| Wheat powdery mildew, which is caused by blumeria graminis f.sp. tritici, is a worldwide diseaseoccurring in the major wheat regions. At present main control measures against the expansion of wheatpowdery mildew are breeding for disease resistance and application of chemicals. Use of cultivarmixtures can be a safe, effective and sustainable measure in the control of powdery mildew. In this study,based on the SSR analysis of variety diversity and the resistance of the varieties, we chose eightvarieties. Mixtures with three, four, five, six, or eight varieties and the pure stands were inoculated witha mixture of six powdery mildew isolates and tested for the disease occurrence and some of the yieldcomponents and the content of crude protein in the fields in Langfang, Hebei Province, in2010~2011season. We also chose five varieties based on the above idea, Mixtures with two, three, four and fivevarieties and pure stands were plant in the fields with natural conditions for the disease to occur inXinxiang, Henan Province, in2010~2011. The changes of AUDPC, the disease index, the wheat yieldand the crude protein content were investigated and analyzed. Tthe results are as follows:The analysis of AUDPC for the trial in Langfang shows that the average control efficacy of thethree-cultivar mixtures was9.91%, and the range of control efficacy was-23.23%~45.39%. The averagecontrol efficacy of the four-cultivar mixtures was31.15%, and the range of control was11.19%~56.65%.The average control efficacy of the five-cultivar mixtures was11.53%, and the range of control efficacywas-14.74%~43.67%. The mixtures with four-cultivars are the best in all practices. Comparison of theactual and the theoretical AUDPC in different treatments shows that mixtures with both resistant andsusceptible varieties are better than mixtures with only resistant varieties, and the higher the proportionof the resistant cultivars the better the control efficacy. There is no clear trend that the more diversifiedthe mixtures are the better the control efficacy is.The analysis of DI of Xinxiang used with two methods shows that the average control efficacy ofthe two-cultivar mixtures of the two methods, under flag-leaf investigation and improved “0~9”, were16.07%and4.08%, respectively, and the range of control efficacy was-32.46%~76.42%and-20.85%~44.29%, respectively. The average control efficacies of the three-cultivar mixtures of the twomethods were3.22%and-3.13%, respectively and the ranges of control efficacy were-37.62%~28.78%and-33.33%~24.46%, respectively. The average control efficacy of the four-and five-cultivar mixturesof the two methods were27.75%and12.18%, respectively, and the ranges of control efficacy were5.52%~44.21%and-3.45%~30.02%, respectively. The mixtures with four cultivars are the best in allpractices. Comparison of the actual and the theoretical DI in different treatments shows that mixtureswith both resistant and susceptible varieties are better than mixtures with only resistant varieties, and thehigher the proportion of the resistant cultivars the better the control efficacy. However, there’s no cleartrend that the more diversified the mixtures are the better the control efficacy is.The analyses of wheat thirty-ear weight and crude protein content obtainted in trial in Langfangindicate that the average thirty-ear weight increase of the three-, four-, five-, six-/eight-variety mixtureswere5.07%，4.39%，4.18%and3.24%, respectively. The average crude protein content increase of the three-, four-, five-, six-/eight-variety mixtures were2.57%，3.51%，0.16%and3.44%, respetively. Theanalyses of wheat yield and crude protein content obtained from the trial in Xinxiang indicate that theaverage yield increase of the two-, three-, four-/five-variety mixtures were1.84%,2.96%and2.70%,resptectively. The average crude protein content increase of the two-, three-, four-/five-cultivar mixtureswere0.69%,0.20%and-1.12%, respectively. The mixtures with three and four cultivars are the best inall practices except protein content obtained from trial in Langfang. There were some differences indifferent cultivar mixtures treatments, and there were interactions between varieties composed of themixtures. The mixtures composed with certain varieties displayed more increase to yield while othershad negative impact. For example, Aikang58, Zhengmai004and Zhengnong16had a negative impacton yield；Lunxuan987had a positive impact on crude protein content and Zhengmai9694had anegative impact on Crude Protein Content. The component varieties that have major difference betweentheir yield and Crude Protein Content showed more significant increase in terms of yield and CrudeProtein Content.A number of3815wheat powdery mildew expression sequence tags (ESTs) that originated fromour laboratory were used to search for simple sequence repeats (SSRs). The SSRIT program was runonline and the parameters were set for detection of di-, tri-, tetra-, penta-, and hexa-nucleotide motifswith minimum of6,5,4,3and2repeats, and77simple sequence repeats (EST-SSRs), which accountedfor2.02%of EST database, were identified. Based on these SSR sequences,46EST-SSR primer pairswere designed.42EST-SSR primer pairs can amplify clear bands in7isolates of Blumeria graminis f.sp.tritici, and7primer pairs showed good polymorphisms. Among the7polymophic loci, five are6-baserepeats, two3-base repeats and one two-base repeats. Cross ampliphication indicates that the developedSSR primers can be used to amplify barley mildew, wheat rusts and wheat head blight pathogen. |
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