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Differences in Sensitivity of Verticillium Species to Ultraviolet Irradiation. John E. Puhalla, Research Geneticist, USDA, ARS, Southern Region, Oklahoma-Texas Area, National Cotton Pathology Research Laboratory, P. O. Drawer JF, College Station, Texas 77840; Phytopathology 63:1488-1492. Accepted for publication 25 May 1973. DOI: 10.1094/Phyto-63-1488.

Fifteen isolates each of Verticillium dahliae and V. albo-atrum from several plant hosts and geographical locations were tested for sensitivity to ultraviolet light. Two major groups were found: a very sensitive group, which included 14 of the 15 V. albo-atrum isolates, and a relatively resistant group, which included the 15 V. dahliae isolates. The one remaining isolate of V. albo-atrum, from lucerne in the United Kingdom, was intermediate in sensitivity. Two dark mycelial variants of V. dahliae, derived from germinated microsclerotia, were resistant like their progenitors. Ultraviolet sensitivity is apparently a characteristic difference between the two species, and is offered as an additional criterion for separating them.