield of new Australian oil-seed rape cultivars from Victoria and Western Australia. The highest yields obtained were around 5·5 t seed/ha, from an autumn sowing with supplementary irrigation. Spring sowings with irrigation or autumn sowings without produced up to 4 t/ha. The Victorian lines with Japanese parentage clearly outyielded the Western Australian cultivars or Midas, a widely grown Canadian cultivar. When autumn sown, the Victorian lines grew more rapidly at low temperature, which under conditions of later stress contributed to a high yield relative to the other cultivars. However, the most consistent feature from both autumn and spring sowing was high rates of seed survival, up to near the potential number of around 30 per pod, giving very large numbers of seeds per m2. While individual seeds in the Victorian lines, particularly Marnoo, were smaller than in Midas, oil content remained high except under extreme stress in the later stages of seed development.