Genetics of grain mineral density in rice grain

The nutritional quality of rice can be improved by a breeding approach. Initial evaluations have shown that some rice varieties have high Fe, Zn, and other micronutrient in their edible portion. The genetic mechanisms of grain mineral density (GMD) to determine the best selection technique were studied. A complete diallel population was developed using nine rice varieties with varying GMD. The diallel population was planted in a randomized complete block design in the IRRI field and the grain Ca, Cu, Fe, K, Mg, Mn, P, S, and Zn contents were analyzed. Combining ability analysis showed a highly significant general combining ability (GCA), specific combining ability (SCA) and reciprocal mean square for all GMD. Rice varieties with a positive GCA effect for most of the GMD were for the micronutrient - dense parents. All commercial varieties showed a negative combining ability for GMD. The size of the GCA effect of a parent varies, depending on the mineral element. A differential SCA effect of crosses across mineral elements and highly significant positive correlation coefficients among SCA effects of the crosses on grain Fe, Zn, Mg, P, K, and S were observed. However, there were significant negative correlation coefficients between the SCA effect on grain Ca and other minerals such as Mg, Mn, P, S, and Zn. Similarity, the SCA effect on grain Mn showed a negative correlation effect on grain Cu, Fe, K, Mg, Mn, P, and Zn. This suggest that selection of parents to breed for enhancing the overall GMD based on GCA and SCA should be applied with caution. This genetic study showed the complexity of the mode of inheritance of GMD, demonstrating the role of additive and dominant gene action and environmental effects. Breeding strategies were developed based on these genetic findings. Three important quantitative trait loci (QTLs) were detected for the high Fe trait and these are located on chromosomes 7, 8 and 9, explaining 30.3%, 21.3%, and 19.0%, respectively, of phenotypic variation. The use of biotechnological tools such as the molecular marker-assisted selection approach will significantly increase the prospects of breeding to improve the Fe concentration of rice