Evaluation of a Push-Pull System for the Management of Frankliniella Species (Thysanoptera: Thripidae) in Tomato.

A push-pull strategy for reducing populations of the thrips Frankliniella occidentalis (Pergande), F. bispinosa (Morgan) and F. tritici (Fitch) in tomato was evaluated. Push components consisted of ultraviolet (UV)-reflective mulch and foliar applications of kaolin and the pull component consisted of the companion plant Bidens alba (L.). Replicated field experiments were conducted in 2011 and 2012. Adult and larval thrips were reduced by UV-reflective mulch during early and mid-flowering of tomato. Spray applications of kaolin were effective in reducing adult and larval thrips during early, mid- and late-flowering. The pull effects of the B. alba companion plants were additive and sometimes interactive with the push effects of UV-reflective mulch and kaolin in reducing the adult males of each thrips species and the females of F. bispinosa. The strategy was not effective in reducing the adult females of F. tritici and F. occidentalis. In addition to attracting the Frankliniella species adults, the companion plants were hosts for the thrips predator Orius insidiosus (Say). The companion plants combined with UV-reflective mulch and kaolin proved effective as a push-pull system for suppressing flower thrips, including F. occidentalis which is a serious pest of tomato worldwide.

Biotic resistance limits the invasiveness of the western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), in Florida.

The spread of the western flower thrips, Frankliniella occidentalis (Pergande), has resulted in the world-wide destabilization of established integrated pest management programs for many crops. It is hypothesized that frequent exposure to insecticides in intensive agriculture selected for resistant populations, which allowed invasive populations in the eastern USA to overcome biotic resistance from the native community of species. Research conducted in Florida to understand the role of biotic factors in limiting the abundance of the western flower thrips is reviewed. Orius spp. (Hemiptera: Anthocoridae) are effective predators that suppress populations of thrips on crop and non-crop hosts in southern and northern Florida. Orius are more effective predators of the western flower thrips than the native flower thrips, F. tritici (Fitch) and F. bispinosa (Morgan). The native species are competitors of the western flower thrips. Excessive fertilization and the use of broad-spectrum insecticides in crop fields further enhances populations of the western flower thrips. Interactions with native species clearly limit the abundance of western flower thrips in Florida, but populations are abundant in fertilized crop fields where application of insecticides excludes predators and competitor species.

Population Dynamics of Frankliniella bispinosa (Thysanoptera: Thripidae) and the Predator Orius insidiosus (Hemiptera: Anthocoridae) as Influenced by Flower Color of Lagerstroemia (Lythraceae).

Crapemyrtle is a common landscape planting that is a resource subsidy for beneficial insects. Field studies were conducted to determine the influence of crapemyrtle flower color on the population abundances and predator-prey dynamics of the herbivorous Frankliniella species and the predator Orius insidiosus. Adults and immatures of predator and prey were highly anthophilous, preferring white 'Acoma' flowers compared with lavender 'Apalachee', red 'Carolina Beauty', and pink 'Choctaw'. The predator was aggregated with its prey in a density-dependent manner: the adults by preferring the crapemyrtle clones also preferred by the thrips and the nymphs by direct tracking or as a function of increased prey and fecundity. Acoma was best for preference and buildup of O. insidiosus populations, and it was the only clone where there was no buildup in thrips populations. Two species of Karnyothrips (Thysanoptera: Phlaoethripidae), predators of small insects, were common in Tillandsia usneoides, an epiphyte on the crapemyrtle. Crapemyrtle is a bridge to enhance populations of O. insidiosus during summer months when there are few other hosts in the southern USA.

Comparison of arsenic accumulation in 18 fern species and four Pteris vittata accessions.

This study evaluated the ability and mechanisms of 19 Pteris and non-Pteris species to accumulate arsenic (As) in a hydroponic system spiked with 300 microM As. The study included four Pteris vittata accessions (China, India, Poland, and the United Kingdom), P. biaurita and 17 non-Pteris species. Among the accessions, P. vittata from China and UK were the most and the least efficient in terms of As accumulation. The non-Pteris species Chielanthes sinuta, Adiantum raddianum, Polystichum acrostichoides, Actiniopteris radiata, Pellaea rotundifolia, and Nephrolepis cordifolia concentrated As as effectively as the least efficient P. vittata ascension. As (III) in the fronds of P. vittata accessions ranged from 59% to 89% and for non-Pteris species it ranged from 47% to 65%. Maximum As accumulation coincided with highest percentage of As (III) in the fronds. The phosphorus (P) uptake of P. vittata accessions was 12-15 and 6-12 times greater than the As-uptake in the roots and fronds, respectively. In contrast, the P-uptake of non-Pteris species ranged from 9 to 151 and from 4 to 162 times the As-uptake, in the roots and fronds, respectively. Arsenic accumulation occurs at the expense of root and frond P-uptake. Root P-reduction is lower than frond and the P:As in the plant acquisition part (roots) is 1-3 times greater than that in accumulation part (fronds). A. radiata, C. sinuta, and P. acrostichoides were identified as potential As accumulators.

Effect of fertilizer amendments on phytoremediation of Cd-contaminated soil by a newly discovered hyperaccumulator Solanum nigrum L.

Phytoremediation is a cost-effective, simple and sustainable beneficiary technique to purify the polluted environment. Solanum nigrum L., a newly found cadmium (Cd) hyperaccumulator, has shown the potential to remediate Cd-contaminated soils. Present study investigated the effects of fertilizer amendments on the Cd uptake by S. nigrum. Chicken manure and urea are usual agricultural fertilizers and more environmental friendly. The results showed that Cd concentrations in shoots of S. nigrum were significantly decreased (p<0.05) by 28.2-34.6%, as compared to that of without the addition of chicken manure, but not the case for urea treatment. However, Cd extraction capacities (microg pot(-1)) in shoot biomass of S. nigrum were significantly increased (p<0.05) due to increased shoot biomass. In addition, available Cd concentration in soil significantly decreased due to addition of chicken manure. Thus, urea might be a better fertilizer for strengthening phytoextraction rate of S. nigrum to Cd, and chicken manure may be a better fertilizer for phytostabilization.

Seed germination of a newly discovered hyperaccumulator Solanum nigrum L. affected by illumination and seed-soaking reagent.

Solanum nigrum is a newly found Cd-hyperaccumulator which showed very high remediation efficiency in polluted soil. Seed germination experiments with different illumination and seed-soaking reagents were conducted in constant temperature box and greenhouse with soil as burgeon base. The results showed that the germination rate with alternating light/dark photoperiod was about twice of that without lighting (p < 0.05), suggesting that illumination is one of the important conditions for seed germination of S. nigrum. All treatments with seed-soaking reagents significantly increased the seed germination rate of S. nigrum (p < 0.05). Treatment with H2O2 (0.1%) had the shortest germination time. The germination rate of seeds that were not washed in water following soaking was 2-3 times higher than that of seeds that were washed after soaking.

Bidens tripartite L.: a Cd-accumulator confirmed by pot culture and site sampling experiment.

Characteristics of accumulation and tolerance of cadmium (Cd) in Bidens tripartite L. were investigated to identify Cd-accumulating properties. In this study, pot culture experiment and site sampling experiments were conducted to assess whether this plant is a heavy metal hyperaccumulator or accumulator. The results indicated that the Cd enrichment factor (concentration in plant/soil) and Cd translocation factor (concentration in shoot/root) of B. tripartite was principally >1 in pot culture and concentration gradient experiments. Shoot biomass was not reduced significantly (p<0.05) compared to the controls. However, the Cd concentration in B. tripartite shoots was not higher than 100 mg kg(-1), the threshold concentration for a Cd-hyperaccumulator. In the site sampling experiment, B. tripartite also showed Cd-accumulator properties. Based on these results, B. tripartite could be identified as a Cd-accumulator. Thus, B. tripartite should only be considered as a Cd-accumulator.

Kalimeris integrifolia Turcz. ex DC.: an accumulator of Cd.

Phytoremediation is a traditional technique that uses vegetation to remediate contaminants from water, soil and sediments. This is a solar-driven, aesthetically pleasing, and cost effective technology. In a former published article, Kalimeris integrifolia Turcz. ex DC. indicated some basic properties of hyperaccumulators for cadmium (Cd). In this study, concentration gradient experiment and sample-analyzing experiments were used to assess whether this plant is a Cd-hyperaccumulator. The results showed the Cd enrichment factor (concentration in plant/soil) and Cd translocation factor (concentration in shoot/root) of K. integrifolia was basically >1 in concentration gradient experiment. Shoot biomass was not reduced significantly (p<0.05) compared to the control. However, the Cd concentration in K. integrifolia shoots was not higher than 100 mg kg(-1), the threshold concentration for a Cd-hyperaccumulator. Thus, K. integrifolia should only be considered as a Cd-accumulator. In the sample-analyzing experiments conducted in a Pb-Zn mine area and a wastewater irrigation region, K. integrifolia also showed Cd-accumulator properties. Based on these results, K. integrifolia could be identified as a Cd-accumulator.

Effects of selenium on arsenic uptake in arsenic hyperaccumulator Pteris vittata L.

Selenium (Se) is a non-metallic element, which has the capability to increase the antioxidative capacity and stress tolerance of plants to heavy metals. Plants vary considerably in their physiological response to Se. The reported research investigated the effects of Se on arsenic (As) uptake by As hyperaccumulator Pteris vittata L. and determined possible mechanisms of interaction. Pteris vittata plants were exposed hydroponically to 0, 150 or 300 microM of Na(2)HAsO(4) in the presence of 0, 5 or 10 microM of Na(2)SeO(4) for 5 or 10d. Application of 5 microM Se enhanced As concentration by P. vittata fronds by 7-45%. At 5 microM, Se acted as an antioxidant, inhibiting lipid peroxidation (reduced by 26-42% in the fronds) via increased levels of thiols and glutathione (increased by 24% in the fronds). The results suggest that Se is either an antioxidant or it activates plant protective mechanisms, thereby alleviating oxidative stress and improving arsenic uptake in P. vittata.

Arsenic hyperaccumulation in the Chinese brake fern (Pteris vittata) deters grasshopper (Schistocerca americana) herbivory.

Brake fern, Pteris vittata, not only tolerates arsenic but also hyperaccumulates it in the frond. The hypothesis that arsenic hyperaccumulation in this fern could function as a defense against insect herbivory was tested. Fronds from control and arsenic-treated ferns were presented to nymphs of the grasshopper Schistocerca americana. Feeding damage was recorded by visual observation and quantification of the fresh weight of frond left uneaten and number of fecal pellets produced over a 2-d period. Grasshopper weight was determined before and after 5 d of feeding. Grasshoppers consumed significantly greater amounts of the frond tissue, produced more fecal pellets and had increased body weight on control plants compared with grasshoppers fed arsenic-treated ferns. Very little or none of the arsenic-treated ferns were consumed indicating feeding deterrence. In a feeding deterrent experiment with lettuce, sodium arsenite at 1.0 mm deterred grasshoppers from feeding whereas 0.1 mm did not. In a choice experiment, grasshoppers preferred to feed on lettuce dipped in water compared with lettuce dipped in 1.0 mm sodium arsenite. Our results show that arsenic hyperaccumulation in brake fern is an elemental defense against grasshopper herbivory.

Arsenic resistance in Pteris vittata L.: identification of a cytosolic triosephosphate isomerase based on cDNA expression cloning in Escherichia coli.

Arsenic hyperaccumulator Pteris vittata L. (Chinese brake fern) grows well in arsenic-contaminated media, with an extraordinary ability to tolerate high levels of arsenic. An expression cloning strategy was employed to identify cDNAs for the genes involved in arsenic resistance in P. vittata. Excised plasmids from the cDNA library of P. vittata fronds were introduced into Escherichia coli XL-1 Blue and plated on medium containing 4 mM of arsenate, a common form of arsenic in the environment. The deduced amino acid sequence of an arsenate-resistant clone, PV4-8, had cDNA highly homologous to plant cytosolic triosephosphate isomerases (cTPI). Cell-free extracts of PV4-8 had 3-fold higher level of triosephosphate isomerase (TPI) specific activities than that found in E. coli XL-1 Blue and had a 42 kD fusion protein immunoreactive to polyclonal antibodies raised against recombinant Solanum chacoense cTPI. The PV4-8 cDNA complemented a TPI-deficient E. coli mutant. PV4-8 expression improved arsenate resistance in E. coli WC3110, a strain deficient in arsenate reductase but not in AW3110 deficient for the whole ars operon. This is consistent with the hypothesis that PV4-8 TPI increased arsenate resistance in E. coli by directly or indirectly functioning as an arsenate reductase. When E. coli tpi gene was expressed in the same vector, bacterial arsenate resistance was not altered, indicating that arsenate tolerance was specific to P. vittata TPI. Paradoxically, P. vittata TPI activity was not more resistant to inhibition by arsenate in vitro than its bacterial counterpart suggesting that arsenate resistance of conventional TPI reaction was not the basis for the cellular arsenate resistance. P. vittata TPI activity was inhibited by incubation with reduced glutathione while bacterial TPI was unaffected. Consistent with cTPI's role in arsenate reduction, bacterial cells expressing fern TPI had significantly greater per cent of cellular arsenic as arsenite compared to cells expressing E. coli TPI. Excised frond tissue infiltrated with arsenate reduced arsenate significantly more under light than dark. This research highlights a novel role for P. vittata cTPI in arsenate reduction.

Three new arsenic hyperaccumulating ferns.

Phytoremediation, an emerging, plant-based technology for the removal of toxic contaminants from soil and water, has been receiving increased attention. The prerequisite for successful phytoremediation is the existence of hyperaccumulator plants. Designed to search for new arsenic (As) hyperaccumulators, an experiment was conducted under greenhouse conditions in a completely randomized design with four replications. This experiment identified Pteris biaurita L., P. quadriaurita Retz and P. ryukyuensis Tagawa as new hyperaccumulators of As and re-confirmed Pteris cretica as a hyperaccumulator. The average As concentration ranged from 1770 to 3650 mg kg(-1) DW in the fronds and 182 to 507 mg kg(-1) DW in the roots of P. cretica, P. biaurita, P. quadriaurita and P. ryukyuensis after having been grown in 100 mg As kg(-1) soil. There was a greater percentage of As(III) as compared to As (V) in the fronds of these plants. Based on our study, P. ryukyuensis is the most promising candidate to phytoremediate As contaminated soils compared to the other three species. The nutrient requirements or distributions within the Pteris species were altered distinctly when the plants were exposed to As.

Uptake and distribution of selenium in different fern species.

There has been an interest in using hyperaccumulating plants for the removal of heavy metals and metalloids. High selenium (Se) concentrations in the environment are detrimental to animals, humans, and sustainable agriculture, yet selenium is also an essential nutrient for humans. This experiment was conducted to screen fern plants for their potential to accumulate selenium. Eleven fern species, Pteris vittata, P. quadriaurita, P. dentata, P. ensiformis, P. cretica, Dryopteris erythrosora, Didymochlaena truncatula, Adiantum hispidulum, Actiniopteris radiata, Davallia griffithiana, and Cyrtomium fulcatum, were grown under hydroponic conditions for one week at 20 mg L(-1) selenate or selenite. Root Se concentrations reached 245-731 and 516-1082 mg kg(-1) when treated with selenate and selenite, respectively. The corresponding numbers in the fronds were 153-745 and 74-1,028 mg kg(-1) with no visible toxicity symptoms. Only three fern species were able to accumulate more Se in the fronds than the roots, which were D. griffithiana when treated with selenate, P. vittata when treated with selenite, and A. radiata regardless of the forms of Se. A. radiata was the best species overall for Se accumulation. More research is needed to further determine the potential of the fern species identified in this study for phytoremediation of the Se contaminated soils and water.

Antioxidant responses of hyper-accumulator and sensitive fern species to arsenic.

Plant species capable of hyper-accumulating heavy metals are of considerable interest for phytoremediation, and differ in their ability to accumulate metals from the environment. This work aims to examine (i) arsenic accumulation in three fern species [Chinese brake fern (Pteris vittata L.), slender brake fern (Pteris ensiformis Burm. f.), and Boston fern (Nephrolepis exaltata L.)], which were exposed to 0, 150, or 300 muM of arsenic (Na(2)HAsO(4).7H(2)O), and (ii) the role of anti-oxidative metabolism in arsenic tolerance in these fern species. Arsenic accumulation increased with an increase in arsenic concentration in the growth medium, the most being found in P. vittata fronds showing no toxicity symptoms. In addition, accumulation was highest in the fronds, followed by the rhizome, and finally the roots, in all three fern species. Thiobarbituric acid-reacting substances, indicators of stress in plants, were found to be lowest in P. vittata, which corresponds with its observed tolerance to arsenic. All three ferns responded differentially to arsenic exposure in terms of anti-oxidative defence. Higher levels of superoxide dismutase, catalase, and ascorbate peroxidase were observed in P. vittata than in P. ensiformis and N. exaltata, showing their active involvement in the arsenic detoxification mechanism. However, no significant increase was observed in either guaiacol peroxides or glutathione reductase in arsenic-treated P. vittata. Higher activity of anti-oxidative enzymes and lower thiobarbituric acid-reacting substances in arsenic-treated P. vittata correspond with its arsenic hyper-accumulation and no symptoms of toxicity.