Charcoal rot, caused by
Macrophomina phaseolina
(Tassi) Goid., is an economically important disease of oilseed plants
in Northern Iran. Seventy isolates of
M. phaseolina were obtained from different hosts, including soybean (
Glycine max
L.), and sunflower (
Helianthus annuus
L.) in the northern oilseed planting regions of Iran. RAPD-PCR amplification
profiles, by using of six random OPA primers (kit A) showed polymorphisms among the isolates. The primer OPA-13 (5'_
CAGCACCCAC_3') amplified the genomic DNA of all isolates of
M. phaseolina producing 4-12 bands of sizes between
0.25 and 2.3 kb. Unweighted pair-group method with arithmetic mean (UPGMA) analysis classified the isolates into the
nine major groups with 64% similarity. Pathogenicity of isolates was evaluated at seedling stage of soybean, sunflower, and
maize (
Zea mays
L.) plants under
in vitro conditions. None of the isolates were pathogenic on corn, while all of the isolates
infected soybean and sunflower seedlings. Isolates were more virulent on soybean than sunflower. The disease index on
sunflower and soybean varied between 19-24 and 27-30 respectively. These results indicated a significant pathogenic and
genetic variability within the Iranian isolates of
M. phaseolina. Cultivation with crop rotation was probably tended to
induce less diversity of the pathogen isolates.
