The parameters of grain filling and yield components in common wheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. var. durum)
Final grain dry weight, a component of yield in wheat, is dependent on the duration and the rate of grain filling. The purpose of the study was to compare the grain filling patterns between common wheat, (Triticum aestivum L.), and durum wheat, (Triticum turgidum L. var. durum), and investigate relationships among grain filling parameters, yield components and the yield itself. The most important variables in differentiating among grain filling curves were final grain dry weight (W) for common wheat genotypes and grain filling rate (R) for durum wheat genotypes; however, in all cases the sets of variables important in differentiating among grain filling curves were extended to either two or all three parameters. Furthermore, in one out of three environmental conditions and for both groups of genotypes, the most important parameter in the set was grain filling duration (T). It indicates significant impact of environmental conditions on dry matter accumulation and the mutual effect of grain filling duration and its rate on the final grain dry weight. The medium early anthesis date could be associated with further grain weight and yield improvements in wheat. Grain filling of earlier genotypes occurs in more temperate environments, which provides enough time for gradual grain fill and avoids the extremes of temperature and the stress of dry conditions.
Postanthesis temperature effects on duration and rate of grain filling in some winter and spring wheats
To help define traits that are likely to improve wheat (Triticum aestivum L.) grain yield in a warm, humid continental climate, genotypic variations in various grain growth characteristics in wheat were examined. Winter habit cultivars were grown indoors under a 16-h photoperiod and at day/night temperatures of 20/15 °C, and spring habit cultivars at temperatures ranging from 15/15 °C to 30/25 °C. Grain-filling duration of the winter wheats varied from 36.4 d for Peking-10 to 31.8 d for Priboy. Final kernel weights, which varied from 61.7 mg for Lovrin-10 to 38.3 for Jokionen-3057, were highly correlated with rates of dry matter accumulation. Grain-filling duration of the spring wheats ranged from 56.4 to 47.0 d at 15/15 °C, and from 23.8 to 18.1 d at 30/25 °C. Grain number per spike decreased from 15/15 °C to 30/25 °C. The inverse of grain-filling duration was linearly related to mean temperature, with the intercept on the x-axis (the base temperature of grain filling) being the same for all cultivars. V...
Remobilization of Nitrogen and Carbohydrate from Stems of Bread Wheat in Response to Heat Stress during Grain Filling
When wheat (Triticum aestivum L.) is grown under heat-stress conditions during grain filling, preanthesis stored total non-structural carbohydrates (TNC) and nitrogen (N) could serve as alternative source of assimilates. This study was performed to evaluate wheat genotypes for their ability to accumulate and remobilize TNC and N stored in their stem to support grain filling under heat stress. Eighteen genotypes were used for N remobilization study while nine of them were used for TNC remobilization study. They were grown in pots and placed in a vinyl house with the maximum temperature kept below 30 °C. Five days after anthesis (5DAA), half of the pots were taken to phytotrons where temperature was gradually increased and the maximum was set at 38 °C. Grain yield and grain weight decreased by about 35 % under heat stress. Significant differences were found among genotypes in percentage reduction in grain yield, grain weight, grain filling duration and harvest index because of heat stress. The N and TNC concentrations of the stem at 5DAA were significantly different among genotypes. Heat stress significantly reduced the N remobilization efficiency of most of genotypes. However, heat stress significantly increased TNC remobilization efficiency and significant variation were observed among genotypes. N remobilization efficiency across treatments significantly correlated with grain yield, grain weight, harvest index and grain filling duration. TNC at 5DAA negatively correlated with N at 5DAA and harvest index, but the TNC remobilization efficiency under heat stress positively correlated with mainstem grain yield, grain weight and harvest index. The rate of chlorophyll loss from flag leaf positively correlated with N and TNC remobilization efficiencies under heat stress suggesting a link between leaf senescence and remobilization efficiency. The results indicate that heat stress negatively affected grain yield, its components and N remobilization while it increased TNC remobilization because of the increasing demand for resources.