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Induced-mutation breeding is a viable, proven approach to improve certain qualitative traits. More than 440 rice and 2,200 other crop varieties have been released through induced-mutation work. A combination of potent mutagenic agents and genomic information will streamline product development through specific, oriented targets and direct identification of nucleotide changes associated with the new traits. One of the research goals is to improve nutritional quality as an added value to common rice grain. Rice is a nutritionally rich source of complex carbohydrates that provide most nutrition value from calories consumed to provide energy for physical activities. In addition to the starchy endosperm where most complex carbohydrates are located, whole rice grains contain nutrient-dense bran and an inner germ layer where most of the beneficial compounds are found. A good source of nutrients, B vitamins and minerals, rice is also an important source of phytochemicals, including γ-oryzanol, phytosterols, phenolic compounds and tocotrienols. These phytonutrients have been linked to health-beneficial agents.
Improved total protein content with more essential amino acid quantity is an important step for enhancing the rice health-benefit potential. Five promising high-protein lines are currently under intensive testing through replicated multi-year field evaluations. Amino acid profiles from each of five high-protein lines developed vary. The composition of essential amino acids in the FRN936 line, for example, is 18, 19, 35, 13, 40, 44, 15, 37 and 30% higher in lysine, threonine, phenylalanine, methionine, isoleucine, valine, tryptophan, histidine and arginine, respectively, compared with that found in its parental Francis wildtype check. While WLS97 has 47, 11, 46, 18, 37, 34, 30, 20 and 21% higher levels of lysine, threonine, phenylalanine, methionine, isoleucine, valine, tryptophan, histidine and arginine, respectively, than that found in its parental line Wells.
Genes coding for key amino acid synthesis enzymes among high protein lines are being evaluated using Eco/TILLING (Targeting Induced Local Lesions IN Genomes) approaches. Molecular characterization of these genes will facilitate gene isolation and marker development. Utilization of reverse and forward genetics in these particular genes of interest will provide a genetic framework to conduct large-scale production of rice mutants. Since rice is a model crop with a relatively small-sized, completely sequenced genome, the resulting reverse and forward genetics can be applied to other crop species.
A portion of the research efforts in this project has been devoted to conducting cellular selection to improve salt-tolerance levels in California bulrush (Schoenoplectus californicus). Hundreds of regenerated plants derived from high-salt-tolerant cells have been obtained. These lines are being grown in the greenhouse and will be used for further testing.For more information, contact Dr. Ida Wenefrida.