United States Horticultural Research Laboratory

Fort Pierce, FL, United States

United States Horticultural Research Laboratory

Fort Pierce, FL, United States
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Pascacio-Villafan C.,Institute Ecologia | Lapointe S.,United States Horticultural Research Laboratory | Williams T.,Institute Ecologia | Sivinski J.,Center for Medical | And 2 more authors.
Journal of Chemical Ecology | Year: 2014

Host plant resistance to insect attack and expansion of insect pests to novel hosts may to be modulated by phenolic compounds in host plants. Many studies have evaluated the role of phenolics in host plant resistance and the effect of phenolics on herbivore performance, but few studies have tested the joint effect of several compounds. Here, we used mixture-amount experimental design and response surface modeling to study the effects of a variety of phenolic compounds on the development and survival of Mexican fruit fly (Anastrepha ludens [Loew]), a notorious polyphagous pest of fruit crops that is likely to expand its distribution range under climate change scenarios. (+)- Catechin, phloridzin, rutin, chlorogenic acid, and p-coumaric acid were added individually or in mixtures at different concentrations to a laboratory diet used to rear individuals of A. ludens. No effect was observed with any mixture or concentration on percent pupation, pupal weight, adult emergence, or survival from neonate larvae to adults. Larval weight, larval and pupal developmental time, and the prevalence of adult deformities were affected by particular mixtures and concentrations of the compounds tested. We suggest that some combinations/concentrations of phenolic compounds could contribute to the management of A. ludens. We also highlight the importance of testing mixtures of plant secondary compounds when exploring their effects upon insect herbivore performance, and we show that mixture-amount design is a useful tool for this type of experiments. © 2014 The Author(s).


Hilf M.E.,United States Horticultural Research Laboratory | Sims K.R.,United States Horticultural Research Laboratory | Folimonova S.Y.,University of Florida | Achor D.S.,University of Florida
Phytopathology | Year: 2013

'Candidatus Liberibacter asiaticus' is the bacterium implicated as a causal agent of the economically damaging disease of citrus called huanglongbing (HLB). Vertical transmission of the organism through seed to the seedling has not been demonstrated. Previous studies using real-time polymerase chain reaction assays indicated abundant bacterial 16S rRNA sequences in seed coats of citrus seed but the presence of intact bacterial cells was not demonstrated. We used microscopy to verify that intact bacterial cells were present in citrus seed coats. Bacterial cells with the morphology and physical dimensions appropriate for 'Ca. L. asiaticus' were seen in phloem sieve elements in the vascular bundle of grapefruit seed coats using transmission electron microscopy (TEM). Fluorescence in situ hybridization (FISH) analyses utilizing probes complementary to the 'Ca. L. asiaticus' 16S rRNA gene revealed bacterial cells in the vascular tissue of intact seed coats of grapefruit and pummel and in fragmented vascular bundles excised from grapefruit seed coats. The physical measurements and the morphology of individual bacterial cells were consistent with those ascribed in the literature to 'Ca. L. asiaticus'. No bacterial cells were observed in preparations of seed from fruit from noninfected trees. A small library of clones amplified from seed coats from a noninfected tree using degenerate primers targeting prokaryote 16S rRNA gene sequences contained no 'Ca. L. asiaticus' sequences, whereas 95% of the sequences in a similar library from DNA from seed coats from an infected tree were identified as 'Ca. L. asiaticus', providing molecular genetic corroboration that the bacterial cells observed by TEM and FISH in seed coats from infected trees were 'Ca. L. asiaticus'. © 2013 The American Phytopathological Society.


Zhang M.,Guangxi University | Zhang M.,University of Florida | Guo Y.,University of Florida | Powell C.A.,University of Florida | And 4 more authors.
PLoS ONE | Year: 2014

Citrus huanglongbing (HLB), caused by three species of fastidious, phloem-limited 'Candidatus Liberibacter', is one of the most destructive diseases of citrus worldwide. To date, there is no established cure for this century-old and yet, newly emerging disease. As a potential control strategy for citrus HLB, 31 antibiotics were screened for effectiveness and phytotoxicity using the optimized graft-based screening system with 'Candidatus Liberibacter asiaticus' (Las)-infected citrus scions. Actidione and Oxytetracycline were the most phytotoxic to citrus with less than 10% of scions surviving and growing; therefore, this data was not used in additional analyses. Results of principal component (PCA) and hierarchical clustering analyses (HCA) demonstrated that 29 antibiotics were clustered into 3 groups: highly effective, partly effective, and not effective. In spite of different modes of actions, a number of antibiotics such as, Ampicillin, Carbenicillin, Penicillin, Cefalexin, Rifampicin and Sulfadimethoxine were all highly effective in eliminating or suppressing Candidatus Liberibacter asiaticus indicated by both the lowest Las infection rate and titers of the treated scions and inoculated rootstock. The noneffective group, including 11 antibiotics alone with three controls, such as Amikacin, Cinoxacin, Gentamicin, Kasugamycin, Lincomycin, Neomycin, Polymixin B and Tobramycin, did not eliminate or suppress Las in the tested concentrations, resulting in plants with increased titers of Las. The other 12 antibiotics partly eliminated or suppressed Las in the treated and graft-inoculated plants. The effective and non-phytotoxic antibiotics could be potential candidates for control of citrus HLB, either for the rescue of infected citrus germplasm or for restricted field application.


Diaz R.,University of Florida | Dickey A.M.,U.S. Department of Agriculture | Shatters R.G.,United States Horticultural Research Laboratory | Manrique V.,University of Florida | And 2 more authors.
Florida Entomologist | Year: 2015

Four populations of Calophya spp. (Hemiptera: Calophyidae) collected in Brazil were characterized using molecular and morphological methods. Examination of adults revealed the presence of 2 morphotypes, which were identified as C. latiforceps and C. terebinthifolii. However, morphological examination of 5th instar nymphs detected differences within C. latiforceps, with a population from Ubu, Espírito Santo, being distinct from the other 2 populations. Molecular characterization of the mitochondrial CO1 gene supported the presence of a new species of Calophya. .


Chris Wilson P.,University of Florida | Albano J.P.,United States Horticultural Research Laboratory
Journal of Environmental Management | Year: 2013

Nitrate losses in surface runoff water from nursery production areas can be significant. This study evaluated the potential use of microbial-based (denitrification), flow-through bioreactors for their nitrate-remediation ability. Duplicate bioreactor systems were constructed at a local foliage plant nursery. Each bioreactor system consisted of four 242L tanks with connections alternating between bottom and top. Each tank was filled with approximately 113L of Kaldness media to provide surface area for attachment of native microflora. Molasses was supplied as a carbon source for denitrification and water flow rates through the systems ranged from 5 to 18Lmin-1 during tests. Automatic water samplers were used to collect composite samples every 15min from both the inflow and the exit flow water. Results indicate consistent removal of 80-100% of the nitrate flowing into the systems. Accumulation of ammoniacal and nitrite nitrogen did not occur, indicating that the nitrate-nitrogen was removed from the water, and not simply transformed into another water-soluble species. Occasions where removal rates were less than 80% were usually traced to faulty delivery of the carbon source. Results indicate that modular microbial-based bioremediation systems may be a useful tool for helping water managers meet stringent nitrogen water quality regulations, especially at nurseries with limited space for expansion of water retention facilities. © 2013 Elsevier Ltd.


Lin Y.,University of Florida | Lin Y.,Fujian Agriculture and forestry University | He Z.,University of Florida | Rosskopf E.N.,United States Horticultural Research Laboratory | And 3 more authors.
Plant Disease | Year: 2010

A new nylon membrane bag (NMB) assay was developed for studies to determine the effect of chemicals added to soil on survival of soilborne plant pathogens. The rapid and effective assay can be used to study organisms for which there are no selective media or for which a selective medium is expensive or difficult to prepare. This assay consists of placing pathogens inside a bag made of small-pore (0.22-μm) nylon filtration membrane, which is placed in soil and later retrieved to determine survival of the pathogens on nonselective media. Chemicals but not other microorganisms can enter the bag from the soil. Using this assay, Streptomyces scabies, Fusarium oxysporum f. sp. lycopersici race 3, and Ralstonia solanacearum were successfully recovered from soil after 72 h as demonstrated by growth on a semiselective Streptomyces medium (S.scabies) or nonselective potato dextrose agar medium (F. oxysporum f. sp. lycopersici race 3 and R. solanacearum) with minimal microbial contamination. Addition of acetic acid (200 mM) to soil killed 100% of S. scabies. SPK (a mixture of organic chemicals) at a concentration of 1,500 mg kg-1 of soil killed 83.3% of F. oxysporum f. sp. lycopersici race 3 culture plugs, 100% of F. oxysporum f. sp. lycopersici race 3 spores, and 97.2% of R. solanacearum cells. SPK at 1,000 mg kg-1 of soil killed 50% of F. oxysporum f. sp. lycopersici race 3 culture plugs, 68.2% of F. oxysporum f. sp. lycopersici race 3 spores, and 12% of R. solanacearum. Benlate (500 to 1,500 mg kg-1 of soil) did not kill the culture plugs of F. oxysporum f. sp. lycopersici race 3 but reduced the growth rate of F. oxysporum f. sp. lycopersici race 3. Benlate (500, 1,000, and 1,500 mg kg-1 of soil) reduced F. oxysporum f. sp. lycopersici race 3 spore germination by 39.4, 49.3, and 50.4%, respectively. Streptomycin sulfate (1,500, 800, 400, and 200 mg kg-1 of soil) caused 75.3, 21, 11.9, and 0.9% mortality, respectively, of R. solanacearum. Copyright © 2010 The American Phytopathological Society.


Vahling-Armstrong C.M.,United States Horticultural Research Laboratory | Zhou H.,United States Horticultural Research Laboratory | Benyon L.,United States Horticultural Research Laboratory | Morgan J.K.,United States Horticultural Research Laboratory | Duan Y.,United States Horticultural Research Laboratory
PLoS ONE | Year: 2012

The Znu system, encoded for by znuABC, can be found in multiple genera of bacteria and has been shown to be responsible for the import of zinc under low zinc conditions. Although this high-affinity uptake system is known to be important for both growth and/or pathogenesis in bacteria, it has not been functionally characterized in a plant-associated bacterium. A single homologue of this system has been identified in the plant endosymbiont, Sinorhizobium meliloti, while two homologous systems were found in the destructive citrus pathogen, Candidatus Liberibacter asiaticus. To understand the role of these protein homologues, a complementation assay was devised allowing the individual genes that comprise the system to be assayed independently for their ability to reinstate a partially-inactivated Znu system. Results from the assays have demonstrated that although all of the genes from S. meliloti were able to restore activity, only one of the two Ca. Liberibacter asiaticus encoded gene clusters contained genes that were able to functionally complement the system. Additional analysis of the gene clusters reveals that distinct modes of regulation may also exist between the Ca. Liberibacter asiaticus and S. meliloti import systems despite the intracellular-plant niche common to both of these bacteria.


PubMed | United States Horticultural Research Laboratory
Type: Journal Article | Journal: PloS one | Year: 2012

The Znu system, encoded for by znuABC, can be found in multiple genera of bacteria and has been shown to be responsible for the import of zinc under low zinc conditions. Although this high-affinity uptake system is known to be important for both growth and/or pathogenesis in bacteria, it has not been functionally characterized in a plant-associated bacterium. A single homologue of this system has been identified in the plant endosymbiont, Sinorhizobium meliloti, while two homologous systems were found in the destructive citrus pathogen, Candidatus Liberibacter asiaticus. To understand the role of these protein homologues, a complementation assay was devised allowing the individual genes that comprise the system to be assayed independently for their ability to reinstate a partially-inactivated Znu system. Results from the assays have demonstrated that although all of the genes from S. meliloti were able to restore activity, only one of the two Ca. Liberibacter asiaticus encoded gene clusters contained genes that were able to functionally complement the system. Additional analysis of the gene clusters reveals that distinct modes of regulation may also exist between the Ca. Liberibacter asiaticus and S. meliloti import systems despite the intracellular-plant niche common to both of these bacteria.

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