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Survival of Colletotrichum graminicola: Importance of the Spore Matrix. Ralph L. Nicholson, Associate professor, Department of Botany and Plant Pathology, Purdue University, W. Lafayette, IN 47907; Walkyria B. C. Moraes, visiting professor, Plant Biochemistry Department, Biological Institute, CP 7119, São Paulo, Brazil. Phytopathology 70:255-261. Accepted for publication 14 September 1979. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-255.

Spores of Colletotrichum graminicola are produced in association with a water-soluble matrix material composed of polysaccharide(s) and protein. Spore masses (spores embedded in spore matrix) placed at relative humidities of 90, 80, 70, 60, and 45% lost moisture rapidly and at low relative humidities (70% or less) became dry and powdery within 48 hr. Spores in masses stored at these relative humidities retained viability (measured by germination bioassay) throughout a 4-wk period. However, when the spore matrix was removed prior to storage, viability of the population was significantly reduced within 24 hr (at each relative humidity treatment) and viability was completely lost within 48 hr. Addition of concentrated crude matrix or partially purified matrix components to washed (matrix-free) spores prior to storage at low relative humidity maintained viability of the spore population. The data suggest that in the field spores may survive and be dispersed in dry particulate matter. Hydrolase and invertase enzymes are present in the matrix. Desiccation of the matrix at low relative humidity did not result in a complete loss of enzyme activity. Two roles for the spore matrix in survival of the pathogen are suggested: protection of spores against desiccation and increase in efficiency of germination and penetration through invertase and hydrolase activities.

Additional keywords: corn anthracnose, corn, Zea mays L., cuticle.