Genetic diversity of Melon necrotic spot virus and Olpidium isolates from different origins

The geographic incidence, genetic diversity and phylogenetic relationships of Melon necrotic spot virus (MNSV) and Olpidium isolates were studied in three cucurbit species from several Latin American and European countries on different collecting dates. Of the 112 cucurbit samples analysed, 69 from Guatemala, Honduras, Mexico, Panama and Spain were DAS‐ELISA‐positive for MNSV. Olpidium bornovanus and O. virulentus infections, and MNSV infections mixed with these Olpidium species, were observed for all these countries. Twenty‐nine MNSV isolates from all the origins where the virus was detected were selected and amplified by RT‐PCR. The resulting RT‐PCR of the p29, p89, p7A, p7B and p42 proteins was used to estimate the genetic diversity and the phylogenetic relationships of the MNSV population. The sequences obtained in this study were compared with the MNSV sequences of the NCBI database, and three groups were recovered by nucleotide composition according to geographical origins: the EU‐LA genotype group (with two subgroups: EU and LA, European and Latin American isolates, respectively), the JP melon genotype group (Japanese melon reference isolates) and the JP watermelon genotype group (Japanese watermelon reference isolates). The genetic diversity in the entire p7A and p7B proteins of MNSV suggests that these coding regions are under strong selective pressure. Additionally, the rDNA‐ITS region was analysed in 40 O. bornovanus and O. virulentus isolates associated with each geographical location and host examined. Phylogenetic analysis showed two groups for each Olpidium species, and these groupings were related to the host from which they were originally isolated.     

Ultrastructural aspects of tomato leaves infected by Tomato torrado virus (ToTV) and co‐infected by other viruses

Optical and electron microscopy studies were carried out to investigate the cytopathology induced in tomato leaves infected by Tomato torrado virus (ToTV), a new picorna‐like virus associated with the ‘Torrado’ disease. Infected leaves, showing typical Torrado disease symptoms were surveyed in commercial greenhouses in the main tomato production areas of Spain. The effect of the co‐infection of ToTV with other viruses which commonly infect tomato crops was also studied. Ultra‐thin sections of ToTV‐infected tomato leaves did not show a strong cellular alteration. However, crystalline arrays of isometric virus‐like particles (VLPs) of 20–30 nm in the inclusion bodies were observed in phloem parenchyma cells of the infected tissues. Tissues co‐infected by ToTV and either Tomato chlorosis virus (ToCV) or Pepino mosaic virus (PepMV) presented more severe cellular alterations. The most deleterious consequences for tomato cells were found in triple infections of ToTV, PepMV and Tomato spotted wilt virus (TSWV), where characteristic cell wall overgrowth was distinguishable, together with a large amount of necrotic cells.     

Physicochemical, Rheological and Structural Characteristics of Starch in Maize Tortillas

Fresh and stored maize (white and blue) tortillas were evaluated for physicochemical, rheological and structural characteristics assessed by calorimetry, x-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, dynamic viscoelastic tests, and high-performance size-exclusion chromatography. Two endotherms were found in studies of fresh and stored tortillas. The low temperature endotherm (50–56 °C) was due to reorganized (retrograded) amylopectin, while the high temperature endotherm (105–123 °C) was attributed to retrograded amylose. The enthalpy value for the lower temperature transition was minor than that of the high temperature transition. Fresh tortillas showed an amorphous starch arrangement by x-ray diffraction study. Stored samples showed the presence of peaks at 2θ = 17o and 23o, indicating re-crystallization of starch components. FTIR results confirmed the development of higher levels of starch crystals during storage. Differences in the viscoelastic parameters were also observed between fresh and stored samples. At the longest storage times, white tortillas were more rigid than blue tortillas. Molar mass values for starch increased for both white and blue tortillas as storage time progressed, though relatively higher values were obtained for white tortillas. More starch reorganization occurred in white tortillas, in accordance to calorimetric, x-ray diffraction, FTIR and rheological results. These results corroborate that changes occurring in tortillas during storage are related to reorganization of starch components, and the maize variety more than the color plays an important role.     

Attraction of Chrysoperla carnea complex and Chrysopa spp. lacewings (Neuroptera: Chrysopidae) to aphid sex pheromone components and a synthetic blend of floral compounds in Hungary

BACKGROUND: The deployment of synthetic attractants for the manipulation of lacewing populations as aphid predators is currently used in integrated pest management. This study investigates a synthetic bait comprising floral compounds previously found to attract the Chrysoperla carnea complex, and, for the first time, the aphid sex pheromone components (1R,4aS,7S,7aR)‐nepetalactol and (4aS,7S,7aR)‐nepetalactone, in field experiments in Hungary, for their ability to manipulate lacewing populations. RESULTS: The synthetic floral bait attracted both sexes of the Chrysoperla carnea complex, and Chrysopa formosa Brauer showed minimal attraction. The aphid sex pheromone compounds alone attracted males of C. formosa and C. pallens (Rambur). When the two baits were combined, Chrysopa catches were similar to those with aphid sex pheromone baits alone, but carnea complex catches decreased significantly (by 85–88%). CONCLUSION: As the floral bait alone attracted both sexes of the carnea complex, it showed potential to manipulate the location of larval density via altering the site of oviposition. Aphid sex pheromone compounds alone attracted predatory males of Chrysopa spp. and can potentially be used to enhance biological control of aphids. For the carnea complex, however, a combination of both baits is not advantageous because of the decrease in adults attracted. Assumptions of intraguild avoidance underlying this phenomenon are discussed. Copyright © 2010 Society of Chemical Industry     

Indirect response to selection for improving resistance to the Mediterranean corn borer (<Emphasis Type="Italic">Sesamia nonagrioides</Emphasis> Lef) in maize

Mediterranean corn borer (MCB) (Sesamia nonagrioides Lef) and European corn borer (ECB) (Ostrinia nubilalis Hbn) are the most important biotic stresses of maize in Europe. The first selection program to improve stalk resistance to MCB was carried out in the maize population EPS12. It has shown that selection was effective to improve stalk resistance to MCB and ECB, while yield was not significantly diminished. The objective of this research was to determine if correlated changes in EPS12 occurred due to selection for resistance to MCB. Cycles of selection per se and testcrosses to three testers were evaluated under MCB and ECB artificial infestation at two different Spanish locations during 2 years. Selection has significantly reduced cob damage, days to silking, plant and ear height, and 100-kernel weight; meanwhile early vigor was increased. These changes could rather be a consequence of unconscious selection and/or the genetic correlation of these traits with resistance than a consequence of genetic drift.     

Intraspecific variation in growth and allocation patterns in seedlings of Pinus pinaster Ait. submitted to contrasting watering regimes: can water availability explain regional variation?

? Interpopulation variation in key functional traits of Pinus pinaster Ait. is well recognized. However, the relative importance of drought tolerance to explain this regional variation in the species remains elusive.

? Here, we raise the question whether water availability constitutes a likely driver of regional variation in biomass allocation, growth and morphological traits of ten populations that cover the distribution range of P. pinaster. We carried out an experiment where seedlings of five families per population were submitted to two contrasting watering treatments.

? The effects of water availability and population were significant for relative diameter and height growth rate, biomass allocation and number of lateral stems and dwarf shoots. Total dry mass significantly differed between watering treatments but it did not among populations. Populations could be clustered into four main groups. Root mass fraction explained most of the variation and significantly correlated to altitude but not to aridity.

? The geographical pattern of genetic variation found in morphology and biomass allocation did not translate into population differences in drought tolerance or phenotypic plasticity to water availability, indicating that water availability is not a likely driver of the regional variation observed in the studied traits of P. pinaster at the seedling stage.

     

A novel application of the ecological field theory to the definition of physiographic and climatic potential areas of forest species

A new approach to the definition of physiographic and climatic potential areas for forest species, based on the ecological field theory, is outlined in this paper. The proposed formulation is tested on the Spanish juniper (Juniperus thurifera L.), using data from 883 permanent and temporary plots throughout its distribution area in the Spanish autonomous region of Castilla y León. The suitability of the territory for the species is assessed by previously studying its habitat, which in turn is analyzed through physiographic and climatic parameters. This new method is rooted in an additive index that depends on the Mahalanobis distance in the parametric space that evaluates the ecological resemblance between the studied site and each of the points defining the parametric habitat. Thereby the ecological potential of any site within the territory can be established, integrated in a geographical information systems and accordingly charted. The results are compared with those obtained with the methodology traditionally used by Spanish foresters (factorial index), showing that the overall potential area is similar in size but quite different in its distribution.     

Antifeedant and toxic effects of acetogenins from <Emphasis Type="Italic">Annona montana</Emphasis> on <Emphasis Type="Italic">Spodoptera frugiperda</Emphasis>

Several species of the large family of tropical plants Annonaceae have been intensely investigated over the last 20 years, mainly because of the discovery of annonaceous acetogenins. These compounds are powerful cytotoxics, with potential applications as insecticides, antiparasitics, acaricides, fungicides, and antitumor drugs. Annona montana Macfad. (Annonaceae) grows in Santa Cruz de la Sierra, Bolivia, where an infusion of leaves is used for the treatment of lice, influenza, and insomnia. The major acetogenins from a Bolivian collection of A. montana, annonacin (1), cis-annonacin-10-one (2), densicomacin-1 (3), gigantetronenin (4), murihexocin-B (5), and tucupentol (6), were evaluated for their antifeedant and toxic effects on Spodoptera frugiperda Smith (Lepidoptera: Noctuidae), a serious pest affecting corn crops in Argentina. All the acetogenins produced 100% mortality during the larval or pupal stages at 100 μg of treatment per gram of diet. In addition, compounds 2, 3, and 4 deterred more than 80% feeding at the same dose. Relative toxicity values of LD₅₀ for the strongest larvicidal compounds 1, 2, and 4 were determined, indicating that the three compounds are effective natural insecticides. This is the first report on the antifeedant and toxic effects produced by the particular type of acetogenins, the mono-THF acetogenins, on the lepidopteran S. frugiperda. No correlation was detected between the toxicity of the mentioned compounds to larvae and the known capacity of the acetogenins 1, 2, and 4 to inhibit the NADH oxidase, indicating that the inhibition of the mitochondrial complex I is not the only cause for larval mortality of S. frugiperda.