Emerald Ash Borer

Development of In Vitro Protocols for Ash Species

Research Issue

Ash timber and materials, harvested from trees in the genus Fraxinus, are valued for a variety of applications. White ash is the primary commercial hardwood used in the production of baseball bats, tool handles, furniture, flooring, doors, cabinets, and other specialty products such as canoe paddles and boats. Green ash is used for both solid wood applications (crating, boxes, and tool handles) and for fiber in the manufacture of high grade paper. Black ash is typically used for interior furniture, cabinets, and Native Americans require this species for the art of basketry. Ash trees also play an important role in the urban environment because of their historical resistance to pests and tolerance of adverse growing conditions such as soil compaction and drought, they sequester gaseous air pollutants, help conserve energy by providing shade, and contribute to the aesthetics of urban landscapes. Ash trees are considered vital to natural forest environments and shelterbelts as they are fast growing species, often the first hardwoods to colonize disturbed sites, tolerant of a wide variety of soil conditions including wetlands and riparian corridors, and provide habitat and food for wildlife.

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), an aggressive pest of ash from Asia, is attacking and killing ash in North America. First identified in southeast Michigan and nearby Windsor Ontario in 2002, EAB was inadvertently introduced during the 1990’s in solid-wood packaging materials used in international trade. EAB has spread rapidly throughout North America and is now known in 31 states and two eastern provinces of Canada. The high density of EAB attacking ash trees in North America is fatal to most mature ash trees, and the extensive mortality of ash trees in both urban and forested ecosystems is causing significant costs to communities as well as widespread environmental damage. Several researchers in North America are working to develop EAB-resistant ash cultivars by seeking innate resistance genes in Asian ash species, which are more resistant to EAB, and in some surviving or “lingering” ash trees that remain in forests in the aftermath of the EAB invasion. To facilitate the development and propagation of EAB-resistant genotypes, we developed tissue culture and transformation systems for several ash species native to North America.

Research Results

We developed in vitro protocols for propagating several Fraxinus species (black, green, pumpkin, and white ash) in tissue culture, including adventitious shoot regeneration, rooting, and an Agrobacterium-mediated transformation system . These in vitro protocols are now available for use in the development and propagation of ash cultivars resistant to EAB.

Lee, Jun Hyung; Pijut, Paula M. 2017. Adventitious shoot regeneration from in vitro leaf explants of Fraxinus nigra. Plant Cell, Tissue and Organ Culture. 130:335-343.

Lee, Jun Hyung; Pijut, Paula M. 2017. Isolation and characterization of a floral homeotic gene in Fraxinus nigra causing earlier flowering and homeotic alterations in transgenic Arabidopsis. Plant Gene. 10: 17-25. https://doi.org/10.1016/j.plgene.2017.03.003.

Palla, Kaitlin J.; Pijut, Paula M. 2015. Agrobacterium-mediated genetic transformation of Fraxinus americana hypocotyls. Plant Cell, Tissue and Organ Culture. 120(2): 631-641.

Stevens, Micah E.; Pijut, Paula M. 2014. Agrobacterium-mediated genetic transformation and plant regeneration of the hardwood tree species Fraxinus profunda. Plant Cell Reports. 33(6): 861-870.

Beasley, R.R.; Pijut, P.M. 2013. Regeneration of plants from Fraxinus nigra Marsh. hypocotyls. HortScience 48(7):887-890.

Stevens, M.E.; Pijut, P.M. 2012. Hypocotyl derived in vitro regeneration of pumpkin ash (Fraxinus profunda). Plant Cell Tissue and Organ Culture 108:129-135.

Palla, K.J.; Pijut, P.M. 2011. Regeneration of plants from Fraxinus americana hypocotyls and cotyledons. In Vitro Cellular and Developmental Biology-Plant 47:250-256.

Du, N.; Pijut, P.M. 2010. Isolation and characterization of an AGAMOUS homolog from Fraxinus pennsylvanica. Plant Molecular Biology Reporter 28:344–351.

Du, N.; Pijut, P.M. 2009. Agrobacterium-mediated transformation of Fraxinus pennsylvanica hypocotyls and plant regeneration. Plant Cell Reports 28: 915-923.

Du, N.; Pijut, P.M. 2008. Regeneration of plants from Fraxinus pennsylvanica hypocotyls and cotyledons. Scientia Horticulturae 118: 74-79.

Research Participant

Principal Investigator

Paula M. Pijut, USDA Forest Service, Northern Research Station (NRS), Hardwood Tree Improvement and Regeneration Center, Research Plant Physiologist