EFFECTS OF SEED MANGANESE CONCENTRATION ON LUPIN EMERGENCE

Seed of narrow-leafed lupin (Lupinus angustifolius L.) produced in Western Australia often has low manganese (Mn) concentration because of low Mn availability in the soil during grain filling. A major problem of lupin production is poor seedling establishment. We tested the hypothesis that low Mn concentration in lupin seeds decreases emergence. The experiment was a factorial design comparing emergence of lupins (cv.'Gungurru') grown under glasshouse conditions from seed with 2 different internal Mn concentrations (7 or 35 mg Mn kg(-1) DW) and with 2 external Mn fertiliser treatments (O or 10 mg MnSO4.H2O kg(-1) soil). There were no visible differences between the seeds. Emergence was monitored and plants were harvested 17 days after sowing. Emergence was approximately 60% in all pots sown with low Mn compared to 100% in pots sown with high Mn seed. Application of Mn did not increase the final emergence of low Mn seed. Seed viability was assessed by staining with tetrazolium chloride, a common test used in seed testing laboratories. All high Mn seed were viable while 34% of low Mn seed were completely or partly unstained and therefore were non-viable. We have shown that low Mn supply during seed filling may lead to production of non-viable seed that cannot be visually distinguished from viable seed.