Marker-Assisted Rice



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Project Leader and Principal UC Investigators

Pamela C. Ronald, Dept. of Plant Pathology, UC Davis

Christie E. Williams, Dept. of Plant Pathology, UC Davis

David J. Mackill, research genetist, USDA-ARS, UC Davis

MABreed2.jpg (30263 bytes)The long-term goal of this project is to develop an easy screening technique utilizing DNA-based markers to identify genes for economically significant but difficult-to-measure traits in California rice cultivars and wild relatives. Researchers report success in completing two important objectives toward that end:

• Development of a micro-assay technique that can be done on a small segment of leaf tissue.

• Optimize methods for converting dominant gene markers into codominant markers that give more information from a cross and are easier to use.

Researchers developed a method of quickly isolating DNA from small leaf segments so that many samples could be processed in a short time. Samples were then used in a biological reaction to generate markers linked to genes that are important in rice breeding.

"Co-dominant" markers are useful because they enable researchers to quickly determine whether progeny from a particular line will breed true for the trait of interest. Two approaches were successful in converting dominant markers into co-dominant markers that give this increased information from a cross. Both methods involved modifying laboratory procedures to make the DNA-spreading gel easier to "read."

Using these techniques researchers produced a gene marker for the wide compatibility gene in javanica rice. The presence of this gene makes it possible to intercross indica, japonica and javanica varieties in order to transfer useful traits. In the future, these techniques will be applied to the development of DNA-markers that can distinguish California rice varieties.

In other experiments these scientists used these techniques to clone a gene that confers resistance to bacterial leaf blight disease. When this gene was introduced into normally susceptible plants, the plants gained resistance to the disease. This is the first time a disease resistant gene has been cloned from rice. This opens the door to genetic engineering of new disease-resistant varieties.

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A technician (above) prepares a rice leaf tissue sample that will ultimately yield a "picture" of the DNA contained in the plant's cells. Such information is giving scientists the tools they need to pinpoint genes of interest to plant breeders and geneticists.

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