Easy and Accurate assessment of sclerotinia stems rot of canola

Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum, is one of the most damaging diseases of canola in many areas of the world, including Iran. The relationship between disease incidence (I) and severity (S) is an epidemiologically significant concept, because incidence is quicker and easier to measure than severity. It is generally perceived that measures of incidence are often more accurate, precise, and reproducible than measures of severity, but severity is often considered a more important and useful measure of disease intensity than incidence for certain objectives. The I-S relationship of SSR of canola was studied in Golestan province, northern Iran. Statistical analyses were performed on three factors: fields, location/year combinations, and all data collected for the final model. For the first factor, allometric (ln transformation of I and S) model had the best fit, but in the second factor, the slope of linear and ln models at the Gonbad location was significantly different from three other locations (Gorgan, Ali Abad, and Kalaleh). Final models were evaluated based on R2, SEEy and residual plots of regression analysis of raw and back-transformed data. Based on these criteria, final models were of allometric family, both in Gonbad (S = (0.526) I (1.2)) and three other locations (S=(0.82) I (1.073)).