Canker Control

07/01/2007 02:00:00 AM

In addition, Florida citrus shipped to states not producing citrus is required to originate in groves inspected and deemed canker-free no more than 30 days before harvest commences.

But on June 21, APHIS proposed amending the quarantine regulations to eliminate those pre-harvest grove inspections. Instead, absence of disease would be verified by mandatory sampling of each lot of citrus at packinghouses.

APHIS proposed this action because a completed risk management analysis concluded that mandatory packinghouse inspections of commercially packed fruit would provide an effective safeguard in preventing canker spread, according to an APHIS news release.

The proposed rule would continue to prohibit shipments of Florida citrus to citrus-producing states and territories.

The quarantine is unlikely to affect the chances of citrus-producing areas acquiring canker from Florida citrus because the chance of it happening in the first place was low, says Raymond Royce, executive director of the Highlands County Citrus Growers Association Inc., Sebring

Transgenic plants

As greening has commanded more attention from growers, it also has stolen much of the focus of research. But transgenic plants still are being developed and tested for resistance to canker.

“Transgenic work has shifted more over to greening since it’s a way bigger problem,” says Jude Grosser, professor of plant cell genetics at the Citrus Research and Education Center, Lake Alfred.
Current transgenic research on canker resistance at the center includes post-doctoral research associate Ahmad Omar’s work on Hamlin oranges.

“He transferred a Xanthomonas resistance gene from rice into a Hamlin sweet orange,” Grosser says. “We don’t know (yet) if the genetically engineered plants are resistant, as they are currently being challenged in the quarantine facility in Gainesville. We are also working with several other antibacterial genes in our genetic engineering work.”

The center in Lake Alfred also plans on setting up a similar quarantine facility in the next couple months to test transgenic plants’ resistances to greening and canker, he says. The center’s work with transgenic citrus now is in its third year.

Also being tested is the transfer of canker resistance from kumquats, by conventional breeding, into seedless triploid hybrids. Doing so is useful for breeding canker-resistant limes and possibly other types of citrus such as lemons or mandarins, Grosser says.

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