University of Tehran Iranian Journal of Plant Protection Science 2008-4781 51 1 2020 08 22 A comparative study on disease progression curves of grapevine downy mildew in North Khorasan province A comparative study on disease progression curves of grapevine downy mildew in North Khorasan province 109 119 77684 10.22059/ijpps.2020.295838.1006925 FA Hamid Namvar-hamzanlue Plant Protection Department, North Khorasan Agricultural and Natural Resources Research and Training Center,Agricultural Research,Education and Extension Organization (AREEO), Bojnourd, Iran. 0000-0002-4629-6404 Mohammad Aghajani Plant Protection Research Department, Golestan Agricultural and Natural Resources Research and Education Center, AREEO, Gorgan, Iran. 0000-0001-6002-3149 Safarali Mahdian Plant Protection Department, Agricultural Faculty, Sari Agricultural Sciences and Natural Resources University, Sari, Iran Esmail Bakhshandeh Genetics and Agricultural Biotechnology Institue of Tabarestan, Sari Agricultural Sciences and Natural Resources University, Sari, Iran Journal Article 2020 01 14 Grapevine downy mildew caused by Plasmopara viticola is the most important factor in decreasing grape production in temperate and rainy regions. To investigate the disease progression curve in vineyards of North Khorasan province during two years of 2018 and 2019, Scoring of the target vineyards was carried out each week on a regular schedule from mid-April at the bud swelling time from the vineyard. The incidence rate and severity of the disease in 80 vineyards from four counties of Bojnourd, Maneh and Samolghan, Shirvan and Farouj were calculated. Linear regression was fitted to disease time progression curves with five population growth models as exponential, monomolecular, logistic, log-logistic and gompertz models. The model fitness was determined based on statistics as coefficient of determination (R2), standard error of estimates (SEE) and adjusted coefficient of determination (Ra2). The results showed that exponential, monomolecular, logistic, log-logistic and Gompertz models were fitted with 5, 27.5, 12.5, 17.5 and 37.5% of the disease in the studied gardens, respectively. Accordingly, Gompertz model with 96.76% coefficient of determination was selected as the most suitable model to describe disease progression in North Khorasan province. Rates of increase (rG) per unit of disease in each vineyard was 0.005 to 0.048 (with an average of 0.026). This is the first report of a study of the progression curve of grapevine downy mildew in Iran. Grapevine downy mildew caused by Plasmopara viticola is the most important factor in decreasing grape production in temperate and rainy regions. To investigate the disease progression curve in vineyards of North Khorasan province during two years of 2018 and 2019, Scoring of the target vineyards was carried out each week on a regular schedule from mid-April at the bud swelling time from the vineyard. The incidence rate and severity of the disease in 80 vineyards from four counties of Bojnourd, Maneh and Samolghan, Shirvan and Farouj were calculated. Linear regression was fitted to disease time progression curves with five population growth models as exponential, monomolecular, logistic, log-logistic and gompertz models. The model fitness was determined based on statistics as coefficient of determination (R2), standard error of estimates (SEE) and adjusted coefficient of determination (Ra2). The results showed that exponential, monomolecular, logistic, log-logistic and Gompertz models were fitted with 5, 27.5, 12.5, 17.5 and 37.5% of the disease in the studied gardens, respectively. Accordingly, Gompertz model with 96.76% coefficient of determination was selected as the most suitable model to describe disease progression in North Khorasan province. Rates of increase (rG) per unit of disease in each vineyard was 0.005 to 0.048 (with an average of 0.026). This is the first report of a study of the progression curve of grapevine downy mildew in Iran. https://ijpps.ut.ac.ir/article_77684_22e67dc512e60e5c4494a280ddd41d71.pdf