Identification and distribution of fungi associated with root and crown rot of Hopbush (Dodonaea viscosa ) in some regions of Khuzestan province

Hopbush (Dodonaea viscosa) is a member of Sapindaceae family which is used as an ornamental hedge plant and has valuable medicinal properties. Its cultivation in Khuzestan province is faced with some difficulties including root and crown rot diseases caused by different soil borne pathogens. In order to identify fungi associated with Dodonaea viscosa crown and root rot and their distribution during 2011, samples were collected from Ahvaz, Sousangerd and Hamidieh regions in Khuzestan province. The Samples were sterilized with 1% and 5% sodium hypochlorite or ethanol and were finally transfered on PDA, CMA and Nash & Snyder media. The recovered isolates were purified using single spore and hyphal tip methods. Sixty-five fungal isolates were obtained including 60 isolates of the genus Fusarium, 3 isolates of Lasiodiplodia hormozganensis and 2 isolates of Pythiumsp. Based on their morphological characters, Fusarium isolates were identified as F. solani and F. equiseti. The frequencies of the isolates of F. solani, F. equiseti, L. hormozganensis and Pythium sp. were 84.6, 7.6, 4.6, and 3.0 percent respectively. Pthogenicity tests conducted in petri plates revealed that all the fungi isolates were able to cause seed rot, root rot and damping off. Invivo pathogenicity tests that were conducted using 2 of the most virulent isolates of F. solani, each one from Ahvaz and Sousangerd, showed that the inoculated plants were severely infected by the fungi and showed severe crown and root rot and damping off. This appears to be the first report of L. hormozganensis on Dodonaea viscose in the world. It seems that Lasiodiplodia is an aggressive pathogen whose different strains could cause diseases in plants as well as humans.