Distribution ofVerticilliumin Stems of Resistant and Susceptible Species of Mint

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Abstract
Two methods were used to ascertain whether the ascent or proliferation of V. dahliae is retarded in the stems of the resistant Mentha crispa compared to that in the susceptible M. piperita. In the greenhouse, young cuttings of both mint species were planted in soil artificially infested with V. dahliae. Surface-sterilized nodes of these plants were plated out on agar weekly and the presence of V. dahliae was ascertained for each node. In the field, rooted cuttings were planted into heavily infested soil; once a week, the stem of each sampled plant was cut into segments and the segments were individually fragmented in a small amount of distilled water. The resulting suspension was plated out and the relative amounts of propagules of V. dahliae were ascertained. No difference in the ascent of V. dahliae in stems of either mint species was detected. However, 2/3 of the infected plants of M. piperita yielded 100-15,000 propagules/mm of stem length. Most plants of M. crispa yielded fewer than 10 with a maximum of 57 propagules/mm of stem. Evidently, M. crispa suppresses the proliferation of V. dahliae, but not the ascent of the fungus within the stems.