Abstract

Durum wheat (Triticum turgidum L. var. durum) is a tetraploid species of wheat that is mainly used in pasta production. Grain quality is an important feature that mainly encompasses nutritional value, yellowness, and protein (gluten) content and strength. Semolina (milled, coarse durum wheat product used as raw material for pasta production) yellowness is an important quality trait as it provides a natural bright yellow color to pasta, without the need of adding expensive synthetic pigments or artificial coloring during pasta making, which has been prohibited in several parts of the world in the last decades. This project will evaluate the potential increase of semolina yellowness of durum wheat grains derived from a mutagenized population from the University of California-Davis subjected to Targeting-Induced Local Lesions IN Genomes (TILLING), a powerful non-transgenic reverse-genetic approach that also increases the genetic diversity. TILLING can result in improved genotypes with enhanced yellowness as result of mutating the durum wheat Lipoxygenase (Lpx-1) genes. Lipoxygenase is the major contributor of oxidative degradation of carotenoids in durum wheat, and reduced LOX activity is strongly associated with an increase in pasta yellow color. At the end of this project, advanced breeding lines with reduced LOX activity using three generations of backcrossing will be obtained. Grain yellowness enhanced Lpx-1 mutant lines will be phenotypically analyzed and studied through several methods, including High Pressure Liquid Chromatography (HPLC). In parallel, a highly genetically diverse durum wheat population of 192 genotypes (advanced breeding lines + cultivars) mainly from the Pontificia Universidad Católica de Chile (UC) and the International Maize and Wheat Improvement Center (CIMMYT) will be grown in the UC´s research stations of Pirque and Curacaví (Central Chile) and studied. Both phenotypic (grain protein content (GPC), gluten strength, semolina yellowness) and genotypic (grain quality molecular markers) data will be used to conduct association analysis with the objective to identify the best individuals of that population, and the superior grain quality molecular markers for their introduction into the Chilean breeding programs (UC and INIA). Concerning the genotypic characterization, grain quality genes as Low-molecular weight Glutenin subunits (Glu-A3 and Glu-B3), High-molecular weight Glutenin subunit (Glu-B1), Grain protein content (Gpc-B1), Glutamine synthetase (GSe), and Lipoxygenase (Lpx-1), and their associated markers, will be employed in this project. In addition, the marker-trait association analysis will identify the 5 best/5 intermediate/5 worst individuals of the durum wheat population, and quantitative real-time PCR of those materials will be conducted to study whether those grain quality genes/markers relate to their corresponding phenotypes. In this way, the superior grain quality gene alleles/molecular markers will be selected for their incorporation into the marker-assisted selection (MAS) programs of the UC. Overall, these multi-faceted approaches will lead to the development of new local genotypes of durum wheat with improved grain quality and the incorporation of new molecular markers for MAS for their use in the national breeding programs. These are the two main expected outcomes of this project that will directly benefit the Chilean agricultural sector. Finally, in addition to the practical significance that the results of this project will have for pasta production and its improvement, there are potential results that will generate an important contribution for our basic and scientific knowledge of the carotenoid and the grain protein metabolic functioning. In this regard, these results will contribute to a better understanding of how Lpx-1 affects the carotenoids metabolic pathway, associated to different semolina yellowness levels. Also, studying Glu-A3, Glu-B3, Glu-B1, Gpc-B1, and GSe, will provide a better insight about how these genes and associated markers influence GPC and gluten strength and quality. To our understanding, there is no published research in Chile associated to studies to improve durum wheat grain protein (gluten) content and quality using genetic tools, which is one the most important novelties of this initiative that will generate valuable new scientific knowledge.