METHOD: Visual Examination CONDITIONS: Green House METHOD NARR: Testing was done by inoculating circular leaf discs with sporangial suspensions of P. infestans and examining them 4-6 days later for evidence of sporulation. Afterntage of each leaf disc showing necrosis with sporulation was estimated. The test was repeated using leaves that were pretreated by soaking in water to remove water soluble residues. The residues were largely found to be su P. infestans sporulated more profusely on leaf discs of tbr than any ber clone. Those ber clones containing type B glandular tricomes showed considerably less sporulation than those without. Discs soaked to remove sucrose este intense sporulation than nonsoaked discs. Results of a sucrose ester dilution study support the conclusion that sucrose esters are the most likely source of fungitoxic activity. AUTHOR EXPLANATION: Accessions of ber containing tyd generate more interest as sources of novel fungitoxins and possibly provide potato breeders with means of resistance to late blight disease.