Mutational breeding and genetic engineering in the development of high grain protein content.

Cereals are the most important crops in the world for both human consumption and animal feed. Improving their nutritional values, such as high protein content, will have significant implications, from establishing healthy lifestyles to helping remediate malnutrition problems worldwide. Besides providing a source of carbohydrate, grain is also a natural source of dietary fiber, vitamins, minerals, specific oils, and other disease-fighting phytocompounds. Even though cereal grains contain relatively little protein compared to legume seeds, they provide protein for the nutrition of humans and livestock that is about 3 times that of legumes. Most cereal seeds lack a few essential amino acids; therefore, they have imbalanced amino acid profiles. Lysine (Lys), threonine (Thr), methionine (Met), and tryptophan (Trp) are among the most critical and are a limiting factor in many grain crops for human nutrition. Tremendous research has been put into the efforts to improve these essential amino acids. Development of high protein content can be outlined in four different approaches through manipulating seed protein bodies, modulating certain biosynthetic pathways to overproduce essential and limiting amino acids, increasing nitrogen relocation to the grain through the introduction of transgenes, and exploiting new genetic variance. Various technologies have been employed to improve protein content including conventional and mutational breeding, genetic engineering, marker-assisted selection, and genomic analysis. Each approach involves a combination of these technologies. Advancements in nutrigenomics and nutrigenetics continue to improve public knowledge at a rapid pace on the importance of specific aspects of food nutrition for optimum fitness and health. An understanding of the molecular basis for human health and genetic predisposition to certain diseases through human genomes enables individuals to personalize their nutritional requirements. It is critically important, therefore, to improve grain protein quality. Highly nutritious grain can be tailored to functional foods to meet the needs for both specific individuals and human populations as a whole.

Current patents and future development underlying marker-assisted breeding in major grain crops.

Genomics and molecular markers provide new tools to assemble and mobilize important traits from different genetic backgrounds, including breeding lines and cultivars from different parts of the world and their related wild ancestors, to improve the quality and yield of the existing commercial cultivars to meet the increasing challenges of global food demand. The basic techniques of marker-assisted breeding, such as isolating DNA, amplifying DNA of interest using publicly available primers, and visualizing DNA fragments using standard polyacrylamid gel, have been described in the literature and, therefore, are available to scientists and breeders without any restrictions. A more sophisticated high-throughput system that includes proprietary chemicals and reagents, parts and equipments, software, and methods or processes, has been a subject of intensive patents and trade secrets. The high-throughput systems offer a more efficient way to discover associated QTLs for traits of economic importance. Therefore, an increasing number of patents of highly valued genes and QTLs is expected. This paper will discuss and review current patents associated with genes and QTLs utilized in marker-assisted breeding in major grain crops. The availability of molecular markers for important agronomic traits combined with more efficient marker detection systems will help reach the full benefit of MAS in the breeding effort to reassemble potential genes and recapture critical genes among the breeding lines that were lost during domestication to help boost crop production worldwide.