ABSTRACT

The soil-borne fungal pathogen Sclerotium rolfsiii is a basidiomycete that typically exists only as mycelium and sclerotia. It causes the disease Southern Blight and typically overwinters as sclerotia. This study was carried out to evaluate the effect of carbohydrate sources and illumination on mycelial growth and sclerotia production of Sclerotium rolfsii. Sclerotia of Sclerotium rolfsii were obtained from cassava petiole in the University of Benin, Benin City.  Sclerotia was aseptically transferred into a sterile petri dish, washed severally with distilled water, filtered and dried. Sclerotium rolfsii was cultured in Plantain Dextrose Agar, Cassava Dextrose Agar, Cocoa Yam Dextrose Agar, Yam Dextrose Agar, Potato Dextrose Agar, Guinea Corn Dextrose Agar and Maize Dextrose Agarfor five days to evaluate the effect of light on the production of sclerotia. Results revealed that the effect of selected carbohydrate sources on the mycelial extension of Sclerotium rolfsii exposed to light were as follows; PLDA ranged from 1.35±0. 15 - 4.90±3.15, CDA (1.35±0. 15 - 8.07±5.17), CYDA (1.35±0.15 - 6.23±4.61), YDA (0.93±0.07 - 3.67±2.00), PDA (0.90±0.05 - 5.07±3.41), GCDA (0.90±0.05 - 4.72±3.05) and MDA (0.90±0.05 - 4.25±2.72). While the effect of selected medium without carbohydrate sources showed that day 1 ranged from 0.90±0.05 - 3.76±1.31, day 2 (0.90±0.05 - 7.36±3.16), day 3 (1.60±0.03 - 8.50±5.89), day 4 (1.03±0.11 - 6.83±3.51), and day 5 (0.97±0.07 - 6.30±1.15) respectively. The mycelial growth of pathogen exposed to continuous darkness resulted in minimum mycelial growth and their no growth of sclerotia  except those exposed to continues light(without dextrose).This study have shown that a proper media formulation and light conditions is essential for the mycelial growth and development of sclerotia of S. rolfsii. However further investigations are needed to examine the effect of other selected environmental and nutritional factors on the growth and development of S. rolfsii