Location: Floral and Nursery Plants Research2009 Annual Report
1a. Objectives (from AD-416)
This study will include three objectives. First, we will evaluate 46 Spiraea accessions using over 30 descriptor traits used in GRIN by the WLPCGC in two distinct physiographic locations within the state of Georgia (Athens and Savannah). This information will be provided to GRIN for inclusion in the GRIN database. Second, we will measure the overall landscape quality of each accession with an emphasis on heat tolerance and plant form in each of the two aforementioned physiographic regions. Third, we will measure the invasive potential of these accessions by conducting seed viability and germination tests on each accession.
1b. Approach (from AD-416)
Experimental design for this study will be a randomized complete block design with three replications. We will use the expected mean squares from the analysis of variance to calculate broad sense heritabilities, which will distinguish proportions of genetic and environmental variance for each trait. Each replication will consist of one individual per taxa. Plant material will be acquired from Chicago Botanic Garden, the official NAPCC Spiraea collections repository. Cuttings of accessions will be taken in the fall of 2007 and rooted in greenhouses using the protocol of Dirr and Heuser (2006). Plants will be transferred to in-ground beds in the spring of 2008 at two locations: Athens, GA (USDA Zone 7b) and Savannah, GA (USDA Zone 8b). Planting beds will be arranged in linear-rows with individuals planted on 5’ staggered centers. Drip-irrigation will be applied as needed the first growing season while plants are becoming established and subsequently removed for the remainder of the study unless severe drought warrants irrigation. Measurement of the aforementioned USDA-ARS woody landscape plant descriptor traits and mortality will begin April 1, 2009, and conclude on November 15, 2010. Disease and insect measurements will include pathogen/pest ID and percent of plant affected. Attractiveness, floral impact, persistence of foliage, plant vigor, and summer drought/heat tolerance will be measured on a 1-10 scale with one being the least and 10 being the highest. Color measurements will all be performed using the Royal Horticultural Society Colour Chart. All size measurements will be taken in centimeters. Number of fruit produced per umbel will be taken from an average of five randomly selected umbels per individual. All date measurements will be reported on a 1-365 scale beginning with January 1 and ending with December 31. Invasive potential will be measured by calculating the percentage of viable seed and germination percentage of 100 seed per individual using two techniques: 1) Tetrazolium tesing in 0.1% solution of 2,3,5-triphenyltetrazolium chloride (Miller, 2004). 2) Germination test on moist filter paper. Additionally, we will qualitatively measure seed production of each genotype by assessing the mean number of seed produced per umbel using five umbels per plant. We will also calculate the mean number of umbels for each genotype. By multiplying the mean number of seed produced per umbel with the mean number of umbels per genotype, we will ascertain a overall value for seed production of each genotype in the study.
3. Progress Report
Twenty nine aronia accessions were grown in 2-gallon containers to a size where they were large enough for field planting in spring 2009. Each of these 29 accessions was planted in triplicate in the aronia accessions field collection in May 2009 for future evaluation of ornamental and fruit traits. An additional 30 accessions collected as cuttings or basal suckers during the 2008 season were put into accelerated growth conditions in late winter 2009 and will continue to be grown to size for field planting in spring 2010. Seeds from 37 accessions collected in fall 2008 were stratified and germinated. Seedlings are being grown in quart pots during the 2009 growing season. These plants may be ready for field installation in spring 2010 if accelerated growth facilities are available. Flow cytometry was conducted on 60 aronia accessions to determine ploidy. Findings were consistent with previous ploidy analyses of other aronia accessions. Most A. melanocarpa from New England are diploids, while A. arbutifolia are tetraploids and A. prunifolia are either tetraploid or triploid. Aronia accessions were sent to the USDA-ARS North Central Regional Plant Introduction Station in Ames, Iowa and have been added to the National Plant Germplasm System. Twenty two accessions were provided as liner plants and an additional 11 accessions were provided as seed. These additions have more than doubled USDA’s germplasm holdings of Aronia. Numerous crosses were made between Aronia and various other genera in the rose family, including Photinia, Malus, Amelanchier, Sorbus, and Chaenomeles. Preliminary observations suggest that Photinia and Sorbus crosses may have been successful. Previous crosses made between genotypes of Aronia species with varying ploidy levels suggest that to get genetic mixing, diploid plants should be used as the female parent. Tissue was collected from 75 Aronia accessions and rose family genera in preparation for AFLP analysis. AFLP analysis will focus on speciation within the genus Aronia and geographic distribution. In addition, we hope to determine the genetic background of large fruited black chokeberries. Progress on this project was monitored through e-mails and written reports.