Wpływ różnych metod traktowania kultur na ekspresję wirulencji i agresywności Phytophthota infestans [Effect of various culture treatments on virulence and aggressiveness expression of Phytophthora infestans]

Abstract

The effect of experiment date, inoculum concentration and number of passages through potato tissue on virulence spectrum and aggressiveness level of four Phvtophthora infestans isolates was examined in four tests. All these experimental variants significantly influenced the expression of virulence. Isolates chosen for study were characterized initially by complex wirulence and high aggresssiveness. The narro west spectrum of virulence was noted atJune and December in comparison with March and September. The inoculum concentration of 200 sporangia in 1 mm³ influenced stronger frequency of virulence factors, that concentration of 50 sporangia in 1 mm³. The cultures passaged many times showed the wider virulence spectrum than single or double passaged isolates. The double passages of pathogen cultures influenced stronger expression factors of virulence than single one. The significant interaction between experiment dates and number of passages and experiment dales and inoculum concentrations were observed. Higher inoculum concentration and more abundant passages on potato tissues positively affected detection of particular virulence factors, especially v5 and v8. The cultures, both double and many times passaged on potato tuber slices, were significantly more aggressive in comparison with single passaged ones. The isolate MP 425 was the most stable in expression of its virulence and aggressiveness. The P. infestans cultures that lost infectivity on rye agar medium can recover their virulence and aggressiveness expression after double and frequent culturing on potato tissues.