POPULATIONS OF PLANT PATHOGENS: THEIR STRUCTURE, DISTRIBUTION AND DYNAMICS
All-Russian Institute of Plant Protection, 189620, St Petersburg, Pushkin, Russia
Background and objectives
Materials and methods
Results and conclusions
Populations of B.sorokiniana have significantly larger areas compared with P. teres. The differences in the population structure were observed only between geographically distant populations; for example, between the populations of north-western Russia and the Urals. Analysis of F. graminearum populations showed that geographically distant populations from the North Caucasus and Far East differ in morphological characteristics, isozyme spectra, aggressiveness and the ability to produce mycotoxins. Soil populations of F. oxysporum are very local because soil conditions prevent active migration of the fungus. Therefore, the contacts between the populations are limited.
The population structure of fungi is a dynamic system. Investigation of changes in the population structure of P. teres showed the following. (1) Under the influence of host-plant genotype, the virulence of the population increases to the end of the vegetative period at the expense of accumulation on the susceptible cultivars of complicated races with many virulence genes; however, on the cultivars with high levels of nonspecific resistance, simple races are accumulated at the expense of the elimination of unnecessary virulence genes. (2) During over-wintering, unnecessary virulence genes are also eliminated; however, in P. recondita most of the unnecessary genes are neutral for influence on competitive pathogen ability, but the frequency of some differ significantly during the vegetation period.
These population studies have practical application in breeding for disease resistant cultivars and their territorial distribution.