Occurrence Of Wheat Powdery Mildew In Diversified Hosts And The Pathogen Population Genetic Structure

Wheat powdery mildew is caused by Blumeria graminis f.sp. tritici, which is a worldwide disease and the world's major wheat region are happening. At present main control measures of wheat powdery mildew are planting resistant varieties and chemical control. Research use of cultivar mixtures for controling wheat diseases and esTable lish the technical system can be more safe and effective continuous control powdery mildew. In this experiment, we chose five species with different resistance, Jingshuang16, Jing411, Jingdong8, Lunxuan987, Bao feng104. Mixtures with two, three, four or five species and single varieties were inoculated with mix powdery mildews field test in 2009~2010. The changes of AUDPC, the wheat yield and the crude protein content were investigated and analyzed. The genetic diversity and genetic structure of the powdery mildews in trial field were analyzed with ISSR molecular marker, and the results are as follows:The analysis of AUDPC shows that the average control efficacy of the two cultivar mixtures was 4.27%, and the changes of control efficacy were 13.5% ~ 17.73%. The average control efficacy of the three cultivar mixtures was 3.81%, and the changes of control efficacy were -25.55%~27.7%. The average control efficacy of the two cultivar mixtures was -17%, and the changes of control efficacy were -13.37%~2.08%. Comparison of the real and the theoretical AUDPC in different treatments shows that mixture of different varieties show different disease control effect. There are many differences between in cultivar mixtures treatments, and the higher the proportion of the resistant cultivars the better the control efficacy. This is possible that there are many differences in the genetic background of the cultivar mixtures. So, we should choose wheat cultivar with difference genetic background as much as possible, and the control efficacy of cultivar mixtures would decrease when there are foreign pathogen.The analysis of wheat yield and the crude protein content indicate that the average yield increase of the two cultivar mixtures was -7.45%, the average yield increase of the three cultivar mixtures was -12.85%, and the average yield increase of the more cultivar mixtures was-16.88%. There were some differences in different cultivar mixtures treatments, and there were interactions between varieties used in mixtures. For example, Jing 411 and Bao feng104 had a positive effect on yield, and Lun xuan987, Jingdong8 and Jingshuang16 have a negative impact. the cultivar mixtures can increase the wheat yield when the wheat powdery mildew was not serious. The analysis of wheat yield and thousand kernels weight indicate that the increase of wheat yield was not in accorodance with the thousand kernels weight. The average increase of the crude protein content in two cultivar mixtures was -1.72%, the average increase of the crude protein content in three cultivar mixtures was -0.735%, and the average increase of the crude protein content in more cultivar mixtures was -2.81%, There were many differences in different two cultivar mixtures treatments, as the number of cultivar mixtures is increasing, the difference decreases.The populations of wheat powdery mildew from field experiment treatment were studied with 8 pairs of ISSR primers. The results show that the genetic diversity of the wheat powdery mildew samples from different mixtures had some differences. The genetic diversity of the second wheat powdery mildew samples from Jingshuang16, Jing411 and Jingdong8 were lower than the first, and the number of powdery mildew lineage is little, the proportion of dominant lineage is more. The genetic diversity of wheat powdery mildew samples from cultivar mixtures is higher than from ingle varieties. This shows that the choice of breed is very important. The genetic diversity of wheat powdery mildew samples is not along with the simple increase of the number of cultivar mixtures.