Ham searches for genes to suppress bacterial panicle blight

Frances Gould, Schultz, Bruce  |  3/4/2015 10:33:13 PM

Jong Hyun Ham, LSU AgCenter pathologist, explains how a bacterial panicle blight experiment is being conducted in a greenhouse on the LSU Campus in Baton Rouge. The tops of the rice plants, including the panicles, are stricken with the disease .

Jong Hyun Ham is working to understand which genetic differences between rice varieties determine the susceptibility and resistance to bacterial panicle blight. “We want to know the genetic uniqueness,” he said.

For example, Jupiter is a resistant variety, while Bengal is susceptible.

Bacterial panicle blight kills cells that transport needed nutrients, so an infected plant tends to produce unfilled panicles.

It is likely that the genetic differences include several genes because disease resistance and susceptibility are too complex to be determined by just one gene, Ham said.

Breeding is being conducted to cross resistant varieties with new lines. “So far, we have several lines with resistance,” he said. “That is very challenging because there are always trade-offs.”

For example, some of the lines with the best resistance also tend to have panicles that shatter.

Lines with good resistance may also have quality issues, he said, or they might not yield well.

Some of the crosses have better resistance than Jupiter, he said.

The bacteria that cause the disease sustain themselves on rice seeds. But antibiotics are too expensive and regulated to use on a wide scale to treat seeds, he said. Vitamin C, however, may be an effective suppressant once the plant has grown, and research is ongoing to test its effectiveness. “We don’t know the mechanism of that yet,” he said.

Ham admits that much is unknown about the disease, including how the pathogen survives winters and how it is spread. “Sometimes I feel frustrated because more information is not available,” he said.

This article was published in the 2015 Louisiana  Rice Research Board Annual Report.

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