Severity of walnut anthracnose and its relatively resistant in Iran

Walnut black spot or Anthracnose has been a destructive disease of Juglans in Iran mainly northwest of the country. Current situation of the disease was studied in various regions including Qazvin, Zanjan, Hamedan and East Azarbyjan provinces during 1999 to 2002. Infected samples such as leaves, fruits and foliage were collected and cultured in PDA, CMA and NA media after surface sterilization with sodium hypochlorite. Morphological characteristics and asexual reproduction of isolated pathogen showed that the fungal causal agent was Marssonina jglandis (Lib) Magn. which perfect stage was Gnomonia leptostyla (Fr). The disease was severing under studied areas, especially when it was rainy and humidity. Virulence of the disease caused major defoliation in some walnut trees infected to anthracnose disease. So, investigation showed that the collecting or burning infected leaves and fruits under trees could reduce severity of disease. Study also resulted there was a resistant variety around the Qazvin province traditionally called "Alamoty" which had not any anthracnose infection in natural condition. The result of experimental work with inoculation of different walnut clones by spore suspension (10(5)) in glasshouse has also indicated that this original clone was more resistant than others to anthracnose disease. Alamoty clone had favorite yield production and some trees presented more than 250 years old in Iran.