This study was conducted to evaluate the gene effects, heritability, heterosis and identification of
appropriate breeding methods for improving rice viscosity parameters, during 2014-2016 at Rice
Research Institute of Iran. The progeny obtained from the North Carolina III mating design with their
parents were planted in a randomized complete block design with three replications. Analysis of
variance for viscosity parameters revealed that the effect of females, male effect and interaction
between males and females effect were significant for all parameters with the exception for peak
viscosity. Evaluating of genetic parameters indicated that viscosity characters are affected by additive
and non-additive effects of gene action. The share of non-additive effects in genetic control of peak
viscosity had beyond additive gene action, while, the contribution of additive effects was greater for
the breakdown viscosity, final viscosity and setback viscosity. High estimates of broad sense
heritability revealed that the expression of viscosity parameters is more influenced by genetic effects.
With regard to non-additive gene actions and low narrow sense heritability estimation in peak
viscosity, using hybrid based programs would be promising to improve this trait. For other viscosity
parameters, narrow sense heritability estimates were high. Therefore, the use of selection based
programs to improve these traits is encouraging. Assessing of relative heterosis through mid-parents
showed that heterosis ranged from -3.73 to 1.93%, 5.51 to 21.33%, -4.57 to 1.26% and -26.04 to
9.36%, for the peak viscosity, breakdown viscosity, final viscosity and setback viscosity, respectively.