Adaptation à la sécheresse chez le blé dur (Triticum durumDesf.) Contribution de quelques solutés à l'ajustement osmotique.

Abstract

Various morpho-physiological, biochemical and phonological features related to water stress tolerance (leaf area, osmotic adjustment, osmotic accumulation, root traits and date to heading) were studied in ten genotypes of durum wheat (Triticum durum Desf.) with contrasting agronomic behaviour. Significant variations between the tested genotypes were observed mainly for the relative water content, osmotic potential and the various osmoticums analysed at the symplasmic level indicating that their behaviour with respect to these osmoticums is significantly different from a degree of stress to another. The relationships between these traits and the adaptation strategies developed by each variety have been described. The classification of the genotypes studied according to their sensitivity to water stress indicates that the Cirta, Boussellam, Mohamed Ben Bachir, Bidi 17 and Wahbi genotypes have a long grain filling time, high relative water content (RWC) and are therefore efficient and tolerant to water stress. Varieties that have shown sensitivity to stress are therefore not very productive, just like the Sémito variety. This observation leads us to conclude that tolerance and great capacity of osmotic adjustment are consubstantial. Other results highlight significant negative correlations between nitrate and proline content and thus showing the probable existence of a connection between the proline biosynthesis pathway and nitrate uptake. Close relations have been observed essentially between osmotic adjustment, soluble sugar content and proline. This suggests that the osmoticum that contributes most to osmotic adjustment in order of preference are soluble sugars, proline, potassium and to a lesser degree nitrates. In case of stress, the biochemical response evaluated through the process of accumulation of proline and soluble sugars varieties (Waha, Bousselam, Mohamed Ben Bashir, Cirta and Bidi17) under water stress has proved to be a criterion of effective adaptation. Correlations between osmotic adjustment capacity and yield show the reliable role of osmotic adjustment in water deficit tolerance. The results obtained in the fields reveal the existence of high performance, low productivity and non-performing genotypes. The duration of heading allowed classifying the early and late genotypes.