Effects Of High Temperature And Drought And Their Interactions During Grain Filling On Protein Formation And Protein Traits In Grains And Yield Of Winter Wheat

To evaluate effects of post-anthesis high temperature (HT) and drought stress (D) and their interaction on protein formation and protein quality traits in wheat grains, two wheat cultivars with different gluten-strengths, Yumai 34 ( a strong-gluten cultivar) and Yumai 50 ( a weak-gluten cultivar) were used under pot-cultured conditions. The experiments were carried out at Henan Agricultural University Research farm, Zhengzhou (34oN latitude, 113o E longitude), in wheat growing-seasons of 2006-2007 and 2007-2008. Plants in pot grown in open area till flowering. After anthesis, pots were divided into three groups in the artifical weather room for each variety randomly, were grown under 28℃, 2 day 38℃high temperature stress and 4 day 38℃high temperature stress, respectively. For each temperature regime, two soil water levels were established as moderate water status (relative water content, RWC = 75%±5%), drought ( RWC = 55%±5% ). Thus different temperature and water regimes were established for wheat after anthesis to evaluate post-anthesis high temperature and drought stress effects on activities of key regulatory enzymes of protein accumulation and protein traits in grains and yield ofwinter wheat.The main results were as follows:1. Post-anthesis high temperature decreased both GS and GPT activity in flag leaves of wheat. However, the response of two cultivars to high temperature at different grain filling stages were different: when suffered from high temperature in early and middle grain filling stage, the reduction in GS and GPT activity of Yumai 34 and Yumai 50 was relatively greatest, respectively. During 0 to 10 days after high temperature treatment in early grain filling stage, GS and GPT activity in grains was increased, and then decreased in 10 days after high temperature treatment, the reduction in GS and GPT activity in middle grain filling stage of two cultivars were greatest. GS and GPT activity in flag leaves of the two wheat cultivars was decreased by drought in early and middle grain filling stages. The reduction in GS activity in flags in middle and early grain filling stage of Yumai 34 and Yumai 50 was relatively greatest under drought stress, respectively. While in early grain filling stage, GPT activity in flags was increased by drought stress, but decreased in middle grain filling stage. GS activity in grains the two wheat cultivars was decreased by drought in early and middle grain filling stages. The reduction in GS activity in grains in middle grain filling stage of two wheat cultivars was relatively greatest under drought stress. During 5 to 10 days after drought treatment in early grain filling stage, GPT activity in grains was increased, and then decreased in 10 days after high temperature treatment, when suffered from drought stress in middle and early grain filling stage, the reduction in GPT activity of Yumai 34 and Yumai 50 was relatively greatest, respectively. The results also showed that significant interactions of high temperature and drought on GS and GPT activity in both wheat cultivars. The influence of high temperature was greater than Drought stress.2. Studies on effects of post-anthesis high temperature and drought stress and their interactions on protein concentration and its composition in grains. The results indicated that high temperature and drought stress increased protein concentration, but reduced protein yield, the influence of high temperature and drought stress on protein concentration aggravation follow their stress deepened, and the influence reduction with processing time delay. The influence of high temperature and drought stress on protein of Yumai 50 was greater than that of Yumai 34. While high temperature decreased concentration of albumin and globulin of Yumai 34, however, high temperature increased concentration of albumin of Yumai 50, and when suffered from high temperature in early and middle grain filling stage, the concentration of globulin was increased, but decreased in late grain filling stage. The concentration of gliadin and glutein were increased under high temperature stress. Under drought stress, concentration of albumin and globulin of Yumai 34 was decreased, however, when suffered from high temperature in early and middle grain filling stage, the concentration of that of Yumai 50 was increased, but decreased in late grain filling stage. The concentration of gliadin and glutein were increased under drought stress. High temperature and drought stress reduced ratio of gliadin/glutein. The results also showed that significant interactions of high temperature and drought on protein in both wheat cultivars, and the temperature were the main factor of its protein quality.3. Studies on effects of high temperature and drought stress and their interactions on GMP concentration. The results indicated that high temperature stress increased GMP concentration in both two wheat cultivars. However, the response of two cultivars to drought stress at GMP concentration was different: when suffered from high temperature, the concentration of GMP was decreased in grains of Yumai 34, but increased in grains of Yumai 50. The result also indicated that there had a significant influence of high temperature and drought stress and their interactions on concentration of GMP in both two cultivars. 4. The results indicated that, high temperature stress decreased the Total Amino Acid in grains of Yumai 34, however increased the Total Amino Acid in grains of Yumai 50. When suffered from drought stress, Total Amino Acid was increased by high temperature and drought in both wheat cultivars. High temperature and drought stress reduced concentration of Lysine, and decreased the ratio of Essential Amino Acid to Total Amino Acid. The influence of high temperature and drought stress on Yumai 34 was greater than Yumai 50. The results also showed that there had a significant interaction of high temperature and drought stress on concentration and composition of grain Amino Acid in both cultivars. The influence of interaction of high temperature and drought stress on the treatment W₁T₂ (RWC=75%±5%, 2 day 38℃high temperature stress) and W2T3 (RWC=55%±5%, 4 day 38℃high temperature stress) was injury largest for strong and weak-gluten cultivar respectively.5. The results showed that high temperature stress decreased both grain filling rate and period, and caused early appearance of the maximal grain filling rate, thus reduced grain dry matter accumulation. However, the response of two cultivars to high temperature at different grain filling stages were different: when suffered from high temperature in early and middle grain filling stage, the reduction in grain weight of Yumai 34 and Yumai 50 was relatively greatest, respectively. While in the late grain filling stage, grain weight was less influenced by high temperature and drought in both wheat cultivars. The dry matter accumulation of two cultivars was reduced by drought in early and middle grain filling stages. The reduction in grain weight in middle and early grain filling stage of Yumai 34 and Yumai 50 was relatively greatest under drought stress, respectively. But grain weight was slightly increased in late grain filling stage under drought stress. The results also showed that significant interactions of high temperature and drought on grain filling characteristic existed in both wheat cultivars. The decreased of grain weight was mainly caused by decrease of grain filling rate during slow-increase stage, and duration of rapid-increase and slight-increase stage. High temperature and drought stress and their interactions had a significant influence on grain yield and its components in this experiment. The influence of high temperature and drought stress on Yumai 50 was greater than Yumai 34, indicated that cultivar Yumai 34 with strong-gluten was more sensensive than Yumai 50 with weak-gluten.In conclusion, it was showed that the response of two cultivars with different gluten to high temperature and drought stress at different grain filling stages were different: in generally, weak-gluten wheat cultivar Yumai 50 showed relative sensitive to temperature and drought stress on yield and protein property in grain filling stage. High temperature and drought stress decreased grain yield, thus relative increased grain protein concentration, but caused ratio of gliadin/glutein and processing quality traits significant declined. So, in actual production of wheat, cultivating measures should be taken according to the quality need in different cultivars to avoid or relieve damages of high temperature and drought stress at later growth stages.