Binding of polyphenols to plant cell wall analogues - Part 1: Anthocyanins

Anthocyanins are located within the vacuole of plant cells, and are released following cell rupture during eating or processing at which time they first come into contact with the plant cell wall. The extent of anthocyanin-cell wall interaction was investigated by monitoring the rate of anthocyanin depletion in the presence of pure cellulose or cellulose-pectin composites as cell wall models. It was found that anthocyanins interact with both cellulose and pectin over a two-stage process with initially (mins-hours) 13 similar to 18% of anthocyanins binding to cellulose or cellulose/pectincomposites. With prolonged exposure (days-weeks), a gradual increase in anthocyanin binding occurs, possibly due to anthocyanins stacking on top of a base layer. Binding of acylated and non-acylated anthocyanins followed a similar pattern with slightly more (5-10%) binding of the acylated forms. Composites with the highest pectin content had the greatest anthocyanin binding suggesting the existence of both ionic interactions (with pectin) and hydrophobic interactions (with cellulose) of anthocyanin with plant cell walls.

Genetic effects and genetic relationships among shrunken (sh2) sweet corn lines and F1 hybrids

The objectives of this study were to quantify the components of genetic variance and the genetic effects, and to examine the genetic relationship of inbred lines extracted from various shrunken2(sh2) breeding populations. Ten diverse inbred lines developed from genetic background, were crossed in half diallel. Parents and their F1 hybrids were evaluated at three environments. The parents were genotyped using 20 polymorphic simple sequence repeats (SSR). Agronomic and quality traits were analysed by a mixed linear model according to additive-dominance genetic model. Genetic effects were estimated using an adjusted unbiased prediction method. Additive variance was more important than dominance variance in the expression of traits related to ear aspects (husk ratio and percentage of ear filled) and eating quality (flavour and total soluble solids). For agronomic traits, however, dominance variance was more important than additive variance. The additive genetic correlation between flavour and tenderness was strong (r = 0.84, P <0.01). Flavour, tenderness and kernel colour additive genetic effects were not correlated with yield related traits. Genetic distance (GD), estimated from SSR profiles on the basis of Jaccard's similarity coefficient varied from 0.10 to 0.77 with an average of 0.56. Cluster analysis classified parents according to their pedigree relationships. In most studied traits, F1 performance was not associated with GD.

Corymbia leaf oils, latitude, hybrids and herbivory: a test using common-garden field trials

Foliar oils, particularly monoterpenes, can influence the susceptibility of plants to herbivory. In plants, including eucalypts, monoterpenes are often associated with plant defence. A recent analysis revealed an increase in foliar oil content with increasing latitudinal endemism, and we tested this pattern using three eucalypt taxa comprising a latitudinal replacement cline. We also examined the relative concentrations of two monoterpenes (alpha-pinene and 1,8-cineole), for which meta-analyses also showed latitudinal variation, using hybrids of these three taxa with Corymbia torelliana. These, and pure C. torelliana, were then assessed in common-garden field plots for the abundance and distribution of herbivory by four distinct herbivore taxa. Differing feeding strategies among these herbivores allowed us to test hypotheses regarding heritability of susceptibility and relationships to alpha-pinene and 1,8-cineole. We found no support for an increase in foliar oil content with increasing latitude, nor did our analysis support predictions for consistent variation in alpha-pinene and 1,8-cineole contents with latitude. However, herbivore species showed differential responses to different taxa and monoterpene contents. For example, eriophyid mites, the most monophagous of our censused herbivores, avoided the pure species, but fed on hybrid taxa, supporting hypotheses on hybrid susceptibility. The most polyphagous herbivore (leaf blister sawfly Phylacteophaga froggatti) showed no evidence of response to plant secondary metabolites, while the distribution and abundance patterns of Paropsis atomaria showed some relationship to monoterpene yields.

Host plant records for fruit flies (Diptera: Tephritidae) in Southeast Asia

Plant records, derived largely from field studies in Thailand and Malaysia from 1986-94, are provided for 131 species of Southeast Asian Tephritidae.

Spatial and diurnal pattern of protein foraging by Bactrocera tryoni (Froggatt) on a host plant

Background: Queensland fruit fly, Bactrocera tryoni, is the major pest fruit fly in Australia. Protein bait sprays, where insecticides are mixed with spot applications of a protein based food lure, are one of the sustainable pre-harvest fruit fly management strategies used in Australia. Although protein bait sprays do manage fruit fly infestation in the field, there is little science underpinning this technique and so improving its efficacy is difficult. Lacking information includes where and when to apply protein bait in order to best target foraging B. tryoni. As part of new work in this area, we investigated the effect of height of protein on tree and host plant fruiting status on the spatial and temporal protein foraging patterns of B. tryoni. MEthod: The work was conducted in the field using nectarine and guava plants and wild B. tryoni at Redland Bay, Queensland, Australia. Spot sprays of protein bait were applied to the foliage of randomly selected fruiting and non-fruiting trees. Each tree received protein bait spot sprays on the lower and higher foliage at 0530hrs. The number, sex and species of flies that fed on each protein spot were recorded hourly from 0600hrs through to 1800hrs.Results: For nectarines, there was a significant difference in the number of B. tryoni feeding on protein bait placed at different locations within the tree (ANOVA, F = 8.898, p = 0.001). More flies fed on protein placed on higher foliage relative to lower, irrespective of the fruiting status of the nectarine trees. A significant difference was also observed in the diurnal protein feeding pattern of B. tryoni (ANOVA, F = 2.164, p = 0.024), with more flies feeding at 1600hrs. Results for guava are still being collected and will be presented at the meeting.Conclusions: We conclude that B. tryoni effectively forages for protein at heights higher than 1.3m from ground, indicating greater efficacy of protein bait when applied at foliage higher in the canopy. Bactrocera tryoni actively forages for protein throughout the day, with a highest feeding peak at 1600hrs. The lack of significant difference in the spatial protein foraging pattern between fruiting and non-fruiting nectarine trees may be a real result, or may have resulted from the fruiting tree being very close (within 1 – 2 metres) of the non-fruiting tree. This hypothesis is being tested in the guava trial.

Complementing biological control with plant suppression: Implications for improved management of parthenium weed (Parthenium hysterophorus L.)

Parthenium hysterophorus L. is a weed of global significance that has become a major weed in Australia and many other parts of the world. A combined approach for the management of parthenium weed using biological control and plant suppression, was tested under field conditions over a two-year period in southern central Queensland. The six suppressive plant species, selected for their demonstrably suppressive ability in earlier glasshouse studies, worked synergistically with the biological control agents (Epiblema strenuana Walker, Zygogramma bicolorata Pallister, Listronotus setosipennis Hustache and Puccinia abrupta var. partheniicola) present in the field to reduce the growth (above ground biomass) of parthenium weed, by between 60–86% and 47–91%, in Years 1 and 2, respectively. The biomass of the suppressive plants was between 6% and 23% greater when biological control agents were present than when the biological control agents had been excluded. This shows that parthenium weed can be more effectively managed by combining the current biological control management strategy with selected sown suppressive plant species, both in Australia and elsewhere.

Possible impacts of the invasive plant Rubus niveus on the native vegetation of the Scalesia Forest in the Galapagos Islands

Originally from Asia, Rubus niveus has become one of the most widespread invasive plant species in the Galapagos Islands. It has invaded open vegetation, shrubland and forest alike. It forms dense thickets up to 4 m high, appearing to displace native vegetation, and threaten the integrity of several native communities. This study used correlation analysis between a R. niveus cover gradient and a number of biotic (vascular plant species richness, cover and vegetation structure) and abiotic (light and soil properties) parameters to help understand possible impacts in one of the last remaining fragments of the Scalesia forest in Santa Cruz Island, Galapagos. Higher cover of R. niveus was associated with significantly lower native species richness and cover, and a different forest structure. Results illustrated that 60% R. niveus cover could be considered a threshold for these impacts. We suggest that a maximum of 40% R. niveus cover could be a suitable management target.

The virulence of Finnish Pyrenophora teres f. teres isolates and its implications for resistance breeding

In Finland, barley, Hordeum vulgare L., covers 50 % of the total acreage devoted to cereal cultivation. The most common disease of barley in Finland is net blotch, a foliar disease caused by the ascomycete Pyrenophora teres Drechsler. Disease resistance based on plant genes is an environmentally friendly and economical way to manage plant diseases caused by biotic stresses. Development of a disease resistance breeding programme is dependent on knowledge of the pathogen. In addition to information on the epidemiology and virulence of a pathogen, knowledge on how the pathogen evolves and the nature of the risks that might arise in the future are essential issues that need to be taken into account to achieve the final breeding aims. The main objectives of this study were to establish reliable and efficient testing methods for Pyrenophora teres f. teres virulence screening, and to understand the role of virulence of P. teres f. teres in Finland from a disease resistance breeding point of view. The virulence of P. teres was studied by testing 239 Finnish P. teres f. teres isolates collected between 1994 2007 originating from 19 locations, and 200 P. teres progeny isolates originating from artificially produced P. teres matings. According to the results of this study, screening for P. teres f. teres isolates on barley seedlings under greenhouse conditions is a feasible and cost efficient method to describe the virulence spectrum of the pathogen. Inoculum concentration and the seedling leaf used to gauge virulence had significant effects. Barley grain size, morphological traits of P. teres isolates, spore production and growth rate on agar did not affect the expression of virulence. A common barley differential set to characterize the P. teres virulence was developed and is recommended to be used globally. The virulence spectrum of Finnish P. teres f. teres isolates collected in 1994-2007 was constant both within and between the years. The results indicated differences in the pathogen s aggressiveness and in barley genotypes resistance. However, differences in virulence were rarely significant. Unlike in laboratory conditions, no indications of changes in virulence caused by the sexual reproduction have been observed in Finnish barley fields. In Finland, durable net blotch resistance has been achieved by introducing resistance from other barley varieties using traditional crossing methods, including wide crossing, and testing the breeding material at early generations at several sites under natural infection pressure. Novel resistance is available, which is recommended to minimize the risk of selection of virulent isolates and breakdown of currently deployed resistance.

The Colletotrichum boninense species complex

Although only recently described, Colletotrichum boninense is well established in literature as an anthracnose pathogen or endophyte of a diverse range of host plants worldwide. It is especially prominent on members of Amaryllidaceae, Orchidaceae, Proteaceae and Solanaceae. Reports from literature and preliminary studies using ITS sequence data indicated that C. boninense represents a species complex. A multilocus molecular phylogenetic analysis (ITS, ACT, TUB2, CHS-1, GAPDH, HIS3, CAL) of 86 strains previously identified as C. boninense and other related strains revealed 18 clades. These clades are recognised here as separate species, including C. boninense s. str., C. hippeastri, C. karstii and 12 previously undescribed species, C. annellatum, C. beeveri, C. brassicicola, C. brasiliense, C. colombiense, C. constrictum, C. cymbidiicola, C. dacrycarpi, C. novae-zelandiae, C. oncidii, C. parsonsiae and C. torulosum. Seven of the new species are only known from New Zealand, perhaps reflecting a sampling bias. The new combination C. phyllanthi was made, and C. dracaenae Petch was epitypified and the name replaced with C. petchii. Typical for species of the C. boninense species complex are the conidiogenous cells with rather prominent periclinal thickening that also sometimes extend to form a new conidiogenous locus or annellations as well as conidia that have a prominent basal scar. Many species in the C. boninense complex form teleomorphs in culture. TAXONOMIC NOVELTIES: New combination - Colletotrichum phyllanthi (H. Surendranath Pai) Damm, P.F. Cannon & Crous. Name replacement - C. petchii Damm, P.F. Cannon & Crous. New species - C. annellatum Damm, P.F. Cannon & Crous, C. beeveri Damm, P.F. Cannon, Crous, P.R. Johnst. & B. Weir, C. brassicicola Damm, P.F. Cannon & Crous, C. brasiliense Damm, P.F. Cannon, Crous & Massola, C. colombiense Damm, P.F. Cannon, Crous, C. constrictum Damm, P.F. Cannon, Crous, P.R. Johnst. & B. Weir, C. cymbidiicola Damm, P.F. Cannon, Crous, P.R. Johnst. & B. Weir, C. dacrycarpi Damm, P.F. Cannon, Crous, P.R. Johnst. & B. Weir, C. novae-zelandiae Damm, P.F. Cannon, Crous, P.R. Johnst. & B. Weir, C. oncidii Damm, P.F. Cannon & Crous, C. parsonsiae Damm, P.F. Cannon, Crous, P.R. Johnst. & B. Weir, C. torulosum Damm, P.F. Cannon, Crous, P.R. Johnst. & B. Weir. Typifications: Epitypifications - C. dracaenae Petch.

First report of shoot blight of persimmon caused by Diaporthe neotheicola in Australia

Shoot blight symptom was found on persimmon (Diospyros kaki) in southern Western Australia in December 2010. The pathogen was isolated and identified as Diaporthe neotheicola on the basis of morphology, sequence analysis of the internal transcribed spacer (ITS) and the translation elongation factor 1-α (TEF). A pathogenicity test was conducted and Koch's postulates were fulfilled by re-isolation of the fungus from diseased tissues. This is the first report of D. neotheicola causing shoot blight on persimmon in Australia and worldwide. © 2012 Australasian Plant Pathology Society Inc.

Lack of release of bound anthocyanins and phenolic acids from carrot plant cell walls and model composites during simulated gastric and small intestinal digestion

Separately, polyphenols and plant cell walls (PCW) are important contributors to the health benefits associated with fruits and vegetables. However, interactions with PCW which occur either during food preparation or mastication may affect bioaccessibility and hence bioavailability of polyphenols. Binding interactions between anthocyanins, phenolic acids (PAs) and PCW components, were evaluated using both a bacterial cellulose-pectin model system and a black carrot puree system. The majority of available polyphenols bound to PCW material with 60-70% of available anthocyanins and PAs respectively binding to black carrot puree PCW matter. Once bound, release of polyphenols using acidified methanol is low with only similar to 20% of total anthocyanins to similar to 30% of PAs being released. Less than 2% of bound polyphenol was released after in vitro gastric and small intestinal (S.I.) digestion for both the model system and the black carrot puree PCW matter. Confocal laser scanning microscopy shows localised binding of anthocyanins to PCW. Very similar patterns of binding for anthocyanins and PAs suggest that PAs form complexes with anthocyanins and polysaccharides. Time dependent changes in extractability with acidified methanol but not the total bound fraction suggests that initial nonspecific deposition on cellulose surfaces is followed by rearrangement of the bound molecules. Minimal release of anthocyanins and PAs after simulated gastric and S.I. digestion indicates that polyphenols in fruits and vegetables which bind to the PCW will be transported to the colon where they would be expected to be released by the action of cell wall degrading bacteria.

Binding of polyphenols to plant cell wall analogues - Part 2: Phenolic acids

Bacterial cellulose and cellulose-pectin composites were used as well-defined model plant cell wall (PCW) systems to study the interaction between phenolic acids (PA) derived from purple carrot juice concentrate (PCJC) and PCW components. Significant PA depletion from solution occurred, with pure cellulose initially (30 s-1 h) absorbing more than cellulose-pectin composites in the first hour (ca 20% cf 10-15%), but with all composites absorbing similar levels (ca 30%) after several days. Individual PAs bound to different relative extents with caffeic acid > chlorogenic acid > ferulic acid. Extrapolation of data for these model systems to carrot puree suggests that nutritionally-significant amounts of PAs could bind to cell walls, potentially restricting bioavailability in the small intestine and, as a consequence, delivering PAs to the large intestine for fermentation and metabolism by gut bacteria. (C) 2012 Elsevier Ltd. All rights reserved.

Potential Distribution and Risk Assessment of an Invasive Plant Species: A Case Study of Hymenachne amplexicaulis in Australia

Given the limited resources available for weed management, a strategic approach is required to give the best bang for your buck. The current study incorporates: (1) a model ensemble approach to identify areas of uncertainty and commonality regarding a species invasive potential, (2) current distribution of the invaded species, and (3) connectivity of systems to identify target regions and focus efforts for more effective management. Uncertainty in the prediction of suitable habitat for H. amplexicaulis (study species) in Australia was addressed in an ensemble-forecasting approach to compare distributional scenarios from four models (CLIMATCH; CLIMEX; boosted regression trees [BRT]; maximum entropy [Maxent]). Models were built using subsets of occurrence and environmental data. Catchment risk was determined through incorporating habitat suitability, the current abundance and distribution of H. amplexicaulis, and catchment connectivity. Our results indicate geographic differences between predictions of different approaches. Despite these differences a number of catchments in northern, central, and southern Australia were identified as high risk of invasion or further spread by all models suggesting they should be given priority for the management of H. amplexicaulis. The study also highlighted the utility of ensemble approaches in indentifying areas of uncertainty and commonality regarding the species invasive potential.