Complete Genome Sequence Resource for the Necrotrophic Plant-Pathogenic Bacterium Dickeya dianthicola 67-19 isolated from New Guinea Impatiens

A series of experiments investigated the effects of increasing phosphate–phosphorus (P) concentrations on the growth and development of four horticultural species. In experiment 1, petunia [Petunia atkinsiana (Sweet) D. Don ex W.H. Baxter] plants were grown using eight P concentrations, and we found that the upper bound for plant growth was at 8.72–9.08 mg·L−1 P, whereas concentrations ≤2.5 mg·L−1 P caused P deficiency symptoms. Experiment 2 investigated P growth response in two cultivars each of New Guinea impatiens (Impatiens hawkeri W. Bull) and vinca [Catharanthus roseus (L.) G. Don]. Growth for these plants was maximized with 6.43–12.42 mg·L−1 P. In experiment 3, ornamental peppers (Capsicum annuum L. ‘Tango Red’) were given an initial concentration of P for 6 weeks and then switched to 0 mg·L−1 P to observe whether plants could be supplied with sufficient levels of P, and finished without P to keep them compact. Plants switched to restricted P began developing P deficiency symptoms within 3 weeks; however, restricting P successfully limited plant growth. These experiments indicated that current P fertilization regimens exceed the P requirements of these bedding plants, and depending on species, concentrations of 5–15 mg·L−1 P maximize growth.

Fluorescent amplified fragment length polymorphism (F-AFLP) and microsatellites (SSRs) were used to evaluate new guinea impatiens (Impatiens hawkeri W. Bull) cultivars. Ninety-five quality-selected polymorphic fragments from 10 F-AFLP+3 primer combinations were used to evaluate 100 cultivars representing a variety of colors, forms, and breeding programs. Jaccard similarities and unweighted pair-group method of the arithmetic average (UPGMA) clustering formed a dendrogram with three cultivar groups, to a large extent clustering the cultivars by breeder with a high cophenetic correlation coefficient. A small insert genomic library was created and 442 kb of new guinea impatiens sequence was screened for repetitive motifs, resulting in 14 microsatellite markers. A subset of 46 cultivars representing five commercial breeding companies and 11 cultivar series was selected for microsatellite analysis. Seven loci were polymorphic, with two to six alleles per locus. Although both methods were equally effective in distinguishing the cultivars from one another, the topologies of the dendrograms for the two methods were different. The topology of the AFLP dendrogram reflected possible relationships based on cultivar series and breeding company, while the SSR dendrogram did not. The objectives of this research were to develop and validate both F-AFLP and SSR methodologies for new guinea impatiens, identify markers that can be reliably used for fingerprinting, and create a database for future cultivar comparisons.

Silica (Si) is not considered to be an essential plant nutrient because without it, most plants can be grown from seed to seed without its presence. However, many investigations have shown a positive growth effect if Si is present, including increased dry weight, increased yield, enhanced pollination, and most commonly, increased disease resistance, which leads to its official designation as a beneficial nutrient. Surprisingly, some effects, such as reduced incidence of micronutrient toxicity, appear to occur even if Si is not taken up in appreciable amounts. The literature results must be interpreted with care, however, because many of the benefits can be obtained with the counterion of the Si supplied to the plant. Determining a potential benefit from Si could be a large benefit to greenhouse plant producers because more production is using soilless media that are devoid of Si. Therefore, Si must be supplied either as a foliar spray or nutrient solution amendment. We investigated adding Si to New Guinea Impatiens (Impatiens hawkeri Bull), marigold (Tagetes erecta), pansy (Viola wittrockiana), spreading petunia (Petunia hybridia), geranium (Pelargonium spp.), and orchid (Phalaenopsis spp.). Using SEM, energy dispersive X-ray analysis, and ICP analysis, Si content and location was determined. This information and other growth characteristics will be used as a first step in determining the likelihood of using Si as a beneficial element in greenhouse fertilizer solutions for higher quality bedding plants with fewer agrochemical inputs.

Abstract Conditioning treatments were evaluated for effects on growth of bedding plants during greenhouse production and carryover effects on plant performance in the landscape. Treatments included two fertilization regimes using a complete water soluble fertilizer applied three times/week at 500 ppm N, designated ‘high N’, or at 50 ppm N, designated the ‘low N’ treatment. Other treatments included: ebb and flow irrigation, drought stress for up to 2 h wilt/day, 5000 ppm B-Nine (daminozide), 45 ppm Bonzi (paclobutrazol; 180 ppm on columbine), and brushing (40 strokes twice daily). Unless otherwise noted all plants, including controls, were maintained well-irrigated and fertilized with 250 ppm N three times/week. Marigolds and New Guinea impatiens grown under low N during greenhouse production exhibited reduced plant height and width relative to control plants at 4 weeks after planting (WAP) in the landscape. Plant quality ratings of all species conditioned with low N were lower than those of controls 2 and 4 WAP. Plant height of New Guinea impatiens conditioned with high N was greater than that of controls 4 WAP in the landscape. Marigolds subjected to drought in the greenhouse were still shorter than controls 2 and 4 WAP. Persistent height reductions in the landscape in response to B-Nine were observed in ageratum 2 and 4 WAP and to Bonzi in New Guinea impatiens through 8 WAP. Brushing reduced the height of all species except ageratum in the greenhouse, but had no carryover effect on plant growth in the landscape. At 4 weeks after treatment, plant height of columbine treated with low or high N, drought, brushing, or B-Nine was reduced relative to controls, but all plants were similar in size in the landscape.

Six commercial cultivars (Anna, Aurore, Danhill, Danlight, Melanie, and Thelca), one drought tolerant cultivar (Orangeade), nine breeding selections, and one check genotype of Impatiens hawkeri Bull were evaluated for differences in drought tolerance based on water loss and time to wilt. The six commercially available cultivars had significantly higher mean water loss than the breeding selections and `Orangeade'. These cultivars wilted in 5.11 vs. 7.33 days for `Orangeade' and 9.10 days for the breeding selections. These results suggest that sufficient variability exists in New Guinea impatiens germplasm for the reduction of water loss to improve drought tolerance. Regression analysis revealed that total transpirational water loss 96 hours after withholding water was an excellent predictor of the time to wilting (a simple measure of drought tolerance) after water was withheld (R2 = 0.95). Thus, a simple, efficient and objective method for selection of drought tolerant genotypes has been developed for New Guinea impatiens. A comparison of offspring to parental genotypes showed that after only one cycle of selection, water loss was significantly reduced by >30%. These results suggest that there is sufficient genetic variability present for the development of more drought tolerant cultivars.

Eighteen New Guinea impatiens cultivars were evaluated for performance as bedding plants and for suitability as hanging basket plants. The cultivars were treated with three growth retarding chemicals (B-9, Sumagic and Cutless) to determine their effect on plant growth, branching and overall flower development. Two applications of 2500 ppm B-9 produced the most commercially acceptable plants. Height and spread were reduced by approximately 30 percent with no reduction in the number of flowers produced or the number of days to bloom. Cutless and Sumagic applications reduced growth approximately 50 percent and delayed blooming as much as 2 weeks when compared to the untreated control. Growth regulator treatment had no effect on the number of branches produced except with Sumagic which resulted in an overall reduction in branching.

New Guinea impatiens (Impatiens hawkeri Bull.) were grown in a recirculating ebb-and-flow subirrigation system under increasing levels of salinity stress from a mixture of NaCl and CaCl2 (1:1 equivalent ratio, 2:1 molar ratio) and recommended production levels of other nutrients. Growth and quality decreased as salinity level increased, with a 75% to 80% growth reduction at 18 mol·m-3 NaCl-CaCl2 compared to controls. Among controls, root mass distribution was 10%, 50%, and 40% in the top, middle, and bottom layers of the root zone, respectively. In the highest salinity treatment (18 mol·m-3 NaCl-CaCl2), most of the root mass was in the middle layer (80%), while the root mass in the top and bottom layers was reduced to 5% and 15%, respectively. The electrical conductivity (EC) of the growing medium was high in the top layer in all treatments, but only exceeded maximum recommended levels in the middle and bottom layers in the 4·mol·m-3 or higher treatments. Initial postproduction leaching caused the salts in the top layer to migrate to the middle and bottom layers, which in some experiments induced a rapid and transient wilting. Up to six leaching and drying cycles of a 0.20 leaching fraction were required to reduce EC in all layers to recommended levels. Overall, salable plants of good quality and size were produced with up to 2 mol·m-3 (total 152 mg·L-1) NaCl-CaCl2 in the recirculated nutrient solution.

New Guinea impatiens `Illusion' were grown in a recirculating subirrigation system using a controlled-release complete fertilizer (Osmocote 14–14–14). In a preliminary experiment, plants were grown under varying label rates (0, 0.5x, 1x, 2x, 4x) incorporated throughout the growing medium. Excellent growth and high-quality plants were produced at the 0.5x and 1x rates. Higher rates caused reduced growth and quality. The next study was a factorial experiment of rate (0.25x, 0.5x, 0.75x, and 1x) times placement (incorporated, top dress, bottom placement, and dibble). Slight growth increases and dramatic leaf area increases were observed with increasing fertilizer rate, regardless of placement. Slightly higher fresh and dry weights were observed in the incorporated treatment compared to the top dress treatment. Both the incorporated and top dress treatments yielded better growth than bottom placement or dibble treatments. Other parameters measured (height, chlorophyll content) did not appear to be affected by placement. EC (dS/m) of the growing medium was highest in the top 1/3 of the container in all placement treatments. EC increased with increasing rate. EC was higher in the incorporated than in the top-dress treatment, which may be due to different release rates or may be an artifact of extraction (prill removal). No rates or placements showed damaging EC levels.

New Guinea impatiens (Impatiens hawkeri) are popular bedding plants, but the knowledge of diagnosing abiotic disorders during greenhouse production is evolving. Symptomology of nutrient deficiencies and excessive fertilization have been extensively documented. Exact symptomology of low substrate pH (<5.5) and toxic iron (Fe) and/or manganese (Mn) leaf tissue levels are not defined or photographed, thereby aiding in diagnosis. Therefore, the objective of the diagnostic guide was to photograph symptomology and document the tissue levels in New Guinea impatiens to provide a definitive guide of low substrate pH–induced Fe and/or Mn toxicity.