Diversity among bacteria causing blotch disease on the commercial mushroom, agaricus bisporus /

A total of 251 bacterial isolates were isolated from blotched mushroom samples obtained from various mushroom farms in Canada. Out of 251 stored isolates, 170 isolates were tested for pathogenicity on Agaricus bisporus through mushroom rapid pitting test with three distinct pathotypes observed: dark brown, brovm and yellow/yellow-brown blotch. Phenotypic analysis of 83 isolates showed two distinct proteinase K resistant peptide profiles. Profile group A isolates exhibited peptides with masses of 45, 18, 16 and 14 kDa and fiirther biochemical tests identified them as Pseudomonasfluorescens III and V. Profile group B isolates lacked the 16-kDa peptide and the blotch causing bacterial isolates of this group was identified as Serratia liquefaciens and Cedecea davisae. Comparative genetic analysis using Amplified Fragment Length Polymorphism (AFLP) on 50 Pseudomonas sp. isolates (Group A) showed that various blotch symptoms were caused by isolates distributed throughout the Pseudomonas sp. clusters with the exception of the Pseudomonas tolaasii group and one non-pathogenic Pseudomonas fluorescens cluster. These results show that seven distinct Pseudomonas sp. genotypes (genetic clusters) have the ability to cause various symptoms of blotch and that AFLP can discriminate blotch causing from non-blotch causing Pseudomonasfluorescens. Therefore, a complex of diverse bacterial organisms causes bacterial blotch disease

Cell wall degrading enzymes and interaction between Trichoderma Aggressivum and Agaricus Bisporus

Agaricus bisporus is the most commonly cultivated mushroom in North America and has a great economic value. Green mould is a serious disease of A. bisporus and causes major reductions in mushroom crop production. The causative agent of green mould disease in North America was identified as Trichoderma aggressivum f. aggressivum. Variations in the disease resistance have been shown in the different commercial mushroom strains. The purpose of this study is to continue investigations of the interactions between T. aggressivum and A. bisporus during the development of green mould disease. The main focus of the research was to study the roles of cell wall degrading enzymes in green mould disease resistance and pathogenesis. First, we tried to isolate and sequence the N-acetylglucosaminidase from A. bisporus to understand the defensive mechanism of mushroom against the disease. However, the lack of genomic and proteomic information of A. bisporus limited our efforts. Next, T. aggressivum cell wall degrading enzymes that are thought to attack Agaricus and mediate the disease development were examined. The three cell wall degrading enzymes genes, encoding endochitinase (ech42), glucanase (fJ-1,3 glucanase) and protease (prb 1), were isolated and sequenced from T. aggressivum f. aggressivum. The sequence data showed significant homology with the corresponding genes from other fungi including Trichoderma species. The transcription levels of the three T. aggressivum cell wall degrading enzymes were studied during the in vitro co-cultivation with A. bisporus using R T -qPCR. The transcription levels of the three genes were significantly upregulated compared to the solitary culture levels but were upregulated to a lesser extent in co-cultivation with a resistant strain of A. bisporus than with a sensitive strain. An Agrobacterium tumefaciens transformation system was developed for T. aggressivum and was used to transform three silencing plasmids to construct three new T. aggressivum phenotypes, each with a silenced cell wall degrading enzyme. The silencing efficiency was determined by RT-qPCR during the individual in vitro cocultivation of each of the new phenotypes with A. bisporus. The results showed that the expression of the three enzymes was significantly decreased during the in vitro cocultivation when compared with the wild type. The phenotypes were co-cultivated with A. bisporus on compost with monitoring the green mould disease progression. The data indicated that prbi and ech42 genes is more important in disease progression than the p- 1,3 glucanase gene. Finally, the present study emphasises the role of the three cell wall degrading enzymes in green mould disease infection and may provide a promising tool for disease management.

Protein subcellular targeting inTrichoderma aggressivum f. aggressivum

Trichoderma aggressivum f. aggressivum is a filamentous soil fungus. Green mold disease of commercial mushrooms caused by this species in North America has resulted in millions of dollars in lost revenue within the mushroom growing industry. Research on the molecular level of T aggressivum have jus t begun with the goal of understanding the functions of each gene and protein, and their expression control. Protein targeting has not been well studied in this species yet. Therefore, the intent of this study was to test the protein localization and production levels in T aggressivum with green fluorescent protein (GFP) with an intron and tagged with either nuclear localization signal (NLS) or an endoplasmic reticulum retention signal (KDEL). Two GFP constructs (with and without the intron) were used as controls in this study. All four constructs were successfully transferred into T aggressivum and all modified strains showed similar growth characteristics as the wild type non-transformed isolate. GFP expression was detected from all modified T aggressivum with confocal microscopy and the expression was similar in all four strains. The intron tested in this study had no or very minor effects as GFP expression was similar with or without it. The GFP signal increased over a 5 day period for all transformants, while the GFP to total protein ratio decreased over the same period for all transformants. The GFP-KDEL transformant showed similar protein expression level and localization as did the control transformant lacking the KDEL retention signal. The GFP-NLS transformant similarly failed to localize GFP into nucleus as fluorescence with this strain was virtually identical to the GFP transformant lacking the NLS. Thus, future research is required to find effective localization signals for T aggressivum.

Modelling disease spread and control in networks: implications for plant sciences

Networks are ubiquitous in natural, technological and social systems. They are of increasing relevance for improved understanding and control of infectious diseases of plants, animals and humans, given the interconnectedness of today's world. Recent modelling work on disease development in complex networks shows: the relative rapidity of pathogen spread in scale-free compared with random networks, unless there is high local clustering; the theoretical absence of an epidemic threshold in scale-free networks of infinite size, which implies that diseases with low infection rates can spread in them, but the emergence of a threshold when realistic features are added to networks (e.g. finite size, household structure or deactivation of links); and the influence on epidemic dynamics of asymmetrical interactions. Models suggest that control of pathogens spreading in scale-free networks should focus on highly connected individuals rather than on mass random immunization. A growing number of empirical applications of network theory in human medicine and animal disease ecology confirm the potential of the approach, and suggest that network thinking could also benefit plant epidemiology and forest pathology, particularly in human-modified pathosystems linked by commercial transport of plant and disease propagules. Potential consequences for the study and management of plant and tree diseases are discussed.

Atividade antagônica in vitro de isolados de Trichoderma spp. ao fungo Phytophthora citrophthora

Gummosis is among the main fungal diseases of the citrus. It is caused by Phytophthora sp. and usually shows up in the lap of the plant, provoking rottenness and gum exudation, and expands causing the plant death for constrictions in the cambium or phloem which interrupts the descending flow of sap. The objective of this work was to evaluate the antagonistic in vitro activity of Trichoderma spp. to the fungi Phytophthora citrophthora. Phytophthora citrophthora was exposed to five environments of antagonism (without antagonist and with four strains of Trichoderma viride, T. virens, T. harzianu and T stromaticum), The in vitro essay was accomplished through the method of paired cultures. A completely randomized desing was used with five treatments and three replications, and each plot was represented by three petri dishes. The isolates of Trichoderma demonstrated significant effect in the inhibition of the mycelial growth of the fungi Phytophthora citrophthora, and the fungi Trichoderma stromaticum presented larger antagonism to the fungi P. citrophthora while the T harzianum presented antagonism smaller.

Impacto do aumento da concentração de CO2 atmosférico sobre o período latente e o controle biológico da ferrugem do cafeeiro

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Ocorrência de viroses em mandioquinha-salsa (Arracacia xanthorrhiza brancroft) nas principais regiões produtoras do Brasil

Pós-graduação em Agronomia (Proteção de Plantas) - FCA

Controle biológico como componente do manejo integrado de doenças fúngicas em begônia

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Potyvirus: caracterização parcial de espécies em plantas daninhas associadas a cultura do pimentão, avaliação de genótipos de alface e análise subcelular do eIF4E e de proteínas do Lettuce mosaic virus

Pós-graduação em Agronomia (Proteção de Plantas) - FCA

Efeito de fontes de matéria orgânica sobre a ferrugem em mudas de cafeeiro

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

Viroses do alho: métodos de diagnose e degenerescência do alho semente livre de vírus

Pós-graduação em Agronomia (Proteção de Plantas) - FCA

Validação de metodologias de extração e quantificação de pesticidas, diuron, clorpirifós e metil paration em águas subterrâneas em região de cultura de soja, utilizando QuEChERS/HPLC-UV

Pós-graduação em Química - IQ

Doenças do pimentão em regiões produtoras do Equador: identificação e manejo da pata seca e ocorrência de viroses

Pós-graduação em Agronomia (Proteção de Plantas) - FCA

Indian paint fungus : a method for recognizing and reducing hazard in advanced grand and white fir regeneration in eastern Oregon and Washington /

Bibliography: p. 9.

The citrus nematode and its control in the Southwest /

Issued Nov. 1974.