evaluation the effect of morphological and physiological characteristics of stem on lodging in 12 genotypes of rice

in order to evaluate the morphological characteristics and lodging related traits and carbohydrate content of culm and carbohydrate remobilization in traditional and improved rice cultivars, a field experiment was laid out in randomized complete block design with three replications at rice research institute of iran )rasht( in 2012 and 2013. rice genotypes included three native rice cultivars (hashemi, sang­jo and alikazemi) and six improved (kadous, gohar, khazar, sepidrood, deylam and dorfak) and three promising lines (831, 841 and 416). on the basis of this results, the greatest amount of breaking resistance were observed in third and fourth internods of khazar. furthermore, significant positive correlation were observed between average diameter of internode, fresh weight/length of internode and unsoluble carbohydrate content of culm in anthesis and maturity stages with breaking resistance of third and forth internods. also, significant positive correlation was observed between number of parenchyma cells and unsoluble carbohydrate content of culm in anthesis and maturity stages. on the other hand, there was significant negative correlation between carbohydrate remobilization and breaking resistance of third and forth internods. principal component analysis classified plant characteristics to two groups. the first factor was named as lodgigng resistance factor and included 71.01 percent of total variation. the second factor with 19.74 percent of total variation was named as morphological lodging sensitivity factor. according to the results of this experiment, it seems that average diameter, thikness and weight/length of internode, have major roles in rice plant resistance to lodging.