Parasitic fitness of the major epidemic strains of Puccinia striiformis f. sp. tritici in China

In order to predict the future predominant isolates in the populations of Puccinia striiformis f.sp.tritici in China,parasitic fitness of current prevalent isolates were estimated through testing resistant components.The results showed that the sporulation capacity contributed to most important portion in parasitic fitness,and the next two important characters for rust fungal parasitic fitness were infectivity(represented by number of colonies) and latent period.Germination ability didn't show significant difference among the tested races.The mathematical models had been firstly developed to estimate three principal components of pathogen parasitic fitness:sporulation capacity,infectivity and latent period.According to these models,the relative parasitic fitness of isolates Su11-4,Su11-14 and CY32 was higher than that of other tested races and had already been the predominant races at the present time.Isolate CY31 showed lower parasitic fitness,its occurrence frequency had been decreasing recent years and it was becoming secondary race.Also,for the lower parasitic fitness,the new pathogenic type "T4" infected the seedling of differential host "Zhong 4" couldn't become the prevalent race in the near future.