A Guide to Legal and Genetic Terminology Used in the Sale of Hardwood Seeds and Planting Stock

Paying a premium for better genetics is not new to agriculture or to forestry in some parts of the United States, but paying a premium for genetically improved hardwood trees is new for most consumers. Genetic improvement efforts for hardwoods, especially in the Midwest, have been relatively modest and slow to produce marketable products. However, both public and private nurseries are beginning to sell limited quantities of hardwood seeds, seedlings, and grafted trees variously labeled as “genetically improved,” “improved,” “genetically enhanced,” “superior,” and “select.” Items labeled with these terms usually command higher prices than common planting stock. Landowners in Indiana plant millions of hardwood seedlings each year. Most of these seedlings are planted as 1-0 bare-root stock (Fig. 1). Landowners thinking of investing in planting stock that is sold with an implied assurance of superior performance need information to make informed decisions about the value of these products. This publication describes the laws that apply to those who purchase seeds and nursery stock and explains the methods used by tree breeders to improve trees. This information should help consumers judge the value of the trees they purchase

Pollen gene flow, male reproductive success, and genetic correlations among offspring in a northern red oak (Quercus rubra L.) seed orchard

Northern red oak is a high-value hardwood used for lumber, furniture and veneer. Intensively managed northern red oak seed orchards are required to obtain genetic gain for trait improvement. Data from conifer seed orchards and natural and managed stands of hardwood trees have shed light on the distance over which pollen can move, and underscore the need for managerial attention to seed orchard design, placement, and maintenance. We used eleven microsatellite markers to investigate pollen gene flow, female mate choice, and male reproductive success in a clonal seed orchard of northern red oak based on paternity analysis of seed orchard offspring in progeny tests. Nearly all (93%) offspring were sired by a male parent within the seed orchard. The mean number of male parents per year was 69.5, or 47.6% of all clones in the seed orchard. Female clones in the early phenology group had more offspring sired from extra-orchard pollen (13%) than clones in the intermediate (5%) and late (1%) phenology groups. Distance was the largest influence on pollination success, and pollination occurred most often by male trees in the same subline as the maternal tree. Males in the early phenology group sired more offspring overall in the progeny pool and more offspring per mother tree than males in the intermediate or late phenology groups. Average genetic correlations among all OP progeny ranged between 0.2557 and 0.3529 with a mean of 0.28±0.01. The importance of progeny test genotyping for northern red oak improvement likely is increasing with the demand for improved varieties. The current study demonstrated the feasibility of post hoc assembly of full-sib families for genetic analysis

Spread of butternut canker in North America, host range, evidence of resistance within butternut populations and conservation genetics

Butternut canker is killing trees throughout the range of butternut in North America and is threatening the viability of many populations in several areas. Although butternut is the primary host, other Juglans species and some hardwood species also are potential hosts. Evidence is building that genetic resistance within butternut populations may be exploited for conservation and restoration of the species

Completion of the Chloroplast Genomes of Five Chinese Juglans and Their Contribution to Chloroplast Phylogeny

Juglans L. (walnuts and butternuts) is an economically and ecologically important genus in the family Juglandaceae. All Juglans are important nut and timber trees. Juglans regia (Common walnut), J. sigillata (Iron walnut), J. cathayensis (Chinese walnut), J. hopeiensis (Ma walnut), and J. mandshurica (Manchurian walnut) are native to or naturalized in China. A strongly supported phylogeny of these five species is not available due to a lack of informative molecular markers. We compared complete chloroplast genomes and determined the phylogenetic relationships among the five Chinese Juglans using IIumina sequencing. The plastid genomes ranged from 159,714 to 160,367 bp encoding 128 functional genes, including 88 protein-coding genes and 40 tRNA genes each. A complete map of the variability across the genomes of the five Juglans species was produced that included single nucleotide variants, indels (insertions and deletions), and large structural variants, as well as differences in simple sequence repeats (SSR) and repeat sequences. Molecular phylogeny strongly supported division of the five walnut species into two previously recognized sections (Juglans/Dioscaryon and Cardiocaryon) with a 100% bootstrap (BS) value using the complete cp genomes, protein coding sequences (CDS), and the introns and spacers (IGS) data. The availability of these genomes will provide genetic information for identifying species and hybrids, taxonomy, phylogeny, and evolution in Juglans, and also provide insight into utilization of Juglans plants

Cultivar Identification and Genetic Relatedness Among 25 Black Walnut (Juglans Nigra) Clones Based on Microsatellite Markers

A set of eight microsatellite markers was used to genotype 25 black walnut (Juglans nigra L.) clones within the Purdue University germplasm repository. The identities of 212 ramets were verified using the same eight microsatellite markers. Some trees were mislabeled and corrected as to clone using analysis of microsatellite markers. A genetic dendrogram was constructed to show the degree of genetic relatedness between clones. Two additional dendrograms, one based on crown architecture traits and the other on tree size and form traits, were also built and compared with the genetic dendrogram. The genetic dendrogram showed that these eight molecular markers had the ability to distinguish genetically related clones from less related ones. Crown architecture traits and tree size and form traits were able to group genetically related clones together, but less accurately than the genetic matrix

Breeding Resistance to Butternut Canker Disease

Butternut (Juglans cinerea L.) is being killed throughout its native range by an exotic fungus Ophiognomonia clavigignenti-juglandacearum (Ocj). In recent years, many disease-free trees have been determined to be complex hybrids with an admixture of Japanese walnut (J. ailantifolia). Recently developed molecular and morphological characterizations allow us to accurately identify and separate hybrid and pure butternut progeny. Disease-free-trees, from across butternut’s native range, are the basis of our breeding program in the Central Hardwood Region of the eastern United States. Our first clone banks and seed orchards were grafted and established in the 1990s and 2000s, and are now producing seed for resistance screening. In 2008, we challenged 5-year-old trees from our first two field progeny tests with Ocj. The first test, planted in 2003, had 37 diverse families (n=319). Thirty-two of these seedling families were derived from a grafted orchard of putatively resistant selections. Five additional families were collected from healthy hybrid trees. In early fall of 2008, trees were inoculated with two isolates of Ocj obtained from branch cankers on trees in two locations in Indiana. The trees were scored 8, 12, 20, and 24 months after inoculation for canker incidence and severity. Native butternuts in the adjacent woods provided a source of inoculum whereby natural infections from Ocj began to occur in the third year. Cumulative natural canker incidence and severity were recorded at 5 and 7 years. The second test, planted in 2004, had 12 pure butternut half-sib families collected from a woodlot with: four resistant, four moderately resistant, four susceptible, and one resistant hybrid families (n=213). Resistance ratings were based on the disease status of the mother trees in the stand when the seed was harvested in the fall of 2002. In early fall of 2008, trees were inoculated with the same two isolates of Ocj used in the first test. The trees were scored 8, 12, 20, and 24 months after inoculation for canker incidence and severity. There was no natural infection in the second test. Hybrid butternut families were more resistant to natural infection than the pure butternut families. Eight months after inoculation, canker incidence and severity varied significantly among butternut hybrid families and Ocj isolate, but not among pure butternut families. After 12, 20, and 24 months, canker incidence and severity of pure butternut families changed. By 24 months, hybrid families in general have shown reduced canker expansion and a high level of resistance. Pure butternut families exhibit more variation from highly susceptible to resistant. Year-to-year variation in canker growth suggests that it may take several years to determine the resistance status of butternut with artificial stem inoculations

Screening butternut and butternut hybrids for resistance to butternut canker

Butternut (Juglans cinerea) is being killed throughout its native range by the fungus Sirococcus clavigignenti-juglandacearum (Scj). In recent years, many disease-free trees have been determined to be complex hybrids with an admixture of Japanese walnut (J. ailantifolia). We challenged 5-year-old trees from two progeny tests with Scj in 2008. The first test (northern Indiana), planted in 2003, had 37 diverse families (n=319). Thirty-two of these seedling families were derived from a grafted orchard. Five additional families were collected from hybrid trees. The second test (southern Indiana), planted in 2004, had 12 pure butternut half-sib families collected from a woodlot with: 4 resistant, 4 moderately resistant, 4 susceptible, and 1 resistant hybrid families (n=213). Resistance ratings were based on the disease status of the mother trees when the seed was harvested in the fall of 2002. Eleven black walnut (J. nigra) trees were also included. In early fall of 2008, trees were inoculated with two strains of Scj obtained from branch cankers on trees in two locations in Indiana. The trees were scored 8 months after inoculation for canker incidence and severity. Some trees in the first test were naturally infected by Scj and resulting canker incidence and severity were recorded. Butternut hybrid families were more resistant to natural infection than the pure butternut families. Eight months after inoculation, canker incidence and severity varied significantly among butternut hybrid families and Scj strain but not among pure butternut families

JnCML-like, an EF-hand motif-containing gene seasonally upregulated in the transition zone of black walnut (Juglans nigra L.)

The economic value of a black walnut (Juglans nigra L.) tree is strongly determined by the quality and quantity of darkly colored heartwood in its stem. To understand the regulation of heartwood formation, we analyzed the region of heartwood formation in walnut stems (i.e., the transition zone, TZ) for the expression of 80 ESTs. Semi-quantitative RT-PCR and real-time PCR was performed to detect expression changes of candidate genes in the TZ and sapwood of trees harvested in summer and fall. Results revealed that the transcript of a clone containing two presumed EF-hand motifs was expressed at higher levels in the TZ than in other xylem tissues. Analysis of the full-length coding sequence revealed that the black walnut gene JnCML-like is similar to grancalcin-like calcium-binding EF hand proteins in Arabidopsis thaliana (At3g10300) and Zea mays (NM 001153810). A model of the predicted structure of JnCML-like showed it is similar to grancalcin and m-calpain, penta-EF-hand family proteins associated with cell proliferation, differentiation and programmed cell death. JnCML-like transcript was detected in tissue from the region of the pith meristem, and in roots, embryogenic callus, vascular cambium, female flowers, male flowers, green leaves, and partially and fully senescent leaves of black walnut, although transcript abundance varied considerably among these tissues

Exploration of a rare population of Chinese chestnut in North America: stand dynamics, health and genetic relationships

With the transport of plants around the globe, exotic species can readily spread disease to their native relatives; however, they can also provide genetic resistance to those relatives through hybrid breeding programmes. American chestnut (Castanea dentata) was an abundant tree species in North America until its decimation by introduced chestnut blight. To restore chestnut in North America, efforts are ongoing to test putative blight-resistant hybrids of Castanea dentata and Chinese chestnut (Castanea mollissima), but little is known about the ecology of C. mollissima. In a forest in northeastern USA in which C. mollissima has become established, we explored questions of stand dynamics, health and genetic relationships of C. mollissima offspring to an adjacent parent orchard. We found that C. mollissima was adapted and randomly distributed among native species in this relatively young forest. The genetics of the C. mollissima population compared with its parents indicated little effect of selection pressure as each of the parent trees contributed at least one offspring. The ease with which this exotic species proliferated calls to question why C. mollissima is rare elsewhere in forests of North America. It is likely that a time window of low animal predation allowed seedlings to establish, and the shallow soil at this site limited the maximum forest canopy height, permitting the characteristically short-statured C. mollissima to avoid suppression. Our results indicate that because C. mollissima exhibited pioneer species characteristics, hybrids between C. mollissima and C. dentata have the potential to be successful pioneer species of future forests in North America, and we challenge the paradigm that exotic tree species are wholly detrimental to native biodiversity. We contend that exotic tree species should be assessed not only by their level of threat to native species, but also by their potential positive impacts on ecosystems via hybrid breeding programmes