Submitted to: Biologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 3, 2000
Publication Date: February 27, 2001
Citation: RUSSO, V.M. CULTURE CONDITONS AFFECT COLONIZATION OF WATERMELON BY COLLETOTRICHUM ORBICULARE. BIOLOGIA PLANTARUM. 2001. 44:305-307. Interpretive Summary: Fungal pathogens are some times not successful in the infection process. This can may be due to growth conditions. Colletotrichum orbiculare, the causal agent of anthracnose on watermelon (Citrullus lanatus), was grown on two levels of potato-dextrose agar for 7-, 14-, or 21-days, and watermelon seedlings were inoculated. The amount of watermelon tissues with lesions was not affected by the amount of agar on which the fungus was grown. However, spores harvested from aging colonies did not appear to be as virulent since the amount of resulting lesions on watermelon tissues decreased. As spores aged microscopic examination indicated that their internal integrity was degraded which likely contributed to a reduced ability of spores to colonize plant tissue.
Technical Abstract: The ability of a fungal pathogen to be successful, in part, depends on the substrate on which it grows. The anthracnose causal organism, Colletotrichum orbiculare, was grown on 10- or 20-mL of potato-dextrose agar. At 7-, 14-, or 21-days of culture spores were harvested, and at each harvest watermelon (Citrullus lanatus) seedlings at the third-leaf stage were inoculated. After 7-days the area of plant tissue with developing lesions was determined. Lesion area was not affected by amount of culture medium on which the fungus was grown, and decreased as length of time the fungus was in culture increased. The spores from each harvest were examined with fluorescence microscopy and it was determined that internal integrity of C. orbiculare spores appeared degraded as length of time in culture increased. This degradation was coincident with decreases in lesion area.