Differential sulfur efficiency in canola genotypes at vegetative and grain maturity stage

The breeding process can be facilitated if sulfur efficiency in canola at maturity can be reliably determined by screening germplasm in the vegetative stage. Twelve canola genotypes chosen from a preliminary screening study with either high or low S efficiency indices were tested for consistency in S efficiency between vegetative stage and maturity. Plants were grown under glasshouse conditions using low or adequate S supply. The criteria for efficiency assessment at the vegetative stage were: shoot biomass at deficient S supply, relative biomass production, and S utilisation efficiency. Considering these three criteria of S efficiency, only one canola genotype was classified as efficient ( Surpass 402 CL). Three genotypes were classified as inefficient under two criteria: genotypes IB 1337 and Surpass 300 TT for relative biomass production at low S supply and S-utilisation efficiency, and IB 1368 for biomass production and relative biomass production. In addition to seed yield, relative seed yield, and S utilisation, four additional efficiency criteria were used for the maturity stage: harvest index, S harvest index, and oil and protein concentrations in the seed. For all efficiency criteria used, highly significant genotypic differences existed. IB 1368 was ranked efficient under all criteria. Genotypes Surpass 402 CL and 46C74 were ranked inefficient at maturity but efficient at the vegetative stage. In conclusion, screening canola germplasm for S efficiency requires an assessment of the efficiency at maturity rather than during vegetative growth.