Field Selection of American Sweetgum Transformed for Herbicide Resistance

One American sweetgum clone from an open-pollinated parent was transformed with Agrobacterium tumefaciens containing the gene for acetolactate synthase (ALS), and regenerated through organogenesis. Seventy independently transformed lines were selected in vitro in the presence of an ALS-targeting herbicide. Containerized ramets of the 70 lines were established at an irrigated fiber farm in South Carolina, in May, 2002. Over 1,000 trees were planted in a completely randomized design with up to 15 ramets per transline. Establishment survival in June was near 100 percent. Two months after planting, the actively growing trees received one over-the-top application of a tank mix of two ALS-targeting herbicides to evaluate resistance in each transformed line. Thirty days following application, over 85 percent of the planted ramets from three lines displayed no damage symptoms. Sixteen additional lines had a mean damage rating less than �slight�. Twelve of these nineteen lines had first-year heights that were not significantly different from the non-sprayed control line. One transformed line was significantly taller than the control clone (103 cm vs 91 cm mean height, respectively). At the end of the year, only 11 of 1,027 individual trees (1 ramet from each of 9 lines and 2 ramets of another line) died due to herbicide damage. Although the test was terminated after only one growing season, at least four lines were sufficiently resistant to be considered for further plantation development.Papers and abstracts from the 27th Southern Forest Tree Improvement Conference held at Oklahoma State University in Stillwater, Oklahoma on June 24-27, 2003

Coppice growth and water relations of silver maple

Trees of silver maple (Acer saccharinum L.) planted in southern Illinois were cut at rootstock ages 2, 3, and/or 4 years. In all plantings a single main stem was the predominant growth form prior to initial harvest. The predominant post-harvest growth form was numerous coppice stems. The number of coppice stems per tree and percent tree survival decreased with greater stand density. Coppice growth, as measured by the number of stems and the height of the tallest stem, increased progressively with the number of harvest cycles. This growth was supported by a progressively older root system, and developed from an increasing number of cut stem bases. About 60% of the coppice were tall stems, over one-half the height of the tallest stem. Trees of the southernmost origin, from Mississippi, with high establishment rates had the highest dry weight production of two-year provenance coppice growth (equivalent to 59.5 Mg · ha−1 · 2 year−1, or 13.2 ton · acre−1 · year−1). The northernmost trees, from central Ontario, had low establishment rates and the lowest stand biomass. Dormant season macronutrient cropping losses were estimated related to biomass yield. Foliage density and stem elongation were greater in first-year coppiced compared to uncoppiced trees. Water relations of coppice growth differed from that of uncoppiced trees in both the first and the second year after harvest