ارزیابی کمّی خسارت بیماری نوک سفیدی برگ برنج ناشی از نماتود Aphelenchoides besseyi در شرایط گلخانه و میکروپلات

In order to estimate the loss of rice caused by white tip nematode, (Aphelenchoides besseyi), to Alikazemi cv., two series of experiments were conducted in greenhouse and microplot conditions at Rice Research Institute, Rasht (Guilan province) during 2005-2006. The microplots sizes were 0.5×2 meter. Rice seedlings were inoculated by plastic tube method with 0, 100, 300, 500, 700 and 900 nematodes per plant. The experiments were arranged in greenhouse and microplot conditions as a completely randomized design and completely randomized block design with four replications, respectively. The factors under investigation consisted of symptoms (number of plants and Leaves infected), yield and population density of nematodes. The variance analysis of data showed significant differences among treatments in all parameters. The minimum infestation level leading to symptoms and yield loss in microplot condition (500 nematodes) was greater than greenhouse (300 nematodes). Regression analysis of data revealed that the yield reduction was mainly explained by population of nematodes in greenhouse and microplot (R2= 92.56, R2 = 91.55). Also, there was a positive correlation at 5% level of probability between disease incidence and nematode population (R2= 84.42, R2 = 75.27). The resulting equations from regression can be used to estimate crop loss from population of nematodes.