Author
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Kuykendall, Larry |
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Submitted to: American Society of Sugarbeet Technologists
Publication Type: Proceedings Publication Acceptance Date: 8/1/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Since sugarbeet diseases such as Cercospora leafspot can reduce yields as much as 30%, scientists in the Molecular Plant Pathology Laboratory at Beltsville have been searching to find sources of resistance genes. Two new species of Pseudomonas were found to be good candidates as sources of resistance genes. Biofungicide genes are now being isolated from these newly discovered beneficial bacteria. Technical Abstract: The relative susceptibility of selected Beta vulgaris genotypes to Cercospora leafspot was tested under controlled humidity and temperature in a plant-growth chamber. Replicate plants of two new transgenic clones designated OOT and OsmPrS-2 and their REL-1 parental line were infected with Cercospora beticola and disease progression was followed. Cercospora leafspot symptoms in terms of the number of lesions per leaf in an infection cycle were significantly greater in the two transgenics by a factor of about 4- to 5-fold relative to the nontransformed genotype. When the area of the necrotic lesions is considered this difference is magnified by more than 200x with OOT. These results demonstrate that the presence of the introduced chimeric genes encoding small antimicrobial peptides diminishes rather than enhances Cercospora resistance in these particular transgenic sugarbeets. Species of fungicide-producing Pseudomonas will now be tested to determine whether they can serve as a new source of genes for the bioengineering of disease resistance in sugar beets. The introduction of the Cercospora cfp gene, for toxin export gene, into sugar beet will soon be tested as a potential effective control of leafspot. The cfp gene is currently being transformed into sugar beet in my lab using Rhizobium- (formerly Agrobacterium-) mediated transformation which produces only single genomic insertions. |
