Fine Structure of Conidia and Conidium Formation in Verticillium Albo-Atrum and V. Nigrescens

SUMMARY

The fine structure of hyphae and conidia of 2 isolates of Verticillium albo-atrum and one isolate of V. nigrescens, all pathogens of cotton, was generally similar to that of other fungi. The presence in hyphae of single, central septal pores and associated Woronin bodies indicated that the septal pore apparatus may be typically ascomycetous. Conidia from tracheal fluids of cotton plants or from liquid or agar cultures often germinated by producing a phialide-like conidiophore which produced one or more secondary conidia. The production of secondary conidia did not resemble a budding process but consisted of the extrusion and growth of a conidium from a constricted opening at the end of the conidiophore.