Genetic integrity of shortleaf and longleaf pine seed orchards and seed banks

Longleaf pine (Pinus palustris Mill.) and shortleaf pine (Pinus echinata Mill.) are priority species targeted for increased restoration on the national forests in the Southern Region of the U.S. Department of Agriculture, Forest Service. The genetic integrity of both species is important to ensure adaptation, survival, and resilience of future forests. Longleaf x loblolly pine hybrids (Pinus x sondereggeri H.H. Chapm. ex Sudw. [palustris x taeda]) and shortleaf x loblolly pine hybrids are known to occur in the general forests, but at a rate of less than 5 percent. Climate change can trigger extreme fluctuations in temperatures, which could influence flower receptivity and result in greater potential for increased inter-species hybridization. This hybridization may compromise the genetic purity of a species and present challenges to successful restoration. It is important to know the genetic identity of the seedlings we are deploying in operational plantings, and the seed being sold to State partners. The Southern Region National Forest System Genetics program chose to DNA fingerprint longleaf and shortleaf pine parents (clones) in the regional seed orchards to assess genetic purity. Final results showed no hybrid fingerprint for the 250 longleaf clones tested and a hybrid fingerprint for 17 of the 619 shortleaf clones tested. The regional seed bank inventory for longleaf and shortleaf pines was also DNA fingerprinted. The seed tested had been collected across multiple years and seed zones. Final results showed a hybrid fingerprint for less than 3 percent of the seed. This paper was presented at the Joint Annual Meeting of the Southern Forest Nursery Association and the Northeast Forest and Conservation Nursery Association (Pensacola, FL, July 17–19, 2018).