INVESTIGATION ON GENETIC DIVERSITY OF FUSARIUM OXYSPORUM CAUSING POTATO FUSARIUM WILT BY PATHOGENICITY TESTS AND RAPD MARKERS

Fusarium oxysporum causing potato Fusarium wilt has become widespread in most potato fields of Iran and causes consideraabl yield loss. Using resistant cultivars is still the most effective method of management of this disease. However, for screening cultivars for resistance, knowledge of genetic diversity of a fungal population is necessary. In this study, genetic diversity of the pathogen in Tehran, Hamedan and Ardebil provinces was studied. Seventy isolates of F. oxysporum were isolated from infected plants. Pathogenic variability of the isolates in terms of degree of  wilting and root-rotting was tested and their genetic diversity was studied using seven RAPD primers. Pathogenicity tests were based on completely randomized design (CRD) with four replicates. The result of pathogenicity tests showed that isolates caused potato wilt had lower root-rot potential and vice versa. Cluster analysis of RAPD data using UPGMA method and Dice’s coefficient distinguished 8 main groups at 71% similarity level. Also, 18 molecular phenotypes were detected among isolates. The low number of distinguished groups observed among the populations could suggest that these isolates have probably originated from a common ancestor and sexual reproduction has played a minor role in genetic variability of the fungus in its life cycle. Also no apparent correlation was found between RAPD groups and geographical region and it suggests that they are independent from each other.