LIGHT-INDUCED BIO-CONTROL OF POTATO STORAGE PATHOGENS IN-VITRO

The influence of freeze dried potato powder derived from tubers (cvs D esiree and Epicure) exposed to light as a culture medium on the growth , number and spore size of nine fungal pathogens was determined in vit ro with particular emphasis on the role of glycoalkaloids. Greater red uctions in pathogen growth reflected increased exposure to light of tu bers prior to freeze drying. High correlations (% R-2 adj) were obtain ed between glycoalkaloid concentration and growth rate of the majority of pathogens tested. Where spores were produced, numbers were in gene ral significantly less when cultured on freeze dried powder derived fr om tubers exposed to light. No effects on spore size of Fusarium speci es were recorded, but spore length of remaining pathogens was reduced and spore width increased, with the exception of C. coccodes where spo re length and width was increased following culture onto freeze dried powder derived from tubers exposed to light.