2012 Annual Report
1a.Objectives (from AD-416):
This project will address in oat, one of our important cereals, the needs for an understanding of the molecular/structural organization of its large complex genome, means to effectively identify and manipulate more durable race non-specific quantitative resistance to its major disease, crown rust, and the development of new biotic and abiotic stress resistance germplasm in elite agronomic backgrounds through the following objectives: Objective 1: Characterize the complex segmental homoeologous structure of allohexaploid cultivated oat through molecular marker analysis of monosomic and nullisomic chromosome-deficient stocks. Objective 2: Identify and map key genes (quantitative trait loci or QTLs) for important traits, particularly race non-specific crown rust resistance, by developing and phenotyping mapping populations and employing new molecular markers (EST-SSR and DArT). Objective 3: Develop cultivated oat germplasm with introduced biotic and abiotic stress resistance and high-value traits through introgressing crown rust resistance from wild oat species, exploring heat stress and disease resistance from genes introduced by crosses with corn, and evaluating high-value trait sources through coordination of regional spring oat nurseries.
1b.Approach (from AD-416):
Monosomic (single chromosome deficient) oat plants needed to complete a full series of 21 lines each deficient for a different oat chromosome will be identified cytologically and with molecular markers among derivatives of oat x corn crosses. Molecular marker linkage groups will be assigned to chromosome using these monosomic lines to develop a comprehensive genomic map for cultivated oat. The QTL identification of race non-specific (partial) crown rust in oat germplasm MN841801-1 will be enhanced with additional field and molecular marker data including the use of new DArT markers, and the effectiveness of marker-assisted selection will be tested for efficiency and effectiveness in transfer of the resistance QTLs into other oat backgrounds. New oat crown rust resistance genes will be introgressed into cultivated oat from wild oat species. Previously produced oat lines containing segments of corn chromosomes will be further developed and evaluated for possible enhanced heat tolerance and disease resistance. Coordination of cooperative regional spring oat performance nurseries will be used to identify optimal current oat genotypes for use as parents in crosses for introgressions and germplasm enhancement.
The focus of the research has been to investigate oat seed development, more particularly how and where health-promoting chemicals accumulate in the seeds. In collaboration with ARS researchers in Madison, Wisconsin, patterns of accumulation of related compounds collectively known as vitamin E were monitored at five different stages of development in different parts of the seed. Developing seeds were harvested at 7, 14, 21, and 28 days after pollination, and the embryos were removed for separate analysis from a subset of the seeds. The harvested material as well as mature seed was sent to our ARS collaborator in Madison for chemical analysis to identify which vitamin E compounds were present and in what abundance at the different sampling timepoints. The most abundant forms of vitamin E in the seed as a whole were the tocotrienols, while embryos had higher amounts of tocopherols, another form of vitamin E. Despite their relatively small size, oat embryos contributed a significant proportion of the total seed vitamin E content. In parallel, research to develop a gene expression atlas of developing oat seeds continued. Gene expression data on oat seeds at the same stages of development as those employed for the vitamin E accumulation study above was obtained from four biological replicates using high-throughput DNA sequencing. A total of 134 million high-quality reads was obtained, and they were assembled into a gene expression database representing nearly 27,000 unique transcripts. Searching this transcript database allowed us to identify sequences representing all of the genes involved in the vitamin E synthesis pathway. Further, a set of 60 genes that may be involved in the synthesis of the "heart-healthy" compound beta-glucan was also identified. Integrating gene expression and chemical composition data for developing oat seeds will permit us to relate the accumulation of health-promoting compounds with which genes are turned on or off, and in doing so will provide fundamental knowledge for increasing levels of desirable compounds in oat seeds for improved human health.
Characterizing accumulation of health-promoting compounds in oats. Oats are a good source of health-promoting compounds that collectively constitute vitamin E, the tocopherols and tocotrienols. However, little is known about developmental aspects of their accumulation in this crop. In collaboration with ARS scientists in Madison, Wisconsin, tocopherol and tocotrienol accumulation was quantified for the first time during the course of oat seed development. Tocotrienols were more abundant in whole seeds, while embryos contained higher concentrations of tocopherols. This difference suggests distinct roles for tocotrienols and tocopherols in oat. These findings provide a knowledge base from which to tailor vitamin E content and composition in oats in order to increase the health-promoting properties of this important food grain.
Gutierrez-Gonzalez, J.J., Garvin, D.F. 2011. Reference genome-directed resolution of homologous and homeologous relationships within and between different oat linkage maps. The Plant Genome. 4(3):178-190.
Kynast, R.G., Davis, D.W., Phillips, R.L., Rines, H.W. 2012. Gamete formation via meiotic nuclear restitution generates fertile amphiploid F1 (oat x maize) plants. Sexual Plant Reproduction. 25(2):111-122.