Plant Pathology Science

Wheat is one of the most important cereals grown as human and animal food in the world, including Iran. This crop is infected by various pathogens such as fungi. Graminicolous fungi are important pathogens which cause root and crown rot, leaf blight and black spot on wheat. Some methods, with high efficiency and safety for human and environment, have been employed for controlling these diseases. Since the activity of these fungi depends on some factors such as soil temperature, pH, moisture and nutrients, the proper agricultural practices before planting and suitable irrigation and good fertilization would be effective in pathogen control. Various species of Trichoderma, arbuscular endomycorrhizal fungi and some bacterial species may control the disease through some mechanisms such as biofilm production, plant growth promotion and enzyme production. Generally, integrated management with the aid of simultaneous application of several control measures would give the best results.

Geminiviruses (Geminiviridae family) with small circular ssDNA genome are encoding just four to seven proteins on virion and complementary-sense strands of their genomes. To have a progressive infection, they are dependent mostly on host cellular machineries and interact with wide range of different host plants factors and processes. Geminiviruses alter the cell cycle in infected plants and they can support replication of viral DNA. They change host gene expression patterns, inhibit cell death pathways, alter macromolecule trafficking and interfere with protein modification to redirect or suppress host defenses and hormones signaling. Geminiviruses encode gene silencing suppressors to interfere with post-transcriptional gene silencing and alter plant DNA methylation and microRNA (miRNA) pathways, often causing developmental abnormalities. Here, the geminiviruses are discussed as one of the most destructive plant viruses and their proteins interactions with host cell factors and pathways are described.

Iranian Pistachio is one of the most important horticultural product in export market. Crown and root rot caused by Phytophthora species is the most serious disease of plant, which annually destroys a considerable number of mature and young trees. This disease has been reported from all provinces of Iran. The pathogen is soil-borne and is distributed by sporangia or the released zoospores and infects the healthy trees. In the most Pistachio orchards, the key factors of disease development are the sensitivity of pistachio crown to Phytophthora and the flooding method of irrigation. The symptoms of the disease are include blight in early spring, drying of the green leaves during the growing season, gum exudation from the crown of tree  and the root rot. Gummosis can be successfully controlled by integrated disease management including orchard constructing in non-infected areas, using resistant or tolerant cultivars, using healthy rootstocks, improving the irrigation methods and avoiding the direct contact of water with tree crown, isolating the contaminated parts of the orchard from the healthy parts, using suitable fungicide, and biological control based on Trichoderma and Bacillus species.

Plant diseases play a critical and limiting role in crop production and their control by using pesticides cause serious problems regarding food safety and environmental health and increase the need for other sustainable disease management techniques. Some of plant pathogens may infect the aerial parts of plants, but spent part of their life cycle in the soil and maintained their survival. In such cases, part of the life cycle of the plant pathogen in soil may be very important, even if that microorganism does not infect the roots. Mono culturing and cultivation of crops belonging to the same family increase the potential of disease incidence. Using and applying the suitable and correct cultural practices that limit damage of root diseases is necessary for sustainable management of soil-borne pathogens. Cultural operations, including the use of cover green crops, crop rotation, organic composts, certified seeds and propagative materials, amended organic material to soil, proper tillage systems, soil solarization, resistant cultivars, mycorrhizal fungi, all are reported and confirmed as management options for long time saving soil quality and good sustainable management of soil borne diseases.

Introduction: The Hoplolaimidae family is one of the largest and economically most important families of the order/ infraorder Tylenchida / Tylenchomorpha. The members of this family spread all over the world and can be found under different climatic conditions. Some species in this family are serious plant parasites and significantly reduce crop yields. Materials and Methods: In the forests of Khorramabad city in western Iran 70 samples were collected from the soil around the roots of hawthorn trees in the period of 2017-2019. After recording the properties of each sample, they were transferred to a laboratory and cooled at 4 °C. The nematodes were extracted from the soil using the tray method, then fixed and transferred to pure glycerin, and permanent slides were made. The morphological and morphometric properties of the nematodes were examined using a light microscope equipped with a Dino Capture camera. The nematode species were identified using scientific identification keys. Results: Five species of plant parasitic nematodes belonging to two genera of Hoplolaimidae were identified in this study, including Rotylenchus goodeyi, Helicotylenchus canadensis, H. digonicus, H. vulgaris and H. tunisiensis. Conclusion: R. goodeyi is reporting as a new record for the nematode fauna of Iran. Morphometrical and morphological characteristics of these nemadodes are described here.

Rahimi F, Rahmanpour S, Rezaei S, Larijani K (2020). Identification of growth inhibitor of Sclerotinia sclerotiorum in Indian mustard leaf. Plant Pathology Science
9(2):28-36.       DOI: 10.2982/PPS.9.2.28.

Introduction: Sclerotinia sclerotiorum is the causal agent of white rot in aerial parts of a wide range of plants. The aim of this study was to compare the reaction of living tissue of Indian mustard leaves on the growth of this fungus under open and closed leaf stomata conditions. Materials and Methods: The pure isolate of the fungus was prepared by the hyphal-tip method on water-agar medium. An experiment was conducted in a fully randomized design with four treatments. The formation of fungal growth inhibiting compounds in the leaf tissue of all treatments was examined using GC-MS.
Results: Analysis of variance of the experimental data showed that the diameter of the fungal colony was significantly smaller in the treatment with open leaf stomata than in the other treatments. Gas chromatography data analysis showed that 1-propene-3-isothiocyanate as a volatile compound inhibits fungal growth in this treatment. Conclusion: The production of the volatile allyl isothiocyanate compound in Indian mustard leaf inhibits the growth of S. sclerotiorum.
 

Introduction: Canola is one of the most important oilseeds in the world. Fusarium species can causes of canola root and crown rot. Material and Methods: In order to identify Fusarium species associated with rapeseed, some samples of the roots and crown of infected and suspicious plants were taken from rapeseed fields in the counties of Lorestan Province during the 2018 growing season. The samples were transferred to the laboratory and pathogenic fungi isolated and purified using specific and public media and then identified with valid keys. Results: A total of 88 isolates were obtained from the collected samples, which due to the morphological characteristics as F. acuminatum, F. culmorum, F. diversisporum, F. oxysporum, F. sambucinum, and F. solani. F. culmorum with 21 isolates (23.86%) and F. solani with 7 isolates (7.95%) had the highest and lowest frequency percentage, respectively. Conclusion: Canola is reported for the first time as a new host for F. diversisporum and F. sambucinum in Iran.

Plant viruses cause major losses to agricultural crops worldwide. Plants react to the virus infections via several defense mechanisms, such as ubiquitination. Ubiquitin (Ub) and ubiquitin proteasome system (UPS) play key role in the function modification and degradation of proteins in plants. Ub attachment to the cellular proteins alters the stability, the cellular establishment or activity of the target protein. The key role of UPS has been revealed in defense mechanisms and other plant processes. Viruses as obligate intracellular parasites have evolved mechanisms to interfere UPS. In some cases, it has been shown that viral proteins were targeted by this system. Ubiquitination plays an important role in plant–virus interaction which can lead to plant resistance or pathogenicity in the host plant. Therefore, further understanding of UPS and its role in plant-virus interaction can develop novel methods to increase resistance to viral infections in plants.

Khezri  M, Allahyari Igdir S, Aghazadeh Soureh Z (2021) Tomato bacterial diseases in West Azerbaijan province of Iran. Plant Pathology Science 10(1):86-96. Doi: 10.2982/PPS.10.1.86.

Introduction: Tomato is one of the most important and most widely consumed vegetable in the world. Tomato also is one of the most important products in West Azerbaijan Province of Iran, which plays an important role in the province's agricultural economy. Accurate bacterial disease diagnosis is the first and most important step in designation methods of disease management. Materials and Methods: Tomato farms in the suburbs of the province cities were visited and diseased plants were sampled. Bacteria were isolated and purified from patient tissues and identified based on phenotypic and molecular characteristics. The bacterial pathogenicity test was performed according to Koch principles. Results: Tomato bacterial pathogens in this province include Clavibacter michiganensis subsp. michiganensis, Xanthomonas vesicatoria, Pseudomonas syringae pv. tomato, P. syringae pv. syringae and Dickya chrysanthemi, agents of bacterial canker,  bacterial spot, bacterial speck,  syringe leaf spot and soft stem rot. Disease symptoms, phenotypic and molecular properties of pathogenic bacteria, previous reports on these bacteria from Iran and their distribution in different regions of West Azerbaijan Province are presented. Conclusion: These bacteria, with the exception of the tomato bacterial canker agent, are reported for the first time from West Azerbaijan province.

Introduction: Two soil-borne fungi, Fusarium oxysporum and F. solani, are the causes of important diseases of beans wilting and root rot. The best way to manage these diseases is to identify and cultivate resistant cultivars. This study was conducted to identify the reaction of nine Iranian beans cultivars to these two pathogenic fungi. Materials and Methods: Bean-diseased plants were collected from farms in Aligudarz city in Lorestan province, in western Iran, and F. oxysporum and F. solani were isolated from them in the laboratory. At first the pathogenesis of these fungi was investigated on a local cultivar. Then, the reaction of nine bean cultivars to them was determined in a completely randomized design experiment in the greenhouse. Results: Reaction of cultivars to F. oxysporum and F. solani respectively were, Dadfar red-bean with disease severity of 28.8 and 26.6%, Sayad red-bean  with 33.3 and 28.8%, Koosha pinto-bean  with 35.5 and 33.3%, White 247 with 40 and 37.8%, Pak white-bean with 46.6 and 46.7% and pinto-bean 492 with 48.8 and 46.7% respectively, were grouped as semi-sensitive. Saleh pinto-bean with a disease severity of 64.4 and 62.2%, Yaghot red-bean  with 77.7 and 80% and Almas white with 82.2 and 86.7% respectively, were determined as sensitive. Pearson correlation analysis also showed that there was a significant negative correlation between root length, fresh and dry weight of root with diseases severity. Conclusion: Six cultivars of Iranian beans vs Dadfar, Sayad, Koosha, White247, Pak and 492 are semi-sensitive to these diseases.