(BIVN) – In an effort to save Hawaiʻi’s native forests from the devastation of Rapid ʻŌhiʻa Death, scientists are touting the use of natural, genetic resistance as the most promising tool.

During the Rapid ʻŌhiʻa Death Science Symposium held last month at the ‘Imiloa Astronomy Center in Hilo, officials and environmentalists were given a detailed presentation on genetic resistance for forest diseases, and how it might be used to save and restore ʻōhiʻa in Hawaiʻi.

“The first question, is how bad will [Rapid ʻŌhiʻa Death] get?” said Richard Sniezko, a forest geneticist with USDA Forest Service. “The other thing is: how strong is public support for program, because nowadays, nothing’s cheap, including a resistance program.”

It also depends on the level of natural resistance the ʻōhiʻa species already has, and how it can be harnessed in an efficient and timely manner for restoration.

Sniezko explained how, in some cases, a resistance program might be the only feasible solution. It has proven successful in other situations, he said, and it is considered a “green” solution; organic, sustainable, and with little or no side-effects.

A resistance program involves tree breeding; “an interative process of selection, mating and testing with the goal of producing improved populations of parent trees for production of genetically diverse, adapted seed,” according to Sniezko’s slide presentation.

“Sometimes there’s confusion out there” about tree-breeding, Sniezko said. “It’s not transgenics, it’s not gene-editing, it’s not identification of resistance mechanisms,” he said. “It’s not genomics, transcriptomics, proteomics. Those are tools, but they’re not required for a successful resistance program.”

“You’re gonna have to have a few people who are really passionate and drive this,” in order for a resistance program to work, Sniezko said, “and have the public support it. A sense of urgency.”

The USDA has already been looking into natural resistance in different ʻōhiʻa varieties: newellii, incana, glaberrima, and polymorpha. “I was able to calculate disease severity”, said Blane Luiz with the USDA Agricultural Research Service, after he says he inoculated the 4 varieties with  Ceratocystis lukuohia, the more virulent of the two Rapid ʻŌhiʻa Death pathogens.

“All the polymorpha varieties died,” Luiz said. “100% percent mortality. However, with newellii, incana, and glaberrima, we did see some survivors emerge. After the 17 weeks, incana seems to be the most promising, having the most amount of survivors come out of it.”

“We also are working on other metrosideros species in the Pacific,” Luiz said. “We have already tested M. excelsa/kermacadensis hybrids and the M. collina variety Tahiti Red in the lab. If I believe correctly, the M. excelsa/kermacadensis hybrids were not susceptible, but the M. collina was susceptible to disease.”

There may be some resistance out there on Hawaiʻi Island, “based on what we saw screening the different varieties,” Luiz said, but further testing needs to be done.

That’s where the Ceratocystis Resistance Working Group comes in, which will work to grow the preliminary effort into a full resistance program. Participating in the group are the USDA Forest Service and Agricultural Research Service (PBARC), the Hawaiʻi DLNR Division of Forestry and Wildlife (DOFAW), the University of Hawaiʻi Mānoa, Purdue University, the Hawaiʻi Agricultural Research Center, and the Akaka Foundation for Tropical Forests. The group has secured $150,000 from the USDA Special Technology Development Program, $120,000 from the USDA Pacific Southwest and Region 5, and $50,000 from Hawaiʻi DOFAW.

The Ceratocystis Resistance Working Group effort will hopefully result in an improved understanding of Rapid ʻŌhiʻa Death resistance, and operationalized methods for ʻōhiʻa propagation, as well as operationalized methods for screening and testing for Rapid ʻŌhiʻa Death.

Ideally, scientists say, a large supply of ʻōhiʻa will be created for large-scale planting for restoration, landscaping, and biocultural applications.