Assessment of general and specific combining abilities of the starch paste viscosity properties in parental lines of hybrid rice

Starch comprises about 90% of milled rice, therefor the eating and cooking quality of rice is mainly affected by the starch properties. The eating and cooking quality of rice has usually been evaluated by three major physical and chemical properties of the starch including; amylose content, gel consistency and gelatinization temperature. In addition, other important properties of starch, such as paste viscosity have been established to evaluate more precisely the cooking quality of rice. To determine the general and specific combining ability of starch paste viscosity properties in the parental lines, five restorers and four cytoplasmic male strile (CMS) lines were selected as lines and testers, respectively. These CMS and restoring lines were a random sample of parents from a reference population of rice breeding materials in Iran. Nine parents were crossed in a Line × Tester crossing system in 2005. Twenty F1 hybrids and their parents were evaluated in a randomized complete block design with two replications for evaluating paste viscosity characteristics. The paste viscosity properties were determined by the Rapid Visco Analyzer. General combining ability (GCA) and specific combining ability (SCA) were determined by Kemptrhone method. In this study, mean of the parents and hybrids were also compared with the local rice varieties for paste viscosity properties based on 95% confidence interval. The results revealed that effects of GCA and SCA were significant for all of the paste viscosity properties. The additive effect was greater than dominance and environmental effects for all of the paste viscosity properties, except pasting temperature. For this parameter, environmental effect was high. All of the parents were out of the confidence interval of the pasting properties. Therefore, they were not suitable for cooking and eating quality. However, among the crosses, five hybrids SA15A×IR53R, IR79124A×SepidroodR, SA15A×SA14R, IR79124A×IR53R and IR58025A×SA14R were in the confidence interval of the pasting characteristics based on the paste viscosity properties, and had good cooking and eating quality similar to local rice varieties.