Plant Pathology Science

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Arbuscularfungi are root symbiontsof 80% of plants, such as most field crops and fruit trees. They establish in root tissue, arbuscule in endodermis cells, and an extramatrical fine hyphal net. These fungi byincreasing absorption of water and nutrient elements for plants, making changes in chemical constituents of plant tissues, competition with pathogens for nutrients and establishment site, structural changes in roots, alleviation of environmental stresses, and increasing population of useful bacteria in soil, help management of diseases caused by fungi, fungal like organisms, nematodes, bacteria, phytoplasmas and physiological disorders. Collection, identification, purification, propagation, and inoculation of these useful fungi to plants, can decrease usage of chemical fertilizers and pesticides that are harmful to consumers of agricultural products as well as to the environment

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The Pepper (Capsicum annuum) is one of the important field crops in the worlds, which its cultivation has been developed, because of its food value and consumptions. But, there are certain diseases, which limited the growth and productivity, out of which the fungal diseases are of high severity. Thus, for this very purpose, a survey was conducted in the pepper growing areas including field and glass houses for fungal diseases identification in Isfahan provinces. The infected pepper plants were collected in the plastic bages and transferred, into the lab. The macro and microscopic studies indicated that there are severed fungal diseases infecting the pepper plant on the areal parts, including Powdery mildews, Downy mildews, Sclerotinia stem rot, early blight and Botrytis molds. Except the Downy and Powdery mildews being obligate parasite, which cannot be cultured the rest were culture from the margin in the infected parts, where the disease were under development on PDA for purification and identifications through tip culture. The results revealed that, there are several fungal species involving including Peronosporatabacina for Downy mildew, Levielullatauricafor Powdery mildew, Early blight, Alternariaalteanataand A. solani, fruit rot, Botrytis cinerea and stem rot due to Sclerotiniasclerotiorum from areal parts.

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Genetic engineering has begun about 160 years ago with discover inheritance laws of biological traits, isolation and purification of DNA from inner cell, replication and propagation of its pieces with polymerase chain reaction in vitro, identification and purification favorable genes and transfer them with Agrobacterium  tumefaciens bacterium, or directly to plants cell, by gene gun, and produce whole transgenic  plant, from gene modified cell with tissue culture methods innovation and fully developed in recent 4 decades. With this technology transfering  favorable genes, without accompaniment with  unwanted genes, into plants is possible, and resistance transgenic plants to fungal, bacterial, viral and nematodes, and tolerant to environmental stress produced. Genetic engineering has created hope for better plants diseases management and increase agricultural production to meet food needs of a growing human population.

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Root and crown rot is an important disease in Kohgiluyeh and Boyerahmad province peach orchards. Its signs are wilting, general weakness, loss of foliage and sometimes sudden wilt and death of the tree. To isolate the pathogen, used corn meal-agar with antibiotics, Delvasid, Ampicillin and rifampicin medium. Pathogen is Phytophthora cactorum. For pathogenesis test, 2 inoculation methods, to a tree branch or contaminated soil around the roots and crown of seedling is used. Inoculation roots and crowns of seedlings and saplings of six varieties of peaches with this pathogen, showed that Takheh is resistant, Alberta, Redhoon and Mashhad red peach are semi-resistant, Angiri and J.H.Hill are sensitive to the disease

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Regarding to the need of improving the quality and quantity of agricultural products, the science of plant protection has been taken under consideration. Accurate identification and detection of plant pathogens is one of the best ways for successful plant disease management. One of the useful methods is analysis of the volatile organic compounds, which spread from diseased plants. In this method, specificity of the volatile organic compounds and also the factors that affect the identifying of plant diseases and effective methods on these compounds are important. First, these compounds should be collected and then be analyzed. The best method for analysis of these compounds is dynamic sampling followed by gas chromatography and using the proper probes. Although the high costs of the tools make it difficult to apply this method for agricultural purposes, but by using the statistical methods and estimations the costs can be decrease.

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Powdery mildew disease of beet, cause by the fungus Erysiphe polygoni, is highly epidemic on table beets which are mostly cultivated in cooler regions of Isfahan province. Severity of the disease in fodder beets is lower than that of table beets. Studies on this fungus revealed that there is ascocarp formation as yellow spots which then turned to light to dark brown and then to black spherical bodies on upper, lower and petiols of the leaves, at the end of the season. Asci contain ellipsoid ascospores . Disease symptoms, characters of the pathogen and methods of disease management are described.

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Nanotechnology is the science of identification, production and use of materials at nanometer (10-9 m) scale. Regarding to application of this technology in plant pathology, this technology provides power to organize producing biological nanosensors for rapid detection of pathogens, production of nano silver and nano silica-silver to control bacteria and fungi, and the preparation of pesticides as nano capsules, at molecular level. Metal nanoparticles, the inhibitor of plant pathogens are derived from some fungi, bacteria and some plants including sunflower, alfalfa, Indian mustard, magnolia and Japanese persimmon.

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Metabolomics or analysis of all cellular metabolites is a new and powerful tool that provides possible quick view to the large number of small molecules (metabolites) within the cell and indicates dynamics of these molecules under different conditions. Quantitative and qualitative measurements of large number of cellular metabolites provide a broad view of the biochemical status of an organism that can be used to monitor and assess gene function. Today, metabolomics is widely being used in agriculture for classification of plants, studying phytochemical diversity of medicinal plants, assessment of the changes which occur in the biochemical composition of foods occurring, for example, during the pasteurization of Basmati rice for long-term storage or the boiling for direct consumption. In plant pathology, metabolomics has been mainly used to study plant responses to a wide range of biotic or abiotic stresses including resistance of plants to pathogens and also as a powerful tool for functional genomics studies. Profiling of the transcriptome and proteome has received some criticism due to their inability to predict gene function but profiling of the metabolites is promising as it provides instantaneous large amounts of data from cell physiology. Study of plant genetic resistance is one of the most important applications of metabolomics. Since metabolites are final products of gene expression and all changes in gene expression is reflected in metabolite profiles, hence metabolite profiles produce a more comprehensive understanding of plant defense mechanisms against stresses such as pathogen challenge. On the other hand, breeders are looking for rapid, simple and accurate tools for identifying metabolites associated with resistance as biomarker for screening cultivars resistant to diseases. In addition, understanding resistance mechanisms at the level of metabolome may help breeders for better understanding of resistant gene function and pyramiding suitable resistant gene in elite cultivar. This article is a review of the science, its applications in plant pathology, methods of study metabolites and their administrative problems.

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Plant diseases are the most important limiting factors in agricultural production. Currently the major control method of plant diseases is based on the use of chemicals that raises serious concerns about food quality, environmental hazards and development of resistance to agrochemicals. These concerns have increased the need for other alternative disease management techniques. Macro- and micronutrients are normally applied to increase crop production and improve general plant health and quality. They can also increase the disease tolerance or resistance of plants, however there are some opposing reports. Although our knowledge on the impact of mineral nutrients on plant diseases, many other factors that control plant's response and dynamic interactions among plant, environment and pathogen is not sufficient, manipulating soil nutrients through amendment or modification is always an essential part in plant disease control as well as in sustainable agriculture. Mineral nutrients are generally the first and the most important line of defense against plant diseases which affect all parts of the disease triangle. Nutrients can satisfactory decrease diseases, or at least diminish them to a level at which additional control measures are more successful and less expensive. Here we review the most recent data regarding the influence of mineral nutrients on plant disease resistance and tolerance, plant histological or morphological structure and the virulence or capability of pathogens to survive.

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Phytoplasmas are some plant pathogens that establish and propagate in plant phloems. They have transmitted by sucking insects. Phytoplasmas have a different lifecycle as compare to bacterial pathogens. They have ability to infect different hosts two different kingdoms, planta and animalia (insects). They systemically infect their hosts. Phytoplasmas have various approaches for adaptation to their hosts. Some of adaptation mechanisms include: changes in the level of gene expression, variation and recombination in extrachromosomal DNA and potential mobile units, production of effectors and suppression of defense signaling pathways. These approaches enable them to establish, propagate and infect various hosts. Recognizing these strategies would be a major step on the effective management of these pathogens.

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Food production and food security is an essential precursor to sustainable development in agriculture. Currently, more than 800 million people, generally in Africa and Asia, suffer from hunger and agriculture is considered as the main source of food for them. One of the application of nuclear technology is reducing the damages of plant pest and diseases. The application of nuclear techniques in plant pathology can be grouped in three categories including disease tracing, mutagenesis induction and radiation of crops to induce resistance and destruction of pathogens. As a new method to induce defense responses to biotic and abiotic stresses, nowadays, gamma radiation is used to improve the growth in the way to induce the plant resistance to environmental tensions and plant pathogens as well. Use of this potential, especially in management of seed and seedling diseases is very important to reduce a big portion of crop losses caused by plant pathogens in the first weeks of seedling growth.

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Farahbakhsh F. & Massah A. 2015. Genetic of resistance to plant diseases. Plant Pathology Science 4(2):64-73.

With studying the function and co evolution of the plant resistance genes with virulence genes in the pathogens, the knowledge of molecular genetics is in progress and creates a new opportunity to produce durable resistance against plant diseases.  This article explains the new findings about the different varieties of genetic resistance, performance and evolution of resistance genes involved in detecting, signaling and responding to plant pathogens.

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Dadrezaei S. D. & Torabi M. 2016. Management of wheat rusts. Plant Pathology Science 5(2):81-89.

Wheat is the most important crop in the world and rust diseases cause the most damage to wheat all over the years. There are so many ways to control the disease that the use of resistant cultivars is the most effective and economic way for disease control. Rust has high pathogenicity diversity and evolutionary aptitude. On the other hand, migration and mutation leads to the emergence of non-native races of rusts in a region so virulent pathotypes with the new structures and violence on resistance genes in commercial resistant cultivars were incidence and cause disease in resistant varieties and spread in the wheat fields. Development of effective and sustainable control methods against plant diseases is very much dependent on our knowledge of the disease in our country. This paper introduces wheat important rusts diseases and explains Factors affecting the prevalence, distribution, and relation of air currents in the transmission of rusts and strategies for monitoring and management of rusts in the country.

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Motieeyan  L.  &  Nasr-Esfahani  M.  2016. Management  method of sugar beet cyst nematode. Plant Pathology Science 5(2):32-41.

Sugar beet, is one of the basic source of the raw material for sugar industry in Iran. The beet cyst nematode, Heterodera schachtii Schmidt, 1871, is one of the most damaging pathogens of sugar beet. This nematode has a wide host range, including 218 plant species from 95 genus and 23 families, which include some of the important field crops, ornamental plants and weeds. Nematode management methods include avoiding of cultivation in highly infested soils, disease scape by early cultivation, crop rotation, using resistant varieties, application of bioagents, applying of organic fertilizers, animal manure, plant waste materials, compost, vermicompost and also soil solarization and chemical control are described here.

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Bagheri  A. 2017. Situation of  potato common scab disease in Iran. Plant Pathology Science 6(1):47-56.

Common scab disease of potato has been reported from all of the potato growing regions of the world. Potato scab is one of the serious diseases of potato in Iran. Integrated disease management program on reducing the potato scab in the country, needs to verify the key factors affecting the occurrence and spread of the disease. Growing the potato plants in a soil with a neutral pH with a constant moisture, sprinkler irrigation, crop rotation and a good weed control program, especially against convolvulus, are effective methods for disease control. The use of organic fertilizers and the use of resistant varieties are recommended also. The importance of the bacterial scab of potato, distribution and intensity of infection, disease symptoms, factors affecting the disease severity, disease cycle, response of the common potato cultivars to the disease, the dominant causal bacterial species in Iran and integrated management of disease that were carried out in Iran and other countries, are described in this article.

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Mirtalebi M. & Mostowfizade-Ghalamfarsa R. Integrated management of gray mold disease. Plant Pathology Science 6(2):43-54.
 
Gray mold caused by Botrytis cinerea, is one of the most important postharvest diseases on fresh fruits and vegetables worldwide. The disease may start in the field and remain as a latent infection and then develop after harvest, during transportation, packaging, storage and marketing. Nowadays, application of fungicides is the main strategy to control the gray mold disease in conventional agriculture. The presence of fungicide residues in edible fruits and vegetables is a concern for consumers because pesticides are known to have potential harmful effects. Therefore, the search on finding the safe and effective disease control strategies has been accelerated. Integrated management of the disease by using some methods like optimal method of irrigation and fertilization, biological control, use of bioagents, disinfection of fresh fruits and vegetables after harvesting, storing and shipping in a cool and dry condition with low humidity and suitable ventilation are suggested.

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Ahmadi S, Ghaderi F, Safaee D (2020) Oak charcoal rot disease in Iran. Plant Pathology Science 9(1):118-128.         DOI: 10.2982/PPS.9.1.118.

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Najafiniya M , Azadvar M (2020) Review of durable management of soil-borne plant pathogens. Plant Pathology Science 9(1):68-77. DOI: 10.2982/PPS.9.1.68.

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Dehghan AA, Ghaderi R (2020) Application of seaweeds in plant diseases management. Plant Pathology Science 9(1):101-107.         DOI: 10.2982/PPS.9.1.101.