جستجوی مقالات مرتبط با کلیدواژه « پژمردگی » در نشریات گروه « گیاهپزشکی »

Root and crown rot is a common tomato disease in the major production areas of Hormozgan province. The present study was conducted to isolate, identify, and determine the frequency of fungal agents associated with tomato root and crown rot in Hormozgan province. In total, 984 fungal isolates were obtained from tomato plants with yellowing, wilting, and root and crown rot symptoms. Identification of the isolates was done based on the morphological characteristics and the comparison of the obtained sequences of the ribosomal internal transcribed spacer region (ITS-rDNA) and parts of the translation elongation factor-1 alpha (tef1-α) gene with relevant sequences available in GenBank. According to the results, the highest frequency belonged to Fusarium oxysporum isolates (73%), and afterward to Rhizoctonia solani and F. acutatum species with eight and one percent frequencies, respectively. The results of the pathogenicity tests of the fungal species on tomato seedlings hybrid Sunseed 6189 at the stage of four true-leaves revealed that all three species were pathogenic on tomato seedlings and caused root and crown rot, yellowing, and death of the plant aerial tissues. Pathogenic isolates of F. oxysporum were identified as F. oxysporum f. sp. radicis-lycopersici using sprl-specific primers. To the best of our knowledge, this is the first report of F. oxysporum f. sp. radicis-lycopersici on tomato in Hormozgan province, and the first report of F. acutatum as tomato root and crown rot agent in the world.

Verticillium wilt, caused by Verticillium dahliae, is one of the most important soil-borne diseases of stone-fruit trees.

Samples showing evidence of Verticillium wilt were collected from stone fruit orchards in the suburbs of Shahroud and Damavand and four isolates of V. dahliae were obtained. The fungal inoculum was prepared on sterile wheat grains and the response of 13 peach and nectarine cultivars propagated by grafting on GF305 (almond-peach hybrid) rootstock was inoculated with it in the canopy area in the garden in early spring. Sixteen weeks after inoculation, disease severity was recorded on a three-point scale.

All peach and nectarine cultivars were classified as very susceptible, susceptible, or semi-susceptible and none of them showed resistance. The Nectarine Independence cultivar was highly susceptible to disease, while the peach cultivar had the lowest disease severity index and was therefore classified as semi-susceptible.

Among these cultivars, the Romestar peach cultivar is less susceptible to the disease.

Wilt caused by the soil-borne fungus Fusarium oxysporum f. sp. lycopersici is one of the most common and harmful diseases in most tomato growing areas. The disease damage is reported up to 27% of the yield in Iran. Biological control of the disease is an effective, environmentally friendly, and consumer health management method. The ability of arbuscular mycorrhizal fungi to reduce many soil-borne diseases has been demonstrated, so this study was conducted to investigate the effect of a commercially available arbuscular mycorrhizal fungus on disease severity in three tomato cultivars.

The commercial inoculum of arbuscular mycorrhizal fungus Glomus geosprum was obtained from the market. The experiment was performed in a completely randomized statistical design with four replicates for each treatment. Inoculum of G. geosprum was added to sterile soil in pots and then seeds of Super-Strain, Chef, and Super-Falat tomato cultivars were sown. Seedling roots were inoculated at the three to the six-leaf stage with a spore suspension of a hypervirulent isolate of F. oxysporum f. sp. lycopersici. Data on the severity of the disease, stem height, root length were collected after the appearance of wilting symptoms and analyzed with the SPSS 20 software and the means values were compared.

The severity of the disease was significantly reduced in all cultivars treated with arbuscular mycorrhizal fungus, and the stem height and root length were higher than those with no mycorrhizal fungus.

The ability of G. geosporum, to reduce the severity of Fusarium wilt disease and increase the growth of tomato plants is reported for the first time.

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.

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.

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.

Six cultivars of Iranian beans vs Dadfar, Sayad, Koosha, White247, Pak and 492 are semi-sensitive to these diseases.

Garlic (Allium sativum) is one of the most common and high consumption vegetables in the world specializing in the northern provinces of Iran. Various civilizations and cultures throughout history have realized the importance of this valuable plant in the prevention and treatment of human diseases. One of the most important environmental stresses on garlic plant specialty at the fields of Sari countryside, are different species of soil-borne plant pathogen fungi, which are causing damage to crops and even in the storage of the post-harvest. The most important parts that are damaged by these pathogens are bulbs and roots. Identifying these fungi that cause plant stress and weaken the plant in production or cause drought and eventually plant death, has been a very important issue in plant protection science. In this research, for the first time, an attempt has been made to isolate and identify the cause of garlic wilt and root rot at the farms in Sari countryside, Mazandaran province, Iran.

At the time of harvesting garlic (spring of 2018) several samples were taken from purple garlic farms of Tarom cultivar at Sari countryside. The fungi were isolated and purified on Water-Agar and PDA medium respectively, then transferred to CLA medium to stimulate the production of macro-conidia. The morphological characters of the fungi as the shape, type and size of the spores (length and width), the color of the mycelia and shape of chlamydospores determined by keys of Barnett and Hunter and Nelson et al., DNA of fungus was extracted by CTAB method, amplified and sequenced by the ITS4, ITS5, EFGR and EF1-983F primers. The similarity of the genome compared with other sequences in the NCBI gene bank. In order to test prove the pathogenicity of the fungus, the interaction of the fungus and purple garlic plant (Tarom cultivar) was evaluated by the effect of 30 and 60 g/kg of pathogenic fungus inoculum during seed germination and growth of this plant into the soil.

The morphological characters of the fungus were; purple colony color, cottony growth of mycelia, four to six cell macro-conidia and chain shape chlamydospores, which were confirmed in accordance by the identification keys close to the Fusarium oxysporum fungus. ITS genome aligned with 100 and TEF genome aligned approximately with 98-99 percent similarity to F. oxysporum, which were recorded at the GenBank with NCBI accession number; MK790682.1 and isolate code;7391. Symptoms at pathogenicity test included; wilting, yellowing, necrosing leaf and finally drying of garlic plant appeared at 30g/kg inoculum compared to healthy control treatment. Bulbs were rotted by 60g/kg inoculum and the plant did not grow. It was observed that reducing the amount of inoculation caused damage over a long period.. Garlic plants with few symptoms are usually harvested and transferred to the storehouse which probably causes the spreading of pathogen spores and makes storage rot even on healthy crops. Fewer symptoms are very important at farms and the fungus should be controlled before causing more damage. Also, the transmission of diseased plants with fewer symptoms should be avoided to the storehouse. Therefore, based on morphological and molecular characteristics and pathogenicity test probably F. oxysporum 7391 is one of the important factors of wilt and root rot of garlic plants in Mazandaran province.

Farmers take serious damages from soil-borne plant pathogens every year at the time of harvesting crops especially at the garlic farms from Mazandaran province. The importance of soil-born plant pathogen fungi on garlic has been reported from all around the world. High production of garlic in Sari, storage for planting at the next agricultural year and most important export of these garlic bulbs to other cities of Mazandaran and even neighboringprovinces, will probably cause the spreading of pathogenic fungi inoculum. For the first time, this study reports the fungus F. oxysporum 7391 as one of the important factors in causing the disease of the Garlic-Tarom plant in Sari. More comprehensive studies are needed to identify, diversify and distribute specific forms and subspecies of the fungus F. oxysporum in farms at Mazandaran province. Epidemy criteria need to be defined for these Fusarium spp., and bulbs must be carefully inspected before export or storage. Quarantine should be used to prevent the spread of inoculum to other provinces until the pathogen is completely controlled.

Elm trees are one of the most important ornamental trees and are widely used in the design of urban green spaces. Dutch elm disease is recognized as one of the most important elm diseases in the world. The disease has become an epidemic worldwide and at least three species of Ophiostoma including O. ulmi, O. novo-ulmi and O. Himal-ulmi that differ in geographical distribution and invasion power, are involved in this disease. In Iran, O. ulmi and O. novo-ulmi are known to involve in this disease, with O. novo-ulmi being more virulent. Management of the disease is mainly achieved through preventive and quarantine methods, health measures, resistant cultivars and the use of chemical compounds. Various aspects of the disease, including disease symptoms and signs, pathogen biology and ecology, disease management methods are reviewed in this paper.

Fusarium wilt caused by Fusarium oxysporum f.sp. phaseoli is an important worldwide disease of beans. The pathogenicity of two isolates from the southwest of Iran was tested on cowpea, red bean, and kidney bean. To find the appropriate method for biological control of the disease, the inhibition of mycelial growth of fungal isolates by silver nanoparticle extract of Trichoderma harzianum was investigated in vitro. The extract of superior isolate of T. harzianum was converted into nanoparticles by mixing with silver-nitrate solution, and the formation of nanoparticles was proved by ultraviolet light spectroscopy. The maximum absorption was at 440 nm in a concentration of 5 Mm of silver-nitrate. The inhibitory effect of 10 concentrations of this nanoparticle on the mycelial growth of hyper-virulent isolate of the pathogen examined and the concentration of EC50 = 650 ppm was determined. The effect of EC30, EC50, EC70 concentrations of this synthesized nanoparticles solution, pure T. harzianum extract and silver-nitrate solution on the severity of the disease in kidney and red beans was tested in greenhouse conditions. All treatments significantly reduced the severity of the disease in beans, but their efficacy was lower than those of silver-nitrate and pure extract of T. harzianum. The biological control potential of Fusarium wilt by silver nanoparticle extract of T. harzianum is being reported for the first time.

Interaction between nematode Meloidogyne javanica and fungus Verticillium dahliae on tomato in greenhouses were investigated.Nematode and the fungus inoculated in different time intervals, nematode two weeks before the fungus, nematode and the fungus at the same time, fungus two weeks before the nematode, nematode alone and the fungus alone and the interaction of the pathogen agents were tested.The results showed that the presence of the both of the pathogens in the soil can lead to the greatest reduction in growth factors and the reduction in nematode two weeks before the fungus and nematode fungus (simultaneous) treatments was more significant.The highest disease severity index was observed after 90 days in the nematode two weeks before the fungus treatment, that was significantly different with fungus alone treatment and in all fungus received treatments disease severity index was more than two.Presence of the nematode M. javanica increased severity and rate of wilting caused by V. dahliae on tomato while the presence of fungus, reduced nematode pathogenicity and population indices.The least amount of vascular tissue browning index and stem colonization percent was observed in treatment with fungus alone inoculated and in other words, nematode increases vascular tissue browning index and stem colonization percent.The highest plant height reduction observed in the treatments where both of the pathogens were present.The interaction between pathogen agents with reduction in growth factors indices and increase in tomato wilt disease increases the damage to the plant

Ralstonia solanacearum is an important phytopathogen which reduces quantity and quality of potato. Due to its wide distribution and broad host range and in soil of different regions through irrigation water or latent infected tubers. It is generally difficult to control the damage of this bacterium. It has widely distributed in most of potato growing regions of Iran and by causing wilt and brown rot disease of potato, is a serious treat for cultivation of this crop in the country. Providing and sowing the healthy and certificated seed tubers is the most effective method of controlling the disease. For a successful strategy of disease management, a clear understanding of mode of disease distribution and epidemiology of causal agent is necessary. In this paper, recent scientific findings on this disease are described and new methods of bacterium detection and health assay of seed tubers are introduced.

Fusarium wilt fungiFusarium oxysporum f.sp. nicotionae and root-knot nematodes (Meloidogyne incognita), are the most important soil-borne tobacco pathogens in Iran and over the world. Access to resistance genetic resources and cultivation resistant cultivars to these pathogens, are the most basic control methods to these pathogens and damage reduction come from epidemic disease, especially in the northern province of Iran. This research was studied in order to evaluate the resistance of 6 tobacco genotypes, including (BCE, HBT8, K17, Burley BB163, and Burley Geel 3) and Burley 21(as sensitive control) in a randomized complete block design (RCBD) with 3 replications during 2014-2015 under natural field infection. Fusarium wilt resistance evaluation based on Moorman et al with scale (0 - 4) evaluated on a weekly basis and resistance to root- knot nematode at the end of season based on number of galls, number of egg masses and the average number of egg per mass with scale 0 - 10 was performed. Evaluation the severity and progress of both diseases in the different cultivars showed that prevalence of these diseases by starting the heat season and air humidity has increased and these two pathogens have the synergistic effect together in the soil of field. The results of this research showed that Burley 21, Burley BB163, Burley Geel3 with sensitivity indexes 8,6,6 were respectively in groups susceptible, moderately susceptible, K17 with sensitivity indexes 4 are moderately resistant and BCE, HBT8 cultivars with sensitivity index 2 were in resistant groups to soil-borne pathogens. According to these results the BCE and HBT8 identified as a resistant cultivars and Burley 21 identified as a most sensitive cultivar under natural field infestation conditions.

During the growing seasons of 2009 and 2010، same tomato fields throughout Marvdasht were visited and 96 isolates of Fusarium spp. were collected from root، crown and stem of diseased tomato plants. Isolates were identified as based on morphological characteristics. They were divided into four species namely: Fusarium solani، F. pseudoanthophilum، F. oxysporum and F. equiseti. These species، being highly pathogenic to tomato، accounted for 47. 9%، 18. 7%، 22. 9% and 10. 4% of the isolates، respectively. Of these species، F. solani and F. pseudoanthophilum are the first time reports of on the disase tomato from Iran. The most frequently encountered species were F. solani and F. oxysporum with 46 and 22 isolates، respectively. Pathogenicity test was conducted for all the species of Fusarium on tomato seedlings by the methods of root dip and soil inoculation and as based upon completely randomized design. Data were analyzed through SAS and mean comparison done through LSD test. Results indicated that all the species of Fusarium except F. pseudoanthophilum caused wilt، chlorosis and root rot in tomato host plants. The results indicated isolates of Fusarium spp. To be significantly different in the disease severity at 1% probability. Host range study with F. oxysporum revealed that the pathogen caused wilt and chlorosis only on tomato and was identified as F. oxysporum f. sp. lycopersici. Thid was while، F. solani caused root rot in tomato، chickpea، Arachis hypogea and Amaranthus retroflexus.