Relationship between DNA Content and Spore Volume in Sixteen Isolates of Verticillium lecanii and Two New Diploids of V. dahliae (= V. dahliae var. longisporum Stark)

Summary: Sixteen wild-type isolates of Verticillium lecanii from different insects and non-insect hosts, soils and locations exhibited a wide range in spore volumes, from 2.18 μm3 to 18.25 μm3, as recorded by Coulter counter analysis. A cold hydrolysis technique for Feulgen DNA microdensitometry indicated that all the isolates were haploid. Two wild-type strains of V. dahliae, from rape and sugarbeet from Sweden, were shown to be stable diploids by the criteria of conidial volume and relative DNA content. After treatment with p-fluorophenylalanine, both V. dahliae strains produced haploid segregants with half the conidial volume and relative DNA content of the original parents. Both diploid strains are regarded as new records for V. dahliae var. longisporum (Stark).