[Immunosuppressors in pathogenesis of potato-pathogen blight].

The properties and effects of two plant resistance suppressors (1,3-beta-1,6-beta-glucan and a pentasaccharide of xyloglucan origin) involved in the pathosystem of potato (Solanum tuberosum) and the causal agent of blight (Phytophthora infestans (Mont) de Bary) were compared. The microbial 1,3-beta-1,6-beta-glucan suppressed the defense response over a narrow concentration range (10(-2) M), whereas the plant pentasaccharide had a broad range of effective concentrations (10(-12) to 10(-6) M). In the pathosystem of potato-causal agent of late blight, the beta-glucan caused a local and race-specific suppressor effect on the plant host defense response.

[Modulation of plant resistance to diseases by water-soluble chitosan].

Low-molecular-weight water-soluble chitosan with a molecular weight of 5 kDa obtained after enzymatic hydrolysis of native crab chitosan was shown to display an elicitor activity by inducing the local and systemic resistance of Solanumi tuberosum potato and Lycopesicon esculentum tomato to Phytophthora infestans and nematodes, respectively. Chitosan induced the accumulation of phytoalexins in tissues of host plants, decreased the total content and changed the composition of free sterols producing adverse effects on infesters, activated chitinases, beta-glucanases, and lipoxygenases, and stimulated the generation of reactive oxygen species. The activation of protective mechanisms in plant tissues inhibited the growth of taxonomically different pathogens (parasitic fungus Phytophthora infestans and root knot nematode Meloidogyne incognita).

[Derivatives of chitin and chitosan as elicitors of potato resistance to late blight].

Water-soluble low-molecular-weight (3-10 kDa) chitosan obtained by enzymatic degradation of high-molecular-weight chitosan, as well as its deaminated derivatives, can be used as elicitors of late blight resistance in potato.

[Effect of methyljasmononate on induction of late-blight resistance of potatoes using arachidonic acid].

Methyl ester of jasmonic acid (Me-JA) influences the induced resistance of potato tubers to late blight caused by Phytophthora infestans. Treatment of potato tuber disk surface with Me-JA solution or exposure to an atmosphere containing Me-JA vapors (10(-6)-10(-5) M) increased the rate of rishitin biosynthesis induced by arachidonic acid or P. infestans.