ارزیابی میزان مقاومت ارقام برنج به کرم سبز برگخوار (Naranga aenescens Moore)

Green semilooper, Naranga aenescens Moore (Lepidoptera: Noctuidae) is a major pest in paddy fields of northern Iran. Since plant resistance to pests is a method with high efficacy and safety, a research was conducted to evaluate the resistance of 12 rice varieties (including, Tarom, Shafagh, Hybrid, Khazar, Poya, Fajr, Kados, Shiroodi, Sahel, Tabesh, Nemat and Neda) to N. aenescens on the basis of randomized completely blocked design (RCBD) with 3 replications. All experiments were conducted during the crop season of 2007 in Amol Rice Research Institute, Mazandaran. Samplings were conducted twice in the vegetative and once in the reproductive stages. A total of 10 plants were randomly obtained from each plot (10 × 10 m2) and different characteristics were analyzed. The studied characteristics were tiller number, originally tiller number, infected originally tiller number in the vegetative stage and tiller number, fertile tiller number, leaf flag number, infected leaf flag number in the reproductive stage. Determining damage severity was scored on the basis of IRRI standard. The results indicated that there were significant differences between the varieties' characteristics at 1% level. Duncan test indicated that Tarom and Khazar varieties had the highest damage severity, respectively at the 1st vegetative stage, but Tarom and Sahel varieties had the highest and lowest damage, respectively at the 2nd vegetative stage. At the reproductive stage, Tarom and Sahel varieties had the highest and lowest damage, respectively. Using the IRRI method for scoring of eaten leaves, Tarom and Hybrid varieties had the highest damage, and Sahel had the lowest damage. The severity of damage was decreased from the beginning of vegetative stage to the end of reproductive stage significantly and the measures indicated that Tarom had the highest damage.