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Abstract
Translocation patterns of the triazole plant growth retardants paclobutrazol, triapenthenol, and BAS111 were found to be similar when applied as a trunk paint, soil drench, or in hydroponic systems. Chemical degradation studies indicate that the greatest percentage of parent compound is translocated to roots and mature leaves following soil drench and hydroponic treatments. Generally, residue levels of BAS111 were significantly lower than those of paclobutrazol and triapenthenol. Data from trunk paint applications indicate triapenthenol and BAS111, even at concentrations 5 times greater than paclobutrazol, are not as effective in controlling shoot growth. Significant negative correlations were found between shoot growth and foliar residue levels of paclobutrazol and triapenthenol 13 weeks after trunk paint application. Chemical names used: (2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-pentan-3-ol (paclobutrazol); (E)-(RS)-1-cyclohexyl-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)-pent-1-en-3-ol (triapenthenol); 1-phenoxy-5,5-dimethyl-3-(1,2,4-triazol-1-yl)-hexan-5-ol] (BAS111); trimethylonylpolyethoxyethanol (WK surfactant).
Abstract
Seed leachates of ‘Kentucky 31’ and ‘Rebel’ tall fescue (Festuca arundinacea Schreb.), ‘Citation’ and ‘Manhattan’ perennial ryegrass (Lolium perenne L.), annual ryegrass (Lolium multiflorum Lam.), annual bluegrass (Poa annua L.), and ‘Mystic’ and ‘Victa’ Kentucky bluegrass (Poa pratensis L.) were evaluated for inhibition of lettuce (Lactuca sativa L. ‘Grand Rapids’) germination and seedling growth (a widely used bioassay for allelopathic effects). Different degrees of inhibition of lettuce seedling growth were found in the turfgrass cultivars ‘Rebel’ > ‘Ky31’, ‘Victa’ > ‘Mystic’, ‘Citation’ = ‘Manhattan’, and in annual bluegrass and annual ryegrass. Grass seed leachates were separated into organic and inorganic fractions using XAD-2 polystyrene resin. Organic fractions were inhibitory to lettuce seedling growth. Inorganic fractions were also inhibitory to lettuce seedling growth at high concentrations but were stimulatory at low concentrations. Germination of lettuce was not affected by leachates or their fractions.
Flowering (Cornus florida L.) and kousa (C. kousa Hance) dogwoods are ornamental trees valued for their four-season appeal, but also for their importance to retail and wholesale nurseries. The popularity of kousa dogwood has increased in recent years as a result of its resistance to dogwood anthracnose and powdery mildew as compared with flowering dogwood, which is typically susceptible to those diseases. This range of resistance allows the development of intra- and interspecific cultivars with multiple disease resistance or a combination of disease resistance and specific ornamental traits. Breeding requires controlled crosses that are usually done manually, which is a labor-intensive process. Cornus florida and C. kousa have generally been found to be self-incompatible allowing for the breeding process to be made more efficient by not having to emasculate flowers. We have capitalized on the natural ability of honeybees and the self-incompatible nature of dogwood to perform self- and crosspollinations of flowering and kousa dogwood. Self-pollinations were conducted in 2006 and 2007 with C. florida ‘Appalachian Spring’ and ‘Cherokee Brave’ and with C. kousa ‘Blue Shadow’ and Galilean®. The flowering dogwood self-pollinations resulted in no seed production, whereas the kousa dogwood self-pollinations resulted in low seed production, indicating self-incompatibility. Intra- and interspecific crosses of flowering and kousa dogwood cultivars and breeding lines were conducted in 2006 to 2008. Honeybees were effective in facilitating seed production for all intraspecific crosses conducted. Seedling phenotypes of putative intra- and interspecific hybrids are similar and practically indistinguishable, so dogwood-specific simple sequence repeats were used to verify a sample of the putative hybrids. The results demonstrated that honeybees were effective in performing controlled pollinations and that honeybee-mediated pollinations provide an alternative to time-consuming hand pollinations for flowering and kousa dogwood.
Flowering dogwood (Cornus florida) and kousa dogwood (C. kousa) are popular ornamental species commonly used in the horticultural industry. Both trees are valued for their beautiful floral display and four-season appeal. Species-specific simple sequence repeat (SSR) loci were used to genotype and assess genetic diversity of 24 flowering dogwood cultivars and breeding lines and 22 kousa dogwood cultivars. Genetic diversity was determined by allele sharing distances and principal coordinate analysis and was high in both species. Molecular identification keys were developed for cultivars and breeding lines of each species using a few polymorphic SSRs loci (four in C. florida and five in C. kousa). Most (18 of 24) of the flowering dogwood and all (22 of 22) kousa dogwood accessions could be distinguished from each other using these SSRs; those that could not were resolved using DNA amplification fingerprinting. The reliability of both keys was assessed using five anonymous cultivars for each dogwood species, which were correctly identified using the molecular keys. The genetic information presented here will be useful for identification and verification of cultivars for nurseries and as molecular markers for breeders and researchers.
Cross-species transferability of simple sequence repeats (SSRs) is common and allows SSRs isolated from one species to be applied to closely related species, increasing the use of previously isolated SSRs. The genus Cornus consists of 58 species that are ecologically and economically important. SSRs have previously been isolated from C. florida and C. kousa. In this study, 36 SSRs were tested on taxa from 18 Cornus species and hybrids for cross-species transferability and genetic diversity was calculated for each locus using polymorphism information content (PIC). Cross-species transferability of SSR loci was higher in more closely related species and PIC values were high. Evidence was found for conserved primer sites as determined by the amplification of SSR loci in the taxa examined. Polymerase chain reaction products were cloned and sequenced for three SSR loci (CF48, CF59, and CF124) and all individuals sequenced contained the appropriate repeat. Phylogenetic relationships of 14 Cornus species were inferred using nucleotide sequences of SSR locus CF48. The most parsimonious tree resulting from this analysis was in concordance with phylogenies based on matK and internal transcribed spacer sequences. The SSR loci tested in this study will be useful in future breeding, population, and genetic studies within Cornus.