ارزیابی ویژگی‌های مورفولوژیک و صفات مرتبط با خوابیدگی بوته در ارقام اصلاح‌‌شده برنج (Oryza sativa L.)

In order to evaluate the morphological characteristics and lodging-related traits and comparison of improved cultivars of rice plant resistance to lodging, a field experiment was carried out in randomized complete block design with three replications in 2012 at the Rice Research Institute of Iran )Rasht(. Rice cultivars were Kadus, Khazar, Gohar, Dorfak, Sepidrood and Deylam and local rice cultivar (Hashemi; susceptible to lodging as a control). Plant height, stem length, internode length for the first, second, third and fourth internodes, diameter, thickness and cross- section area of third and fourth internodes, ratio of fresh weight and dry weight of third and fourth internodes to internode length, breaking resistance, bending moment and lodging resistance of third and fourth internodes and pushing resistance were examined. Khazar cultivar with greater thickness of third and fourth internodes (4.11 and 4.26 mm), diameter of third and fourth internodes (8.33 and 9.46 mm), cross- section area of the third and fourth internodes (40.96 and 52.32 mm2) and ratio of fresh weight of third and fourth internodes to internode length (301.48 and 444.15 mg.cm-1) and ratio of dry weight of third and fourth internodes to internode length (49.46 and 50.38 mg.cm-1), breaking resistance of the third and fourth internodes (14.43 and 20.87 N, respectively) was found to be the most resistant cultivar. Khazar cultivar with a plant height of 121 cm was found to be the tallest among all studied cultivars. Considering the strong correlation found between thickness, stem diameter, cross- section area of third and fourth internodes and ratio of fresh weight and dry weight of third and fourth internodes to internode length with breaking resistance and pushing resistance, it seems that these traits could be considered as indirect indices in selection for higher resistance of rice cultivars to lodging.