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Oscar Riera-Lizarazu
Associate Professor, Crop and Soil Science
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RESEARCH:
Our research efforts focus on the application of novel technologies for the improvement of wheat and other cereals. One broad area of interest includes the use of DNA-based markers and quantitative trait mapping to study the inheritance of agronomically important traits and to identify molecular markers that may be used for indirect selection of these traits. Another area of interest focuses on the development of radiation hybrid maps of cultivated grasses to facilitate the development of physical genomic maps and cloning genes of agronomic importance.
The application of DNA-based markers and quantitaive trait mapping in wheat. Cephalosporium stripe of wheat (caused by Cephalosporium gramineum) is a limiting factor in wheat production areas where soil and water conservation practices are exercised. We have recently discovered that the parents of a recombinant inbred line population of wheat have a differential response to the causal agent of Cephalosporium stripe of wheat. One parent, 'Opata 85', was found to be highly susceptible while the other parent, 'M6', showed a higher level of resistance than any other wheat cultivar or line that has been tested to date. These results indicate that the wheat mapping population may be suitable to study the inheritance of Cephalosporium stripe resistance. In collaboration with Drs. Chris Mundt, Tom Wolpert, Lynda Ciufetti, and James Peterson, we have initiated a project at Oregon State University to utilize this population to study the genetic inheritance of Cephalosporium stripe resistance and to identify molecular tags linked to resistance loci. Ultimately, molecular marker-assisted screening for resistance without the pathogen and marker-assisted transfer of a high level of resistance into common wheat cultivars adapted to Oregon may be feasible.
Radiation hybrid mapping in plants.
The development of physical maps and map-based cloning in cereal is complicated because of large genome sizes, a high proportion of repeated DNA sequences in a genome, and extensive gene or chromosome duplication or polyploidy. To overcome these limitations, we are exploring the use of plant interspecific radiation hybrids. In this system, we use plants where a chromosome has been introduced in an alien background (the addition lines). Because a chromosome in an alien background has been physically separated from chromosomes of its original genome and can be analyzed separately from the chromosomes of its new host, analysis of this single chromosome represents a dramatic reduction of the complexity of materials to be manipulated. Further reduction in complexity may be achieved by irradiating an addition line and isolating lines that possess different pieces of the chromosome of interest. These sub-chromosome fragment stocks (known as radiation hybrids) can then be used to study a specific region of the chromosome in question. In the end, the information that is gained by analyzing a population of radiation hybrids may be used to piece together the original chromosome.
Radiation hybrid lines derived from a maize-chromosome 9 addition line of oat have been recently produced (Fig. 1). In collaboration with Dr. M. Isabel Vales, we are investigating the inheritance and stability of radiation-induced maize-chromosome 9 rearrangements in these radiation hybrids. The specific objectives of the project will be: 1) to characterize the transmission of the maize-chromosome 9 rearrangements in progenies from oat-maize radiation hybrids, and 2) to identify lines that stably transmit maize-chromosome 9 rearrangements and may be suitable for sub-chromosome fragment analyses and mapping.