Presenter Information

Jillian M. Lenne, CIAT

Publication Date

1985

Location

Kyoto Japan

Description

Recent advances in the understanding of anthracnose (Colletotrichum gloeosporioides), the most damaging disease of Stylosanthes spp., are described with reference to the tropical American lowlands. During the past seven years, anthracnose evaluations of promising Stylosanthes spp., at major screening and RIEPT sites throughout the tropical American lowlands have revealed that although anthracnose is present at all sites, its severity varies among species and across ecosystems. From 1978 to 1981, field screening of S. capitata in Colombia and Brazil, found 94.2% of accessions resistant to anthracnose in Colombia while 85.1 % were susceptible in Brazil. These findings together with results from comparative seedling pathogenicity studies with C. gloeosporioides isolates from both ecosystems strongly suggest that specialized isolates pathogenic to S. capitata exist in Brazil, the native habitat of this legume, and not in Colombia where S. capitata is an exotic species. Similarly, field screening from 197�� to 1984 of up to 30 accessions of S. guianensis at 21 sites in the forest ecosystems showed only slight anthracnose whereas the same accessions were killed within a year in the savannas. The presence of antagonistic phylloplane bacteria, the high frequency and widespread occurrence of latent infection and its minimal development due to prevailing narrow diurnal temperature fluctuations are largely responsible for lack of anthracnose development in forest ecosystems. The importance of studies of the host, pathogen, environment and their interactions in the understanding of the basis and stability of resistance to anthracnose is stressed.

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Recent Advances in the Understanding of Anthracnose of Stylosanthes in Tropical America

Kyoto Japan

Recent advances in the understanding of anthracnose (Colletotrichum gloeosporioides), the most damaging disease of Stylosanthes spp., are described with reference to the tropical American lowlands. During the past seven years, anthracnose evaluations of promising Stylosanthes spp., at major screening and RIEPT sites throughout the tropical American lowlands have revealed that although anthracnose is present at all sites, its severity varies among species and across ecosystems. From 1978 to 1981, field screening of S. capitata in Colombia and Brazil, found 94.2% of accessions resistant to anthracnose in Colombia while 85.1 % were susceptible in Brazil. These findings together with results from comparative seedling pathogenicity studies with C. gloeosporioides isolates from both ecosystems strongly suggest that specialized isolates pathogenic to S. capitata exist in Brazil, the native habitat of this legume, and not in Colombia where S. capitata is an exotic species. Similarly, field screening from 197�� to 1984 of up to 30 accessions of S. guianensis at 21 sites in the forest ecosystems showed only slight anthracnose whereas the same accessions were killed within a year in the savannas. The presence of antagonistic phylloplane bacteria, the high frequency and widespread occurrence of latent infection and its minimal development due to prevailing narrow diurnal temperature fluctuations are largely responsible for lack of anthracnose development in forest ecosystems. The importance of studies of the host, pathogen, environment and their interactions in the understanding of the basis and stability of resistance to anthracnose is stressed.