Gene Action and Combining Ability for Certain Agronomic Traits in Red Rice Lines and Commercial Cultivars

Cultivated red rice (Oryza sativa L.) is the most important special type of rice in Brazil and makes an excellent food, mainly because of its nutritional value. Genetic variability, useful for rice breeding programs, exists among red rice accessions. The objectives of the present study were: (i) to determine the nature of gene action and magnitude of genetic components conditioning grain yield (GY), plant height (PH), and days to flowering (DTF); and (ii) to determine the combining ability for these traits in nine red rice lines (female parents) and four commercial cultivars (male parents). Thirteen parents, an F2 generation of 18 crosses, and a check cultivar were evaluated at two locations (Goianira and Teresina, Brazil) using a randomized complete block design with four replications. Data (unbalanced because of lost plots) from this incomplete set of crosses in a factorial mating design were subjected to variance analyses using a general linear model. According to Baker's ratio, nonadditive genetic effects were more important than additive effects for the expression of the three traits. The dominance deviations were predominantly negative for GY and DTF and were positive for PH. Crosses tended to be more productive (higher GY) and earlier (fewer DTF) than parental lines. General combining ability was largest for the MNA1106 line with red pericarp. The MNA1106/SCS 119 Rubi cross exhibited the highest potential for selection of high‐yielding red rice lines. MNA1101/SCS 119 Rubi, MNA1101/SCS 116 Satoru, MNA1102/SCS 119 Rubi, MNA1103/IRGA 424, MNA1104/SCS 116 Satoru, and MNA1108/IRGA 424 crosses were considered the most promising sources of earliness for developing early‐maturing red rice lines.