Issue 6

The Promise of Cottonwood

by Zoë Hoyle

A multinational collaborative effort sequenced the first tree genome earlier this year. Researchers chose to work on poplar (specifically black cottonwood or Populus trichocarpa), a tree which is widely used for pulpwood and papermaking— as well as for forest and riverbank restoration. Researchers at the SRS Southern Institute of Forest Genetics (SIFG) in Saucier, MS, are using information from the genome project to develop new tools to improve eastern cottonwood (Populus deltoides), a member of the poplar family native to the Lower Mississippi Alluvial Valley.

As a native, eastern cottonwood is well adapted to the region, and has long been a favorite among tree breeders and forest geneticists working to improve fiber and wood characteristics. Named for the cottony appearance of its seeds, the tree is relatively easy to propagate from cuttings and grows quickly, making it an ideal choice for restoring riverbanks and flood plains, as well as a renewable source of biomass for energy—and eventually, carbon credits.

In the 1960s, researchers at the SRS unit in Stoneville produced a number of valuable cottonwood clones that were used to establish forest plantations or tree farms. Later federally funded research and work by the forest industry enhanced this early effort, providing many of the high-quality clones now used in afforestation efforts across the South. Recently SIFG scientist Tom Kubisiak participated in a research group that mapped an important disease resistance gene in cottonwood. “Diseases are a limiting factor in cottonwood production,” says Dana Nelson, project leader for SIFG. “Using genetic markers to map the resistance gene is an important step in reducing this limitation.”

SIFG scientists usually work on pine genetics, mapping traits to improve growth and resistance to disease, but are now also working on the poplar genome itself, mapping each DNA sequence to its 19 chromosomes. “Poplar was chosen in part because its genome is relatively compact, around 40 times smaller than that for pines,” says Nelson. “Sequencing the genome has resulted in an explosion of basic information about the poplar family. It’s becoming the research model for all deciduous forest trees, and our cytogenetics research lead by Nurul Faridi is playing an important role.”

“In addition to enhancing the afforestation efforts in the Lower Mississippi Valley, eastern cottonwood holds a lot of promise as a renewable source of quality biomass for conversion into bioenergy and biofuels,” adds Nelson. “The genetic materials developed to date—combined with available data on how well they perform on various sites and the new genetic information and tools that we are helping to develop— should lead to a valuable tree crop for river bottomlands throughout the Southern United States.”

Back to Research Makes Afforestation Work

For more information:

Dana Nelson at 228–832–2747 x 201 or dananelson@fs.fed.us.