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Cytology and Histology

Histopathology of Colletotrichum gloeosporioides f. sp. aeschynomene on Northern Jointvetch. D. O. TeBeest, Research Associate, Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701; G. E. Templeton(2), and R. J. Smith, Jr.(3). (2)Professor, Department of Plant Pathology, University of Arkansas, Fayetteville, AR 72701; (3)Research Agronomist, Agricultural Research Service, U.S. Department of Agriculture, University of Arkansas Rice Branch Experiment Station, Stuttgart, AR 72160. Phytopathology 68:1271-1275. Accepted for publication 15 March 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1271.

The histopathological relationship of Colletotrichum gloeosporioides f. sp. aeschynomene with its host, Aeschynomene virginica, was investigated by microscopic examination of diseased seedlings and inoculated explants. Inoculation of A. virginica seedlings with suspensions of C. gloeosporioides, resulted in the formation of pinpoint lesions (0.5 to 1 mm diam) on stems or explants within 48 hr after inoculation. Lesions found within 48 hr after inoculation resulted from direct penetration of trichome bases. Spores of the fungus germinated and produced appressoria within 4 to 5 hr after inoculation, but did not penetrate the stem epidermis via the appressoria until 48 hr after inoculation. Infection resulted in the formation of stem lesions, 2 to 3 cm long, which encircled the stem within 6 to 8 days after inoculation. Intracellular mycelium grew within the cortex, cambium, xylem, and pith ray tissues. Death of A. virginica seedlings was caused by collapse of infected stem tissues. Coalescence of lesions enhanced girdling of stems and hastened death. The fungus sporulated abundantly on lesion surfaces.