Analyses of drought tolerance in durum wheat (Triticum turgidum var. durum) genotypes

[摘要] English: In order to identify yield components associated with drought tolerance in durumwheat and evaluate the performace of Ethiopian durum wheat genotypes, 26durum wheat genotypes, from different agro-ecologies of Ethiopia wereevaluated under simulated moisture stress conditions. Stress caused dramaticreductions in grain yield and harvest index. Yield was significantly correlatedprimarily with number of kernels per spike and 100 kernel weight. Furtherdecomposition of simple correlation coefficients into direct and indirect effectsshowed that number of kernels per spike and 100 kernel weight had the largestdirect effects on grain yield, under both stressed and non-stressed conditions'The expression of drought tolerance in the F1generation obtained from allpossible combinations among genotypes differing in their responses to moisturedeficit stress was studied. Analysis of variance revealed significantly highvariability among genotypes for yield, yield components and drought tolerancemeasurements due to the effects of treatments. Drought tolerance wasexpressed in the crosses involving tolerant parents. The diallel analysis showedthat mean squares for both GCA and SCA were significantly high at bothmoisture regimes. GCA:SCA ratios indicated predominance of additive geneaction for all characteristics positively correlated with grain yield under stress ornegatively correlated with drought susceptibility index. Differences in water use and transpiration efficiencies andinterrelationships among water use and transpiration efficiencies and associatedtraits were investigated among durum wheat genotypes with differing responsesto moisture stress. Significantly high genotypic variability in the amount ofcumulative water used before (ETba) and after (ETpa) anthesis was observed. Susceptible genotypes used higher amounts of water before anthesis and loweramounts after anthesis. In contrast, tolerant genotypes used a higher proportionof water during the post-anthesis period. Significantly high variability among thegenotypes was observed for various measures of water use and transpirationefficiencies, total dry matter and harvest index. Ranking of cultivars for wateruse efficiency based on grain yield (WUEG) and transpiration efficiency based ongrain yield, was consistent with ranking of cultivars for drought susceptibilityindices. Drought susceptibility index was significantly but negatively correlatedwith harvest index, WUEG and grain yield. However, it was positively andsignificantly correlated with the ETba:ETpa ratio. A high positive correlation ofWUEG with harvest index and grain yield with harvest index was found.Differences in flag leaf water potential were significant only for genotypes understress treatments. Water potential declined with age under both treatmentconditions, however, the fall was faster in stress sensitive types than in toleranttypes in more advanced growth stages. Inheritance of water use and transpiration efficiencies was studied in ahybrid population obtained from six parents, selected for their differentresponses to moisture stress. GCA and SCA effects were significant at both themoisture levels. The interactions of GCA and SCA with moisture levels werealso highly significant. Analysis of the genetic components of variationdemonstrated that WU E and T were under the control of additive anddominance type of genes. Narrow sense heritability estimates for water use andtranspiration efficiencies based on grain yield (WUEG) were higher at themoisture stress level. Measures of water use and transpiration efficienciesshowed significantly high and positive genotypic and phenotypic correlationsamong them as well as with grain yield and harvest index.The impact of the effect of moisture stress on growth and phenologicaldevelopment was examined among durum wheat genotypes differing in theirtolerance to moisture stress. Drought stress was found to delay major growthstages and shorten the grain filling period. Drought tolerant genotypes had fastearly growth, whereas susceptible ones had slow RGR initially. Variation in RGR was associated with NAR and LAR. Differences in hybrid performance were dueto significant GCA and SCA effects. Interactions of GCA and SCA with moisturelevel were also highly significant. Moderate to high levels of broad senseheritability estimates were found for most of the traits. Significantly high geneticand phenotypic correlations between NAR and RGR, and LAR and RGR werefound. The genetic and phenotypic correlations of grain yield with total drymatter, harvest index, RGR and LAR were significant. The effect of moisture stress on the content of water soluble carbohydrate(sucrose and D-glucose) was investigated in durum wheat (Triticum turgidum L.var. durum) above ground organs to assess and characterise the responses ofgenotypes with differing responses to drought stress. In all organs examined,drought tolerant genotypes accumulated more glucose and sucrose, particularly,at an early age. Stress caused an overall increase in the level of thesecarbohydrates, but the levels were highest in the stems compared to otherorgans. Level of drought (drought susceptibility index, 'S') was strongly relatedwith the level of carbohydrates in the various plant organs Genetic differences among genotypes with differing responses to droughtstress and their progenies obtained from all possible cross combinations wereassessed using AFLP markers. Moderate to high level polymorph isms wereobtained with the primer combinations evaluated. Euclidean genetic distanceestimates showed that there was considerable genetic diversity among thematerials studied. The correlation coefficient for pair wise genetic distanceestimates based on AFLP data and yield, yield components, and morphophysiologicaltraits was significant and positive. Cluster analysis showed thatgrouping of genotypes on the basis of AFLP data and agro-morphological datafairly agreed. A number of AFLP fragments were significantly correlated with thevarious traits evaluated under stress conditions. AFLP fragments were observedto affect a number of traits that were strongly correlated with droughtsusceptibility index.

[发布机构] University of the Free State