Nitrogen and sulphur: uptake, transport and remobilisation in canola genotypes at vegetative stage and at maturity

[Truncated abstract] Canola (Brassica napus) is the major oilseed crop in Western Australia. The areas sown to canola vary between 600,000 and 700,000 hectares per season, with the potential for an increase by up to half a million hectares per season, with the seed production of up to million tonnes per year. Canola production in Western Australia is constrained by poor soil fertility. In Western Australia, soils are among the most ancient and therefore heavily leached in the world, and have low availability of P, N and S. Identification and breeding of genotypes that could use soil N and S as well as fertilizer N and S more efficiently than standard genotypes would be a sustainable long-term approach to dealing with (i) high N and S requirements in canola, and (ii) low N and S availability in Western Australian soils. In the study presented here, modern Australian canola germplasm was screened for N and S efficiency during the vegetative stage. Group of genotypes either with high or low N or S efficiency in the preliminary study were then screened for N or S efficiency at maturity. The mechanisms involved in transport and remobilization of N- or S- containing compounds were investigated via analyses of the xylem and phloem analyses following soil and leaf labeling with stable isotopes 15N and 34S. Nitrogen and S efficiency in Australian canola germplasm was successfully differentiated in the vegetative growth stage in 84 canola genotypes. Nitrogen and S efficiency ranking among six N- or S-efficient and six N- and S-inefficient from preliminary screening study was verified in the additional experiment during the vegetative stage.