Plant Pathology Science
Year:2022 | Volume:11 | Issue:2|Papers Count:12

Ghaderi F, Hasehemi SAA (2022) Phytophthora citricola as the causal agent of persimmon root rot in Fars province of Iran. Plant Pathology Science 11(2): 1-10. Introduction: Phytophthora species are a serious threat to plant products worldwide. Therefore, identifying them is the first step in finding a way to treat the disease. The aim of this study was to identify Phytophthora species causing root and crown rot of persimmon trees in Fars province. Materials and methods: Samples were taken from the crowns and roots of diseased persimmon trees, in the summer of 2018-2019. Infected root and crown tissues were cultured in CMA-PARPH medium. Isolates of Phytophthora species were purified by single spore method and morphological and molecular characteristics were used to identify them. Results: Six isolates were obtained from the roots of diseased persimmon trees and identified as Phytophthora citricola based on their morphological characteristics. Phylogenetic studies based on beta-tubulin (βtub) and 28S rDNA genes showed that all isolates (Iran-Pc1 to Iran-Pc6) were grouped into clade 2 with a validation scale of 100 and confirmed the identification of P .citricola. Conclusion: This is a new report of persimmon root and crown rot caused by Phytophthora citricola in Fars Province.

Introduction: Huanglongbing or Fruit Greening is one of the major citrus diseases in Iran that has spread to most of the country's citrus growing provinces. In this study, the prevalence trend of the disease in seven provinces was investigated and analyzed. Materials and Methods: Citrus orchards in Sistan-Balochestan, Hormozgan, Bushehr, Khuzestan, Fars, Kerman and Mazandaran provinces were visited and samples suspected of having this disease were collected, in 2007-2009 and 2017-2019 years. After DNA extraction from the samples, the PCR test was performed using the specific primers OI1/OI2c and A2/J5. Results: It was found that the percentage of infected specimens, infected areas and number of hosts of Candidatus Liberibacter asiaticus, the causative agent of this disease, has increased over this period. At the end of this period, some samples of oranges, tangerines, grapefruits, bitter oranges, Lisbon lemons and Mexican limes were obtained from the provinces: Kerman, Hormozgan, Sistan-Baluchestan, and Fars were infected with the disease. Conclusion: The study of the disease during these years showed that: the infected areas and the host range of the disease have expanded a lot during this period, and the spread of the disease in citrus cultivation areas in the south of the country has been with a gentle slope. The reduction of the disease-carrying psyllium population during these years seems to have been effective in slowing down the spread of the disease.

The golden cyst nematode, Globodera rostochiensis, is considered as one of the most damaging potato pathogens in the world. Considering the skin composition of cyst nematodes and the ability of some fungi to produce enzymes that decompose it, this research was conducted to identify the fungi associated with potato cyst nematode. Materials and Methods: Eighty-six fungal isolates infecting potato golden cyst nematode in Hamedan province in western Iran were isolated and purified and identified based on morphological characteristics by valid keys. Results: Eight species of fungi belonging to three genera Alternaria, Clonostachys, Fusarium were isolated and identified from potato golden cyst nematode. The highest frequency was related to different species of Fusarium. Conclusion: The morphological characteristics of these eight fungi have been described and illustrated.

Arbuscular mycorrhizal fungi (AMF) in symbiosis with plant roots help to absorb more phosphorus, and increase the growth and development of plants. The aim of this study was to determine the correlation between population and diversity of AMF, and physicochemical characteristics of soil in wheat fields of Kohgiluyeh and Boyer-Ahmad province in southwestern Iran. Materials and Methods: Thirty wheat fields in this province, were visited near harvest time, and their rhizosphere and aerial organs were sampled. AMF spores were isolated by sieving the rhizosphere suspension in water and centrifuging in Sucrose solution. The spore population of these fungi was count. The percentage of root length colonization by these fungi was calculated in every sample. The morphological characteristics of the isolated spores were studied and the collected information was compared with the descriptions of AMF and the fungi present in each sample were identified. Texture, soil dispersion, soil and plant phosphorus content were determined and the correlation coefficient between AMF population and diversity with physical and chemical characteristics of soil and wheat plant were calculated. Results: Fifteen arbuscular mycorrhizal fungi belonging to nine genera: Acaulospora, Archaeospora, Entrophospora, Gigaspora, Claroideumglomus, Funeliformis, Rhizoglomus, Septoglomus and Scutellospora were identified. The diversity of these fungi in the samples was (2-)2.9(-5) and F. mosseae was dominant species with 90% relative frequency. The population of these fungi had a negative correlation with soil pH, but with soil soluble phosphorus and plant phosphorus content had a positive correlation. The diversity of these fungi had a positive correlation with soil soluble phosphorus. There was a positive correlation between the amount of sand in the soil and the root length colonization. Conclusion: AMF have a greater population and diversity in soils with light texture, less moisture along with low amounts of soluble phosphorus and organic matter. The positive correlation between the population of these fungi and plant phosphorus indicates their usefulness for the plant.

Introduction: Plant-pathogenic fungi are considered a serious threat to world food security, causing spoilage in plant products and food poisoning. One of the ways to identify fungi is to examine their mycelium using a scanning electron microscope (SEM). In order to take high-resolution microscopic images and obtain the surface properties of mushroom mycelium samples, it is very important to prepare the samples, i.e. the method of dehydrating and drying them. Materials and Methods: In this research, the effect of two dehydration methods and two drying methods on the mycelia of two fungi, Rhizoctonia solani and Rhizopus stolonifer, were compared to study them with SEM. Results: Microscopic observations showed that for R. stolonifer, dehydration with 100% ethanol and drying and for R. solani at room temperature and dehydration with 50% ethanol and the freezing method produce a smooth and high-resolution image compared to other methods. Conclusion: Dehydration of fungal mycelium with 50% to 100% ethanol and drying at room temperature or freezing are the optimal methods to prepare them for examination with SEM and produce a smooth and high-resolution image, and the surface features of their mycelium are preserved and well-defined.

Hosseini SM, Darvishnia M, Rezaei Nejad A, Bazgir E, Darvishnia F (2022) The effect of essential oils of thyme, peppermint, savory and two fungicides on the growth of three plant pathogenic fungi. Plant Pathology Science 11(2):52-60. Introduction: Some plant essential oils have antifungal properties. This study was conducted to determine the effect of three plant essential oils and two chemical fungicides on the growth of three plant pathogenic fungi in vitro. Materials and methods: The effect of different concentrations of three essential oils of thyme (Thymus vulgaris L.), peppermint (Mentha piperata L.) and khuzestani savory (Satureja khuzestanica Jamzad), compared to two chemical fungicides; mancozeb and carbendazim were investigated on the growth of three fungi Alternaria solani, Botrytis cinerea and Fusarium solani by dilution in Yeast Extract Sucrose Broth medium method and their minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were calculated. Results: Thyme essential oil had the greatest inhibitory effect on A. solani and F. solani among these essential oils, and savory essential oil had the greatest inhibitory effect on B. cinerea. Among the chemical fungicides, mancozeb had the most inhibitory effect on A. solani and carbendazim had the most inhibitory effect on B. cinerea and F. solani. Conclusion: Thyme and khuzestani savory essential oils have a significant inhibitory effect on the growth of these three plants pathogenic fungi.

The stem and bulb nematode, Ditylenchus dipsaci, is an important and damaging pathogen in a number of agricultural and ornamental plants, including alfalfa. The aim of this study was to investigate the effect of raw and pure saponins of six alfalfa ecotypes on the hatching of this nematode's eggs in order to find a biological method for its management. Materials and Methods: The effect of raw and pure saponins of six alfalfa ecotypes on the hatching of stem nematode eggs was investigated in a completely randomized factorial design with two factors of alfalfa ecotypes (six ecotypes) and their saponins (raw and pure) in vitro. Results: Analysis of variance showed that the interaction effect between two factors, ecotype and saponin, is statistically significant. At concentrations of 50 and 90 microliters of crude saponin from different ecotypes, 30-42% and 33-59% of the nematode eggs did not hatch, respectively. The Nishaburi ecotypes caused the most and the Shiraz and Khrisari polycross caused the least number of egg hatching. Concentrations of 10 and 50 microliters of pure saponin resulted in between 56 and 69% and 61 and 79% of total nematode eggs failing to hatch, respectively. The local ecotypes Miandoab and Nishaburi had the highest and Shiraz Polycross the lowest number of egg hatches. Conclusion: Pure saponins of alfalfa ecotypes have a greater effect on nematode egg hatching than raw saponins. Saponins of Shiraz Polycross alfalfa ecotype have a better effect than other ecotypes.

Introduction: Nematodes are one of the harmful factors for cucumber production in the world. This research was conducted to identify plant parasitic nematodes in cucumber fields and greenhouses in Lorestan province in western Iran. Materials and Methods: Eighty-five soil samples containing cucumber roots were collected from different cities of Lorestan province in western Iran. Extraction of nematodes, their fixation and the production of permanent microscopic slides and species identification were carried out using scientific references. Results: Twenty plant-parasitic nematode species from 12 genera of the order Tylenchina have been identified. The morphological characteristics of Amplimerlinius globigerus and Meloidogyne incognita have been described as the most harmful cucumber nematodes in the province. Conclusion: Eleven new species of cucumber root-associated nematode for Iran are reported here.

Root-knot nematode (Meloidogyne javanica) is considered as one of the limiting factors in the cultivation of greenhouse crops, including tomatoes. This research was conducted to investigate the effect of rosemary and ferula extracts compared to chemical nematicides of rugby and volum to find an environmentally friendly method for disease management. Materials and Methods: The effect of rosemary and ferula extracts with rugby and volum nematicides on tomato root-knot nematode was investigated in a completely randomized design under greenhouse conditions. Seedlings of Mobil variety were inoculated with second instar larvae of M. javanica at the 4-6 leaf stage and the effects of plants extracts and nematicides were investigated. After 60 days, the plants were removed from the pot and their growth indicators and disease severity were measured. Results: The simultaneous use of rosemary and ferula extracts had the greatest effect in reducing pathogenicity indicators such as gall index, number of larvae and number of eggs and increasing plant growth indicators such as fresh and dry weight of root and fresh weight of stem compared to control infected with nematode and nematicides treatments. Conclusion: The good effect of the combination of ferula and rosemary extracts compared to chemical nematicides shows the appropriate potential of its use as an environmentally friendly method for disease management.

Pistachio is one of the most important horticultural products in Iran which its production is always affected by biotic and abiotic limiting factors. Armillaria crown and root rot caused by Armillaria mellea, is an important disease in pistachio orchards, which causes the death of fertile trees. Control of the disease is difficult, costly and rarely successful. Symptoms of the disease in shoots of affected trees includes yellowing, early defoliation, sudden wilting, dieback of branches and reduction shoot growth. These symptoms, together with the decay and browning of woody tissues and the formation of white to creamy mycelial sheets in the roots and crown, as well as the observation of rhizomorphs of the fungus, are sufficient evidence for definitive diagnosis of Armillaria crown and root rot in pistachio trees. The infection process begins with the growth of hyphae or rhizomorphs and their firm attachment to the surface of the roots. The pathogen uses a combination of methods such as mechanical pressure, toxin production, and cell wall-degrading enzymes to penetrate the root tissues. Successful control of the disease is possible only by combining chemical, cultural, biological control methods and use of resistant rootstocks and cultivars due to delay in diagnosis of the disease before the spread of the pathogen in plant and soil and the appearance of symptoms, the presence of an extensive network of rhizomorphs at a distance from the tree and deep in the soil and formation of the mycelium beneath the plant bark or inside dead wood.

Bacterial mosaic of wheat is caused by the gram positive bacterium Clavibacter tessellarius. The symptoms of the disease are uniformly distributed small chlorotic spots with mosaic pattern on the entire leaf surface resemble those symptoms of nutrient deficiencies and some viral diseases, and it may be difficult to determine. Due to the seed-borne nature of the disease, use of healthy and certified pathogen free seeds is the most important strategy for managing this disease. The wheat bacterial mosaic has been reported in wheat fields in several provinces of Iran and it seems to be widespread in different wheat growing areas. In order to better understand the disease, its various aspects including the symptoms, pathogen biology and its host ranges, and management of the disease are reviewed in this article

The world's population is growing rapidly. To feed this large population, more crops must be produced. The broad use of fertilizers, pesticides and other inputs increases the productivity of existing agricultural lands and the amount of food production, but this increase in yield causes damage to the environment, soil degradation and the destruction of its natural microbial population. To prevent these harmful effects of the chemicals, an eco-friendly approach is needed to ensure human health and the environment. In the innovative view of agricultural production, there is a growing demand for the use of biofertilizers instead of agrochemicals. The use of beneficial microorganisms can be a new strategy to improve plant health and productivity. Natural microbial populations play an important role in the solubilizing and mineralizing of soil nutrients, which is very important for plant growth and development. Among the various microbial populations, fungi known as plants growth promoting fungi (PGPF) have recently received increasing attention. For decades, plant growth promoting fungi such as Trichoderma, Penicillium, Phoma, Aspergillus and Fusarium have been studied. Studies have shown that these fungi, regulate plant growth without environmental pollution and increase plant tolerance to plant pathogens. In this review a brief description of plant growth promoting fungi is given first. In the following, the nature and composition of these fungi as well as the mode of actions, formulation and related challenges will be concidered.