Populations of Phytophthora infestans in the Slovak Republic in 1996-2003

Kvetoslava Forišeková

forisek@sinet.sk
Potato Research and Breeding Institute, 059 52 Ve¾ká Lomnica, Slovak Republic (Slovakia)

Ján Heldák

Potato Research and Breeding Institute, 059 52 Ve¾ká Lomnica, Slovak Republic (Slovakia)

Abstract

The effective management of protection against Phytophthora infestans must be established on the perfect knowledge of the pathogen. From a practical point of view this means identification of races and mating types as well as the pathotypes resistant to systemic compounds of fungicides. The main goal of our project was to characterize populations of late blight, especially in the most important area of seed potato production. Recognition of races and mating types and evaluation of resistance to metalaxyl of the isolates in potato-growing area were performed in laboratory tests. Isolates of late blight for laboratory tests were collected in commercial and research potato crops in the regions of Poprad and Kežmarok. The first occurrence of metalaxyl-resistant strains was noticed in 1999, and the greatest incidence was recorded in 2000. In the following years a significant decrease was observed. This was due, among others, to omitting fenylamide fungicides in crop protection in our region. The occurrence of isolates virulent to potato with R2, R5, R9 and R11 genes was noted neither in 1996 nor in 1997, and tested isolates had maximum six virulence factors. Since 1999, the occurrence of isolates with seven, eight or even ten virulence factors has been recorded. Presence of A2 mating type was not confirmed in our area until 2002. In 2003, more A2 than A1 isolates were found. It is likely that problems concerning the ability of oospores to survive in soil as well as sexual reproduction of the pathogen may appear also in our potato-growing area.

Keywords:

late blight, mating type, metalaxyl, Phytophthora infestans, race