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Resistance

Susceptibility of Peanut Leaves to Cercosporidium personatum. Marion Cook, Former graduate student, University of the West Indies, Jamaica, Present address: c/o EMRO, c/o WHO/OMS, 1211-Geneva-27, Switzerland; Phytopathology 71:787-791. Accepted for publication 25 November 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-787.

Germination of Cercosporidium personatum conidia did not differ on the leaves of 12 peanut cultivars that were investigated. Although abaxial leaf surfaces retained more conidia and subsequently had more penetration of stomata by germ tubes than did adaxial surfaces, the resulting leaf spot density did not differ. There were indications of a hydrotropic response in stomatal penetration. Variations in stomatal density and stomatal length were not related to resistance to infection. The leaves of peanut plant introductions PI 259747 and PI 341879, both highly resistant to C. personatum, showed a positive regression of leaf spot density on leaf age. A necrotic-type defense reaction appeared to be operative. The leaves of the 10 other cultivars, ranging from highly resistant to highly susceptible to C. personatum, displayed a differential susceptibility to infection related to leaf size; regardless of leaf or plant age, a positive regression of leaf spot density on leaflet area was demonstrated for each of these cultivars. Knowledge of the variation in leaf susceptibility both within and between cultivars enabled standardization in leaf sampling during preliminary screening for resistance to leaf spot caused by C. personatum.