Application of culture filtrates of Ophiostoma novo-ulmi and O. ulmi under in vitro condition as a bioassay to screen for disease tolerant Ulmus parvifolia and Ulmus campestris

Dutch elm disease is the most important disease of elm trees in most planting regions. The use of tissue culture of plant under in vitro condition, to make easy study of interaction elm trees and Dutch elm disease agent and help for control disease via selection, improvement and reproduction resistant genotype. For this purpose during years 2004 until 2006, samples were collected from Ulmus campestris and Ulmus parvifolia in Golestan and Mazandaran provinces forest. In order to study ability and value of callus growth this two species, after use sterilized treatment, samples cultivated on MS media with different treatments from growth regulator. Growth callus from U. parvifolia and U. campestris were inoculated with different concentration of culture filtrates of Ophiostoma novo-ulmi. Fresh weight callus and vital cells after exposed to different concentration of culture filtrate was measured. Results showed the weight callus on two species was different and growth of callus of U. parvifolia (Chinese elm) was more significant (P= 0/05) than U. campestris. As thought the rate of weight decrease of callus in U. parvifolia and U. campestris, at 10% concentration was 13/3 and 28% respectively. Rate of cell vitality at 50% concentration of culture filtrate in U. campestris was 2 % but in U. parvifolia in the same concentration was 23 %. So it could concluded that the rate of tolerance and viability Chinese elm cells was more after exposed to media culture filtrate. On the basis of this study, U. parvifolia (Chinese elm) show most resistant to Dutch elm disease. Therefore, this method can fast of screening with select of tolerant calli.