Comparative performance of δ¹³C, ion accumulation and agronomic parameters for phenotyping durum wheat genotypes under various irrigation water salinities

The use of efficient selection traits for screening under contrasting irrigation water salinity is a challenge for breeders. To identify patterns, grain yield (GY) and yield components (kernels m−2, thousand kernels weight), growth traits (plant height, biomass), flag leaf ion accumulation (Na+ and K+), carbon isotope composition (δ13Cgrain) and nitrogen concentration (Ngrain) of grains were assessed on 25 durum wheat genotypes (G) in two consecutive growing seasons (2010 and 2011), in three semi-arid locations in Tunisia. Each location differed in their irrigation water salinity as measured by electrical conductivity: Echbika (S1, 6 dS m−1), Barrouta (S2, 12 dS m−1) and Sidi Bouzid (S3, 18 dS m−1). GY was shown to be negatively correlated to Ngrain as well as to δ13Cgrain. This is confirmed by a multiple linear regression analysis that showed that both δ13Cgrain and Ngrain were the major determinant components for GY variability under S3. A high genotypic variability was observed and the improved genotype Maali exhibited the most stable GY under the three irrigation water salinities and the two cropping seasons. Maali showed the lowest δ13Cgrain. This indicates that tolerance in durum wheat is likely to be correlated to the ability of maintaining a high stomatal conductance. According to our data suggests δ13Cgrain can be used for an efficient screening of salt tolerant durum wheat. Under our experimental conditions, Ngrain was shown to be highly correlated to δ13Cgrain and can therefore be easier-to-use trait to assess the tolerance to salinity.