Plant Pathology Science

Glume blotch caused by the fungus Parastagonospora nodorum is an important disease of bread and durum wheat. The disease reduces the quantity and quality of wheat product. Disease history, pathogen morphology, and disease management methods, including crop rotation, plowing, post-harvest collection of plant debris , weed control, healthy seed culture or seed disinfection with a systemic fungicide, and cultivation of resistant cultivars are described.

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: Lysine motif receptor-like kinases (LysM-RLKs) play an important role in the defense reaction of plants to diseases and environmental stresses. This study was conducted to investigate the effect of chitin as a stimulus for the expression of genes that encode LysM-RLKs. Materials and Methods: The expression levels of three genes PGSC0003DMP400010799, PGSC0003DMP400010800 and PGSC0003DMP400061331, which encoded LysM-RLKs due to chitin treatment (150 μg / ml) in young seven-week potato leaves of Jely cultivar, were examined in treated and control leaves. Results: Analysis of the gene expression data showed that the expression of all three genes increased significantly due to the use of chitin compared to the control. Conclusion: Increasing the expression of genes encoding LysM-RLKs using chitin can be effective to induce systemic resistance to plant diseases and environmental stresses.

Hazelnut tree has natural habitats in northwestern Iran in the forests of Ardabil and Gilan provinces. Decline disease is a threatening agent of hazelnut trees in these areas. Symptoms of the disease include weakness, reduced growth, leaf fall and dieback of the branches, branch and trunk canker and root rot that eventually lead to the gradual death or decline of the tree. In Iran the fungi cause hazelnut decline disease, Diaporthe amygdali, and Cytospora fuckelii as canker and Fusarium semitectum, F. lateritium, F. anthophilum and Armillaria mellea as root rot causative agents. This article describes symptoms of hazelnut decline in Iran, pathogenic fungi and management strategies.

Apple postharvest diseases are usually caused by a wide range of pathogenic fungi. Postharvest rot of this crop is one of the most important economic diseases and also one of the main factors in reducing the lifespan of this crop. In contrast, our current knowledge of the occurrence and latent contamination during storage and its epidemiology is limited. The pathogenic fungi Botrytis cinerea and Penicillium expansum causing gray mold and blue mold, respectively, are the most common pathogens in the cultivation areas, which are usually inhibited by the use of synthetic fungicides. However, due to the growing concern over the use of synthetic fungicides, alternative control measures such as using physical treatments, natural compounds, and biocontrol agents are highly desired. Although no method has been approved as a definitive method of postharvest diseases management, the effectiveness of yeasts such as Candida saitoana, bacteria such as Rahnella aquatilis, and fungal species such as Trichoderma harzianum has been suggested.

Introduction: Root-knot nematode Meloidogyne javanica is the most economically important plant-parasitic nematode worldwide. Because of the environmental hazards of chemical nematicides used to control this nematode, there is an urgent need to replace these nematicides with alternative compounds that are environmentally friendly. Material and methods: An experiment was conducted to control M. javanica infestation on tomato plants (cv. Early-Urbana) using wood vinegar at the rates of 0.3, 0.6 and 0.9 percent (v/v), Effective Microorganisms (EM^®) at the rates of 5, 10 and 15 percent (v/v), humic acid at the rates of 0.2, 0.4 and 0.6 percent (v/v) and tervigo (positive control) at the rate of 0.4 percent (v/v), in greenhouse. Results: EM^® at the highest concentration (15%) was the most effective organic compound which reduced the nematode indices. Shoot length, shoot fresh weight and shoot dry weight increased by 41, 28 and 36%, respectively. The number of eggs, galls, egg masses per root system and reproduction factor were decreased by 58, 48, 49 and 57% in treated tomato with EM^® at the rate of 15%, compared to control (non-treated) plants, respectively. Conclusion: The organic compounds used in the present study are effective to control M. javanica on tomato under greenhouse conditions.

Introduction: Changes in the resistance to bacterial soft rot in potatoes can be linked to the expression of pathogenesis-related (PR) genes. The aim of this study was to investigate the relationship between the accumulation of PR genes and the induction of resistance through infection of potato tuber cells with pathogenic bacteria at different temperatures in order to effectively combat bacterial soft rot disease in potatoes. Materials and Methods: Pectobacterium carotovorum 2A, Pectobacterium atrosepticum 36A, and Dickeya dadantii ENA49 were used in this study. For bacterial infection, the potato cultivars semi-resistant cultivar Scarab  and susceptible cultivar Vesnianka, were used. The factorial experiment with three replications was carried out according to a completely randomized design. The relative level of mRNA copies of PR genes was determined by RT-PCR using primers of these genes. The mean values were compared according to the LSD test. Results: The experiments demonstrated the induction of PR-3, PR-5t and PR-10 in potato tuber cells in response to infection with  P. carotovorum 2A, P. atrosepticum 36A  and D. dadantii ENA49. It has been shown that the degree of induction of resistance genes depends on the temperature and the potato cultivar. Conclusion: It can be concluded that significant changes in potato resistance to bacterial soft rot at temperatures of 28 and 33 ° C are associated with the expression of these PR genes.

Introduction: Antibacterial, antifungal and antioxidant activity of methanolic extracts of Colocynth (Citrullus colocynthis) seeds, Camelthorn  (Alhagi maurorum) fruit and Chinaberry (Melia azedarach) leaves on eight bacteria and three fungi, which usually cause damage to agricultural products examined in this research. Material and Methods: Antimicrobial activity of selected plants in six concentrations on 11 microorganisms including, three gram-positive bacteria vs. Bacillus subtilis, Staphylococcus aureus, and Rathayibacter toxicus, and five gram-negative bacteria vs. Escherichia coli, Pseudomonas aeruginosa, Pseudomonas syringae subsp. syringae, Pseudomonas viridiflava, and Xanthomonas campestris pv. campestris, as well as three fungi vs. Pyricularia oryzae, Fusarium oxysporum and Botrytis cinerea was measured using the disk diffusion method. Also, the antioxidant activity of the extracts of these  plants was evaluated by measuring the enzymes of catalase and guaiacol peroxidase and evaluating the ability to trap DPPH radicals. In addition, the amount of total phenols and flavonoids in these plants extracts were measured. Results: Methanolic extract of Colocynth seeds had the highest antibacterial activity, the highest activity of catalase and guaiacol peroxidase enzymes and the highest percentage of DPPH radical inhibition. Methanolic extracts of these plants had no effect on fungal colony growth. Conclusion: Methanolic extract of Colocynth seeds can be considered as potential sources of bactericides in agriculture.

Introduction: Root-knot nematodes are one of the most important groups of plant parasitic nematodes in terms of economic damage to agricultural products. Biological control is one of the most environmentally friendly methods for management of nematodes. Material and Methods: The effects of aqueous extracts of jimsonweed  (Datura stramonium), metel (Datura metel) and henbane (Hyoscyamus niger) was evaluated against Meloidogyne javanica on cucumber, under greenhouse condition, in this study. Cucumber plants were inoculated with suspension of eggs and second stage juveniles of nematode. After a week, 1.66% concentration of each plant extract were irrigated in the pots. Plants were harvested after 45 days and some plant growth parameters and nematode reproductive parameters were recorded. Results: The extract of any of the plants did not affect the number of knots on the roots and per gram of the roots. However, number of egg- masses per root and gram of root, treatments including nematodes and extracts had fewer masses compared to treatments without plant extracts. Final population and reproductive factor had also lower values in treatments with plant extract compared to treatments without it. In addition, the plant extracts had no negative effect on the growth factors of the cucumber in the greenhouse. Conclusion: The extracts of Datura stramonium, Datura metel and Hyoscyamus niger reduced the reproduction of nematodes respectively, therefore they can be considered as potential agents in biological control of root-knot nematodes.

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.

Introduction: Poaceous plants such as corn, wheat, barley, sorghum, oats and millet are an important part of agricultural ecosystems. Smuts are one of the most important fungal diseases of these plants, which often cause economic damage and the destruction of part or all of their yields. Materials and Methods: Poaceous smut infected plants in farms and pastures of Markazi and Lorestan provinces were sampled. Morphological characteristics of these fungi and their germination type of teliospores were studied with bright field and fluorescent microscopes and identified using valid keys. The phylogenetic relationship of these fungi with other smuts was also investigated based on ITS-rDNA region sequencing. Results: According to the type of host, morphological characteristics and mode of teliospores germination 12 species vs. U. maydis, U. hordei, U. turcomanica, U. avenae, U.nuda, U. bromivora, U. cynodontis, U. tritici, Tilletia laevis, Tilletia controversa Sporisorium reilianum and S. cruentum were diagnosed. The morphological characteristics and phylogenetic relationship of these fungi with other smuts are described. Conclusion: The smuts of poaceous plants in Markazi and Lorestan provinces include eight species of the genus Ustilago, two species of the genus Sporisorium and two species of the genus Tilletia.

Many plant pathogens can spread into irrigation water in farms, gardens or greenhouses and cause disease in various crops. So far, a large number of plant pathogens including 43 fungal-like organisms, 27 fungi, eight bacteria, 26 viruses and 13 nematodes have been isolated and reported from water sources and water transmission systems. In many greenhouses, various pesticides are used to prevent the spread and control of these pathogens, which imposes costs, soil or water pollution, and the possibility of resistance in pathogens. Different methods of water treatment to control aquatic pathogens in the irrigation system using chemicals such as chlorine, chlorine dioxide, copper, silver and ozone, physical methods such as water filtration, heat, ultraviolet rays and the use of biosurfactants such as rhamnolipid and  nitrapyrin, are described in this article.

Walnut is one of the most important fruit trees in Iran, which is always exposed to pathogens, especially bacteria. The three most important bacterial diseases of walnut in Iran are bacterial blight (Xanthomonas arboricola pv. juglandis), skin cankers (Brenneria nigrifluens, Brenneria rubrifacians) and crown gall (Agrobacterium tumefaciens). Bacteriological characteristics and pathogenicity of pathogenic bacteria, methods of managing these diseases, along with suggestions for identifying resistant genotypes of walnut trees by molecular methods are described in this article.

Fusarium root and crown rot is one of the most important wheat diseases in the world, which causes a significant reduction in yield. The disease is also common in many wheat production areas in Iran. F. acuminatum, F. avenaceum, F. culmorum, F. solani, F. semitectum, F. equiseti, F. crookwellense, F. lateritium, F. moniliforme, F. oxysporum, F. pseudograminearum, F. sambucinum, F. subglutinans,F. proliferatum, F. longipes, F. nygamai, F. compactum, F. diversisporum, F. fujikuroi, F. javanicum, F. flocciferum and F. tricinctum have been reported from rotten tissues of wheat root and crown in Iran and F. culmorum and F. pseudograminearum are known as the most important disease agents. Disease management methods including crop rotation, removal of diseased plant debris, setting planting date, biological control, seed disinfection with protective fungicides and cultivation of relatively resistant cultivars are described in this article.

Introduction: Powdery mildew caused by Podosphaera pannosa is one of the most important diseases of peaches and nectarines worldwide, including Iran. The aim of this research was to investigate the response of peaches and nectarines under cultivation in Iran to the disease. Materials and Methods: Reaction of ten peach cultivars vs. Robin, Early Red, Red Top, Shasta, Amesdn, Velvet, Anjiri, Paeizeh, Dixi Red, and Sun Crest, and ten nectarine cultivars vs. Independence, Stargold, Sangold, Sanking, Giuta, Shabrang Karaj, Vega, Orion, Jiova and Veinberger were evaluated for disease in natural and artificial infection conditions in two experiments in a randomized complete block design with three replications over two years at the Meshgin Shahr Agricultural and Natural Resources Research Station. Results: Analysis of variance of experimental data showed that there was a significant difference between cultivars of each plant at a probability level of 1%. Peach cultivars Anjiri and Red top were very resistant, Velvet, Shasta and Early red ‎were resistant; Amesdn, Dixi red and Robin were moderately resistant; Sun ‎crest was susceptible and Paeizeh was in very susceptible. Weinberger nectarine cultivars were resistant and Independence, Stargold, Sanking, Giuta, Shabrang Karaj, Vega, Orion and Jiova cultivars were semi-resistant and Sangold was very susceptible to disease.  Conclusion: Eighty percent of the studied peach cultivars are very resistant to semi-resistant and 20% sensitive and very sensitive, 90% of the studied nectarine cultivars are resistant to semi-resistant and 10% susceptible to powdery mildew. Findings of this research should be considered in the management of peach and nectarine powdery mildew.

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.