Serpentine leafminer (Liriomyza trifolii) on potato (Solanum tuberosum): field observations and plant photosynthetic responses to injury

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nicotiana tabacum as an experimental host for the study of plant-Xylella fastidiosa interactions

Xylella fastidiosa causes citrus variegated chlorosis (CVC). Information generated from the X. fastidiosa genome project is being used to study the underlying mechanisms responsible for pathogenicity. However, the lack of an experimental host other than citrus to study plant-X. fastidiosa interaction has been an obstacle to accelerated progress in this area. We present here results of three experiments that demonstrated that tobacco could be an important experimental host for X. fastidiosa. All tobacco plants inoculated with a citrus strain of X. fastidiosa expressed unequivocal symptoms, consisting of orange leaf lesions, approximately 2 months after injection of the pathogen. CVC symptoms were observed in citrus 3 to 6 months after inoculation. The pathogen was readily detected in symptomatic tobacco plants by polymerase chain reaction (PCR) and phase contrast microscopy. In addition, X. fastidiosa was reisolated on agar plates in 4 of 10 plants. Scanning electron microscopy analysis of cross sections of stems and petioles revealed the presence of rod shaped bacteria restricted to the xylem of inoculated plants. The cell size was within the limit typical of X. fastidiosa.

Size and lipid content of nonmyrmecochorous diaspores: Effects on the interaction with litter-foraging ants in the Atlantic rain forest of Brazil

Ants are often attracted to diaspores not adapted for dispersal by ants. These diaspores may occasionally benefit from this interaction. We selected six nonmyrmecochorous plant species (Virola oleifera, Eugenia stictosepala, Cabralea canjerana, Citharexylum myrianthum, Alchornea glandulosa and Hyeronima alchorneoides) whose diaspores differ in size and lipid content, and investigated how these features affect the outcome of ant-diaspore interactions on the floor of a lowland Atlantic forest of Southeast Brazil. A total of 23 ant species were seen interacting with diaspores on the forest floor. Ants were generally rapid at discovering and cleaning the diaspore pulp or aril. Recruitment rate and ant attendance were higher for lipid-rich diaspores than for lipid-poor ones. Removal rate and displacement distance were higher for small diaspores. The large ponerine ant Pachycondyla striata, one of the most frequent attendants to lipid-rich arillate diaspores, transported the latter into their nests and discarded clean intact seeds on refuse piles outside the nest. Germination tests with cleaned and uncleaned diaspores revealed that the removal of pulp or aril may increase germination success in Virola oleifera, Cabralea canjerana, Citharexylum myrianthum and Alchornea glandulosa. Gas chromatography analyses revealed a close similarity in the fatty acid composition of the arils of the lipid-rich diaspores and the elaiosome of a typical myrmecochorous seed (Ricinus communis), corroborating the suggestion that some arils and elaiosomes are chemically similar. Although ant-derived benefits to diaspores - secondary dispersal and/or increased germination - varied among the six plant species studied, the results enhanced the role of ant-diaspore interactions in the post-dispersal fates of nonmyrmecochorous seeds in tropical forests. The size and the lipid-content of the diaspores were shown to be major determinants of the outcome of such interactions.

The role of multiple partners in a digestive mutualism with a protocarnivorous plant

Background and aimsThe protocarnivorous plant Paepalanthus bromelioides (Eriocaulaceae) is similar to bromeliads in that this plant has a rosette-like structure that allows rainwater to accumulate in leaf axils (i.e. phytotelmata). Although the rosettes of P. bromelioides are commonly inhabited by predators (e.g. spiders), their roots are wrapped by a cylindrical termite mound that grows beneath the rosette. In this study it is predicted that these plants can derive nutrients from recycling processes carried out by termites and from predation events that take place inside the rosette. It is also predicted that bacteria living in phytotelmata can accelerate nutrient cycling derived from predators.MethodsThe predictions were tested by surveying plants and animals, and also by performing field experiments in rocky fields from Serra do Cipó, Brazil, using natural abundance and enriched isotopes of 15N. Laboratory bioassays were also conducted to test proteolytic activities of bacteria from P. bromelioides rosettes.Key ResultsAnalyses of 15N in natural nitrogen abundances showed that the isotopic signature of P. bromelioides is similar to that of carnivorous plants and higher than that of non-carnivorous plants in the study area. Linear mixing models showed that predatory activities on the rosettes (i.e. spider faeces and prey carcass) resulted in overall nitrogen contributions of 26·5 % (a top-down flux). Although nitrogen flux was not detected from termites to plants via decomposition of labelled cardboard, the data on 15N in natural nitrogen abundance indicated that 67 % of nitrogen from P. bromelioides is derived from termites (a bottom-up flux). Bacteria did not affect nutrient cycling or nitrogen uptake from prey carcasses and spider faeces.ConclusionsThe results suggest that P. bromelioides derive nitrogen from associated predators and termites, despite differences in nitrogen cycling velocities, which seem to have been higher in nitrogen derived from predators (leaves) than from termites (roots). This is the first study that demonstrates partitioning effects from multiple partners in a digestion-based mutualism. Despite most of the nitrogen being absorbed through their roots (via termites), P. bromelioides has all the attributes necessary to be considered as a carnivorous plant in the context of digestive mutualism. © 2012 The Author. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.

The role of prophage in plant-pathogenic bacteria

A diverse set of phage lineages is associated with the bacterial plant-pathogen genomes sequenced to date. Analysis of 37 genomes revealed 5,169 potential genes (approximately 4.3 Mbp) of phage origin, and at least 50 had no function assigned or are nonessential to phage biology. Some phytopathogens have transcriptionally active prophage genes under conditions that mimic plant infection, suggesting an association between plant disease and prophage transcriptional modulation. The role of prophages within genomes for cell biology varies. For pathogens such as Pectobacterium, Pseudomonas, Ralstonia, and Streptomyces, involvement of prophage in disease symptoms has been demonstrated. In Xylella and Xanthomonas, prophage activity is associated with genome rearrangements and strain differentiation. For other pathogens, prophage roles are yet to be established. This review integrates available information in a unique interface (http://propnav.esalq.usp.br) that may be assessed to improve research in prophage biology and its association with genome evolution and pathogenicity. © Copyright ©2013 by Annual Reviews. All rights reserved.

Beta Diversity of Plant-Pollinator Networks and the Spatial Turnover of Pairwise Interactions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Postharvest harpin or Bacillus thuringiensis treatments suppress citrus black spot in 'Valencia' oranges

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Infestation of froghopper nymphs changes the amounts of total phenolics in sugarcane

The increased rate of sugarcane harvest without previous burn has provided a very favorable environment to the froghopper Mahanarva fimbriolota (Stal, 1854), with high Moisture and low temperature variation. Few works have Studied the response of sugarcane to this pest, so little is known about resistant cultivars. Plant phenolics are widely studied compounds because of their known antifierbivore effect. This research aims to determine if the attack of M.fimbriolata nymphs stimulates the acccumulation of total phenolics in sugarcane. The experiment was carried Out in greenhouse and arranged in completely randomized design, in a 3 x 2 x 4 factorial with three replications. Second instar nymphs of M. fimbriolota were infested at the following rates: control, 2-4 and 4-8 nymphs per pot (first-second infestations, respectively). Pots were covered with nylon net and monitored daily to isolate the effect of leaf Sucking adults. Leaf and root samples were collected and kept frozen in liquid nitrogen until analyses. Infested plants showed higher levels of phenolics in both root and leaf tissues. In roots, the cultivar SP80-1816 accumulated more phenolic compounds in response to the infestation of M. fimbriolata. on the other hand, higher levels were found in leaves and roots of control plants of SP86-42, which might be an indication of a non-preference mechanism. The increase of total phenolics in sugarcane infested with root-sucking froghopper nymphs does not seem to be useful to detect the resistance to this pest.

Cultivo de melão rendilhado com dois e três frutos por planta

O objetivo deste trabalho foi avaliar cultivares de melão rendilhado produzidas em plantas sob raleio dos frutos. Foram estudadas as cultivares Maxim, Louis, Fantasy, Shinju 200, e Bônus nº2, com as plantas conduzidas com dois e três frutos. O delineamento experimental foi em blocos ao acaso, em esquema fatorial 5x2, com quatro repetições e com as plantas dispostas no espaçamento de 1,0 m entre linhas e 0,5 m entre plantas. O experimento foi realizado em casa de vegetação, utilizando-se fertirrigação e vasos plásticos de 13 L, preenchidos com fibra da casca de coco Golden Mix® Misto 98. As mudas foram produzidas em bandejas de poliestireno expandido de 128 células e quando estavam com a primeira folha definitiva completamente desenvolvida foram transplantadas aos vasos. Foram avaliados o rendilhamento da casca, os diâmetros longitudinal e transversal do fruto, o índice de formato do fruto, os diâmetros longitudinal e transversal do lóculo, o índice de formato do lóculo, a espessura do mesocarpo, a massa média dos frutos e a produção por planta. Não houve interação entre os fatores estudados. Nas condições deste experimento, a condução de dois frutos por planta resultou em maior rendilhamento da casca, maior diâmetro transversal do fruto, maior diâmetro longitudinal do lóculo e maior massa média dos frutos. Porém, as maiores produções por planta foram observadas quando conduzidas com três frutos. Os híbridos Fantasy e Shinju 200 apresentaram as melhores características de frutos e maiores produções.

Análise do perfil de expressão dos genes da cana-de-açúcar envolvidos na interação com Leifsonia xyli subsp: xyli

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Genome-Wide Analysis of Differentially Expressed Genes During the Early Stages of Tomato Infection by a Potyvirus

Plant responses against pathogens cause up-and downward shifts in gene expression. To identify differentially expressed genes in a plant-virus interaction, susceptible tomato plants were inoculated with the potyvirus Pepper yellow mosaic virus (PepYMV) and a subtractive library was constructed from inoculated leaves at 72 h after inoculation. Several genes were identified as upregulated, including genes involved in plant defense responses (e. g., pathogenesis-related protein 5), regulation of the cell cycle (e. g., cytokinin-repressed proteins), signal transduction (e. g., CAX-interacting protein 4, SNF1 kinase), transcriptional regulators (e. g., WRKY and SCARECROW transcription factors), stress response proteins (e. g., Hsp90, DNA-J, 20S proteasome alpha subunit B, translationally controlled tumor protein), ubiquitins (e. g., polyubiquitin, ubiquitin activating enzyme 2), among others. Downregulated genes were also identified, which likewise display identity with genes involved in several metabolic pathways. Differential expression of selected genes was validated by macroarray analysis and quantitative real-time polymerase chain reaction. The possible roles played by some of these genes in the viral infection cycle are discussed.

Proteomic analysis reveals suppression of bark chitinases and proteinase inhibitors in citrus plants affected by the citrus sudden death disease

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Habitat heterogeneity and pollinators: Bees in fragmented landscapes (Hymenoptera : Apidae)

This text presents the main studies that report the effect of habitat degradation upon plant-pollinator interactions and the importance of the presence of native vegetation remnants to pollinators, which leads to the need for conservation measures.

Why are fruits colorful? The relative importance of achromatic and chromatic contrasts for detection by birds

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Photosynthetic response of soybean to twospotted spider mite (Acari: Tetranychydae) injury

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)