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  • Author or Editor: Eugene K. Blythe x
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One-year-old liners of Encore® azalea ‘Chiffon’ (Rhododendron sp.) were transplanted in Apr. 2013 into two types of one-gallon containers: black plastic container and paper biodegradable container. Azalea plants were fertilized with 250 mL of nitrogen (N) free fertilizer solution twice weekly plus N rate of 0, 5, 10, 15, or 20 mm from ammonium nitrate (NH4NO3). All plants were irrigated with the same total volume of water through one or two irrigations daily. Plant growth and N uptake in response to N fertilization, irrigation frequency, and container type were investigated. The feasibility of biodegradable paper containers was evaluated in 1-year production of Encore® azalea ‘Chiffon’. Paper biocontainers resulted in increased plant growth index (PGI), dry weights (leaf, stem, root, and total plant dry weight), leaf area, and root growth (root length and surface area) compared with plastic containers using N rates from 10 to 20 mm. Biocontainer-grown plant had more than twice of root length and surface area as plastic container–grown plant. Leaf SPAD reading increased with increasing N rate from 0 to 20 mm. One irrigation per day resulted in greater PGI, root dry weight, root length, root surface area, and root N content than two irrigations per day. Higher tissue N concentration was found in plants grown in plastic containers compared with those grown in biocontainers when fertilized with 15 or 20 mm N. However, N content was greater for plants grown in biocontainers, resulting from greater plant dry weight. The combinations of plastic container and one irrigation per day and that of 20 mm N and one irrigation per day resulted in best flower production, 21.9 and 32.2 flowers per plant, respectively. Biocontainers resulted in superior vegetative growth of azalea plant compared with plastic containers with sufficient N supply of 10, 15, and 20 mm.

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This study reports on the performance of 34 clones of crapemyrtle (Lagerstroemia indica L., L. fauriei Koehne, and L. indica × L. fauriei hybrids) grown in field plots at four locations representative of different environments in the southeastern United States. Traits evaluated were spring leaf-out and initiation of flowering in the second season after field planting and plant height after 3 years of growth. Cluster analysis (Ward's method) was used for grouping and comparison of means across locations for each trait. Best linear unbiased prediction was used for estimating random effects in linear and generalized linear mixed models to better determine the general performance of the clones under a variety of environmental conditions. Each clone's trait stability was quantified using the regression of an individual genotype's performance for each of the three studied traits on an environmental index based on the trait mean for all genotypes grown in an environment. Sequence of clone leaf-out and size rankings were more stable across the environments than the sequence in which the various clones initiated flowering. L. fauriei clones and clones originating from the initial cross between L. indica and L. fauriei were generally later to leaf out, earlier to flower, and more vigorous growers than L. indica or the complex L. indica × L. fauriei clones that were evaluated. First flowering was affected by environmental variation more with interspecific hybrids than with L. fauriei and L. indica clones. Performance, particularly with respect to plant height, of several clones did not agree with previously published classifications. Information generated by this study will allow crapemyrtle breeders, landscape professionals, and consumers to better select the most appropriate crapemyrtle clone for a particular application.

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Inoculation of detached strawberry leaves with Colletotrichum species may provide an accurate, rapid, nondestructive method of identifying anthracnose-resistant germplasm. The purpose of this study was to statistically compare two methods (visual and image analysis) of evaluating disease severity of strawberry germplasm screened for anthracnose resistance. Detached leaves of 77 susceptible and resistant strawberry clones were inoculated with one Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. and two C. fragariae A. N. Brooks isolates. Anthracnose disease symptoms on each leaf were assessed quantitatively via computer-based image analysis to determine percentage lesion area and qualitatively by two independent raters using a visual disease severity rating scale (0 = no symptoms to 5 = entire leaf dead). The two visual raters’ average disease severity ratings (n = 3413) were in substantial agreement with a weighted Cohen’s kappa coefficient (k) of 0.80 [95% confidence interval (CI) 0.79–0.82]. There was a strong positive correlation between percent lesion area determined by image analysis and the visual disease scores of the two raters (r p = 0.79). Image analysis provided a precise measurement of percent lesion area of infected leaves while visual assessment provided more rapid results. Our results indicate that detached leaf inoculations can be used as a rapid preliminary screen to separate anthracnose-susceptible from -resistant germplasm in large populations within breeding programs. It also may be used for assessing the resistance/susceptibility of parental breeding lines to various Colletotrichum species and isolates, for mapping germplasm for resistance genes, and in pesticide development studies.

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Strawberry anthracnose diseases are caused primarily by three Colletotrichum species: C. acutatum J.H. Simmonds, C. fragariae A.N. Brooks, and C. gloeosporioides (Penz.) Penz. & Sacc. Molecular markers are being used in breeding programs to identify alleles linked to disease resistance and other positive agronomic traits. In our study, strawberry cultivars and breeding germplasm with known anthracnose susceptibility or resistance to the three anthracnose-causing Colletotrichum species were screened for two sequence characterized amplified region (SCAR) markers linked to the Rca2 gene. The Rca2 resistant allele SCAR markers were associated with varying degrees of significance for a strawberry plant’s anthracnose resistance to C. fragariae but not to C. acutatum or C. gloeosporioides. Although the presence or absence of the markers associated with the Rca2 resistance gene is an imperfect indicator of anthracnose resistance, it may serve as a useful starting point in selecting germplasm for breeding programs.

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The use of glyphosate-tolerant perennial ryegrass (Lolium perenne L.) (PRG) cultivars JS501 and Replay provides turfgrass managers a unique option for annual bluegrass (Poa annua L.) (ABG) control. Both cultivars can tolerate a maximum glyphosate rate of 0.81 kg·ha−1 acid equivalent (a.e.) after establishment under optimal growing temperatures (16 to 24 °C). However, tolerance to applications made immediately after germination and during low air temperatures has received limited investigation. Therefore, objectives of this research were to determine the seedling tolerance and low-temperature response after a fall season glyphosate application to both cultivars. Field trials were conducted in Idaho and Oregon. For the fall application response trial in Idaho, glyphosate was applied at 0, 0.15, 0.29, 0.58, 1.16, 1.74, 2.32, and 3.48 kg·ha−1 a.e. In Oregon, glyphosate was applied at 0, 0.15, 0.29, 0.44, 0.58, 1.16, and 3.48 kg·ha−1 a.e. At both sites, applications were made between late September and early October. To determine seedling tolerance, both cultivars were sprayed with glyphosate at the one-leaf stage (LS), two LS, three LS, or four LS at rates of 0, 0.15, 0.29, and 0.58 kg·ha−1 a.e. Across all trials, ratings included PRG color, cover, and injury. At both trial locations, regression analysis revealed a rate of ≈0.27 kg·ha−1 a.e. was required to cause 20% leaf firing in the fall application response trial. In the seedling tolerance trial, glyphosate applied at 0.58 kg·ha−1 a.e. at the one LS, two LS, and three LS had color ratings 8.0 or greater; however, color ratings dropped to 4.6 when an application was made at the four LS. Based on the environmental conditions of each trial, results suggest glyphosate applications greater than 0.27 kg·ha−1 a.e. as minimum air temperatures approach 0 °C should be avoided. Also, applications should be avoided at the three to four LS if the application rate is greater than 0.29 kg·ha−1 a.e.

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Tall bearded (TB) iris (Iris germanica L.) has great potential as a specialty cut flower due to its fragrance and showy, multicolor display; however, limited research has been reported on optimal nitrogen (N) nutrient management for TB iris. The objectives of this study were to investigate the effects of N fertilizer rate on plant growth and flowering of ‘Immortality’ iris and determine the influence of both stored N and spring-applied N fertilizer on spring growth and flowering. On 14 Mar. 2012, rhizomes of ‘Immortality’ iris were potted in a commercial substrate with no starter fertilizer. Plants were fertigated with 0, 5, 10, 15, or 20 mm N from NH4NO3 twice per week from 28 Mar. to 28 Sept. 2012. In 2013, half of the plants from each of the 2012 N rate were supplied with either 0 or 10 mm N from 15NH4 15NO3 twice per week from 25 Mar. to 7 May 2013. Growth and flowering data including plant height, leaf SPAD, number of fans and inflorescence stems, and length of inflorescence stem were collected during the growing season. Plants were harvested in Dec. 2012 and May 2013 to measure dry weight and N concentration in leaves, roots, and rhizomes. Results showed higher 2012 N rates increased plant height, leaf SPAD reading, and number of inflorescence stems at first and second blooming in 2012. Greater 2012 N rates also increased plant dry weight and N content in all structures, and N concentration in roots and rhizomes. Rhizomes (58.8% to 66.3% of total N) were the dominant sink for N in Dec. 2012. Higher 2012 N rates increased plant height, number of fans, and the number of inflorescence stems at spring bloom in 2013. In May 2013, N in leaf tissue constituted the majority (51% to 64.3%) of the total plant N. Higher 2012 N rates increased total dry weight, N concentration, and N content in all 2013 15N rates; however, leaf dry weight in all plants was improved by 2013 15N rate. Percentage of tissue N derived from 2013 15N (NDFF) decreased with increasing 2012 N rate. New spring leaves were the dominant sink (56.8% to 72.2%) for 2013 applied 15N. In summary, ‘Immortality’ iris is capable of a second blooming in a growing season, this second blooming dependent on N fertilization rate in current year. A relatively high N rate is recommended to produce a second bloom.

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Wood-based substrates have been extensively evaluated for greenhouse and nursery crop production, yet these substrates have not been evaluated for propagation. The objective of this study was to evaluate processed whole loblolly pine trees (WPT) (Pinus taeda) as a rooting substrate for stem cutting propagation of a range of ornamental crops. Substrates included processed WPT, pine (Pinus sp.) bark (PB), and each mixed with equal parts (by volume) peatmoss (PM) (WPT:PM and PB:PM, respectively). Substrate physical (air space, container capacity, total porosity, bulk density, and particle size distribution) and chemical [pH and electrical conductivity (EC)] properties were determined for all substrates. Rooting percentage, total root length, total root volume, and total shoot length were evaluated for four species in 2008 and five species in 2009. Substrate air space was similar between PB and WPT in the 2008 experiment, and likewise between PB:PM and WPT:PM. In the 2009 experiment, PB and WPT had similar substrate air space. The addition of PM to PB and WPT resulted in reduced air space and increased container capacity in both experiments. The proportion of fine particles doubled for PB:PM and WPT:PM compared with PB and WPT, respectively. Substrate pH for all substrates ranged from 6.0 to 6.9 at 7 days after sticking (DAS) cuttings and 6.9 to 7.1 at 79 DAS. Substrate EC was below the acceptable range for all substrates except at 7 DAS. Rooting percentage was similar among substrates within each species in both experiments. The addition of PM resulted in significantly greater total root length for PB:PM and WPT:PM compared with PB and WPT, respectively, for five of the eight species. Shoot growth was most vigorous for PB:PM compared with the other substrates for all species. The study demonstrated a range of plant species can be propagated from stem cuttings in whole pine tree substrates alone or combined with PM.

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In five experiments, singlenode cuttings of `Red Cascade' miniature rose (Rosa) were treated with a basal quick-dip (prior to insertion into the rooting substrate) or sprayed to the drip point with a single foliar application (after insertion) of Dip `N Grow [indole-3-butyric acid (IBA) + 1-naphthaleneacetic acid (NAA)], the potassium salt of indole-3-butyric acid (K-IBA), or the potassium salt of 1-naphthaleneacetic acid (K-NAA); a single foliar spray application of Dip `N Grow with and without Kinetic surfactant; or multiple foliar spray applications of Dip `N Grow. Spray treatments were compared with their respective basal quick-dip controls {4920.4 μm [1000 mg·L-1 (ppm)] IBA + 2685.2 μm (500 mg·L-1) NAA, 4144.2 μm (1000 mg·L-1) K-IBA, or 4458.3 μm (1000 mg·L-1) K-NAA}. Cuttings sprayed with 0 to 246.0 μm (50 mg·L-1) IBA + 134.3 μm (25 mg·L-1) NAA, 0 to 207.2 μm (50 mg·L-1) K-IBA, or 0 to 222.9 μm (50 mg·L-1) K-NAA resulted in rooting percentages, total root length, percent rooted cuttings with shoots, and shoot length similar to or less than control cuttings. Exceptions were cuttings sprayed with 0 to 2.23 μm

(0.5 mg·L-1) K-NAA, which exhibited shoot length greater than the control cuttings. Addition of 1.0 mL·L-1 (1000 ppm) Kinetic organosilicone surfactant to spray treatments resulted in greater total root length and shoot length. Repeated sprays (daily up to seven consecutive days) had no or negative effects on root and shoot development.

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A field experiment was conducted from 1995 to 1999 in central Alabama to determine the effect of repeated applications of glyphosate herbicide on young ‘Sumner’ pecan trees. Herbicide treatments were applied on ‘Sumner’ pecan trees varying in age from newly established (first growing season) to established fourth-year growing season trees. Measurements taken included tree mortality, trunk cross-sectional area, nut yield, and nut quality in the third and fourth years of the study. Glyphosate applications were targeted at the lowest 5 to 8 cm of the tree trunk (“standard” treatment), a percentage (lowest 33%, 67%, or 100%) of the tree trunk below the first scaffold limb, or a percentage (lowest 25%, 50%, 75%, or 100%) of tree foliage to simulate situations ranging from minor spray drift to major misapplication. No adverse effects were detected when glyphosate was applied to trunks, regardless of tree age. However, repeated application of glyphosate to 75% to 100% of tree foliage resulted in a significant reduction of growth and, in some cases, tree death. Results indicate that limited contact of glyphosate with the lowest 5 to 8 cm of the trunk of the young pecan tree, which usually occurs during conventional orchard weed management, is unlikely to result in adverse effects on young pecan trees.

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Regalia®, a commercial extract of giant knotweed [Fallopia sachalinensis F. Schmidt (synonyms: Reynoutria sachalinensis (F. Schmidt) Nakai, Polygonum sachalinense F. Schmidt, Tiniaria sachalinesis (F. Schmidt) Janch.)], was evaluated for its potential to enhance drought tolerance of container-grown impatiens (Impatiens walleriana Hook. f. ‘Super Elfin XP White’). In two separate experiments, Regalia® was foliar-applied once a week for 4 weeks at four different rates (0, 5, 10, or 15 mL·L−1). In Expt. 1, Regalia® was applied to impatiens grown under three target substrate volumetric water contents (TVWCs): 85%, 55%, or 25%. In Expt. 2, Regalia® was applied to impatiens watered with 1, 3, or 6 days between waterings (DBW). In Expt. 1, root dry weight (RDW) of impatiens receiving applications of Regalia® at the 0.5× rate was greater compared with the 0.0× rate across all TVWCs. Additionally, soluble protein content was greater after Regalia® application at the 0.5×, 1.0×, or 1.5× rates compared with the 0.0× rate for plants grown at 55% TVWC. In Expt. 2, leaf greenness (SPAD) and leaf net photosynthetic rate (Pn) were greater with Regalia® applied at the 0.5× and 1.0× rates compared with the 0.0× rate, respectively. Soluble protein content was greater in impatiens treated with Regalia® at the 1.5× rate and 1 DBW and the 0.5× rate with 3 DBW compared with the 0.0× rate with 1 or 3 DBW. However, there was no indication that impatiens grown under different moisture levels had increased drought tolerance after application of Regalia®.

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