N- and S-fertiliser effects on grain composition, industrial quality and end-use in durum wheat

Grain composition, industrial and end-use qualities were analysed in four cultivars of durum wheat subjected to four different nitrogen (N) and sulphur (S) fertiliser treatments in field trials conducted in two successive years in soils not deficient in S:N1S1 (both N and S applied), N1S0 (N application only), N0S1 (S application only) and N0S0 (no fertiliser application). Characters analysed were grain protein content (%P), grain sulphur content (%S), SDS-sedimentation (SDSS), Farinograph energy level (EL), Farinograph tolerance (TOL) and viscoelasticity of cooked pasta (VISCO). Important differences were found between the results from the 2 years, where all parameters showed superior performance in the year of lower rainfall and higher mean temperatures in the final phase of the crop cycle. Significant differences were observed between fertilisers and between cultivars for all parameters. In spite of the non-limiting conditions for S-availability, S-fertiliser application caused significant differences in grain %P, SDSS and N:S ratio, although it did not generate changes in rheological parameters and end-use; these latter parameters were only influenced by N-fertiliser application. For SDSS, the fertiliser treatment N1S1 was generally the best treatment. SDSS was, in general, strongly correlated with the rheological parameter EL and the end-use parameter VISCO, verifying the potential utility of this small-scale test in early generation selection during breeding. However, one cultivar, Chagual, with a very distinct glutenin and gliadin allelic composition compared to the other three cultivars, showed markedly inferior performance for SDSS and EL, yet acceptable performance for VISCO. Given that previous studies have shown that this cultivar shows superior grain yield compared to the other three cultivars, this sounds a cautionary note for the use of SDSS in breeding: selection based upon SDSS performance would have meant this valuable line would have been eliminated from consideration early in the breeding programme.