Plant Disease Resistance Inducing Activity of 7-Oxo- and 7-Hydroxysterols

The 7-oxosterols 1-2 and the 7-hydroxysterols 3-6 induce resistance toward the fungal pathogens Puccinia striiformis West, and Puccinia hordei Otth in barley and wheat. Primary leaves of the plants were sprayed with solutions of the compounds ( 10^-4 mol/l in 1% aqu. ethanol) followed, 2 days later, by challenge inoculation with the fungal pathogens. The results indicate that 7α- and 7β-hydroxylated epimers of β-sitosterol and cholesterol show the highest value of induced resistance (39-49% reduction of infection sites). No enhanced resistance toward the fungi Erysiphe graminis DC f.sp. tricitic and hordei and Cochliobolus sativus Ito & Kuribayashi was observed.