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Abstract
Factors affecting natural infestation of flowering dogwoods (Cornus florida L.) by the dogwood borer, Synanthedon scitula Harris (Lepidoptera: Sesiidae), were studied in an urban cemetery in Louisville, Kentucky. Two tree characteristics, severity of trunk wounding and exposure to sun, were most important in determining the probability of borer attack. Degree of crown dieback or color of bloom did not significantly affect the rate of infestation. There was no correlation between tree diameter and probability of attack, but height of attack sites increased linearly with increasing tree size.
Abstract
Resistance to the twospotted spider mite (Tetranychus urticae Koch) of 18 cultivars of ivy geranium [Pelargonium peltatum (L.) L’Her ex Ait.] was evaluated under greenhouse conditions by mass screening, by measuring fecundity on isolated leaves, and by paired leaf tests for selected cultivars. ‘Sybil Holmes’, ‘Yale’, and ‘Cornell’ were among the most susceptible, whereas ‘Double Lilac White’, ‘Sunset’, and ‘Salmon Queen’ were relatively mite-free. ‘Madeline Crozy’ and ‘Cornell’ were preferred for oviposition over the resistant ‘Double Lilac White’. Mite resistance was not related to density of simple or glandular leaf trichomes, but there was an apparent relationship between mite susceptibility and severity of oedema.
Abstract
Three genetically diverse Kentucky bluegrasses (Poa pratensis L. cvs. Kenblue, Vantage, and Adelphi) and 6 other turfgrasses were evaluated for susceptibility to the greenbug, Schizaphis graminum Rondani. Nine common lawn weed species were also tested as potential alternative hosts. Heavy greenbug populations and feeding damage occurred on all 3 bluegrasses and on tall fescue (Festuca arundinacea Schreb. cv. Kentucky 31) and chewings fescue (Festuca rubra var. cummutata Guad. cv. Jamestown). Creeping bentgrass (Agrostis palustris Huds. cv. Penncross), bermudagrass (Cynodon dactylon L. cv. Midiron), perennial ryegrass (Lolium perenne L. cv. Derby), and zoysia grass (Zoysia japonica Steud. cv. Meyer) were not suitable hosts. No greenbugs survived on the 9 weed species tested.
The renowned horticultural artist and plant breeder Luther Burbank worked with many species of plants. During his 50-year career, he introduced more than 800 cultivars, including more than 150 accessions of plums (Prunus spp.) in the late 1800s and early 1900s. Burbank preferred using wide, interspecific crosses to create a vast range of phenotypic variation and then artificially select from the extremes. Although a great artist, Burbank was a substandard scientist because he was derelict in pedigree note-taking. Although many of his introductions are extinct, hobbyists, enthusiasts, and international collections retain nearly a third of the economically viable cultivars he bred. For a century, many of his hybridizations remained inscrutable mysteries until modern genomic and computational tools developed their resolution and statistical power. Today, genotyping by sequencing (GBS) is a useful tool for pedigree reconstruction in the absence of reliable records. GBS can inform principal component analyses, identity by descent (IBD) kinship, and phylogenetic admixture, revealing complex relationships among taxa. In this study, whole genome sequencing was performed on 53 Prunus taxa used by Burbank in his breeding experiments in the most comprehensive genetic survey of his work to date. Exact parent–offspring relationships between this population may be impossible to discern due to years of back crossing, sibling mating, and open pollination. However, the proportion of genomic similarity among these taxa provides information on the relatedness of the genotypes in Burbank’s Prunus experiments, defining four primary lineages within his breeding population. These lineages comprised primarily P. salicina and P. simonii but also have influences from P. americana, P. cerasifera, P. domestica, and P. rivularis. The prevalence of P. simonii in Burbank’s Prunus introductions appears to have been vastly underreported, indicating that some of the seedstock founders of his breeding population could have been P. salicina × P. simonii hybrids at the inception of his career. This research has implications for pedigree reconstruction and prioritizing conservation in collections curation for future studies.