2012 Annual Report
1a.Objectives (from AD-416):
Characterize germplasm of elms with potential importance to the American nursery industry, concentrating on recently introduced species and on newly discovered genetic races of native species. Analyze genetic diversity among elm accessions and the phylogenetic relationships among them. Provide genetic markers and taxonomically well-identified and characterized germplasm that will be useful for elm research and breeding in the future.
1b.Approach (from AD-416):
Accessions will be identified according to the latest understanding of elm taxonomy, collecting herbarium specimens at different times of the year to allow coding of characters of the flowers, fruit, and leaves, and winter buds. Genetic diversity and phylogenetic relationships will be analyzed by DNA analysis of appropriate nuclear and chloroplast regions, evaluating new markers as necessary. Genome size and ploidy of representative accessions will be investigated using flow cytometry and (if necessary) chromosome counts.
DNA sequencing has concentrated on two single-copy nuclear genes, nitrate reductase (nia) and chloroplast expressed glutamine synthetase (ncpGS); sequencing work this fiscal year has concentrated on nia. Some sequences were successfully obtained from some taxa using direct sequencing of gel-purified DNA products, but cloning has proven necessary to obtain sequences from other individuals. Some technical problems were encountered with the cloning of nia in these elms, but these have been overcome and an array of nia sequences should be edited and at least partly analyzed by the end of the fiscal year.
In addition to the sequencing work, collection of herbarium specimens to preserve flowering, fruiting, and leaf material of elm germplasm in the living collections of the National Arboretum (DC and Maryland) and Morton Arboretum (Illinois) continues, and we have already found some errors in identification of this material, used for research and (potentially) for future breeding and commercial release.