introductory identification of resistant lines against the striped stem borer, chilo suppressalis (walker) under field conditions

in sustainable agriculture, using of resistant plants is one of the best methods for integrated pest management. resistance of 140 rice promising lines against striped stem borer was evaluated in two planting date in the field under natural infections in sari agricultural science and natural resources university during 2008-2009. this study carried out as a factorial experiment in randomized complete block design with three replications. the results showed that lines of 131 (noksiah×fajr) with 94.2% and 27 (sang tarom×deylamani) with 91.4% had the highest percentage of infection and lines 2 (tarom × deylamani) and 70 (ir58025a×ir-19r/neda) had the lowest percentage of infection against the striped stem borer. therefore, these lines identified as lines of susceptible and relatively resistant, respectively. in evaluation of white head in lines to striped stem borer, the results showed that 21.42% of total lines were susceptible and 11.63% were resistant. also, percentage of infection (9.62%) and white head (14.17%) in second planting date (mid june) were higher than first planting date. coefficients of correlation for morphological traits showed that plant height (r = 0.197) and tiller number (r = -0.101) had effect on percentage of infection and tiller number (r = -0.25) on percentage of white head. also, it represented correlation between stem diameter and tiller number. increasing of tiller number causing decreasing of stem diameter make effective resistance.