Genetic Structure Of The Wheat Powdery Mildew Populations From Henan, Hubei And Chongqing Province (City)

In order to disclose the genetic structure and genetic relationship of wheat powdery mildew population of Henan, Hubei and Chongqing, the research analyzed the virulence of wheat powdery mildew originated from Henan (50 isolates), Hubei (40 isolates) and Chongqing (50 isolates) using 41 differential hosts, and for the first time, the population genetic structure using the method of multigene genealogy.1. The virulence analysis shows that the virulence frequency of the wheat powdery mildew populations from the three provinces to Pml, Pm3a, Pm3b, Pm3c, Pm3e, Pm5, Pm6, Pm7, Pml9, Pm1+2+9, Pm34 has surpassed 90% or even reached 100%. It reveals that the resistance of these resistant genes has been lost, and cannot be separately used as the resistant sources in wheat breeding against powdery mildew. The virulence frequency of wheat powdery mildew population from the three provinces to Pm2+6, Pm5 (Mi), Pml2, Pm13, Pml6, Pm21, Pm2+MLD, Pm30, Pml8, and Pm23 is lower(<40%), indicating that these genes have better resistance and can be used in the breeding programmes for disease resistance. Meanwhile, the detection result has also found that the virulence spectra of the isolates were different among provinces. For example, the virulence frequencies of Henan population to Pm (4+8), Pm4b, Pm4b+Mli, Pm13 are higher than that of Hubei, the virulence frequencies of Hubei population to Pm2, unknown genes (the host is Era) and Pm3d are higher than that of Henan, and the virulence frequencies of Chongqing population to Pm2, unknown genes (Era), Pm2+6, Pm (4+8), PmXBD, Pm4a, Pm5 (Mli), Pm (5+6), Pm21, Pm2+MLD, Pm30, Pm23, Pm25, Pm35 are higher than that of Henan and Hubei, while the virulence frequency of Chongqing population to Pm4b, Pm17 is lower than that of Henan and Hubei. In general, the virulence frequency of Chongqing population is a higher than that of Henan and Hubei.2. The virulence clustering of population from Henan, Hubei and Chongqing, constructed by the NTSys pc 2.10e, shows that the similarity coefficient is between 0.73 and 1.00,0.77 and 0.98, and 0.67 and 1.00, respectively. It reveals that the virulence variation of Chongqing population is large and Henan population takes the second place. The distribution of virulence range of Hubei population is the smallest. In the three phylogenetic trees contructed with virulence of the, with PopGen32, the braches are complex showing diversified virulence in the three populations. The tree shows also isolates from different province are clustered together apart from the ones clustered from the same provinces. The isolates from Henan and Hubei have more cross clustered together, indicating closer virulence between these two provinces population. From the evolution relation of phylogenetic tree, the isolates from Chongqing City have clustered at the lower part of the tree, and may therefore be differentiated earlier and followed by population from Hubei and Henan. We can draw a conclusion from the results above that the wheat powdery mildew populations of the three provinces probably migrate among the three provinces while they spread and inside the province. The isolates from Chongqing can be spread, by wind, to Hubei and Henan, and, meanwhile, part of isolates of Hubei can be also spread to Henan. The spread opposite the direction also exists.3. Four house keeping genes PPA, PKA, AOX and EFA were used to contruct phylogenetic tree, the genetic polymorphism expressed by the splicing sequence is the high and the genetic diversity is abundant. Isolates from different provinces were clused together displaying the dispersal between the provinces. Analyses to the neibour joining (NJ) phylogenetic tree reveal that the mildew population from the flat area of Henan Province spread in the southwest-northeast direction mainly. The pathegen in Hubei probably dispersed along Yangtze River, from the west, Wanzhou, Yunyang, etc., in Chongqing, to the east and get into Yangtze River-Han River Plain. Or, the pathogen spread, from the northwest of the province along the Han River meandering in the northern foot of Wudang Mountain, headed southeast, into the Yangtze River-Han River Plain. The Chongqing population has the highest diversity among the three populations studied and disperses also along the direction of southwest-northeast. This is consistent to the result of virulence analysis.4. The comparison of the clustering of virulence and the four-gene segment sequence of the 140 isolates studied indicates that the genetic structure differentiation of virulence displayed by virulence cluster analysis is more obvious inside the province, and it is slightly weaker among provinces. The genetic structure differentiation, however, displayed by polygenetic cluster analysis is more obvious both inside and among the provinces showing a better description to the genetic structure of the populations. There is no matching relationship between the DNA genetic diversity and the virulence diversity of the wheat powdery mildew populations although they showed certain relatedness.