Grain yield and its components study and their association with normalized difference vegetation index (NDVI) under terminal water deficit and well-irrigated conditions in wheat (Triticum durum Desf. and Triticum aestivum L.)

Six genotype of Triticum aestivum L. in 1991 and one genotype of Triticum durum Desf. and three of T. aestivum L. in 1992 were studied under different water regimes: full irrigation (R1), mild water stress (R3) and severe water stress (R2) at Magneraud (France). Traits evaluated were grain yield and its components, stress susceptibility index (SSI) and normalized difference vegetation index (NDVI). The analysis of variance revealed significant differences between regimes and among the cultivars for all traits except between regimes for thousand grains weight in 1991. The regime × variety interaction was significant for grain yield, thousand grains weight and NDVI in 1992 and for grain yield in 1991. For all traits, durum wheat (T. durum Desf.) has higher reduction in the two water stress than the common wheat (T. aestivum L.). Correlations studies revealed that grain yield, grains number/m², thousand grains weight and NDVI were associated with each other except for correlations between thousand grains weight on one hand and grain yield (1992) and grains number/m² (1991) on the other hand. 51.55, 27.88, 4.12% (1991) and 75, 43 and 20.2% (1992) of grain yield, grains/m² and thousand grains weight variability, respectively were explained by means NDVI variability. The grain yield and grains number/m² could be predicted using a single regression with NDVI.Keywords: Grain yield, grain yield components, NDVI, durum wheat and bread wheat

Rôle de la sélectivité K/Na et de l'accumulation de proline dans l'adaptation à la salinité de l'orge (Hordeum vulgare L.) et du blé (Triticum durum Desf.)

L'étude de l'adaptation à la salinité a été àbordée chez deux céréales, l'orge (espèce tolérante) et le blé dur (espèce moyennement sensible). Plusieurs mécanismes physiologiques d'adaptation (caractère plus ou moins inclusif (transfert du sodium vers les parties aériennes) ; sélectivité KlNa (capacité d'absorption et de transfert préférentiels du potassium) ; osmorégulation cytoplasmique, partiellement caractérisée par l'accumulation de proline) ont été pris en compte. Pour chaque mécanisme, on note des différences importantes entre les deux espèces étudiées. Le rapport de sélectivité KlNa est plus élevé et l'accumulation de proline est plus importante chez l'orge que chez le blé dur dans le milieu salin. Ces diflèrences rendent possible une meilleure compréhension des modes d'adaptation spécifiques de l'orge et du blé dur; on note également des différences génotypiques au sein de chaque espèce, mais celles-ci ne permettent pas de rendre compte totalement de la tolérance variétale: les mécanismes étudiés ne peuvent donc pas constituer, à eux seuls, une méthode de criblage variétal et d'autres aspects de l'adaptation physiologique (compartimentation ionique, effets de la salinité sur la photosynthèse) doivent être pris en considération.The function of KlNa selectivity and the accumulation of proline on adaptation to sallnity of barley (Jlordeum vulgare L.) and wheat (Triticum durum Desf.)Adaptation to salt has been studied on two cereals, barley (tolerant) and durum wheat (moderately sensitive). Several physiological mechanisms of adaptation (character more or less inclusive (sodium translocation to above ground parts of the plant) ; KlNa selectivity (ability for preferential absorption and translocation of potassium); cytoplasmic osmoregulation partially characterized by proline) have been taken in account. For each mechanism, important differences have been noted between both species. The selective index KlNa and the accumulation of proline are higher for barley than for Durum wheat in salt milieu, that make possible a better understanding of the specific modes of adaptation ofbarley and durum wheat. Genotypic differences within each species have been noted but they do not permit a good understanding of the varietal tolerance: the mechanisms studied allme cannot constitue a method of varietal screening and other aspects of the physiological adaptation (such as ionic compartimentation, effects of sali nit y on the photosynthesis) have to be considered

Does geographic origin dictate ecological strategies in Acacia senegal (L.) Willd.?: evidence from carbon and nitrogen stable isotopes

Background and aims: Acacia senegal, a leguminous dryland tree, is economically and ecologically important to sub-Saharan Africa.Water-use efficiency (WUE) and biological nitrogen fixation (BNF) are fundamental to plant productivity and survival.We quantify provenance differences in WUE, BNF, photosynthesis, biomass and gum arabic production from A. senegal assessing genetic improvement potential. Methods: Using stable isotope ratios, we determined WUE (δ13C) and BNF (δ15N) from provenances of mature A. senegal in field-trials (Senegal), sampling leaves at the beginning (wet) and end (dry) of the rainy season. Seedling provenance trials (UK) determined photosynthesis, and biomass and δ13C in relation to water table. Environmental data were characterised for all provenances at their sites of origin. Results: Provenances differed in both δ13C and δ15N. Gum yield declined with increasing WUE. Virtually no BNF was detected during the dry season and seedlings and mature trees may have different WUE strategies. Wind speed and soil characteristics at provenance origin were correlated with isotope composition and gum production. Conclusion: Provenance differences suggest that selection for desirable traits, e.g., increased gum production, may be possible. As ecological strategies relate to native locality, the environmental conditions at plantation site and provenance origin are important in assessing selection criteria