GENETIC-VARIATION IN CYLINDROCLADIUM-FLORIDANUM AND OTHER MORPHOLOGICALLY SIMILAR CYLINDROCLADIUM SPECIES

Species of Cylindrocladium (C.) are anamorphs of the genus Calonectria (Ca.), and are important pathogens of numerous crops worldwide. C. fl oridanum is characterized by short, l-septate, straight, cylindrical c onidia and sphaeropedunculate vesicles. Isolates of Ca. kyotensis (ana m. C. floridanum), Ca. candelabra (anam. C. scoparium), Ca. morganii ( anam. C. candelabrum), C. ovatum and C. naviculatum were compared base d on morphology, sexual compatibility, radial growth on media with dif ferent osmotic potentials, RAPD markers and A + T-rich DNA (AT-DNA) po lymorphisms. In CLUSTER analyses of the data using the average linkage method, all five species clustered separately. RAPD profiles of ex-ty pe cultures of the two acknowledged synonyms of Ca. kyotensis (Ca. flo ridana, Ca. uniseptata) shared 78-97% similarity, supporting their con specificity. Strains of the opposite mating type of the respective het erothallic species studied shared high similarity coefficients of 77% for Ca. candelabra, and 92% for Ca. morganii. Two opposite mating type s of C. ovatum with 99% similarity mated to produce a new teleomorph, described here as Calonectria ovata. Based on their RAPD and AT-DNA pr ofiles, two major groups could be distinguished within Ca. kyotensis. Group two (including most of the Canadian isolates) shared only 12-45% similarity with the ex-type strains (group one) and clustered with me an correlation coefficients of r = 0.56 (RAPD analysis) and r = 0.37 ( AT-DNA analysis), respectively. An isolate similar to Ca. kyotensis bu t with curved conidia had distinct RAPD and AT-DNA profiles, and share d less than 35% similarity (r = 0.00) with any of the species studied. These findings suggest that strains with curved conidia and sphaerope dunculate vesicles represent an undescribed taxon, and the name Cylind rocladium curvisporum is thus proposed for them.