Abstract: 【Objective】 This study is to make clear the poisoning effect of phytophthora infestans toxins for potato, and to discover the toxicity different from physiological race to potato verieties.【Method】 Putative P. infestans toxins were prepared by culturing in liquid medium ( 60 g rye and 10% tomato juice per litre) for 1 month at 17℃, filtering through 4 layers of cheesecloth, and being precipitated by ammonium sulfate. The resulted putative toxin solutions were used to examine the reactions of 3 potato varieties (both leaf and tuber tissues) to the putative toxins. 【Result】 The results show that potato leaves and tubers exhibit symptoms similar to the late blight resulted from P. infestans infection. Potato varieties reacted differentially to both the toxin dilutions and toxins produced by different P. infestans isolates, suggesting the presence of toxin-mediated specificities between potato and P. infestans. Potato leaf and tuber tissues have different and contrary reactions to the toxin. 【Conclusion】 Toxin-mediated specificities are likely present between potato and P. infestans.

Key words: P. infestans, toxin, potato variety resistance