This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: With the invasive emerald ash borer beetle decimating black ash across North America, according to the U.S. Forest Service, a team led by researchers at Penn State conducted an expansive study of genetic diversity in black ash seeds collected across the tree's geographic range and stored in seed banks.
The research was done with an eye toward someday reintroducing the ecologically and culturally important tree to U.S. and Canadian forests. As part of the research, the team established three large common gardens—experimental plantings—of black ash that someday may play a role in producing seeds needed to bring the species back. Black ash is a vital wetland tree renowned for regulating forest hydrology, supporting rich biodiversity and serving as the foundational material for basketry and cultural heritage for Indigenous communities, including Wabanaki, Iroquois and Great Lakes tribes.
In findings published in Annals of Botany, the team reported that differences in climate have caused black ash trees in different regions to evolve different seed traits that affect how seeds and seedlings develop over time, and these differences affect how well their seedlings survive and grow. That knowledge will be critical in selecting seed for eventual reforestation, the researchers said. "From a conservation perspective, many of the populations represented in these collections are trees that don't exist on the landscape anymore, so we like to consider this a little bit like Noah's Ark for black ash," said study senior author Jill Hamilton, associate professor in the Department of Ecosystem Science and Management and director of the Schatz Center for Tree Molecular Genetics in the Penn State College of Agricultural Sciences.
"We need the collected and preserved germplasm for emerald ash borer-resistance breeding and future restoration." To conduct their wide-ranging study, researchers led by study first author Kyra LoPiccolo, a doctoral candidate in the intercollege graduate degree program in plant biology administered by the Huck Institutes of the Life Sciences, analyzed collections of black ash seeds obtained from the U.S. Department of Agriculture's National Plant Germplasm Network and Canada's National Tree Seed Centre. The team evaluated variation in seed form and structure and early life-history traits of black ash using X-ray imaging to look inside seeds without damaging them, and measured seed characteristics.
More than 700 seed lots from different regions were X-rayed, and those images were used to train a machine learning model—a type of artificial intelligence (AI)—to develop an algorithm that would automate measurements of their characteristics. AI then enabled the team to characterize approximately 35,000 seeds. The researchers also engaged in climate modeling to predict the success of seeds sourced from different climates.
Finally, the team germinated 22,000 seeds at Penn State's Mendel's Way Farm and Greenhouses to gauge their early life growth and production, and then used those seedlings to establish three common garden experiments: at the Ag Progress Days site near Penn State's University Park campus, as well as in Syracuse, New York, and Quebec City, Quebec, Canada. The team partnered with State University of New York (SUNY) College of Environmental Science and Forestry and the Canadian Forest Service on the common garden plantings. A common garden experiment is a scientific method used to test whether differences observed in traits among populations are due to genetics or the environment, LoPiccolo said.
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