'Candidatus Liberibacter brunswickensis' colonization has no effect to the early development of Solanum melongena.

This study is the first to investigate the presence and movement of the novel Liberibacter species 'Candidatus Liberibacter brunswickensis' (CLbr) in eggplant, Solanum melongena. The psyllid, Acizzia solanicola can transmit CLbr to eggplant and CLbr can be acquired by CLbr-negative A. solanicola individuals from CLbr-positive eggplants. In planta, CLbr can replicate, move and persist. Investigation into the early development of eggplants showed that CLbr titres had increased at the inoculation site at 14 days post inoculation access period (DPIAP). CLbr had become systemic in the majority of plants tested by 28 DPIAP. The highest bacterial titres were recorded at 35 DPIAP in all samples of the inoculated leaf, the roots, stems and the midrib and petiole samples of the newest leaf (the top leaf). This finding strongly suggests that CLbr movement in planta follows the source to sink relationship as previously described for 'Ca. Liberibacter asiaticus' (CLas) and 'Ca. Liberibacter solanacearum' (CLso). No symptoms consistent with Liberibacter-associated diseases were noted for plants colonised by CLbr during this study, consistent with the hypothesis that CLbr does not cause disease of eggplant during the early stages of host colonisation. In addition, no significant differences in biomass were found between eggplant colonised with CLbr, compared to those that were exposed to CLbr-negative A. solanicola, and to control plants.

Current issues involved with the identification and nutritional value of wood grubs consumed by Australian Aborigines.

The so called witchetty grub is a publicized food source for Australian Aborigines. Despite heavy use, the identities and number of species consumed is still not known because of the lack of identified voucher specimens. Taxonomy based on adults makes identification of larval forms difficult. Dwelling in the root, trunks, and stems of woody plants, grubs are a reliable and highly valued food source that may be in decline. Much information on edible insects may already be lost in parts of Australia heavily settled by Europeans. However, there are many parts of Australia where information on edible insects is still strong and needs to be recorded accurately for long-term use. Recent identification of "witchetty grubs" from the witchetty bush at Barrow Creek has revealed that those there, based on their DNA, are not Endoxyla leucomochla. As grubs are collected and eaten before they mature and scientific taxonomy is based on adults, there are many unanswered questions on the grub identification and biology, host plants, and plant and grub distributions.

Virus incidence in wheat increases under elevated CO2: A 4-year study of yellow dwarf viruses from a free air carbon dioxide facility.

The complexities behind the mechanisms associated with virus-host-vector interactions of vector-transmitted viruses, and their consequences for disease development need to be understood to reduce virus spread and disease severity. Climate has a substantial effect on viruses, vectors, host plants and their interactions. Increased atmospheric carbon dioxide (CO2) is predicted to impact the interactions between them. This study, conducted under ambient and elevated CO2 (550µmolmol-1), in the Australian Grains Free Air Carbon Enrichment facility reports on natural yellow dwarf virus incidence on wheat (including Barley/Cereal yellow dwarf viruses (B/CYDV)). A range of wheat cultivars was tested using tissue blot immunoassay to determine the incidence of four yellow dwarf virus species from 2013 to 2016. In 2013, 2014 and 2016, virus incidence was high, reaching upwards of 50%, while in 2015 it was relatively low, with a maximum incidence of 3%. Across all years and most cultivars, BYDV-PAV was the most prevalent virus species. In the years with high virus incidence, a majority plots with the elevated levels of CO2 (eCO2) were associated with increased levels of virus relative to the plots with ambient CO2. In 2013, 2014 and 2016 the recorded mean percent virus incidence was higher under elevated CO2 when compared to ambient CO2 by 33%, 14% and 34%, respectively. The mechanism behind increased yellow dwarf virus incidence under elevated CO2 is not well understood. Potential factors involved in the higher virus incidence under elevated CO2 conditions are discussed.

Acizzia solanicola (Hemiptera: Psyllidae) probing behaviour on two Solanum spp. and implications for possible pathogen spread.

Piercing-sucking insects are vectors of plant pathogens, and an understanding of their feeding behaviour is crucial for studies on insect population dynamics and pathogen spread. This study examines probing behaviour of the eggplant psyllid, Acizzia solanicola (Hemiptera: Psyllidae), using the electrical penetration graph (EPG) technique, on two widespread and common hosts: eggplant (Solanum melongena) and tobacco bush (S. mauritianum). Six EPG waveforms were observed: waveform NP (non-probing phase), waveform C (pathway phase), G (feeding activities in xylem tissues), D (first contact with phloem tissues), E1 (salivation in the sieve elements) and E2 (ingestion from phloem tissues). Results showed that A. solanicola is predominantly a phloem feeder and time spent in salivation and ingestion phases (E1 and E2) differed between hosts. Feeding was enhanced on eggplant compared to tobacco bush which showed some degree of resistance, as evidenced by shorter periods of phloem ingestion, a higher propensity to return to the pathway phase once in the sieve elements and higher number of salivation events on tobacco bush. We discuss how prolonged phloem feeding could indicate the potential for A. solanicola to become an important pest of eggplant and potential pathogen vector.

Novel 'Candidatus Liberibacter' species identified in the Australian eggplant psyllid, Acizzia solanicola.

A novel candidate species of the liberibacter genus, 'Candidatus Liberibacter brunswickensis' (CLbr), was identified in the Australian eggplant psyllid, Acizzia solanicola. This is the first discovery of a species belonging to the liberibacter genus in Australia and the first report of a liberibacter species in the psyllid genus Acizzia. This new candidate liberibacter species has not been associated with plant disease, unlike other psyllid-vectored species in the genus including 'Candidatus Liberibacter asiaticus' (CLas), 'Candidatus Liberibacter africanus' (CLaf) and 'Ca. Liberibacter solanacearum' (CLso). This study describes novel generic liberibacter genus primers, used to screen Australian psyllids for the presence of microflora that may confound diagnosis of exotic pathogens. CLbr forms a unique clade in the liberibacter genus based on phylogenetic analysis of the 16S ribosomal ribonucleic acid (rRNA) region and multilocus sequence analysis (MLSA) of seven highly conserved genes, dnaG, gyrB, mutS, nusG, rplA, rpoB and tufB. The MLSA mapping approach described in this article was able to discriminate between two 'Ca. Liberibacter' species within a metagenomic data set and represents a novel approach to detecting and differentiating unculturable species of liberibacter. Further, CLbr can confound the Li et al. (2006) quantitative PCR (qPCR) diagnostic tests for CLas and CLaf.

A Review of Perennial Ryegrass Endophytes and Their Potential Use in the Management of African Black Beetle in Perennial Grazing Systems in Australia.

The major insect pest of Australian cool temperate pastures is the root-feeding insect Heteronychus arator (African black beetle, ABB). Significant pasture damage can occur even at low ABB densities (11 individuals per square meter), and often re-sowing of the whole paddock is required. Mitigation of the effects of pasture pests, and in particular subterranean species such as the larval form of ABB, can be challenging. Early detection is limited by the ability to visualize above-ground symptoms, and chemical control of insects in soil is often ineffective. This review takes a look at the historical events that molded the pastoral landscape in Australia. The importation route, changes in land management and pasture composition by European settlers may have aided the establishment of ABB in Australia. Perennial ryegrass Lolium perenne is discussed as it is one of the most important perennial agricultural grasses and is widely-sown in moderate-to-high-rainfall temperate zones of the world. Endophytic fungi from the genus Epichloë form symbiotic relationships with cool season grasses such as Lolium perenne (perennial ryegrass). They have been studied extensively and are well documented for enhancing persistence in pasture via a suite of bioactive secondary metabolites produced by the fungal symbionts. Several well-characterized secondary metabolites are discussed. Some can have negative effects on cattle (e.g., ergovaline and lolitrems) while others have been shown to benefit the host plant through deterrence of insect pests from feeding and by insecticidal activity (e.g., peramine, lolines, ergopeptines). Various control methods for ABB are also discussed, with a focus on the potential role of asexual Epichloë endophytes.

Virus infection mediates the effects of elevated CO2 on plants and vectors.

Atmospheric carbon dioxide (CO2) concentration has increased significantly and is projected to double by 2100. To increase current food production levels, understanding how pests and diseases respond to future climate driven by increasing CO2 is imperative. We investigated the effects of elevated CO2 (eCO2) on the interactions among wheat (cv. Yitpi), Barley yellow dwarf virus and an important pest and virus vector, the bird cherry-oat aphid (Rhopalosiphum padi), by examining aphid life history, feeding behavior and plant physiology and biochemistry. Our results showed for the first time that virus infection can mediate effects of eCO2 on plants and pathogen vectors. Changes in plant N concentration influenced aphid life history and behavior, and N concentration was affected by virus infection under eCO2. We observed a reduction in aphid population size and increased feeding damage on noninfected plants under eCO2 but no changes to population and feeding on virus-infected plants irrespective of CO2 treatment. We expect potentially lower future aphid populations on noninfected plants but no change or increased aphid populations on virus-infected plants therefore subsequent virus spread. Our findings underscore the complexity of interactions between plants, insects and viruses under future climate with implications for plant disease epidemiology and crop production.

Virus disease in wheat predicted to increase with a changing climate.

Current atmospheric CO2 levels are about 400 µmol mol(-1) and are predicted to rise to 650 µmol mol(-1) later this century. Although the positive and negative impacts of CO2 on plants are well documented, little is known about interactions with pests and diseases. If disease severity increases under future environmental conditions, then it becomes imperative to understand the impacts of pathogens on crop production in order to minimize crop losses and maximize food production. Barley yellow dwarf virus (BYDV) adversely affects the yield and quality of economically important crops including wheat, barley and oats. It is transmitted by numerous aphid species and causes a serious disease of cereal crops worldwide. This study examined the effects of ambient (aCO2 ; 400 µmol mol(-1) ) and elevated CO2 (eCO2 ; 650 µmol mol(-1) ) on noninfected and BYDV-infected wheat. Using a RT-qPCR technique, we measured virus titre from aCO2 and eCO2 treatments. BYDV titre increased significantly by 36.8% in leaves of wheat grown under eCO2 conditions compared to aCO2 . Plant growth parameters including height, tiller number, leaf area and biomass were generally higher in plants exposed to higher CO2 levels but increased growth did not explain the increase in BYDV titre in these plants. High virus titre in plants has been shown to have a significant negative effect on plant yield and causes earlier and more pronounced symptom expression increasing the probability of virus spread by insects. The combination of these factors could negatively impact food production in Australia and worldwide under future climate conditions. This is the first quantitative evidence that BYDV titre increases in plants grown under elevated CO2 levels.

The effect of elevated temperature on Barley yellow dwarf virus-PAV in wheat.

Barley yellow dwarf virus-PAV (BYDV-PAV) is associated with yellow dwarf disease, one of the most economically important diseases of cereals worldwide. In this study, the impact of current and future predicted temperatures for the Wimmera wheat growing district in Victoria, Australia on the titre of BYDV-PAV in wheat was investigated. Ten-day old wheat (Triticum aestivum, cv. Yitpi) seedlings were inoculated with BYDV-PAV and grown at ambient (5.0-16.1°C, night-day) or elevated (10.0-21.1°C, night-day) temperature treatments, simulating the current Wimmera average and future daily temperature cycles, respectively, during the wheat-growing season. Whole above-ground plant samples were collected from each temperature treatment at 0 (day of inoculation), 3, 6, 9, 12, 15, 18, 21 and 24 days after inoculation and the titre of BYDV-PAV was measured in each sample using a specific one-step multiplex normalised reverse transcription quantitative PCR (RT-qPCR) assay. Physical measurements, including plant height, dry weight and tiller number, were also taken at each sampling point. The titre of BYDV-PAV was significantly greater in plants grown in the elevated temperature treatment than in plants grown in the ambient treatment on days 6, 9 and 12. Plants grown at elevated temperature were significantly bigger and symptoms associated with BYDV-PAV were visible earlier than in plants grown at ambient temperature. These results may have important implications for the epidemiology of yellow dwarf disease under future climates in Australia.

Reducing the impact of pesticides on biological control in Australian vineyards: pesticide mortality and fecundity effects on an indicator species, the predatory mite Euseius victoriensis (Acari: Phytoseiidae).

Laboratory bioassays on detached soybean, Glycine max (L.) Merr., leaves were used to test 23 fungicides, five insecticides, two acaricides, one herbicide, and two adjuvants on a key Australian predatory mite species Euseius victoriensis (Womersley) in "worst-case scenario" direct overspray assays. Zero- to 48-h-old juveniles, their initial food, and water supply were sprayed to runoff with a Potter tower; spinosad and wettable sulfur residues also were tested. Tests were standardized to deliver a pesticide dose comparable with commercial application of highest label rates at 1,000 liter/ha. Cumulative mortality was assessed 48 h, 4 d, and 7 d after spraying. Fecundity was assessed for 7 d from start of oviposition. No significant mortality or fecundity effects were detected for the following compounds at single-use application at 1,000 liter/ha: azoxystrobin, Bacillus thuringiensis (Bt) subsp. kurstaki, captan, chlorothalonil, copper hydroxide, fenarimol, glyphosate, hexaconazole, indoxacarb, metalaxyl/copper hydroxide, myclobutanil, nonyl phenol ethylene oxide, phosphorous acid, potassium bicarbonate, pyraclostrobin, quinoxyfen, spiroxamine, synthetic latex, tebufenozide, triadimenol, and trifloxystrobin. Iprodione and penconazole had some detrimental effect on fecundity. Canola oil as acaricide (2 liter/100 liter) and wettable sulfur (200 g/100 liter) had some detrimental effect on survival and fecundity and cyprodinil/fludioxonil on survivor. The following compounds were highly toxic (high 48-h mortality): benomyl, carbendazim, emamectin benzoate, mancozeb, spinosad (direct overspray and residue), wettable sulfur (> or = 400 g/100 liter), and pyrimethanil; pyrimethanil had no significant effect on fecundity of surviving females. Indoxacarb safety to E. victoriensis contrasts with its toxicity to key parasitoids and chrysopid predators. Potential impact of findings is discussed.

Phylogenetic relationships of Malvatheca (Bombacoideae and Malvoideae; Malvaceae sensu lato) as inferred from plastid DNA sequences.

Previous molecular phylogenetic analyses have revealed that elements of the former families Malvaceae sensu stricto and Bombacaceae together form a well-supported clade that has been named Malvatheca. Within Malvatheca, two major lineages have been observed; one, Bombacoideae, corresponds approximately to the palmate-leaved Bombacaceae, and the other, Malvoideae, includes the traditional Malvaceae (the mallows or Eumalvoideae). However, the composition of these two groups and their relationships to other elements of Malvatheca remain a source of uncertainty. Sequence data from two plastid regions, ndhF and trnK/matK, from 34 exemplars of Malvatheca and six outgroups were analyzed. Parsimony, likelihood, and Bayesian analyses of the sequence data provided a well-resolved phylogeny except that relationships among five lineages at the base of Malvatheca are poorly resolved. Nonetheless, a 6-bp insertion in matK suggests that Fremontodendreae is sister to the remainder of Malvatheca. Our results suggest that the Malvoideae originated in the Neotropics and that a mangrove taxon dispersed across the Pacific from South America to Australasia and later radiated out of Australasia to give rise to the ca. 1700 living species of Eumalvoideae. Local clock analyses imply that the plastid genome underwent accelerated molecular evolution coincident with the dispersal out of the Americas and again with the radiation into the three major clades of Eumalvoideae.

AFLP phylogeny of Mimulus section Erythranthe and the evolution of hummingbird pollination.

Species in Mimulus section Erythranthe (monkeyflowers) have become model systems for the study of the genetic basis of ecological adaptations. In this study, we pursued two goals. First, we reconstructed the phylogeny of species in Erythranthe using both DNA sequences from the ribosomal DNA ITS and ETS and AFLPs. Data from rDNA sequences support the monophyly of the section, including M. parishii, but provide little support for relationships within it. Analyses using AFLP data resulted in a well-supported hypothesis of relationships among all Erythranthe species. Our second goal was to reconstruct ancestral pollination syndromes and ancestral states of individual characters associated with hummingbird-pollinated flowers. Both parsimony and likelihood approaches indicate that hummingbird pollination evolved twice in Erythranthe from insect-pollinated ancestors. Our reconstruction of individual characters indicates that corolla color and some aspects of corolla shape change states at the same point on the phylogenetic tree as the switch to hummingbird pollination; however, a switch to secretion of high amounts of nectar does not. Floral trait transformation may have been more punctuational than gradual.