Bacterial Blight Breakthrough

Scientists at the University of Toledo have developed a revolutionary new test to screen geranium and pelargonium species for Xanthomonas–the swift-moving bacterial blight that can wipe out an entire crop.

The work was funded through a USDA Agricultural Research Service cooperative agreement. Dr. Shulu Zhang of Louisiana State University managed the project while he was at the University of Toledo’s (UT) Plant Science Research Center along with Dr. Stephen Goldman of UT and Dr. R.V. Sairam at Penn State University. Grower Bill Bettinger of Toledo, Ohio, also supported the project.

Goldman has developed a rapid, reliable test that is specific to 53 strains of Xanthomonas campestris pv. pelargonii (Xcp) but not to 46 other Xanthomonas species. Using Polymerase Chain Reaction (PCR) technology, the test detects a gene to signal the presence of Xcp and then scores infection based on symptom severity. The test defines the presence of bacteria prior to the onset of symptoms and can assist in selecting resistant plants, which would have a negative PCR. A low PCR signal with mild symptoms would indicate disease tolerance.

“Ideally, both the supplier and the receiving grower would profit enormously from a rapid, reliable test for Xcp,” Goldman says. “This test would allow the supplier to warrant that his material is free from infection prior to shipment, and the receiver to warrant that the material is likewise bacteria free upon receipt. The opportunity should be explored to use the availability of this technology to assist in the breeding for resistance to Xanthomonas in geraniums.” The same technology may be used on other solanacea crops, like potatoes, he adds.

According to USDA’s Floriculture Crops Survey, geraniums represented $300 million in wholesale plant sales in 2006. Xcp is the most destructive disease for geraniums, especially zonal geraniums. “Typical annual losses resulting from blight have averaged between 10 and 15 percent. This number, however, to the greenhouse industry is deceptive,” Goldman says. “Infections are known to have run rampant in individual greenhouses and can cause up to 100 percent loss in geraniums.”

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