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Poster: Diseases of Plants: New & Emerging Diseases


Pathogenicity tests confirm Macrophomina phaseolina as an aggressive fungal pathogen of flowering dogwood (Cornus florida L.)
L. MACKASMIEL (1) (1) Tennessee State University, Nashville, TN, U.S.A.

Pathogenicity tests where seedlings of flowering dogwood (C. florida L.) were challenged with extracted spores of Macrophomina phaseolina from 10 day-old cultures, while control were mocked inoculated with plain malt extract agar in sterile deionized water, demonstrated the capability of the pathogen to cause severe root rot in C. florida. Roots of juvenile seedlings vernalized in sterilized vermiculite; then grown on large water agar petri plates overlaid with sterile, moisten-filter paper, after being inoculated with the pathogen, showed high percentage of necrotic tissue in the first 10 mm of root tips. Concurrently, juvenile seedlings grown in large containers after similar treatment exhibited presence of fungal structures in roots from challenged plants that were not observed in the control. On 35 day-young dogwood seedlings grown in sterile soil under greenhouse conditions and inoculated on wounded stems, fungus-treated plants produced decay and large canker-like lesions that were not on the control. The extent of fungal growth in millimeter (mm) as the index to evaluate the host’s response(s) showed marked difference between treatments and control. The level of aggressiveness of the pathogen was determined by measuring the duration and number of dead tissues or plants per given time, and cell death confirmed the amount of infection inside the roots.