The occurrence of root rot and crown rot of rice in Gilan and Zanjan provinces, Iran.

Root rot and crown rot of rice is one of the important fungal diseases of rice in Gilan and Zanjan provinces, Iran. During 1999--2002, samples of plant and soil around the roots of infected rice plants were collected and used to identify the causal agent. Root and crown parts were surface sterilized with sodium hypochlorite and then cultured on PDA (potato dextrose agar), PPA (pepton pentacholoritobenzene agar) and CLA (carnation leaf agar) media. Soil samples prepared in water agar were used to isolate the pathogen. The causal agent was identified as Fusarium moniliforme. Colonies were initially white but turned violet to grey late. Microconidia were arranged in chain and macroconidia were cylindrical and long with 3-5 septa. The disease was severe in Zanjan province particularly along Ghezel Ozan river where the infection ranged from 70-80%. Root and crown rot was more prevalent in areas where Champa and Gerdeh were being cultivated continuously. On the other hand, Sadri cultivars had relatively less infection. Persistent cultivation of rice and seed sowing method intensified disease development and caused significant economic losses.

Identification of physiological races of Blumeria graminis f. sp. tritici and evaluation of powdery mildew resistance in wheat cultivars in Sistan province, Iran.

Powdery mildew of wheat caused by Blumeria graminis f. sp. tritici (Bgt) is one of the most important fungal diseases in Iran. During the years 1998-2001, wheat fields in Sistan province were surveyed and powdery mildew infected samples were collected from various areas and transferred to the laboratory. In the greenhouse, fungal spores were purified and inoculated onto susceptible wheat cultivars using single pustule and single spore procedures. Selected pure isolates were inoculated onto the first leaves of eight differential wheat varieties for identifying physiological races. The results showed the existence of Bgt races 5, 11, 14, 19, 21, 24, 27, 28, 31, 32, 44, 50, 53, 58, 66, 73 and 84 in Sistan. These races were new to Sistan province and Iran as a whole. Among 17 races studied, races 11, 53 and 73 were important dominant races thus constituting 40% of total population. Race 53 constituted 16% of all isolates and was the dominant race in the area with 62.5% pathogenicity. Therefore, this race was introduced as the most virulent race during the period of this study. This study showed that Bgt isolates were compatible with host plant genes pm8, pm3 and pm3b but incompatible with gene pm4b. Powdery mildew resistance was evaluated using race 11 on 70 wheat cultivars during seedling stage as well as adult plant under both greenhouse and field conditions between 1999 and 2001. Among wheat lines tested for resistance against powdery mildew, cultivar Hirmand resembled the differential line Weihenst M1 in that both may possess gene pm4b and showed no symptoms under the greenhouse and field conditions. Cultivar Chamran was found to be highly resistant whereas Sorkhtokhm was susceptible. Other cutivars showed partial and gradual resistance against the powdery mildew disease.