Effect of Temperature and Dew Period on Infection of Northern Jointvetch by Wild-Type and Mutant Strains ofColletotrichum gloeosporioidesf. sp.aeschynomene1

Abstract

Abstract Colletotrichum gloeosporioides f. sp. aeschynomene causes an anthracnose on Aeschynomene virginica, northern jointvetch. Infectivity, measured as the number of lesions per plant caused by three strains of the fungus including a wild-type strain (3-1-3), a benomyl-resistant strain (B21), and a nitrate nonutilizing strain (Nit A), was measured on seedling plants. Infectivity of each strain was measured for nine combinations of three dew temperatures (20, 26, and 32°C) and incubation temperatures (20, 28, and 32°C). Generally, results show that 3-1-3 and B21 caused significantly more lesions than did Nit A at all dew and incubation temperature combinations. However, strain 3-1-3 caused significantly more lesions than did B21 when given 20°C dew at 28°C incubation temperature treatments. Infection of northern jointvetch by the mutant strains was reduced at the highest and lowest temperatures studied while infection by 3-1-3 was reduced only at 32°C. Thus, the wild-type strain appeared to be more tolerant to temperature changes than did the mutant strains. In addition, the length of dew period required for infection of northern jointvetch by each strain was studied at each dew temperature. The wild-type strain appeared to require shorter dew periods than did the mutant strains to cause a similar number of lesions.