Diversity and plant growth-promoting potential of (un)culturable bacteria in the Hedera helix phylloplane.

BACKGROUND: A diverse community of microbes naturally exists on the phylloplane, the surface of leaves. It is one of the most prevalent microbial habitats on earth and bacteria are the most abundant members, living in communities that are highly dynamic. Today, one of the key challenges for microbiologists is to develop strategies to culture the vast diversity of microorganisms that have been detected in metagenomic surveys. RESULTS: We isolated bacteria from the phylloplane of Hedera helix (common ivy), a widespread evergreen, using five growth media: Luria-Bertani (LB), LB01, yeast extract-mannitol (YMA), yeast extract-flour (YFlour), and YEx. We also included a comparison with the uncultured phylloplane, which we showed to be dominated by Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes. Inter-sample (beta) diversity shifted from LB and LB01 containing the highest amount of resources to YEx, YMA, and YFlour which are more selective. All growth media equally favoured Actinobacteria and Gammaproteobacteria, whereas Bacteroidetes could only be found on LB01, YEx, and YMA. LB and LB01 favoured Firmicutes and YFlour was most selective for Betaproteobacteria. At the genus level, LB favoured the growth of Bacillus and Stenotrophomonas, while YFlour was most selective for Burkholderia and Curtobacterium. The in vitro plant growth promotion (PGP) profile of 200 isolates obtained in this study indicates that previously uncultured bacteria from the phylloplane may have potential applications in phytoremediation and other plant-based biotechnologies. CONCLUSIONS: This study gives first insights into the total bacterial community of the H. helix phylloplane, including an evaluation of its culturability using five different growth media. We further provide a collection of 200 bacterial isolates underrepresented in current databases, including the characterization of PGP profiles. Here we highlight the potential of simple strategies to obtain higher microbial diversity from environmental samples and the use of high-throughput sequencing to guide isolate selection from a variety of growth media.

Isolation of a phytotoxic isocoumarin from Diaporthe eres-infected Hedera helix (English ivy) and synthesis of its phytotoxic analogs.

BACKGROUND: The fungus Diaporthe eres was isolated from a fungal pathogen-infected leaf of Hedera helix (English ivy) exhibiting necrosis. It is hypothesized that the causative fungus produces phytotoxins as evidenced by necrotic lesions on the leaves. RESULTS: The fungus was isolated and grown in Czapek Dox broth culture medium and potato dextrose broth culture medium and identified as Diaporthe eres. The ethyl acetate extracts of the culture broths were phytotoxic to lettuce (Lactuca sativa) and bentgrass (Agrostis stolonifera). 3,4-Dihydro-8-hydroxy-3,5-dimethylisocoumarin (1) and tyrosol (2) were isolated and identified as the phytotoxic constituents. Six analogs of 3,4-dihydro-isocoumarin were synthesized and shown to be phytotoxic. The synthesized 3,4-dihydro-8-hydroxy-3,7-dimethylisocoumarin and 3,4-dihydro-8-hydroxy-3,3,7-trimethylisocoumarin were two- to three-fold more phytotoxic than the naturally occurring 1 in a Lemna paucicostata growth bioassay. CONCLUSION: Synthesis and herbicidal activities of the several new analogs of 1 are reported for the first time. These promising molecules should be used as templates for synthesis and testing of more analogs. © 2017 Society of Chemical Industry.

Comparison of the performance between a spray gun and a spray boom in ornamentals.

Flemish greenhouse growers predominantly use handheld spray guns and spray lances for their crop protection purposes although these techniques are known for their heavy workload and their high operator exposure risks. Moreover, when these techniques are compared with spray boom equipment, they are often found to be less effective. On the other hand, handheld spraying techniques are less expensive and more flexible to use. Additionally, many Flemish growers are convinced that a high spray volume and spray pressure is needed to assure a good plant protection. The aim of this work was to evaluate and compare the spray deposition, penetration and uniformity between a manually pulled horizontal spray boom and a spray gun under controlled laboratory conditions. In total, six different spray application techniques were evaluated. In general, the total deposition results were comparable between the spray boom and the spray gun applications but the boom applications resulted in a more uniform spray distribution over the crop. On a plant level, the spray distribution was not uniform for the different techniques with highest deposits on the upper side of the top leaves. Using spray guns at a higher spray pressure did not improve spray penetration and deposition on the bottom side of the leaves. From the different nozzle types, the XR 80 03 gave the best results. Plant density clearly affected crop penetration and deposition on the bottom side of the leaves.

Host-related variability in arbuscular mycorrhizal fungal structures in roots of Hedera rhombea, Rubus parvifolius, and Rosa multiflora under controlled conditions.

The arbuscular mycorrhizal (AM) morphology of three host plant species inoculated with single and mixed fungal culture and the distribution of AM fungal species in roots of the hosts treated with a mixed culture of AM fungi were determined. The aim was to investigate the effect of host plants and AM fungi on AM morphology of coexisting plant species. Noncolonized rooted cuttings of Hedera rhombea (Miq) Bean, Rubus parvifolius L., and Rosa multiflora Thunb. were inoculated with five fungal species as single and mixed culture inocula. The fungal species used were Gigaspora rosea and Scutellospora erythropa, previously isolated from H. rhombea; Acaulospora longula and Glomus etunicatum from R. parvifolius; and Glomus claroideum from both plant species. A few hyphal and arbusculate coils were seen in the mixed culture-inoculated roots of R. parvifolius; all fungal treatments produced this Paris-type AM in H. rhombea and Arum-type AM in R. parvifolius, and R. multiflora indicates that AM morphology is strongly controlled by the identity of the host plants used in this study. AM fungal rDNA was extracted separately from roots of each replicate plant species inoculated with the mixed fungal culture, amplified, cloned, sequenced, and analyzed to determine the AM fungal species and their respective proportions in roots of each plant species. Glomus etunicatum and G. claroideum of the family Glomaceae generally occurred more frequently in R. parvifolius and R. multiflora, which form Arum-types, whereas S. erythropa, of the family Gigasporaceae, was the most frequently detected species in H. rhombea, which produced Paris-type AM. Although the genotype of the plant species used appears to determine the AM morphologies formed, there was preferential association between the hosts and AM fungal inoculants.

Cooccurring plants forming distinct arbuscular mycorrhizal morphologies harbor similar AM fungal species.

Arbuscular mycorrhizal (AM) fungal spores were isolated from field transplants and rhizosphere soil of Hedera rhombea (Miq) Bean and Rubus parvifolius L., which form Paris-type and Arum-type AM, respectively. DNA from the spore isolates was used to generate molecular markers based on partial large subunit (LSU) ribosomal RNA (rDNA) sequences to determine AM fungi colonizing field-collected roots of the two plant species. Species that were isolated as spores and identified morphologically and molecularly were Gigaspora rosea and Scutellospora erythropa from H. rhombea, Acaulospora longula and Glomus etunicatum from R. parvifolius, and Glomus claroideum from both plants. The composition of the AM fungal communities with respect to plant trap cultures was highly divergent between plant species. Analysis of partial LSU rDNA sequences amplified from field-collected roots of the two plant species with PCR primers designed for the AM fungi indicated that both plants were colonized by G. claroideum, G. etunicatum, A. longula, and S. erythropa. G. rosea was not detected in the field-collected roots of either plant species. Four other AM fungal genotypes, which were not isolated as spores in trap cultures from the two plant species, were also found in the roots of both plant species; two were closely related to Glomus intraradices and Glomus clarum. One genotype, which was most closely related to Glomus microaggregatum, was confined to R. parvifolius, whereas an uncultured Glomeromycotan fungus occurred only in roots of H. rhombea. S. erythropa was the most dominant fungus found in the roots of H. rhombea. The detection of the same AM fungal species in field-collected roots of H. rhombea and R. parvifolius, which form Paris- and Arum-type AM, respectively, shows that AM morphology in these plants is strongly influenced by the host plant genotypes as appears to be the case in many plant species in natural ecosystems, although there are preferential associations between the hosts and colonizing AM fungi in this study.

Phytophthora tropicalis on Hedera helix and Epipremnum aureum in Polish greenhouses.

Phytophthora tropicalis was isolated from Hedera helix and Epipremnum aureum showing discoloration of leaves, necrosis of shoot base, spread upwards and on roots. The species was detected from 7/8 plants of Hedera and 3/4 of Epipremnum. Additionally Botrytis cinerea, Fusarium avenaceum and Rhizoctonia solani were recovered from some of diseased plants. P. tropicalis caused leaf necrosis of 13 plant species and tomato seedlings. The quickest spread of necrosis was observed on leaves of Peperomia magnoliaefolia, Pelargonium zonale and Phalaenopsis x hybridum. The disease developed at temperature ranged from 10 degrees to 32.5 degrees C with optimum 30 degrees C.