Dry rot of potato caused by Fusarium species is a common and commercially important disease of potato tubers found in all production areas of the world, including Malaysia. The objective of this study was to identify Fusarium species associated with wet market potatoes and their pathogenicity on potato tubers in Malaysia. In this survey, 65 Fusarium strains were isolated and identified from diseases decayed potato's segments collected from different regions in Malaysia. All of these 65 isolates, which belong to two morphotypes of Fusarium solani species complex (FSSC) and Fusarium oxysporum, were evaluated to study their pathogenicity on healthy potato tubers. The tubers rot symptoms were observed on the 21st day after inoculation of F. solani and F. oxysporum strains on the tubers tested. In the tubers inoculation tests, lesion sizes were quite variable; therefore, the measurement was done to compare the depth and width of lesion expansion among the strains. The results of the pathogenicity test revealed that F. solani isolates FSO4, FSO12 (morphotype I), FSO18 (morphotype II) and F. oxysporum isolates FOX4 and FOX16 were strongly pathogenic to inoculated potato tubers. The inoculated fungi were re-isolated from the diseased potato tubers to prove the Koch’s postulates. The present study showed that two morphotypes of F. solaniwere associated with tuber rot of potato in Malaysia. This is the first comprehensive report on identity and distribution of major pathogenic fungi causing potato dry rot in Malaysia.

Key words: Occurrence, pathogenicity, dry rot, potato, Malaysia.