Postanthesis temperature effects on duration and rate of grain filling in some winter and spring wheats

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Abstract
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. Variation for grain-filling duration among the genotypes tested was present, although small in relation to temperature effects. Breeding for extended grain-filling duration as a strategy for increasing wheat grain yield in a warm climate will thus be difficult. However, an application of the degree-day concept would be desirable. Key words: Triticum aestivum (L.), grain-filling duration, rate of grain filling, temperature

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