Study On Carbon Isotope Discrimination As Substitution Indexes For Selection Of Drought Resistance In Wheat

Carbon isotope discrimination (Δ) has been proposed as a selection criteria for highwater use efficiency (WUE) and grain yield of wheat grown under drought stress. However,the association between WUE, grain yield and variation in Δdepend highly on the rainfall,distribution and water storage in the field. To elucidate the association is important to thefuture breeding efforts at the local area.24selected low–Δ lines and24selected high-Δ linesfrom154F4lines from the cross between XiNong389and LuoHan6which carbon isotopediscrimination had been analyzed on grain at maturity, grown in two ecological areas(Yangling and Yongshou) in Shaanxi province. The correlations between the physiologicalindices of leaves and carbon isotope discrimination were analyzed. Analysis of variance tocompare the differences of physiological indices and yield traits between low-Δ selected andhigh-Δ selected lines in the two ecological area. Furthermore, ash content and mineral content(K, Mg, Ca, Fe, Mn, Zn) were measured on the grain at maturity, the association betweenthese traits and Δ were analyzed. The main results are as follows:1.Differences were existed in stomatal conductance (Gs), instantaneous water useefficiency (WUEi) of leaves and grain yield between high-Δ selected lines and low-Δselected lines, and differences varied in two areas. Lower stomatal conductance (Gs) andhigher instantaneous water use efficiency (WUEi) of leaves were found in low-Δ selectedlines both in Yangling and Yongshou areas. Transportation rate (Tr) and Ci/Ca wereSignificantly different in Yangling area. High-Δ selected lines had higher grain yield, biomassand harvest index (HI) in two areas, and grain yield in Yangling area was significant.2. The correlations existed between yield related traits, photosynthetic traits andΔ. thesignificance betweenΔand photosynthetic traits varied at different grain-filling stages.Positive correlations were noted between Tr, Pn, Gs, Ci/Ca and Δ and reached tosignificant level at middle filling stage in two areas. Grain yield, biomass and harvest indexwere positively related to Δ both in Yangling and Yongshou areas, and grain yield andbiomass significantly related toΔ.3. Weak positive or negative correlations betweenΔand mineral contents in grain inboth areas. And ash content was negative withΔsignificantly in the two areas. weak positivecorrelation between K and Δ, and weak negative correlation between Mg, Ca, Zn, Mn and Δin the two areas. The correlation between SPAD andΔvaried at different growth stage.To summarize, in the area where rainfall is abundant (Yangling), high-Δ selected lineshad high grain yield，and the difference was significantly between high-Δ selected lines andlow-Δ selected lines. In Yongshou area, high-Δ selected lines also have high grain yield butno significant difference between high and lowΔ lines; In Yongshou area, low-Δ selectedlines had high WUEi and low stomatal conductance(Gs), and the differences were significant.The relationship between photosynthetic indices andΔ at middle grain filling stage wassignificant and reflected photosynthetic capacity veritably. The ash content in grain wasfound association with Δand can be used by breeding programs as the substitution indexesfor Δ.