Leaf gas exchange theory indicates that carbon isotope discrimination (∆) is negatively associated with CER/g3 (leaf CO2 exchange rate/conductance). Discovery of genetic variation for ∆ in wheat (Triticum aestivum L.) and other species has generated interest in using carbon isotope discrimination in plant breeding. However, the hypothesized negative association between CER/g3 and & has sometimes not been observed in field‐grown crops. In the present study, CER/g3, & of peduncle tissue, plant productivity and yield were examined in eight winter wheat genotypes under both irrigated and nonirrigated field conditions. Water stress‐ and genotype‐induced variations in CER/g3 were more consistently correlated with variations in gs than with CER. However, low CER in ‘Bezostaya’ wheat resulted in a consistently low genotypic ranking for CER/g3. In 1988, values of CER/g3 increased with water stress, while ∆ values dropped from 18.17 to 17.48‰. These results imply a negative relationship between CER/g3 and ∆, consistent with leaf gas exchange theory; however, ∆ was both positively (1988; r = 0.83** [P ≤ 0.01]) and negatively (1989; r = ‐0.79* [P ≤ 0.05]) associated with CER/g3 in irrigated plots. Positive correlations were obtained between ∆ and both biomass productivity (1988, r = 0.54*; 1989, r = 0.45 [P = 0.08]) and grain yield (1988, r = 0.66*; 1989, r = 0.55*) when data were averaged across genotypes and irrigation treatments. Consistently low ∆ values were obtained for ‘Sturdy’, an early‐released, drought‐susceptible cultivar with low productivity. These results suggest that genotypic rankings for peduncle ∆ must be carefully interpreted, as low ∆ can be associated with low yield and stress susceptibility in wheat.
. 2005. Strongfield durum wheat. Can. J. Plant Sci. 85: 651-654. Strongfield durum wheat (Triticum turgidum L. var durum) is adapted to the durum production area of the southern Canadian prairies. It combines high yield, high grain protein concentration, and low grain cadmium concentration. Strongfield has shorter, stronger straw than Kyle, and has similar maturity and disease resistance to other currently registered durum cultivars.
Field studies were undertaken to relate dry matter accumulation and loss patterns to drought resistance and yield performance of wheat. A total of 23 hexaploid (Triticum aestivum L.) and tetraploid (T. turgidura var. durum L.) wheat genotypes were grown under rainfed field conditions at Swift Current, Saskatchewan from 1975to 1978, and under both rainfed and irrigated conditions in 1979 and 1980. Weekly dry matter samples were taken in the 1975 to 1979 trials, starting before anthesis and continuing to maturity. Growth parameters were then related to apparent drought resistance, which was characterized by comparing rainfed and irrigated yields. The genotypes were divided into drought susceptible and drought resistant groups on the basis of a drought susceptibility index. In contrast to results in some other studies, Pitic 62 appeared to be somewhat drought susceptible, perhaps because of late flowering. Mean head yield:biological yield ratios (approximation of harvest index) ranged from 0.52 to 0.60 over the 5 years, and tended to be higher under moist or irrigated conditions than under dry conditions. Significant differences in preanthesis growth rates occurred in only I of the 5 years, and did not appear to be related to drought resistance or yield. There were consistent cultivar differences in stem dry weight reduction prior to maturity, but there was no obvious relationship between this trait and drought resistance. Leaf duration after anthesis was not correlated with yield or drought susceptibility index. Growth analysis is a labor intensive procedure that is unlikely to identify traits which are strongly related to drought resistance.
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