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Scientists develop portable tool to test for ohia disease

Identifying cases of rapid ohia death on Hawaii Island just became easier thanks to a new tool that allows teams to diagnose infected trees while in the field.

The “lab in a suitcase” is described in a paper published last month by researchers from the U.S. Geological Survey, Hawaii Cooperative Studies Unit at the University of Hawaii at Hilo, University of Hawaii at Manoa College of Tropical Agriculture and Human Resources, and U.S. Department of Agriculture Pacific Basin Agricultural Research Center.

“It really is a true collaborative thing,” said Carter Atkinson, a molecular biologist at the USGS Pacific Island Ecosystems Research Center.

The cause of rapid ohia death, a fungus called Ceratocystis, was identified in 2014 (two separate Ceratocystis species have since been named). Diagnosing whether a tree was infected required a trip to the PBARC laboratory led by Lisa Keith.

To date, more than 50,000 acres of ohia forest on the Big Island have been affected by ROD. So far, the disease has not spread to other islands.

“One of the issues that we saw early on was that, as this problem starts to get bigger and bigger, the existing diagnostic capabilities in Lisa’s lab were probably going to get overwhelmed,” Atkinson said.

Diagnosing every possible case of ROD also took valuable time away from research at the lab, said JB Friday, CTAHR extension forester.

“But they’re doing both,” he said. “Just knocking themselves out. With this (portable lab) … routine diagnostics can be done by other agencies.”

Friday and Atkinson are part of an ROD working group that meets monthly. Atkinson’s USGS research tends to involve bird pathogens, but he also knew of a molecular test that would work for fungi.

“He knows a lot about this, and said, ‘How can we help?’” Friday said.

The PBARC laboratory provided genetic samples to help test the lab in a suitcase.

Researchers began working about a year ago on the portable unit, which runs off a battery and includes a fluorometer, miniature centrifuge and heat block. It works by amplifying any Ceratocystis DNA in the ohia.

“If it’s not there, then nothing will amplify, and if it is, then you’ll get a sample,” Atkinson said.

The amplification process usually involves cycling the sample’s temperature between highs and lows, but the team used a different technique that allows the test to be done at room temperature.

“That’s what makes it really portable,” Atkinson said.

It takes about 90 minutes to extract DNA from a sample and get results.

“It’s exciting,” Friday said. “(You) can just set it up on the table and get an answer while the team’s eating their lunch.”

The technology also is a less expensive solution to diagnostics. Assembling a unit costs about $8,000, Atkinson said, but that is considerably less than the cost of the equipment in a stationary laboratory.

Funding from the USGS Ecosystems Mission Area allowed the team to build three portable units. One is being used by the Big Island Invasive Species Committee and its ROD Early Detection and Rapid Response team.

Another unit went to the state Department of Agriculture, where it will be used to help with screening of ohia logs. As part of a DOA quarantine established in August 2015, all logs being shipped off-island must go through a screening process to make sure they are free of Ceratocystis.

The team now is working to refine the test so it can distinguish between the two species of Ceratocystis.

“We’re working on that now; we’re not quite there yet,” Atkinson said. “If we can get that to work, that would reduce the equipment cost even more.”

Email Ivy Ashe at iashe@hawaiitribune-herald.com.

 

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