Summary
Auxotrophic and morphological mutants of Verticillium albo-atrum (producing darkly pigmented resting mycelium) and V. dahliae (forming dark microsclerotia) were isolated after treatment of conidia (haploid and uninucleate) with ultraviolet light. Hyphal tip and conidial analysis revealed that complementation between pairs of auxotrophs on minimal medium was due to a mosaic of homokaryotic and heterokaryotic regions with some hyphal tips growing syntrophically. A degree of incompatibility was observed in a few intraspecific, but in most of the interspecific, heterokaryon tests. Heterozygous diploid conidia (6–11 μ in length compared with 3–6 μ for haploids) were recovered at a frequency of 1 in 8x106 by plating spores at high density on MM. Young diploid colonies segregated to give haploid and diploid sectors, some of which were recombinant types (parasexual cycle). Heterokaryons between complementary auxotrophs which were wild-type for dark pigmentation (hyl+) resembled wild-type and only darkly pigmented colonies were recovered by conidial analysis. Heterokaryons between hyl+ and hyaline (hyl) auxotrophs again resembled hyl+ morphology and usually only hyl+ colonies of both auxotrophic genotypes were recovered. Conidia from heterokaryons formed by stable hyl auxotrophs produced only hyl colonies of both auxotrophic genotypes. The important role played by cytoplasmic factors in the inheritance of darkly-pigmented resting structures in Verticillium was strongly confirmed by the present work.
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Typas, M.A., Heale, J.B. Heterokaryosis and the role of cytoplasmic inheritance in dark resting structure formation in Verticillium spp . Molec. Gen. Genet. 146, 17–26 (1976). https://doi.org/10.1007/BF00267978
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DOI: https://doi.org/10.1007/BF00267978