STUDIES ON FUSARIUM WILT OF BANANAS: VIII. DIFFERENTIATION OF CLONES BY CULTURAL INTERACTION AND VOLATILE SUBSTANCES

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Abstract
Cultural interaction between paired clones A and C of F. oxysporum f. cubense on peptone dextrose agar was a reliable tool for identification of these clones. Cultural interaction consisted of the formation of two bands of dense mycelial growth. The first and largest band formed in clone C colonies back of the tips of the outermost hyphae in contact with adjacent clone A colonies. A second much smaller band formed with clone C hyphae outside of and adjacent to the large band. The smaller band sometimes merged with the larger. This specific band reaction was distinct from a non-specific "interaction" occurring on rice agar. Mutants were produced by clones A and C, which reacted with the parents by the formation of a single band of raised, dense mycelia. These reactions were unstable and non-specific. Cultural interaction was erratic and often poorly defined with ropy mutants of clones A and C. Cultural interaction with clone A readily identified clone C from banana roots from areas where a locus of infection had been initiated by inoculation 3 years previously. Thus, cultural interaction was useful in "tagging" F. oxysporum f. cubense for studies with mixed indigenous soil populations of F. oxysporum.‘Odoratum’ and ‘Inodoratum’ clones (readily separated by smell on steamed rice) were subjected to gas chromatography. All 'Odoratum' cultures gave a characteristic spectrum showing qualitative and quantitative differences from the 'Inodoratum' cultivar in volatiles produced. The characteristic 'Odoratum' smell after 7 days on steamed rice was associated with a spectrum not shown by 'Inodoratum' clones.