فیتوفترا

Late blight (PLB), caused by Phytophthora infestans, is the most important diseases of potato in the world and Iran that 16 models have been developed for forecasting so far. Gorgan county had the largest potato cultivated area in the province and during recent 17 years, PLB appeared in 11 years with different severities. In order to developing a forecasting model based on “blight favorable day” concept, daily weather data converted to periodic and conditional variables, at last three predictor variables were developed. FTP was the best predictor variable which composed of three temperature variables and two precipitation variables and its daily score was -2 to 4. Accumulated FTR from 21 March to disease appearance was 64 and in no-disease years was 4. Prediction accuracy of the model was 75% and 89% based on logistic regression and discriminant analysis, respectively and sensitivity and specificity of final model was 92 and 100%, respectively.

This research was performed to determine the host range of tomato isolates of Phytophthora capsici، among other common crops in Fars province. Seeds of tomato، squash، cucumber، melon، pepper، watermelon، pea، french bean، onion، carrot، corn، cantaloupe، eggplant، and wheat were sown in sterilized soil and kept in a greenhouse. Seedlings were inoculated by adding 50 ml of a zoospore suspension (1×105 spores per ml) of Ph. capsici onto the soil surface around the stem of each plant in the pot. Plants were kept in a growth chamber. Disease incidence was measured three times at 5، 10، 15 days post inoculation. Twelve of the tested plant species became infected with Ph. capsici and developed symptoms including crown and root rot، and yellowing، which led to plant death after two weeks. Ph. capsici was re-isolated from all symptomatic plants. Tomato، squash، cucumber، melon، pepper، watermelon، cantaloupe and eggplant were the most susceptible، while، pea، french bean، onion، carrot and sugar beet were less susceptible to the pathogen. Wheat and corn did not show any disease symptoms and were considered as non-hosts. The results of this study showed that common Poaceae crops in Fars province are non-host to Ph. capsici and can be used in crop rotation for disease management.