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 <i>Phvtophthora infestans</i> 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 mm<sup>3</sup> influenced stronger frequency of virulence factors, that concentration of 50 sporangia in 1 mm<sup>3</sup>. 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 <i>P.infestans</i> cultures that lost infectivity on rye agar medium can recover their virulence and aggressiveness expression after double and frequent culturing on potato tissues.

Host–pathogen interaction between Phytophthora infestans and Solanum tuberosum following exposure to short and long daylight hours

“…Studies on P. infestans genome revealed a wide spectrum of fast-evolving effector genes localized to a highly dynamic and expanded region of its genome, and may play a crucial role in the rapid adaptability of the pathogen to host plants (Haas et al 2009). The assessment of virulence is not easy due to many factors influencing the expression of potato R-genes: age of plant, position of tested leaflet, source of inoculum, growing media for pathogen maintenance, spores concentration, and range of environmental conditions, such as humidity, temperature and light intensity (Hodgson and Sharma 1967;Victoria and Thurston 1974;Carnegie and Colhoun 1982;Stewart 1990;Sobkowiak et al 2004;Rubio-Covarrubias et al 2005). From our previous observations, the virulence of P. infestans isolates assessed on differential plants grown in late autumn was more complex than virulence assessed on plants in summer.…”

The influence of long-term storage in liquid nitrogen on survival and pathogenicity of Phytophthora Infestans isolates

“…The cultures maintained under paraffin oil at 7°C, survive for three years (Zarzycka 1996). This method has been applied in our P. infestans collection so far (Sobkowiak et al 2004b). The growing size of the collection, though, has demanded growing amounts of space, and work on refreshing cultures every three years.…”