| The present studies, combined pot culture and field experiments with strong- and weak-gluten wheat cultivars, were carried out to characterize effects of post-anthesis high temperature (HT) and drought and their interactions on content and components of starch and protein in grains, on starch pasting properties and flour processing quality and yield of different wheat cultivars in the farm of HeNan Agricultural university in 2002-2003 and 2003-2004 growing seasons.The main results are as follows:1. Two winter wheat (Triticum aestivum) cultivars with different gluten strength, a strong-gluten cultivar Yumai 34 and a weak-gluten cultivar Yumai 50, were used in pot culture to investigate the effects of post-anthesis HT and drought and their interactions on content and components of starch in grains. The results indicated that HT and drought reduced content of amylose, amylopectin, and total starch in grains. The effects became stronger with the increase of stress degrees. Under adverse conditions, as decrease was much greater in amylose content than in amylopectin content, the ratio of amylose content to amylopectin content decreased. The results also showed that, for most starch parameters (starch content and components), effects of post anthesis HT and drought were additive, and interactions of these two factors appeared on some parameters. HT stress in the early stage of grain filling (5 days after anthesis, DAA) had greater effects on starch concentration and components than that in the middle stage (17 DAA). Responses of two-type cultivars to HT and drought were also located. Yumai 50 was proved more sensitive to HT and drought than Yumai 34.2. In the same experiment stated above, studies were carried out to evaluate effects of HT and drought and their interactions on swelling power (SP) and pasting properties of starch in wheat grains. Obvious difference in change trend of SP was observed between strong-gluten cultivar Yumai34 and weak-gluten cultivar Yumai50 under HT or drought conditions. The former's SP increased, but the latter's SP decreased. It was suggested thatHT stress in the early grain filling stage (5 DAA) had greater influence on SP. Relatively, HT and drought and their interactions had stronger effects on Yumai 50 than on Yumai 34. HT and drought resulted in an increase in pasting temperature, and elongated pasting time, but resulted in a decrease in breakdown of flour. Under HT or drought conditions, changes of two-type cultivars' starch peak viscosity (PV), hold-through (HT) and final viscosity (FV) were different. PV, HT and FV of Yumai 50 all increased significantly, especially under 38°C HT conditions; those of Yumai 34 increased under 35°C HT conditions, but decreased under 38°C HT conditions, and decreased under drought stress in 5 DAA, but increased under drought stress in 17 DAA. Relatively, Yumai 50 was more sensitive to HT than Yumai 34 in the terms of pasting properties of starch. For the two cultivars, in 5 DAA the effect of drought stress was stronger than that of HT stress, but in 17 DAA the effect of HT stress was stronger than that of drought stress.3. In the same pot experiment, effects of post-anthesis HT and drought and their interactions were investigated on concentration and components of protein in wheat grains. The results indicated that under HT conditions the content of protein increased. For Yumai 34, the content of glutenin decreased but that of gliadin increased, as a result, the ratio of glutenin content to gliadin content decreased. For Yumai 50, the content of glutenin and gliadin increased equally, leading to almost no change in the ratio of glutenin content to gliadin content. Post-anthesis drought increased the content of protein of Yumai 34, but that of Yumai 50 deceased a little under light drought stress and increased under severe drought stress, this possibly having something to do with the degree of decrease in grain weight. For the two cultivars, severe drought stress reduced the ratio of glutenin content to gliadin content, and stress in 5 DAA had greater effects on pertein concentration and components than that in the 17 DAA, with strong-gluten cultivar Yumai 34 suffering stronger impact than weak-gluten cultivar Yumai 50.4. In field experiment, three wheat cultivars, Yumai 34, Yumai 50, and Annong 9805 (also a weak-gluten cultivar), were used to evaluate effects of HT stress on concentration and components of protein in wheat grains. HT stress was obtained by covering plastic greenhouses (boxes) in the field at different grain filling stages. The results indicated that HT stress in the early stage of grain filling increased the content of protein in the three cultivars, thereinto, the proportion of increase in gliadin content was far bigger than that of glutenin content, significantly reducing the ratio of glutenin content to gliadin content. HT in the middle stage increased the content of albumin and globulin, but decreased the content of glutenin and gliadin, resulting in little change in the content of...
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