Piriformospora indica reduces Fusarium head blight disease severity and mycotoxin DON contamination in wheat under UK weather conditions

Piriformospora indica (Sebacinaceae) is a cultivable root endophytic fungus. It colonises the roots of a wide range of host plants. In many settings colonisation promotes host growth, increases yield and protects the host from fungal diseases. We evaluated the effect of P. indica on Fusarium head blight (FHB) disease of winter (cv. Battalion) and spring (cv. Paragon, Mulika, Zircon, Granary, KWS Willow and KWS Kilburn) wheat and consequent contamination by the mycotoxin deoxynivalenol (DON) under UK weather conditions. Interactions of P. indica with an arbuscular mycorrhizal fungus (Funneliformis mosseae), fungicide application (Aviator Xpro) and low and high fertiliser levels were considered. P. indica application reduced FHB disease severity and incidence by 70%. It decreased mycotoxin DON concentration of winter and spring wheat samples by 70% and 80% respectively. P. indica also increased above ground biomass, 1000 grain weight and total grain weight. P. indica reduced disease severity and increased yield in both high and low fertiliser levels. The effect of P. indica was compatible with F. mosseae and foliar fungicide application. P. indica did not have any effects on plant tissue nutrients. These results suggest that P. indica might be useful in biological control of Fusarium diseases of wheat.

Proposal for a unified nomenclature for target site mutations associated with resistance to fungicides

Evolved resistance to fungicides is a major problem limiting our ability to control agricultural, medical and veterinary pathogens and is frequently associated with substitutions in the amino acid sequence of the target protein. The convention for describing amino-acid substitutions is to cite the wild type amino acid, the codon number and the new amino acid, using the one letter amino acid code. It has frequently been observed that orthologous amino acid mutations have been selected in different species by fungicides from the same mode of action class, but the amino acids have different numbers. These differences in numbering arise from the different lengths of the proteins in each species. The purpose of the current paper is to propose a system for unifying the labelling of amino acids in fungicide target proteins. To do this we have produced alignments between fungicide target proteins of relevant species fitted to a well-studied “archetype” species. Orthologous amino acids in all species are then assigned numerical “labels” based on the position of the amino acid in the archetype protein.

Antioxidant Capacity and Larvicidal and Antifungal Activities of Essential Oils and Extracts from Piper krukoffii

The leaves and twigs of Piper krukoffii, collected in the Carajas National Forest, north Brazil, yielded essential oils (2.0% and 0.8%), the main constituents of which were myristicin (40.3% and 26.7%), apiole (25.4% and 34.1%) and elemicin (2.8% and 3.0%). The antioxidant activities of the oils, methanol extract and its sub-fractions were evaluated. The DPPH EC(50) values varied from the ethyl acetate sub-fraction (73.4 +/- 3.7 mu g/mL) to the methanol extract (24.9 +/- 0.8 mu g/mL), and the ABTS TEAC values ranged in the same order from 265.7 to 349.2 mu Mol TE/g. These results indicated a significant antioxidant activity for the plant. The lignans (-)-kusunokin, yatein, (-)-hinokin and cubebin were identified in the methanol extract. The hydro-methanolic sub-fraction showed a high value for total phenol content (106.5 +/- 0.7 mg GAE/g), as well as (1)H NMR signals for sugar moieties. Crude extracts and sub-fractions were also able to inhibit beta-carotene bleaching, varying from 22.4 to 47.1%. The oils from the leaves and twigs showed strong larvicidal (21.4 and 3.6 mu g/mL) and fungicide (0.5 and 0.1 mu g/mL) activities.

Matrix effects observed during pesticides residue analysis in fruits by GC

The influence of the sample matrix in the CC-electron-capture detection analysis of the pesticides dimethoate, diazinon, chlorothalonil.. parathion methyl and fenitrothion in fruits samples has been studied. Experiments have been carried out where the pesticide responses in standard solutions prepared in selected solvent were compared with their response when present in apple, mango, papaya, banana, pineapple and melon extracts. The presence of matrix effects (MEs) and their extent were shown to be simultaneously influenced by several factors (matrix concentration, matrix type, pesticide concentration, analytical range). Pronounced MEs were observed particularly for dimethoate and diazinon in all matrices tested; in lower concentrations, all pesticides presented significant ME. The other pesticides presented variable ME. Higher ME enhancement was detected at lower pesticide concentration levels of and/or at higher matrix concentration solutions. The ME detected for fenitrothion, in the analytical range evaluated, were dependent on matrix type. For each pesticide, solvent and matrix-matched calibrations were compared for all fruit samples, and it could be concluded that quantitation based on standard solutions prepared in blank matrix extract (matrix-matched calibration) should be used to compensate the MEs and to obtain more accurate results for the pesticides studied.

Characterization of the raw essential oil eugenol extracted from Syzygium aromaticum L.

Eugenol is the main volatile compound extracted oil from clove bud, Syzygium aromaticum L., and used in traditional medicine, as a bactericide, fungicide, anesthetic, and others. Its extraction was performed using hydrodistillation which is the most common extraction technique. Its components and thermal behavior were evaluated using gas chromatography (GC) and differential scanning calorimetry (DSC), which provide a better characterization of these natural compounds. This extracted product was compared to the standard eugenol results. The GC results suggested similar to 90% eugenol was found in the total extracted oil, and some of its boiling characteristics were 270.1 A degrees C for peak temperature and 244.1 J g(-1) for the enthalpy variation.

Use of phosphite as a control for Phytophthora cinnamomi in southeastern Victorian vegetation communities

One of the major aims of the research presented in this thesis was to assist managers of native vegetation communities in southeastern Australia in understanding the dynamics of P. cinnamomi with an important ecological species, Xanthorrhoea australis. It trialed the use of phosphite in large-scale field applications to establish the usefulness of this management option for the first time on Victorian flora. This thesis describes the process of disease development within mature X. Australia plants. For the first time it was shown that within X. australis plants, secondary disease symptoms are related to the percentage of stem that has been infested by the disease. It was evident that after initial invasion the pathogen moves via root xylem and throughout the plant within vascular to the stem, especially within the desmium. The research shows that the pathogen could not be isolated consistently even though it was considered to be responsible for disease symptoms. Trials of a control fungicide (Foli-R-fos 200) shows that protection occurs in many susceptible plants when 2 and 6g a.i./L phosphite is applied. Phytotoxicity occurred in native plants at Anglesea and within controlled environment trials when using ≥ 6g a.i./L. It will be shown that 2g a.i./L phosphite controls disease in sprayed plots within heathlands at Anglesea and a recently burnt coastal woodland community at Wilson’s Promontory. The proportion of healthy X. australis plants treated with phosphite was significantly higher than the proportion in control plots without phosphite. The research shows that phosphite was recovered from leaves of three species treated with Foli-R-fos 200 in the field. For the first time it has been shown that seed germination was reduced in two species when high concentrations of phosphite were applied. The first documentation of the effect that phosphite has on soil properties showed that nitrogen and oxidised organic carbon were the only parameters to alter significantly. This thesis provides answers to some important questions, answers that can now be used by managers in formulating better policies and actions at an operational level. There has been a dire need in Victoria to address many issues regarding P. cinnamomi and this thesis provides relevant and informative approaches to disease control, and a better understanding of the disease progress.

Aspects of the interaction between Xanthorrhoea australis and Phytophthora cinnamomi in south-western Victoria, Australia

Diseases in natural ecosystems are often assumed to be less severe than those observed in domestic cropping systems due to the extensive biodiversity exhibited in wild vegetation communities. In Australia, it is this natural biodiversity that is now under threat from Phytophthora cinnamomi. The soilborne Oomycete causes severe decline of native vegetation communities in south-western Victoria, Australia, disrupting the ecological balance of native forest and heathland communities. While the effect of disease caused by P. cinnamomi on native vegetation communities in Victoria has been extensively investigated, little work has focused on the Anglesea healthlands in south-western Victoria. Nothing is known about the population structure of P. cinnamomi at Anglesea. This project was divided into two main components to investigate fundamental issues affecting the management of P. cinnamomi in the Anglesea heathlands. The first component examined the phenotypic characteristics of P. cinnamomi isolates sampled from the population at Anglesea, and compared these with isolates from other regions in Victoria, and also from Western Australia. The second component of the project investigated the effect of the fungicide phosphonate on the host response following infection by P. cinnamomi. Following soil sampling in the Anglesea heathlands, a collection of P, cinnamomi isolates was established. Morphological and physiological traits of each isolate were examined. All isolates were found to be of the A2 mating type. Variation was demonstrated among isolates in the following characteristics: radial growth rate on various nutrient media, sporangial production, and sporangial dimensions. Oogonial dimensions did not differ significantly between isolates. Morphological and physiological variation was rarely dependant on isolate origin. To examine the genetic diversity among isolates and to determine whether phenotypic variation observed was genetically based, Random Amplified Polymorphic DNA (RAPD) analyses were conducted. No significant variation was observed among isolates based on an analysis of molecular variance (AMQVA). The results are discussed in relation to population biology, and the effect of genetic variation on population structure and population dynamics. X australis, an arborescent monocotyledon indigenous to Australia, is highly susceptible to infection by P. cinnamomi. It forms an important component of the heathland vegetation community, providing habitat for native flora and fauna, A cell suspension culture system was developed to investigate the effect of the fungicide phosphonate on the host-pathogen interaction between X. australis and P. cinnamomi. This allowed the interaction between the host and the pathogen to be examined at a cellular level. Subsequently, histological studies using X. australis seedlings were undertaken to support the cellular study. Observations in the cell culture system correlated well with those in the plant. The anatomical structure of X australis roots was examined to assist in the interpretation of results of histopathological studies. The infection of single cells and roots of X. australis, and the effect of phosphonate on the interaction are described. Phosphonate application prior to inoculation with P. cinnamomi reduced the infection of cells in culture and of cells in planta. In particular, phosphonate was found to stimulate the production of phenolic material in roots of X australis seedlings and in cells in suspension cultures. In phosphonate-treated roots of X australis seedlings, the deposition of electron dense material, possibly lignin or cellulose, was observed following infection with P. cinnamomi. It is proposed that this is a significant consequence of the stimulation of plant defence pathways by the fungicide. Results of the study are discussed in terms of the implications of the findings on management of the Anglesea heathlands in Victoria, taking into account variation in pathogen morphology, pathogenicity and genotype. The mode of action of phosphonate in the plant is discussed in relation to plant physiology and biochemistry.

Utilization of a new bdelloid rotifer (Philodina acuticornis odiosa) assay to evaluate the effect of salinity on the toxicity of chlorothalonil

Acute (24 h) toxicity tests were conducted to determine the toxicity of the fungicide chlorothalonil towards the freshwater bdelloid rotifer (Philodina acuticornis odiosa). Since rotifers are the dominant zooplankton species in many inland freshwater lakes in Australia, the influence of salinity on chlorothalonil toxicty was also assessed. The rotifers used in this study appeared to be reasonably tolerant to changes in salinity, with little mortality observed at 3760 µS cm-1, increasing thereafter at higher salinity. The bdelloid rotifers were, however, found to be highly sensitive to chlorothalonil (24 h LC50, 3.2 µg L-1) with results also suggesting that as salinity increases, so does toxicity (e.g., 24 h LC50 at 5000 µS cm-1, 0.5 µg L-1).

Copper levels in buccal cells of vineyard workers engaged in various activities

Objectives: Copper-based compounds have been used as agricultural fungicides for many years. Their use in Australia is escalating with increase in the scale of planting and associated pest problems. The objective of this study was to identify viticulture activities associated with high exposure to foliage sprays. It would be determined if occupational exposure of vineyard workers to copper-based sprays was associated with raised body copper levels through analysis of saliva and buccal cells.

Methods: The activities of six vineyard workers from four vineyards in the Yarra Valley Victoria, Australia, were monitored over a period of 2 years. During this period, workers carried out seasonal activities, including fungicide spraying, canopy management, and tractor operation. Saliva and buccal cells from workers were collected and analysed for copper levels that were then correlated with the different types of vineyard activity.

Results: The buccal cells of vineyard workers exposed to copper through seasonal activities including fungicide spraying, canopy management, and tractor operation contained copper levels of 0.87, 1.24, and 0.95 ng Cu per 106 cells, respectively. This was up to 10-fold higher than the copper levels in buccal cells from the control subjects (0.1 ng Cu per 106). Copper levels in buccal cells from workers participating in other viticulture activities such as shoot thinning, bunch counting, and disbudding were not significantly different from those of control subjects. The levels of copper in saliva samples of both workers undertaking any vineyard activity and control subjects were below the level of detection.

Conclusions: Seasonal activities undertaken in vineyards that involved direct contact with copper, in particular canopy management, fungicidal spraying, and tractor operation were associated with high copper levels in buccal cells of workers. This indicates that copper derived from copper-based fungicidal compounds is accumulated within body cells. The lack of detectable copper levels in saliva suggests that the route of transport of copper into buccal cells is not through saliva. The results indicate potential adverse health risks associated with use of copper fungicide. Recommendations are made in relation to the precautions that should be taken in relation to use of copper sprays and to validate buccal cells as an indicator of body copper status.

Viabilidade e frigoconservação de borbulhas de citros

Este trabalho teve como objetivo estudar a manutenção da viabilidade das borbulhas de laranjeira ‘Valência’ e tangerineira ‘Montenegrina’, oriundas de ambiente protegido e pomar, sob diferentes processos de desinfestação e períodos de armazenamento em câmara fria, assim como avaliar o comportamento das substâncias de reserva contidas nos ramos porta-borbulhas nos diferentes períodos de armazenamento. Com estes objetivos foram conduzidos dois experimentos em câmara fria com temperatura em torno de 5ºC. No experimento 1, testou-se borbulhas de duas cultivares de citros oriundas de ambiente protegido, três tratamentos químicos (testemunha, 1x tratado com Captan e 2x tratado com Captan na dose de 10g/L) e três períodos de armazenamento (0, 90, e 180 dias), com quatro repetições. No experimento 2, testou-se borbulhas de duas cultivares de citros oriundas do pomar de citros, três tratamentos químicos (testemunha, 1x tratado com Captan e 2x tratado com Captan na dose de 10g/L) e cinco períodos de armazenamento (0, 45, 90, 135 e 180 dias), com quatro repetições. As borbulhas da cultivar Montenegrina, mantiveram-se viáveis por 90 dias sem tratamento com fungicida e por, no mínimo, 180 dias se submetidas a 1 tratamento com fungicida no momento de seu armazenamento. As borbulhas da cultivar Valência, coletadas de ambiente protegido, mantiveram-se viáveis por, no mínimo, 180 dias sem a necessidade de tratamento com fungicida. As substâncias de reserva dos ramos porta-borbulhas sofreram redução ao longo do armazenamento.

Prácticas culturales para el manejo de la Sigatoka negra en bananos y plátanos

Black sigatoka (Mycosphaerella fijiensis) control consists in the continuous use of fungicide sprays and cultural practices. Cultural control reduces inoculum sources of the pathogen and favorable environmental conditions for its development, as well as it increases the vigor of the plants. In order to manage the disease it is necessary to know its behavior through the time, its relationship with the weather and the crop management. The most important cultural practice to reduce the inoculum source is the removal of the whole affected leaves or only the diseased portions of the leaves. The removed tissue is placed over the ground and the use of urea is feasible to accelerate its decomposition. An alternative practice is the "mini-composting" that consists in forming small heaps with the dead leaves and harvested plants for its quick degradation, which allows to reduce the pathogen inoculum and to incorporate nutrients and organic matters into the soil. The early pruning of the tips of the Young leaves before they show symptoms of the disease and the quick elimination of harvested plants reduce the inoculum. Also, the agronomic management of the crop helps to reduce the favorable conditions and to increase the vigor of the plants: this management considers plantation density, drainage systems, irrigation methods, control of weeds, chemical-biological fertilization, and nematode control.

Respostas fisiológicas em mudas de banananeira tratadas com estrobilurinas

There are reports that strobilurin besides having a fungicide effect can promote physiologic benefits to the plants. However, this effect on banana plants was not studied yet. The objective of the present study was to evaluate the effect of strobirulins on the physiology of banana plantlets. For this purpose, cultivar Grand Naine banana plantlets were transferred to pots containing substrate and kept in a nursery with 50% shading. The experimental design was a completely randomized design with three treatments (water, azoxystrobin and pyraclostrobin) and five replications. The treatments were applied at 15, 30, 45, 60 and 75 days after transplanting at a dose 100 g a. i. ha(-1) with manual spray. Plant height, pseudostem diameter, shoot dry matter in strobilurin treated plants were higher than the untreated plants, however, the effect of fungicide treatment was different, being the most pronounced effect of pyraclostrobin compared to azoxystrobin. Plants treated with pyraclostrobin had higher leaf area, nitrate reductase activity and chlorophyll content of leaf total nitrogen than the plants treated with azoxystrobin and water, which did not differ. Strobilurins affect the physiology of the banana plantlets differently, the effect being more pronounced by pyraclostrobin.

Desempenho de sementes de algodão tratadas quimicamente e armazenadas

Considerando que o armazenamento desempenha papel decisivo na manutenção da qualidade da semente, desenvolveu-se este trabalho com o objetivo de avaliar a qualidade fisiológica e fitossanitária de sementes de algodão, tratadas quimicamente e armazenadas por doze meses. Foram utilizados dois lotes de sementes de algodão cv. DeltaPine-AC90, deslintados quimicamente, que foram submetidos aos tratamentos fungicidas e inseticidas: testemunha; Disulfoton + Carboxin + Thiram; Carbofuran + Carboxin + Thiram; Imidacloprid + Tolylfluanid + Pencycuron. As sementes foram armazenadas em armazém sem controle de temperatura e umidade relativa do ar. Foram retiradas amostras de sementes no início do armazenamento e a cada dois meses e avaliadas quanto ao teor de água, à porcentagem de germinação, ao vigor (testes de envelhecimento acelerado e de germinação à baixa temperatura), à sanidade e à emergência das plântulas. O delineamento utilizado foi o inteiramente casualizado, em esquema fatorial, com quatro repetições. Verificou-se redução da germinação e do vigor de sementes em função do armazenamento. A redução da qualidade fisiológica associou-se com o aumento na ocorrência de Aspergillus sp. e Penicillium sp. nas sementes. A manutenção da qualidade de sementes de algodão foi obtida até o oitavo mês de armazenagem, podendo-se concluir que: a eficiência do tratamento químico de sementes de algodão depende da combinação de produtos utilizados; não se deve tratar com fungicida sementes de algodão com baixo nível de vigor; a ocorrência dos fungos Aspergillus sp. e Penicillium sp. aumentou com o período de armazenamento nas sementes sem tratamento e que a manutenção da qualidade de sementes de algodão para comercialização depende da sua qualidade inicial e do período de armazenamento.

Técnicas de análise multivariada na avaliação de injúrias pelo frio em mangas cv. Tommy Atkins

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

The effects of inter-crop cultivation Between rows of citrus crop on spreading of Guignardia citricarpa Ascospores and in the citrus black spot occurrence

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