The Effects of Host, Geographic Origin, and Gender on the Thermal Requirements of Diaphorina citri (Hemiptera: Psyllidae)

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is the vector of the bacteria that causes citrus greening and is considered one of the world`s most important citrus diseases. We examined how host, geographic region, and gender affect the thermal requirements of D. citri. The insects were reared in climatic chambers at constant temperatures of 18, 20, 22, 25, 28, 30, and 32 1 degrees C, 70 +/- 10% RH, and a 14 h photophase. Host plants for D. citri included orange (Citrus sinensis [Rutaceae]) varieties Pera and Natal, the rootstock, Rungpur lime (C. limonia [Rutaceae]) and the natural host, Orange jessamine (Murraya paniculata [Rutaceae]). To study the influence of geographic origin on thermal requirements, we studied D. citri populations from Piracicaba, SP (warmer region) and Itapetininga, SP (cooler region). The duration and survival of the development stages and the duration of the total development (egg-adult) did not differ significantly on the different hosts, but it did vary with temperature. Nymphs of D. citri created on the different hosts have the same thermal requirements. The thermal requirements for this species collected from the two climate regions were identical; males and females also had the same thermal requirements.

Regulatory effects of an inhibitor from Plathymenia foliolosa seeds on the larval development of Anagasta kuehniella (Lepidoptera)

The Mediterranean flour moth, Anagasta kuehniella, is one of the most important insect pests of grains, reported worldwide, feeding on stored grains and products of rice, rye, corn and wheat. Plants synthesize a variety of molecules, including trypsin inhibitors, to defend themselves against attack by insects. In this study, a trypsin inhibitor (PFTI) was purified from Plathymenia foliolosa (Benth.) seeds and was tested for insect growth regulatory effect. The survival and mass of A. kuehniella larvae feeding on control seeds were about 82.7% and 5 ring, respectively, whereas survival on seeds containing 0.7% PFTI was about 56%, while a 66.1% reduction in the average mass of the larvae was observed. The results from dietary utilization experiments with A. kuehniella larvae showed a reduction in efficiency of conversion of ingested food and digested food, and an increase in approximate digestibility and metabolic cost. The level of trypsin was significantly decreased in larval midgut and increased in the feces of larvae reared on a diet containing 0.7% PFTI. Results indicate that PFTI possesses a toxic effect against A. kuehniella larvae. (C) 2008 Elsevier Inc. All rights reserved.

Fruit flies (Diptera, Tephritidae) and their associations with native host plants in a remnant area of the highly endangered Atlantic Rain Forest in the State of Espirito Santo, Brazil

The results presented in this paper refer to a host survey, lasting approximately three and a half years (February 2003-july 2006), undertaken in the Vale do Rio Doce Natural Reserve, a remnant area of the highly endangered Atlantic Rain Forest located in Linhares County, State of Espirito Santo, Brazil. A total of 330 fruit samples were collected from native plants, representing 248 species and 51 plant families. Myrtaceae was the most diverse family with 54 sampled species. Twenty-eight plant species, from ten families, are hosts of ten Anastrepha species and of Ceratitis capitata (Wiedemann). Among 33 associations between host plants and fruit flies, 20 constitute new records, including the records of host plants for A. fumipennis Lima and A. nascimentoi Zucchi. The findings were discussed in the light of their implications for rain forest conservation efforts and the study of evolutionary relationships between fruit flies and their hosts.

Effects of soybean proteinase inhibitors on development of the soil mite Scheloribates praeincisus (Acari : Oribatida)

Proteinase inhibitors (PI) are present in plant tissues, especially in seeds, and act as a defense mechanism against herbivores and pathogens. Serine PI from soybean such as Bowman-Birk (BBPI) and Kunitz have been used to enhance resistance of sugarcane varieties to the sugarcane borer Diatraea saccharalis (Fabricius) (Lepidoptera: Crambidae), the major pest of this crop. The use of these genetically-modified plants (GM) expressing PI requires knowledge of its sustainability and environmental safety, determining the stability of the introduced characteristic and its effects on non-target organisms. The objective of this study was to evaluate direct effects of ingestion of semi-purified and purified soybean PI and GM sugarcane plants on the soil-dwelling mite Scheloribates praeincisus (Berlese) (Acari: Oribatida). This mite is abundant in agricultural soils and participates in the process of organic matter decomposition; for this reason it will be exposed to PI by feeding on GM plant debris. Eggs of S. praeincisus were isolated and after larvae emerged, immatures were fed milled sugarcane leaves added to semi-purified or purified PI (Kunitz and BBPI) or immatures were fed GM sugarcane varieties expressing Kunitz and BBPI type PI or the untransformed near isogenic parental line variety as a control. Developmental time (larva-adult) and survival of S. praeincisus was evaluated. Neither Kunitz nor BBPI affected S. praeincisus survival. On the other hand, ingestion of semi-purified and purified Kunitz inhibitor diminished duration of S. praeincisus immature stages. Ingestion of GM senescent leaves did not have an effect on S. praeincisus immature developmental time and survival, compared to ingestion of leaves from the isogenic parental plants. These results indicate that cultivation of these transgenic sugarcane plants is safe for the non-target species S. praeincisus.

The effect of host plants on Tetranychus evansi, Tetranychus urticae (Acari: Tetranychidae) and on their fungal pathogen Neozygites floridana (Entomophthorales: Neozygitaceae)

In a series of tritrophic-level interaction experiments, the effect of selected host plants of the spider mites, Tetranychus evansi and Tetranychus urticae, on Neozygites floridana was studied by evaluating the attachment of capilliconidia, presence of hyphal bodies in the infected mites, mortality from fungal infection, mummification and sporulation from fungus-killed mite cadavers. Host plants tested for T. evansi were tomato, cherry tomato, eggplant, nightshade, and pepper while host plants tested for T. urticae were strawberry, jack bean, cotton and Gerbera. Oviposition rate of the mites on each plant was determined to infer host plant suitability while host-switching determined antibiosis effect on fungal activity. T. evansi had a high oviposition on eggplant, tomato and nightshade but not on cherry tomato and pepper. T. urticae on jack bean resulted in a higher oviposition than on strawberry, cotton and Gerbera. Attachment of capilliconidia to the T. evansi body, presence of hyphal bodies in infected T. evansi and mortality from fungal infection were significantly higher on pepper, nightshade and tomato. The highest level of T. evansi mummification was observed on tomato. T. evansi cadavers from tomato and eggplant produced more primary conidia than those from cherry tomato, nightshade and pepper. Switching N. floridana infected T. evansi from one of five Solanaceous host plants to tomato had no prominent effect on N. floridana performance. For T. urticae, strawberry and jack bean provided the best N. floridana performance when considering all measured parameters. Strawberry also had the highest primary conidia production. This study shows that performance of N. floridana can vary with host plants and may be an important factor for the development of N. floridana epizootics. (C) 2011 Elsevier Inc. All rights reserved.

The Infection of Soybean Leaves by Phakopsora pachyrhizi during Conditions of Discontinuous Wetness

The ability of Phakopsora pachyrhizi to cause infection under conditions of discontinuous wetness was investigated. In in vitro experiments, droplets of a uredospore suspension were deposited onto the surface of polystyrene. After an initial wetting period of either 1, 2 or 4 h, the drops were dried for different time intervals and then the wetness was restored for 11, 10 or 8 h. Germination and appressorium formation were evaluated. In in vivo experiments, soybean plants were inoculated with a uredospore suspension. Leaf wetness was interrupted for 1, 3 or 6 h after initial wetting periods of 1, 2 or 4 h. Then, the wetting was re-established for 11, 10 or 8 h, respectively. Rust severity was evaluated 14 days after inoculation. The germination of the spores and the formation of the appressoria on the soybean leaves after different periods of wetness were also quantified in vivo by scanning electron microscopy. P. pachyrhizi showed a high infective capacity during short periods of time. An interruption of wetness after 1 h caused average reductions in germination from 56 to 75% and in appressorium formation from 84 to 96%. Rust severity was lower in all of the in vivo treatments with discontinuous wetness when compared to the control plants. Rust severity was zero when the interruption of wetness occurred 4 h after the initial wetting. Wetting interruptions after 1 and 2 h reduced the average rust severity by 83 and 77%, respectively. The germination of the uredospores on the soybean leaves occurred after 2 h of wetness, with a maximum germination appearing after 4 h of wetness. Wetness interruption affected mainly the spores that had initiated the germination.

Role of healthy nursery plants in orange yield during eight years of Citrus Variegated Chlorosis epidemics

The production and commercialization of citrus seedlings inspected and produced in protected screen-houses has become mandatory in Sao Paulo State, Brazil since January 2003. This law was intended to avoid the dispersion of Citrus Variegated Chlorosis (CVC), disease caused by Xylella fastidiosa. Our objective was to compare the yield over 8 years of `Natal` sweet orange trees grafted onto Rangpur lime obtained from healthy nursery plants and from plants artificially inoculated with X. fastidiosa. Yield was evaluated in an orchard planted in February 1999 with two treatments: (i) trees from healthy nursery plant, and (ii) trees from plants artificially inoculated with X. fastidiosa. The mean yield was 21% higher in trees from healthy nursery plants, as compared to trees from inoculated nursery plants. This difference represents a gain of approximately 203 boxes of 40.8 kg each, considering a planting density of 550 plants per hectare. (C) 2011 Elsevier B.V. All rights reserved.

Bacteriosomes in axenic plants: endophytes as stable endosymbionts

Observations of cells of axenic peach palm (Bactris gasipaes) microplants by light microscopy revealed movements of small particles within the cells. The phenomenon was characterized initially as Brownian movement, but electron microscopy revealed the presence of an intracellular bacterial community in these plants. Microscopy observations revealed the particular shapes of bacterial cells colonizing inner tissues of analyzed plants. Applying a molecular characterization by polymerase chain reaction and denaturing gradient gel electrophoresis, it was revealed the existence of bacterial rRNA within the plants. Sequencing of the rRNA identified three different phylogenetic groups; two bands had a high degree of similarity to sequences from Moraxella sp. and Brevibacillus sp., and a third sequence was similar to a non-cultivated cyanobacterium. The presence of those endosymbionts, called bacteriosomes, in axenic peach palm microplants raises the question of whether these stable endosymbionts were acquired in the process of evolution and how could they benefit the process of plants micropropagation.

Metallomics and chemical speciation: towards a better understanding of metal-induced stress in plants

Most metal ions are toxic to plants, even at low concentrations, despite the fact that some are essential for growth and play key roles in metabolism. The majority of metals induce the formation of reactive oxygen species, which require the synthesis of additional antoxidant compounds and enzymes for their removal. New techniques that have greatly improved the identification, localisation and quantification of metals within plant tissues have led to the science of metallomics. This advancement in knowledge should eventually allow the characterisation of plants used in the process of phytoremediation of soils contaminated with toxic metals.

Diversity of endophytic enterobacteria associated with different host plants

Fifty-three endophytic enterobacteria isolates from citrus, cocoa, eucalyptus, soybean, and sugar cane were evaluated for susceptibility to the antibiotics ampicillin and kanamycin, and cellulase production. Susceptibility was found on both tested antibiotics. However, in the case of ampicillin susceptibility changed according to the host plant, while all isolates were susceptible to kanamycin. Cellulase production also changed according to host plants. The diversity of these. isolates was estimated by employing BOX-PCR genomic fingerprints and 16S rDNA sequencing. In total, twenty-three distinct operational taxonomic units (OTUs) were identified by employing a criterion of 60% fingerprint similarity as a surrogate for an OTU. The 23 OTUs belong to the Pantoea and Enterobacter genera, while their high diversity could be an indication of paraphyletic classification. Isolates representing nine different OTUs belong to Pantoea agglomerans, P. ananatis, P, stewartii, Enterobacter sp., and E. homaechei. The results of this study suggest that plant species may select endophytic bacterial genotypes. It has also become apparent that a review of the Pantoea/Enterobacter genera may be necessary.

The isolation of antioxidant enzymes from mature tomato (cv. Micro-Tom) plants

The activity of catalase (CAT), guaiacol peroxidase (GPOX), ascorbate peroxidase (APX), glutathione reductase (GR), and the isoenzymes of superoxide dismutase (SOD) were determined in the organs of tomato (Lycopersicon esculentum) cultivar Micro-Tom after 104 days of development. The total activities of CAT, GPOX, and GR were higher in the stem than in others tissues, whereas the stem exhibited the lowest APX activity. Activity staining analysis following gel electrophoresis revealed the existence of four SOD isoenzymes in leaves, three in fruits, but only two in the roots and stems. This characterization is essential for an investigation into the effect of abiotic and biotic stresses on the oxidative stress responses by this plant model system.

Biochemical responses of glyphosate resistant and susceptible soybean plants exposed to glyphosate

Glyphosate is a wide spectrum, non-selective, post-emergence herbicide. It acts on the shikimic acid pathway inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), thus obstructing the synthesis of tryptophan, phenylalanine, tyrosine and other secondary products, leading to plant death. Transgenic glyphosate-resistant (GR) soybean [Glycine max (L.)] expressing an glyphosate-insensitive EPSPS enzyme has provided new opportunities for weed control in soybean production. The effect of glyphosate application on chlorophyll level, lipid peroxidation, catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GOPX) and superoxide dismutase (SOD) activities, soluble amino acid levels and protein profile, in leaves and roots, was examined in two conventional (non-GR) and two transgenic (GR) soybean. Glyphosate treatment had no significant impact on lipid peroxidation, whilst the chlorophyll content decreased in only one non-GR cultivar. However, there was a significant increase in the levels of soluble amino acid in roots and leaves, more so in non-GR than in GR soybean cultivars. Root CAT activity increased in non-GR cultivars and was not altered in GR cultivars. In leaves, CAT activity was inhibited in one non-GR and one GR cultivar. GOPX activity increased in one GR cultivar and in both non-GR cultivars. Root APX activity increased in one GR cultivar. The soluble protein profiles as assessed by 1-D gel electrophoresis of selected non-GR and GR soybean lines were unaffected by glyphosate treatment. Neither was formation of new isoenzymes of SOD and CAT observed when these lines were treated by glyphosate. The slight oxidative stress generated by glyphosate has no relevance to plant mortality. The potential antioxidant action of soluble amino acids may be responsible for the lack of lipid peroxidation observed. CAT activity in the roots and soluble amino acids in the leaves can be used as indicators of glyphosate resistance.

Acquired tolerance of tomato (Lycopersicon esculentum cv. Micro-Tom) plants to cadmium-induced stress

The effects of varying concentrations of cadmium (Cd) on the development of Lycopersicon esculentum cv. Micro-Tom (MT) plants were investigated after 40 days (vegetative growth) and 95 days (fruit production), corresponding to 20 days and 75 days of exposure to CdCl(2), respectively. Inhibition of growth was clearly observed in the leaves after 20 days and was greater after 75 days of growth in 1 mM CdCl(2), whereas the fruits exhibited reduced growth following the exposure to a concentration as low as 0.1 mM CdCl(2). Cd was shown to accumulate in the roots after 75 days of growth but was mainly translocated to the upper parts of the plants accumulating to high concentrations in the fruits. Lipid peroxidation was more pronounced in the roots even at 0.05 mM CdCl(2) after 75 days, whereas in leaves, there was a major increase after 20 days of exposure to 1 mM CdCl(2), but the fruit only exhibited a slight significant increase in lipid peroxidation in plants subjected to 1 mM CdCl(2) when compared with the control. Oxidative stress was also investigated by the analysis of four key antioxidant enzymes, which exhibited changes in response to the increasing concentrations of Cd tested. Catalase (EC 1.11.1.6) activity was shown to increase after 75 days of Cd treatment, but the major increases were observed at 0.1 and 0.2 mM CdCl(2), whereas guaiacol peroxidase (EC 1.11.1.7) did not vary significantly from the control in leaves and roots apart from specific changes at 0.5 and 1 mM CdCl(2). The other two enzymes tested, glutathione reductase (EC 1.6.4.2) and superoxide dismutase (SOD, EC 1.15.1.1), did not exhibit any significant changes in activity, apart from a slight decrease in SOD activity at concentrations above 0.2 mM CdCl(2). However, the most striking results were obtained when an extra treatment was used in which a set of plants was subjected to a stepwise increase in CdCl(2) from 0.05 to 1 mM, leading to tolerance of the Cd applied even at the final highest concentration of 1 mM. This apparent adaptation to the toxic effect of Cd was confirmed by biomass values being similar to the control, indicating a tolerance to Cd acquired by the MT plants.

Absorption and Mobility of Boron in Young Citrus Plants

Boron (B) deficiency is widespread in Brazilian citrus orchards and has been considered an important soil constraint to citrus yield. The aim of this work was to study B uptake and its mobility in young citrus trees, under different B statuses, in two rootstocks. The experiment was carried out in a greenhouse, with `Valencia` sweet orange trees budded on Rangpur lime or Swingle citrumelo. The plants were grown in pots containing nutrient solutions under either adequate or deficient B supply. Plants with different B levels were transplanted into solution with adequate level of B, enriched in 10 B in different stages of development ( vegetative growth and fruiting). About 20 to 35% of B content in the new parts of orange tree came from plant reserves. Boron mobility within the plant was influenced by its nutritional status; that is, the longer the period was that the plants were grown under deficient supply, the smaller was the mobility. Boron concentration in the sweet orange trees on Swingle was higher than that on Rangpur, suggesting higher demand of swingle Citrumelo for B.