Field Resistant Cultivars Research Articles

Characteristics of cassava resistance to superelongation disease (Elsinoë brasiliensis)∗

Abstract Cassava cultivars were inoculated, under controlled conditions, with single‐conidium isolates of Elsinoe brasiliensis Bitancourt & Jenkins (Sphaceloma manihoticola Bitancourt & Jenkins) of diverse origins to study cassava resistance to superelongation disease. Disruption of the stem cuticle significantly increased the amount of stem disease on field resistant and field susceptible cultivars. In susceptible and resistant cultivars stem tissue developed a high level of resistance by the age of 10 days. Significant cultivar x isolate interactions indicating pathogenic specialisation were consistently observed. The interactions were weak, not always reproducible and none were characterised by a hypersensitive‐like component. Field resistant and field susceptible cultivars were treated with gibberellin A4 (the plant hormone responsible for shoot elongation) at 0 to 1 μg/μl and inoculated with a virulent isolate of the pathogen to test the possibility of using the hormone as a screening tool. No differ...

Common antigens in extracts of Phytophthora infestans and potatoes

Rabbit antisera were raised against soluble extracts of Phytophthora infestans race 4 and tubers of Arran Banner and Golden Wonder potato cultivars showing field susceptibility and field resistance respectively to late blight. These antisera were then used to test for the presence of common antigens between extracts of the fungus and various host and non-host plants and between potatoes and various pathogens and non-pathogens. Cross-reactions were detected between Phytophthora infestans race 4 and tubers of both the field-susceptible and field-resistant cultivars of potato, and between the fungus and leaves of tomato and tobacco, two other members of the Solanaceae. Common antigens were not detected between Phytophthora infestans race 4 and leaves of non-host representatives of six other higher plant families (mung bean, pea, radish, Perilla, Pelarargonium, cucumber, maize), nor between potatoes and the alternative pathogen Fusarium solani var. caeruleum and two nonpathogens, Ustilago maydis and Phytophthora cinnamomi.