Abstract: The author points out that rust workers should bear in mind the points of view of population,ecology and evolution,since the host and pathogen interact between populations under certain ecological effect and over time. Zhu,et al( 1985) tested 19 promising wheat cultivars with G prevalent races of P.vecinia recondite f.sh, tritici.Eighteen of the cultivars were highly resi-stant to all the races,but when tested respectively with 176 isolates of the fungus from Hebei Province and Beijing,none of the cultivars showed low re-action to all the isolates.The value of、irulence frequency was 9.1-61.4%.What a difference it was when a culti、ar was tested with a single race or with the population of the pathogen. Zhu,et al(1984) compared the tirulence of the population of P.recondite f.sp.tritici between distinct places,injiang and Hebei and Beijing.The rWSt of the former was significantly more、irulent than the t of the latter as shown by the reactions of certain cultivars intermediate in resistance Owing to the fact that the virulence of the population of the pathogen may be different in diffe-rent regions,the author has brought forth the idea fectatype' which means a group of pathotypes formed through the interaction of host and pathogen under certain ecological condition over time has distinct pathogenicity. Zao,et al(1985) compared the virulence of polmlation of P.recondite f. sp. tritici bet,veen adjacent provinces,Hebei and Henan.The average value of virulence frequency was 53.8%in Hebei and 53.0%in I-Ienan,indicating that there was not much difference as the virulence of the whole population was concerned,but there mere significant differences in reactions of certain culti-vars interacting with the pathogen of different rr-inces.The author suggests that it is better to assess the rust resistance of cultivars on regional basis ra-they than making nation wide test by using fcw r: ccs. The author emphasizes that it seems to be necessary to study the fitness of the pathogen in order to know its variation genetically, because the host and pathogen co-exist in evolution.

Key words: Wheat rust, Viewpoint of population, Viewpoint of ecology, Viewpoint of evolution