The Effects Of Wheat Cultivar Mixtures On Blumeria Graminis F.sp. Tritici And Its Population Structure

Cultivar mixture is one of the most economical and effective measures for disease control and yield increase, which has become a big success in rice for control of rice blast. However, to date, Studies on wheat diseases contol in this field are very few.In this study, three monocultures based on three varieties, Bao Feng 104 (a resistance line), Jing 411 (a susceptible line) and Lun Xuan 987 (a moderate resistant line), and four mixtures, inoculated with Blumeria graminis f.sp. tritici, were designed in the field to test the mixture effects on the development of polycyclic epidemics, population strustructure of the pathogen and grain yield. The results are as follows:Data for the area under disease progress curve (AUDPC) and the rate of epidemics showed that not all mixture plots are useful for suppression of disease. The mixture, Bao Feng 104:Lun Xuan 987 2:1, was the most significant for disease control, but the AUDPC of mixtures related to Jing 411, a susceptible line, were all higher than the theoretical AUDPC, and did not show any suppression of disesease development. However, the grain yields of all mixtures were higher than the theoretical figure, which incicated that the grain yield can be increased through cultivar mixing, and there is a trend towards greater benefits from increased number of components of cultivar mixtures.Inter simple sequence repeat (ISSR) as a new technique, has been widely used for detection of DNA development in recent years. In this study, ISSR-PCR amplification system was constructed for Blumeria graminis f.sp. tritici by the orthogonal design and a single factor test. The optimal annealing temperature of 20 primers was confirmed by gradient PCR and some polymorphic primers were screened. Polymorphic bands of 33 isolates generated by primer BDB(CA)₇ indicated that high diversity is conserved in DNA of B. graminis f.sp. tritici and the dendrograms based on ISSR results and isolates virulence were also compared, showing that there is certain relationship between DNA diversity and the virulence of isolates.Futhermore, the population structures of Blumeria graminis f.sp.tritici in four plots, two monocultures and two mixtures, were studied and compared through cluster analysis based on ISSR markers. For Jing 411, there were more abundant genetic groups in mixture than monoculture, otherwise, for Lun Xuan 987, the genetic group numbers changed little between mixture and monoculture. The reasons for this need to be studied further.