"The project was a huge undertaking because at 22 gigabases, the loblolly pine genome is about eight times larger than the human genome," said C. Dana Nelson, SRS Southern Institute for Forest Genetics (SIFG) project leader and research geneticist. "The group chose loblolly pine both because of its economic importance, and the knowledge gained from 60 years of breeding the species and managing millions of trees in genetic trials."
As part of the project, researchers identified a candidate for a gene involved in resistance to fusiform rust, a disease that infects southern pines. SIFG biological science technician Katherine Smith worked with John M. Davis, professor and associate director of the School of Forest Resources and Conservation at the University of Florida (UF), to compare mapped sections of the genome with sections found in loblolly specimens previously inoculated with the pathogen that causes fusiform rust.
"Fusiform rust is the most damaging disease of southern pines—and one of the most complex due to genetic interactions between the pathogen and its host," said Davis, who also serves as faculty and Executive Committee member at the UF Genetics Institute. "Genetic resistance is the only realistic way to manage the disease, which infects young trees within their first five years of growth and weakens or girdles the stem. Chemical control is expensive, impractical, and not very good for the environment."
Researchers and breeders can use the resistance genes as markers to track resistance in pine breeding populations and to guide tree planting at the stand level. "The fusiform rust pathogen has evolved to defeat some rust resistance genes in loblolly," said Nelson. "The increased molecular understanding from the loblolly genome sequencing effort provides managers with a new effective tool to determine how well seedlings will grow on a particular site."
SIFG involvement in sequencing the loblolly genome actually goes back at least two decades, when SIFG helped develop an array of resources to help speed up mapping and sequencing the loblolly pine genome and provide the ability to identify genes that influence factors such as tree growth, wood quality, stress tolerance and resistance to disease. SIFG also conserved and supplied the plant tissue used in the genome sequencing project and provided quality control on the DNA samples that were sequenced.