Bacterial spot and blight diseases of ornamental plants caused by different Xanthomonas species in Turkey

Putative strains belonging to Xanthomonas spp. causing leaf spot and blight diseases on geranium (Pelargonium peltatum and P. hortorum), begonia (Begonia × tuberhybrida), anthurium (Anthurium andraeanum), Chinese hibiscus (Hibiscus rosa-sinensis), and English ivy (Hedera helix) growing in Turkey were isolated. All bacterial strains were classified as Gram-negative, oxidase negative, catalase, levan and starch hydrolysis positive, with hypersensitive reaction positive on tobacco and pathogenic to host plants. Identification of these strains was further confirmed by serological method using ELISA kits, conventional PCR, carbon utilisation, and FAME. Results of the identification showed that 28, 24, 10, 2, and 1 strains were identified as X. axonopodis pv. begoniae, X. hortorum pv. pelargonii, X. axonopodis pv. dieffenbachiae, X. hortorum pv. hederae, and Xanthomonas sp., respectively. This is the first report of X. hortorum pv. hederae on English ivy in Turkey.

First Report of Choanephora Blight Caused by Choanephora infundibulifera on Hibiscus rosa-sinensis in Korea

Hibiscus rosa-sinensis L., commonly known as Chinese hibiscus, is an evergreen flowering shrub belonging to the Malvaceae and is widely cultivated throughout Asia including Korea. In August 2013, blight was observed on Chinese hibiscus in a commercial flower nursery in Seoul, Korea. Initial symptoms began as reddish purple spots at the tip of flowers and expanded to encompass entire flowers. Infected lesions appeared water-soaked, reddish brown, and were followed by rapid rotting of infected tissues. Approximately 50% of the plants surveyed were affected. Monosporous sporangiola formed on infected tissue were transferred to potato dextrose agar (PDA). Fungal colonies were obtained that were at first white with abundant aerial mycelium, and then became yellowish with the appearance of sporangiola. Sporangiophores bearing sporangiola were erect to slightly curved, unbranched, and hyaline. Funnel-shaped secondary vesicles formed on the primary vesicles. Sporangiola were indehiscent, ovoid to subglobose, smooth, non-striated, brown to dark brown, 10 to 27.5 × 8.5 to 17 μm, and sometimes germinated in culture. The fungus was identified as Choanephora infundibulifera (Curr.) D.D. Cunn. based on the morphological and cultural characteristics (2). Voucher specimens were housed in the Korea University Herbarium (KUS). An isolate obtained from KUS-F27535 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC47643) and used for a pathogenicity test and molecular analyses. To confirm identity of the fungus, genomic DNA was extracted with DNeasy Plant Mini Kits (Qiagen Inc., Valencia, CA). The internal transcribed spacer (ITS) region of rDNA and the D1/D2 region of the large subunit (LSU) were amplified with the primers ITS1/ITS4 and NL1/LR3, respectively (3), and sequenced. The resulting 635-bp ITS and 680-bp D1/D2 sequences were deposited in GenBank (Accession Nos. KF486539 and KF486538). A GenBank BLAST search revealed that the ITS sequences showed 100% similarity with that of C. infundibulifera (JN943009) and D1/D2 sequences also showed 100% identity with that of C. infundibulifera (JN939193). A sporangiola suspension (2 × 104 cells/ml) was sprayed over three pots of the shrub, kept in a humid chamber for 2 days, and placed in greenhouse (28°C and 80 to 100% RH). Another three potted plants of the same age were sprayed with sterile water and served as controls. After 4 days, typical blossom blight symptoms, identical to the ones observed in the nursery, developed on the inoculated flowers. No symptoms were observed on controls. C. infundibulifera was re-isolated from inoculated plants. Pathogenicity test was conducted twice with the same results, fulfilling Koch's postulates. Choanephora blight caused by C. infundibulifera on H. rosa-sinenesis has been reported in Japan, Myanmar, Nepal, Guinea, and the United States (1). In Korea, there was one record of this fungus on H. syriacus (1). To our knowledge, this is the first report of C. infundibulifera on H. rosa-sinensis in Korea. This pathogen could be a potential threat to the production of this ornamental shrub over a prolonged period of hot and humid weather. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved February 28, 2014. (2) P. M. Kirk. Mycol. Pap. 152:1, 1984. (3) G. Walther et al. Persoonia 30:11, 2013.

Effects of Fertilization on the Growth and Quality of Container-grown Areca Palm and Chinese Hibiscus during Establishment in the Landscape

The roots of container-grown ornamental plants primarily are concentrated within the original container substrate root ball during the establishment period following transplanting into the landscape. Plants growing in container substrates containing pine bark or peatmoss have higher nitrogen (N) requirements than in most landscape soils due to microbial immobilization of N by these organic components. However, use of high-N fertilizers, such as those used in container production of ornamentals, can cause imbalances with potassium (K) and magnesium (Mg) when used on palms in sandy landscape soils. Areca palm (Dypsis lutescens) and chinese hibiscus (Hibiscus rosa-sinensis ‘President’) that had been growing in containers were transplanted into a landscape soil to determine if high N fertilization during the establishment period could accelerate the rate of establishment without exacerbating K and Mg deficiencies. Although plants of both species had the darkest green color and largest size when continuously fertilized with high N fertilizer, this treatment did induce Mg deficiency in both species. Plant size and color for both species were highly correlated with cumulative N application rates, but also with initial N application rates, suggesting that high N fertilization during the first 6 months affected plant quality at 12 and 24 months after planting, even if high N fertilization was discontinued. However, continued use of a moderate N landscape palm maintenance fertilizer ultimately produced areca palm plants as good as those receiving high N during the establishment period.

Effectiveness of Pasteurized Poultry Litter as a Partial Substitute for Controlled-release Fertilizers in the Production of Container-grown Ornamental Plants

In two experiments, pasteurized poultry litter (PPL) was evaluated as a potential substitute for controlled-release fertilizers in the production of container-grown downy jasmine (Jasminum multiflorum), chinese hibiscus (Hibiscus rosa-sinensis), and areca palm (Dypsis lutescens). Downy jasmine and chinese hibiscus generally grew better when provided with PPL as a micronutrient source than with no micronutrients or with an inorganic micronutrient blend (MN). However, areca palm grew poorly with PPL as a fertilizer supplement compared with MN-fertilized areca palm. PPL provided high levels of ammonium nitrogen, phosphorus, and potassium during the first few weeks, but soil solution levels of these elements dropped off rapidly in subsequent weeks. The large amount of phosphorus leached from the containers fertilized with PPL is an environmental concern.

Effects of Phosphorous and Phosphoric Acids on Growth and Phosphorus Concentrations in Container-grown Tropical Ornamental Plants

Chinese hibiscus (Hibiscus rosa-chinensis), shooting star (Pseuderanthemum laxiflorum), downy jasmine (Jasminum multiflorum), areca palm (Dypsis lutescens), and `Jetty' spathiphyllum (Spathiphyllum) were grown in containers using Osmocote Plus 15-9-12 (15N-3.9P-10K), which provided phosphorus (two experiments), or resin-coated urea plus sulfur-coated potassium sulfate, which provided no phosphorus (one experiment). Plants were treated with water drenches (controls), drenches with metalaxyl fungicide only, drenches with phosphoric acid (PO4-P), drenches with metalaxyl plus phosphorus from phosphoric acid, drenches with PhytoFos 4-28-10 [4N-12.2P-8.3K, a fertilizer containing phosphorous acid (PO3-P), a known fungicidal compound], or a foliar spray with PhytoFos 4-28-10. Plants receiving soil drenches with equivalent amounts of P from PhytoFos 4-28-10, PO4-P, or PO4-P+metalaxyl generally had the greatest shoot and root dry weights and foliar PO4-P concentrations. There were no differences between the control and metalaxyl-treated plants, indicating that root rot diseases were not a factor. Therefore, responses from PhytoFos 4-28-10 were believed to be due to its nutrient content, rather than its fungicidal properties. Foliar-applied PhytoFos 4-29-10 produced plants that were generally similar in size to control plants or those receiving metalaxyl only drenches. Fertilizers containing PO3-P appear to be about as effective as PO4-P sources when applied to the soil, but are relatively ineffective as a P source when applied as a foliar spray. A distinct positive synergistic response for shoot and root dry weights and foliar PO4-P concentrations was observed for the PO4-P+metalaxyl treatment when no P was applied except as a treatment.

Influence of Fertilizer Placement on Plant Quality, Root Distribution, and Weed Growth in Container-grown Tropical Ornamental Plants

In two experiments, chinese hibiscus (Hibiscus rosa-sinensis), bamboo palm (Chamaedorea seifrizii), areca palm (Dypsis lutescens), fishtail palm (Caryota mitis), macarthur palm (Ptychosperma macarthurii), shooting star (Pseuderanthemum laxiflorum), downy jasmine (Jasminum multiflorum), plumbago (Plumbago auriculata), alexandra palm (Archontophoenix alexandrae), and foxtail palm (Wodyetia bifurcata) were transplanted into 6.2-L (2-gal) containers. They were fertilized with Osmocote Plus 15N-3.9P-10K (12-to14-month formulation) (Expt. 1) or Nutricote Total 18N-2.6P-6.7K (type 360) (Expt. 2) applied by either top dressing, substrate incorporation, or layering the fertilizer just below the transplanted root ball. Shoot dry weight, plant color, root dry weights in the upper and lower halves of the root ball, and weed shoot dry weight were determined when each species reached marketable size. Optimal fertilizer placement method varied among the species tested. With the exception of areca palm, none of the species tested grew best with incorporated fertilizer. Root dry weights in the lower half of the root ball for chinese hibiscus, bamboo palm, and downy jasmine were greatest when the fertilizer was layered and root dry weights in the upper half of the root ball were greatest for top-dressed chinese hibiscus. Weed growth was lower in pots receiving layered fertilizer for four of the six palm species tested.