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

 Every year, soli-borne pathogens of beans cause a lot of damage to this crop. Caudex and root rot of beans caused by Macrophomina phaseolina, Rhizoctonia solani, and Fusarium solani are among the most common diseases of this plant. Cultivating resistant species and maintaining shifting cultivation are among the most effective methods of controlling this disease Disease caused by Rhizoctonia solani include seedling death and in some cases cause rot of aerial parts. Macrophomina phaseolina is a plant-borne pathogen that has a wide range of hosts and causes extensive damage to farmers around the world each year. This fungus is a polyphage and causes disease in more than 500 different plant species such as soybeans, peas, pines, kiwis, cotton and sesame, peanuts, cotton, sunflower, melon. Fusarium solani f.sp. phaseoli Burk, is a fungus isolated from peas and red beans, it is present in most soils and causes disease on legumes and plants that grow in hot and humid conditions.

 A factorial experiment in the form of Completely Randomized Design is conducted in order to evaluate the resistance level of beans species to these fungi. The factors consisted of species (five levels, containing Sadri, Shazand, Saleh, Dorsa, and Goli species) and fungi species (8 levels: each of three fungi alone, combined with each other, and a control sample without any fungus). The reaction of beans species was by calculating the severity of disease and evaluating dry and fresh weight of aerial organs and root and height of the bushes. Steps to perform the test: 1- Preparation of seedbed for planting and sowing seeds of bean cultivars 2- Planting seeds and start growing seedlings 3- Inoculation of seedlings 4- Determining the severity of the disease 5- Measuring the height of aerial parts of seedling.

 Plants are equipped with several defense mechanisms to resist the attack of various pathogens. These include pre-existing structural or biochemical defenses that prevent pathogens from invading, or a series of induced structural and biochemical defenses after an attack. In natural ecosystems, most of the existing pathogenic models are the result of long-term evolution of both the host and the pathogen, and there is usually a high genetic diversity between plants and microbial populations. Today, with the widespread cultivation of cultivars with a uniform genetic background, it has led to the increasing development of susceptible strains of pathogens and the occurrence of widespread epidemics of plant diseases. Therefore, there is a great need to produce lasting resistance to pathogens in plants. Rhizoctonia solani, Macrophomina phasolina and Fusarium solani are fungi with widespread global damage to crops. Therefore, strategies to reduce the quantitative and qualitative damage of these fungi should be studied. In this study, it was observed that beans infected with Macrophomina phasolina, the first symptoms after about four weeks, were yellowing of leaves, wilting of the plant and discoloration of root vascular tissue to reddish-black brown. Also, plants infected with Fusarium solani and Rhizoctonia solani turned the root skin brown. With the spread of disease-causing fungi, necrosis of the crown and roots of tissues was observed. In this case, the color of the vessels changed and turned yellow to brown. Restriction of root development, slow growth of plant shoots, symptoms of leaf yellowing and paleness similar to the symptoms of nutrient deficiency and wilting and leaf fall were the obvious symptoms of these diseases. The results of this study showed that Sadri and Darsa cultivars had relative resistance to all three fungi alone, but Sadri cultivar also showed relative resistance to binary combinations of fungi. But none of the cultivars used were resistant to all three fungi. The experimented species reacted differently to the pathogenic fungi. The maximum and minimum severity of the disease was observed in Goli and Sadri species respectively. The maximum height of seedling was observed in Sadri and Shazand species infected with R. solani and M. phaseolina pathogenic fungi and the combination of these two fungi with Shazand. The maximum dry and fresh weight of aerial organs and roots of infected seedlings was observed in Sadri species infected with F. solani fungus.

The research results indicated that Sadri species, with minimum severity of disease and maximum height and fresh and dry weight of aerial organs and root, was the most resistant species to all three fungi solely and combined.

Recently, a devastating decline has been observed in some citrus groves established with cittrange rootsock. The most conspicuous symptom is a frustose rootstock and decline. The suspicious infected samples were collected at different stages of growth and transported to the laboratory. The samples were rinsed under top water and disinfested with 70% ethyl alcohol. Pieces of each sample was separated with a sterile blade and cultured on potato dextrose agar (PDA) medium. Obtained fungal isolates were purified and pathogenicity of the isolates was tested by A mycelial plug (5 mm diam.) obtained from the margin of a fungal colony was placed in the wound with the mycelium facing towards the stem, and the wound was wrapped with Parafilm. Based on the morphological characteristics including colony form, conidia specific feature, and growing on agar cum Foeniculum vulgare stipes, studied fungal isolates were identified as Diaporthe novem Santos. Genomic DNA extraction was done from fungal isolates and amplification was done with ITS1, ITS4 and Bt regions primers and the amplicons were sequenced. Also the sequencing results confirmed fungal species mentioned above. This is the first report of fruit drop and dieback disease and the causal agent identification on local tangerine in north of Iran.

Mungbean (Vigna radiate (Wilczek)) because of having high protein content, short geowing period and good tolerance to high temperature is one of the most important pulse crops in tropical and sub tropical regions. Mungbean is widely planted in Khuzetan province and the area under its cultivation in Khuzestan is significantly more than any other provinces in Iran. Fungal diseases of root and crown of this plant are among its important diseases worldwide. In this investigation, distribution and identification of the causal agents were studied. During summer and fall of 2010 and 2011, 78 samples were collected from Mollasani, Dezful, Shushtar, Abbid, Gotvand, Ramhormoz and Susangerd which are the main Mungbean cultivation areas in Khuzestan. Macrophomina phaseolina, Rhizoctonia solani and Fusariun solani were recovered from these samples. The collected data illustrated that M. phaseolina with the occurrence frequency of 70.51% was the main cause of the disease. R. solani with 17.95 and F. solani with 11.54% occurrence frequency belonged to a statistically separate group. Moreover, the reaction of the M. phaseolina isolates to potassium chlorate was studied. According to the results, the Macrophomina isolates were divided in two groups, chlorate sensitive to 77.3% and chlorate resistant to 22.7%. Among the chlorate sensitive isolates, two phenotypes - feathery and restricted growth- were identified while the phenotype of chlorate resistant isolates was dense growth. Statistically investigation into pathogenicity of different phenotypes of Macrophomina isolates showed that chlorate resistant isolates with dense growth intensively made infection and sensitive isolates with feathery phenotype ranked second, and sensitive isolates with restricted phenotype had the least pathogencity.

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.

The soft rot causal bacteria, species of Pectobacterium and Dickeya, are important pathogens of plants, which have worldwide distribution. These bacteria are very broad host range and cause plant tissues rot. Diseases caused by these bacteria in the form of soft rot, black stem, bulb rot and leaf spot of corn, rice, canola, sugar beet, potatoes, banana, dates, carrots, cabbage, onions, turnips, peppers, philodendron, pandanus, dieffenbachia, Cyclamen, Iris, Aglaonema, Dracaena, Gladiolus, Ficus, ornamental cactus, and Orobanche have been reported from Iran. Some varieties of field crops such as corn, tomatoes, potatoes and sugar beet, as tolerant to these bacteria in Iran.

Citrus gummosis disease cause canker accompanied by gum exudates, crown and root rot, twig dieback, and decline of citrus trees. This disease has been reported from Khuzestan and Fars provinces, now infected by in parts of Kohgiluyeh and Boyerahmad province (southwest Iran), namely: Molabarfi, Bidestan, Posht-e-koh, Tol-e-mavizi, Bidzard, Chaharbish-e-olia and Chaharbish-e-sofla from Gachsaran town and Cheshm-e-belghis, Dehborji, Spar and Marin from Kohgiluyeh town. Sour lemon, sweet lemon, big sour lemon and orange were more infected respectively. Pathogen identified as Phytophthora nicotianae. As it is epidemic in this province for planting diseased seedlings, incorrect planting method, stalk sensitivity, incorrect irrigation method, can manage by planting healthy certified seedlings on sour orange stalk, correction planting and irrigation methods, chemical control, and biological control with antagonistic fungi or bacteria.

Cultivation of bell-pepper has been developed in Esfahan province, due to its nutritional value and consumption amount. In a survey, fields and greenhouses investigated for foliar diseases of this plant and diseased plants were collected. The collected plant materials were kept in clean plastic bags and transferred to lab. Studying the diseases symptom and isolation, purification, and morphological characterization of pathogens, five common diseases of aerial parts of bell-pepper including downy mildew, powdery mildew, Sclerotinia stem rot, Alternaria blight and gray mold, were identified. Causalfungi were Peronospora tabacina, Levielulla taurica, Sclerotinia sclerotiorum, Alternaria alternate and Botrytis cinerea, respectively. Methods of sampling, isolation and purification of pathogens, diseases symptoms and morphological characteristics of pathogens illustrated.

Valerian medicinal plant (Valeriana officinalis) is a perennial succulent plant that is natural lenitive and good ingrained of diazepam. This study was conducted in order to identify the fungal agents of rhizome and root rot of valerian. Infected plant samples that showed the symptoms of rotting and necrosis were collected from Karaj and used in order to isolate disease agents. Symptomatic samples were sterilized with sodium hypochlorite (1%) and cultured on PDA medium in Petri dishes. Two fungal colonies grown from tissue segments and single hyphal tip or monoconidial isolates were obtained on PDA medium followed by incubation in dark. The fungal isolate identified as Rhizoctonia solani based on the following test. Staining was done for hyphae of Rhizoctonia isolate, number of nuclei in each cellule and hyphal diameter was determined. The hyphae contained several nuclei. Single spore culture, were obtained from macroconidia of Fusarium isolate. After 24 hours of incubation, single spores were transferred to selective medium, CLA, for detection of Fusarium isolates and also, were transferred to PDA medium for sufficient mass production of spores and sporulation. After 7 days colonies appeared as white cream on top and cream at the bottom of Petri plate with abundant micro and macro conidia. Based on morphology and dimension of conidia and also, production of chlamydospore, the fungus was identified as Fusarium solani. This is the first report of these fungi on V. officinalis in Iran.