Variability for isozyme, vegetative compatibility and RAPD markers in natural populations of Phomopsis subordinaria

Abstract

Phomopsis subordinaria is a common fungal pathogen which attacks the scapes of Plantago lanceolata in natural populations. Three classes of genetic markers (isozymes, vegetative compatibility (VC) and random amplified polymorphic DNAs (RAPDs)) were tested for their suitability to reveal polymorphisms among isolates of P. subordinaria , originating from 27 locations in the Netherlands and 7 locations in other western European countries. Enzyme electrophoresis failed to show any variation in P. subordinaria . No polymorphisms were found with seven enzymes in 69 isolates originating from 23 locations. Enzyme electrophoresis is, therefore, not a suitable method to identify individual isolates of this species. In contrast, VC tests and RAPDs revealed substantial variation. With VC tests 89 VC groups (VCGs) were found among 134 isolates from 34 locations. Four RAPD primers could distinguish between 15 RAPD groups among 47 isolates from 8 locations. Similarity coefficients were calculated using 18 RAPD characters. These values revealed a high genetic resemblance among the 15 RAPD groups. Shannon-Weaver indexes, based on the VC and RAPD data, were calculated for three locations. Two locations proved to be significantly more diverse than the third. Our study suggests that vegetative compatibility and RAPDs are two independent methods which can be helpful tools for research projects on evolutionary relationships and on genetic structure in fungal populations. The VC test is a sensitive method to find variation in P. subordinaria , but RAPD analysis can be used to calculate phenotypic distances.