Nikoo Kakvan, Hamidreza Zamanizadeh, Bahar Morid, Hossein Taheri and Shahab Hajmansor
Different pathotypes of Alternaria alternata (Fr.:Fr.) Kessl, cause various diseases in citrus including Alternaria brown spot of tangerines, leaf spot in rough lemon and Alternaria black rot on citrus fruits. In order to study genetical structure of A. alternata populations, 36 isolates with the highest diversity in morphological traits and pathogenicity test were chosen from 87 isolates collected from infected leaves, fruits and twigs of various citrus gardens of Iran. Genetic diversity was analyzed based on RAPD-PCR using 15 random 10mer primers. These primers were among 35 random primers, based on clarity, repeatability and the number of polymorphic bands. Cluster analysis of DNA fragments was performed using NTSYSpc V2.2 based on UPGMA method and Jacard coefficient. Results of pathogenicity test showed obvious diversity in Alternaria isolates and they were classified as three groups: severe, moderate and low pathogenic. Cluster analysis of RAPD fragments of all primers revealed that isolates were classified in five groups at 85% similarity level. Molecular diversity of isolates was highly related to geographical region, host and partly virulence of isolates. This is the first study about genetic diversity of Iranian isolates of A. alternata fungus using RAPD molecular marker in its populations.
