Potato wilt and dry rot caused by Fusarium solani are very important agents of yield reduction in potato fields and storages in Iran. Using resistance cultivars is the most effective and economic control measure, therefore evaluation of different pathogenicity tests is necessary in order to choose the most accurate one for experimental purposes. In sampling during the growing seasons of 2003-2004, from the main potato producing areas of Razavi and Northern Khorasan provinces, from total of 74 isolates, 22 F. solani isolates of wilting and dry rot was obtained from stem, crown, root and tuber parts of potato plants. Evaluation of four methods including;1- soil-infestation, 2-root dipping, 3-tuber inoculation with spore suspension and4- tuber inoculation with the fungus pure culture were conducted using complete randomized block design with 3 replications, on susceptible cultivar Agria in green house. Our results indicated that in soil-infestation method, root rotting appeared by 13% of isolates and wilting by 87%. In addition from the 87% isolates causing wilting, 40% showed vascular necrosis in stem region .In second method, severe wilting developed by 60% of isolates and mild wilting by 40%. In third method, 63% of the isolates caused severe dry rot, 32% intermediate, and 5% mild dry rot while in fourth method, 13% of isolates induced severe wilting, 74% intermediate and 13% mild wilting symptoms. In this experiment, it was revealed that tuber inoculation with spore suspension is the most accurate, rapid and time saving method

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