Plant Diseases In Agriculture Research Articles

BACTERIAL AND VIRAL DISEASES OF CROPS: DISTRIBUTION AND DIAGNOSTICS

A workshop devoted to «Problems of bacterial and viral plant diseases in agriculture and development of integrated plant protection» was held at April; 24 t h 2013 at Russian University of People's Friendship.

Trichoderma biocontrol: signal transduction pathways involved in host sensing and mycoparasitism.

Fungi of the genus Trichoderma are used as biocontrol agents against several plant pathogenic fungi like Rhizoctonia spp., Pythium spp., Botrytis cinerea and Fusarium spp. which cause both soil-borne and leaf- or flower-borne diseases of agricultural plants. Plant disease control by Trichoderma is based on complex interactions between Trichoderma, the plant pathogen and the plant. Until now, two main components of biocontrol have been identified: direct activity of Trichoderma against the plant pathogen by mycoparasitism and induced systemic resistance in plants. As the mycoparasitic interaction is host-specific and not merely a contact response, it is likely that signals from the host fungus are recognised by Trichoderma and provoke transcription of mycoparasitism-related genes. In the last few years examination of signalling pathways underlying Trichoderma biocontrol started and it was shown that heterotrimeric G-proteins and mitogen-activated protein (MAP) kinases affected biocontrol-relevant processes such as the production of hydrolytic enzymes and antifungal metabolites and the formation of infection structures. MAPK signalling was also found to be involved in induction of plant systemic resistance in Trichoderma virens and in the hyperosmotic stress response in Trichoderma harzianum. Analyses of the function of components of the cAMP pathway during Trichoderma biocontrol revealed that mycoparasitism-associated coiling and chitinase production as well as secondary metabolism are affected by the internal cAMP level; in addition, a cross talk between regulation of light responses and the cAMP signalling pathway was found in Trichoderma atroviride.

Climate change and plant diseases in Ontario

Current models predict that expected climate change in Ontario will significantly affect the occurrence of plant diseases in agriculture and forestry in the coming years. Direct, multiple effects on the epidemiology of plant diseases are expected, including the survival of primary inoculum, the rate of disease progress during a growing season, and the duration of epidemics. These effects will positively or negatively influence individual pathogens and the diseases they cause. Changes in the spectra of diseases are also anticipated. Abiotic diseases associated with environmental extremes are expected to increase, and interactions between biotic and abiotic diseases might represent the most important effects of climate change on plant diseases. The management of plant diseases will also be affected. In agriculture, plant breeding programs are expected to adapt many crops to increased duration of growing seasons and, concurrently, to develop drought and stress tolerance. There will be opportunities for new crops and cultivars to be introduced, but effective systems must be in place to detect new pathogens and prevent them from entering with these new crops. Because of the long-lived nature of trees, forests are slow to adapt, and the impact of climate change will have to be considered in forest management plans. Adaptations in agriculture and forestry have been occurring in Ontario for over 100 years, but these may need to occur at an accelerated rate because of rapid changes in climate. It is critical that the infrastructure of agricultural and forestry research remains strong to ensure successful transition and adaptation.

Review: Lipopolysaccharide of Burkholderia cepacia complex

BurKholderia cepacia complex (Bcc) is a group of phenotypically similar, genetically distinct bacteria that are beneficial to the environment but can also cause severe human infections. Bcc are being exploited for use as bioremediation agents and as a way to combat agricultural plant diseases. However, Bcc can cause lung infections in patients with chronic granulomatous disease or cystic fibrosis often resulting in mortality of these patients. Since it is unclear what bacterial components are necessary for causing human infections, studies of Bcc have focused on identifying putative virulence factors. As in other Gram-negative bacteria, the lipopolysaccharide (LPS) of Bcc induces a strong immune response that can contribute to host cell damage. The unusual structure of Bcc LPS lowers the anionic charge of the Bcc cell surface, which inhibits the binding and subsequent effects of cationic antibiotics. These distinguishing features include the substitution of a Ko for a Kdo residue in the inner core oligosaccharide and Ara4N residues bound to phosphates of the lipid A backbone. The structures of O antigen subunits and the consequent serotypes will also be discussed, with particular reference to the O antigen biosynthetic loci of two Bcc strains.

Lipopolysaccharide of Burkholderia cepacia complex.

Burkholderia cepacia complex (Bcc) is a group of phenotypically similar, genetically distinct bacteria that are beneficial to the environment but can also cause severe human infections. Bcc are being exploited for use as bioremediation agents and as a way to combat agricultural plant diseases. However, Bcc can cause lung infections in patients with chronic granulomatous disease or cystic fibrosis often resulting in mortality of these patients. Since it is unclear what bacterial components are necessary for causing human infections, studies of Bcc have focused on identifying putative virulence factors. As in other Gram-negative bacteria, the lipopolysaccharide (LPS) of Bcc induces a strong immune response that can contribute to host cell damage. The unusual structure of Bcc LPS lowers the anionic charge of the Bcc cell surface, which inhibits the binding and subsequent effects of cationic antibiotics. These distinguishing features include the substitution of a Ko for a Kdo residue in the inner core oligosaccharide and Ara4N residues bound to phosphates of the lipid A backbone. The structures of O antigen subunits and the consequent serotypes will also be discussed, with particular reference to the O antigen biosynthetic loci of two Bcc strains.

Biocontrol of aerial plant diseases in agriculture and horticulture: current approaches and future prospects

Until recently, the majority of research on the biological control of aerial plant diseases was focused on control of bacterial pathogens. Such research led to the commercialization of the biocontrol agent Pseudomonas fluorescens A506, as BlightBan A506™, for control of fire blight of pear. In contrast, chemical fungicides typically have provided adequate control of most foliar fungal pathogens. However, fungicide resistance problems, concerns regarding pesticide residues and revocation of registration of certain widely used fungicides have led to increased activity in the development of biocontrol agents of foliar fungal pathogens. Much of this activity has centered around the use of Trichoderma spp and Gliocladium spp to control Botrytis cinerea on grape and strawberry. The biocontrol agent Trichoderma harzianum T39 is commercially available in Israel, as Trichodex ™, for control of grey mold in grapes and may soon be registered for use in the US. Also targeted primarily against a foliar disease of grapes, in this case powdery mildew caused by Uncinula necator, is the biocontrol agent Ampelomyces quisqualis AQ10, marketed as AQ10 TM biofungicide. Another promising development in the area of foliar disease control, though one which is not yet commercialized, is the use of rhizobacteria as seed treatments to induce systemic resistance in the host plant, a strategy which can protect the plant against a range of bacterial and fungal pathogens.

Lesions of the peripheral nervous system due to intoxication with Parisian greenery

In increasing productivity, the fight against diseases of agricultural plants and agricultural pests occupies a prominent place.

(1) Fertilisers and Crops, or, The Science and Practice of Plant-Feeding (2) Farm Dairying (3) Fungoid Diseases of Agricultural Plants

(1) THE system of soil depletion as practised in the United States of America and in our colonies is beginning to receive serious consideration from the agricultural economist. The continuous growth of grain crops and the failure to make any adequate returns of plant food to the soil soon lead not only to a lack of food reserve, but also to the loss of those organic compounds which are of such importance in the production of crops in dry regions. This in itself is deplorable enough, but even where manure is to be had much of its fertilising value is wasted. Dr. van Slyke puts forward the interesting computation that the annual loss caused by the careless treatment of the manure produced by the different farm animals in the States is equivalent in value to an annual wheat crop in that country, or to 700,000,000 dollars.

Forthcoming Books of Science

AGRICULTURE. Bailliere, Tindall and Cox.—Fungoid Diseases of Agricultural Plants, Prof. Eriksson (translated from the Swedish). Cambridge University Press.—Soil Fertility, Dr. E. J. Russell; a series of Monographs on Agricultural Science, under the editorship of Prof. T. B. Wood and Dr. E. J. Russell; a series (also edited by Prof. T. B. Wood and Dr. E. J. Russell) entitled “The Farm Institute Series.” Cassell and Co., Ltd.—Dairying, Prof. J. P. Sheldon, illustrated. Methuen and Co., Ltd.—Bacteria as Friends and Foes of the Dairy Farmer, W. Sadler, illustrated; Progressive Poultry Culture, Dr. A. A. Brigham, revised by S. C. Sharpe, illustrated.