Effects of culture medium and lighting condition on induction of conidiation in Cercospora citrullina

Cercospora citrullina, isolated from pumpkin plant (Cucurbita maxima), initially could not produce conidia when cultured on potato dextrose agar, but was able to produce conidia when cultured on oatmeal agar, oat grain agar, wheat grain agar and barley grain agar. C. citrullina also produced conidia when cultured in substrates such as oat grain, wheat grain, barley grain and Trichosanthes sp. dried leaves. Trichosanthes sp. dried leaves induced the highest conidia production (4.81 × 103 conidia / ml) while oatmeal agar and barley grain agar yielded the best result among the agar media by inducing 1.23 × 103 conidia / ml each. Overall, continuous darkness condition was better than other lighting conditions (12 h near UV black light plus 12 h darkness condition; and 12 h fluorescent white light plus 12 h darkness lighting condition). Lastly, inoculation of C. citrullina onto cucurbit plants was successfully conducted by sandwiching inoculum between leaves and plastic cards.