Relationships between ash content, carbon isotope discrimination and yield in durum wheat

Abstract

The relationships between ash content, carbon isotope discrimination and yield were studied in durum wheat (Triticum durum Desf.) grown in a Mediterranean region (north-western Syria) under three different water regimes (hereafter referred to as environments). Ash content (on dry mass basis) was measured in the flag leaf about 3 weeks after anthesis (leaf ash) and in mature kernels (kernel ash), whereas Δ was analysed in the penultimate leaf at heading (leaf Δ) and in mature kernels (kernel Δ). Leaf Δ was weakly or not related with the other parameters. Leaf ash correlated positively with kernel Δ (P≤0.001), even in the driest environment, which gave a mean yield of 1.5 t ha^-1. For the four parameters, correlations with yield remained significant (P≤0.001) after correcting for days to heading. All the parameters showed a higher broad-sense heritability than yield. The parameter that showed the best genetic correlation with grain yield was kernel ash (r²= 0.88), followed by kernel Δ (r² = 0.69) and leaf ash (r² = 0.64), whereas leaf Δ (r² = 0.26) was the least correlated parameter. Except for kernel ash, these parameters always correlated positively with grain yield. The negative relationships of kernel ash (on dry mass basis) with yield and all the other parameters may be attributable to the finding that kernel ash was higher in those genotypes more affected by drought during grain filling. Thus, kernel ash was negatively related (P≤0.001) with total kernel mass per spike. Prediction of grain yield through multiple linear regression suggests that kernel ash can be used as complementary criterion to either kernel Δ or leaf ash.