mehdi sadravi

Early blight caused by Alternaria species is one of the major tomato diseases worldwide, causing losses of up to 86% of yield. Identifying and cultivating resistant varieties is the best method for disease management. Considering the prevalence and importance of diseases in Iran, this study was conducted to identify resistant cultivars among 15 available varieties.

In Kohgiluyeh and Boyer-Ahmad province in southwestern Iran, a severely affected tomato field by the disease was visited and samples of the diseased plants were taken. The pathogenic fungus was isolated on potato dextrose agar medium from the diseased tissues of the plant after their surface disinfection and after its purification by the single spore method and its morphological properties were examined and measured. The collected data were compared with the descriptions of Alternaria species and based on that, the pathogen was identified. Seedlings of 15 tomato varieties were inoculated with a conidia suspension at the 4-leaf stage in a completely randomized statistical design and maintained in a growth chamber with a temperature of 28oC, relative humidity of 90%, and a photoperiod of 16 hours of light and eight hours of darkness. Eighteen days after inoculation, the response of each cultivar to the disease was determined by calculating the percentage of infected leaves as well as the number and size of spots, and the disease index.

Alternaria alternata has been identified as the cause of early blight in tomatoes in this region. Varieties 10552, King Stone, Super Chief and Ventero with minimal symptoms were scored as resistant; 4129, 3725, 4224, Retino, Aras, Flat 111 and Super Pooya as semi-resistant and 7806, Early Pooya, 11057 and CH Pooya were known to be susceptible to the disease.

Cultivation of resistant or semi-resistant varieties can be recommended for disease control. The occurrence of tomato blight disease caused by A. alternata is reporting here for the first time from the region.

Fusarium wilt caused by soil-borne fungus Fusarium oxysporum f. sp. lycopersici (Fol) is one of the most important diseases of tomatoes in the world. Identification and cultivation of resistant varieties is an environmentally friendly method of disease management that leads to the production of a chemical-free and clean yield. This research was conducted to evaluate the reactions of eight tomato varieties to the disease and their correlation with peroxidase enzyme.

Wilted tomato plants were sampled in the greenhouses of southwestern Iran and after isolation and purification and studying the morphological characteristics, two Fol  isolates were identified. The reactions of eight varieties vs. Kingston, Dafnis, Super chef, Karnak, CHpooya, Earlypooya, Superpooya, and CH to these two isolates were investigated in a factorial experiment with a completely randomized statistical design with four replications for each treatment under greenhouse conditions. The disease severity index and the vegetative and reproductive indices of the plant were determined. The level of peroxidase enzyme in the leaves of plants of each treatment was measured by spectrophotometric method at 470 nm wavelength and its correlation coefficient was determined with the disease severity index.

Analysis of the variance of these experimental data revealed a significant difference between Fol isolates in pathogenicity and interaction between Fol isolates and varieties. Fol2 isolate was more aggressive than Fol1 and CH was moderately susceptible, and  Earlypooya, Karnak, Superpooya, Dafnis, CHpooya, were moderately resistant, while Kingston and Super chef  were completely resistant to this hyper-virulent isolate of  the pathogen and disease. The peroxidase level had negatively correlated with the disease severity index.

Among these varieties, Kingstone and Super chef are resistant to the disease. Peroxidase levels can be used as a resistance marker to assess how different tomato varieties react to the disease.

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.

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.

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.

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.

The province of Kohgiluyeh and Boyer-Ahmad in southwestern Iran is an important rice-growing area. Seed-borne fungi can cause harmful diseases, so identifying them is important to prevent these diseases.

Thirty seed samples of four rice varieties were collected from different regions of the province. Seed-borne fungi were isolated by using the potato-dextrose-agar plate, blotter, and deep freezing blotter methods and after purification, their morphological characteristics were studied and they were identified. The total frequency of seeds infected with fungi and the frequency of seeds infected with each fungus were calculated. The effect of these fungi on seed germination and root growth of four cultivars Champa, Shamim, Gerdeh, and Lenjan was tested by placing them between wet sterile filter papers.

Twenty-eight fungi of 11 genera vs. Alternaria, Aspergillus, Bipolaris, Cladosporium, Curvularia, Epicoccum, Fusarium, Penicillium, Pyrenophora, Rhizopus, and Ulocladium were identified in these thirty samples. These fungi did not significantly affect seed germination of these varieties, but caused root rot in them. The average infestation of the Champa variety was lower than the others.

The Champa variety is relatively resistant to these fungi, followed by Shamim, Lenjan, and Gerdeh respectively.

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.

Fusarium root rot with damage reported up to 85% of the crop yield, caused by Fusarium solani f. sp. phaseoli, is one of the most important bean diseases in the world. Biological control is a healthy and environmentally friendly way to manage this soil-borne disease.

Bean farms in Kohgiluyeh and Boyer-Ahmad Province were visited and the rotten roots of diseased plants were sampled. Two isolates of the pathogen were isolated, purified and identified. The pathogenicity of these two isolates was tested on two bean varieties Drakhshan and Pak under greenhouse conditions. The colony growth inhibition rate of the hypervirulant isolate of the pathogen was assessed by 14 native isolates of Trichoderma harzianum, four isolates of Trichoderma virens, two isolates of Trichoderma atroviridae, and five native isolates of Pseudomonas florescens and P. florescens CHAO with hyperparasitic ability and production of antibiotics in vitro. Finally, the effect of four superior T. harzianum isolates, one T. atroviridae isolate and two P. florescens isolates on disease severity were examined in a completely randomized design in the greenhouse.

All isolates of three species of Trichoderma had the ability to hyperparasite and destroy pathogenic hyphae. Four T. harzianum isolates showed a more significant ability to produce non-volatile and volatile antibiotic materials. All treatments significantly reduced the disease severity, but a T. harzianum isolate was more effective in vivo.

Fusarium root rot is also found in bean fields in southwestern Iran. Native isolates of T. harzianum, T. virens and T. atroviridae have the hyperparasitic ability on the pathogen. These fungi and isolates of P. florescens have the ability to inhibit the growth of the pathogen colony by producing antibiotic substances. Isolates of Trichoderma harzianum, T. atroviridae and P. florescens CHAO have the ability to reduce the severity of the disease in vivo.

This study has carried out for distinguishing of Leptosphaeria maculans and L. biglobosa (aggressive and ‎non-aggressive groups respectively) using colony growth, ability for pycnidium and pigment production in four ‎mediums and temperatures of Forty nine isolates (Zaman Mirabadi et al., 2010) (totally 784 treatments) in three ‎replication and three times. The result of analysis variation has shown that significant difference between isolates ‎considering colony growth in the different mediums and temperature treatments. The maximum and the minimum ‎colony growth was observed in 30⁰c –v8 juice Agar (48.05 mm) medium and 15⁰c-Czapek Dox Agar (17.01 mm) ‎respectively after 12 days. The greatest and lowest pigment production in the different temperature was observed in ‎PDA and MEA (except in 30⁰c). The minimum and maximum pigment production was observed in 15⁰c and 30⁰c ‎respectively. The percentage of presence yellow-orange and brown pigment was‏ ‏variable in the different treatments. ‎Brown pigment in V8 and CDA was dominated while yellow- orange was seen in PDA and MEA. 93.78 % isolates ‎produced pigment in Czapek Dox Broth. The maximum pycnidium production was observed in V8 and 20⁰c. ‎According to the obtained results, Dasht-Naz, Eslamabad, Fazelabad, Kohi khail and bykar ayesh were belonged to ‎aggressive species (L.maculans) and Talokola, Lala, Khalkhail and mustard isolate too were located as L.biglobosa.

Early blight caused by Alternaria species is one of the most important tomato diseases in the world. The disease has been reported from most areas in Iran with up to 90% infection. This study was conducted to investigate the effect of nano-chitosan on the severity of the ‎disease and its use as a replacement‎ of the chemical fungicide, chlorothalonil.

Diseased tomato plants of fields and greenhouses of Fars province in southern Iran were sampled. Pathogens were isolated from diseased tissues, purified and identified by studying their morphological characteristics. The effect of nano-chitosan at three concentrations of three, five and seven grams per liter and the fungicide chlorothalonil were tested before and after inoculation of two pathogens. The disease severity indexes were measures in Sunseed and 16 cultivars of tomato under greenhouse conditions using a factorial experimental in completely randomized design with four replications. The data were analyzed with comparing the means.

The isolated pathogens were identified as A. solani and A. alternata. Results of the greenhouse experiment showed that A. solani was more aggressive than A. alternata and the cultivar 16 was more resistant to the disease. Nano-chitosan at 5 and 7 mg/ l significantly reduced disease severity indexes when use before pathogen inoculation, and at 7 mg/l when use after pathogen inoculation.

Nano-chitosan can be used as a bio-fungicide to replace chlorothalonil as a chemical fungicide for disease management.

Damping-off is an important disease of cucumber in Iran. Greenhouses cucumber production were visited in Kohgiluyeh and Boyer-Ahmad Province, in south-west Iran, and sampled from infected seedlings to evaluate the appropriate biological control method for the disease. The pathogens were isolated and purified from infected tissues of the seedlings, and their morphological characteristics were studied and Phytophthora capsici and Phytophthora megasperma were known. One hyper-virulent isolate of each pathogen was selected from nine isolates after the pathogenesis test, and were subjected to hyper- parasitism and dual-culture tests against 20 Iranian isolates of Trcihoderma harzianum. All isolates of this fungus had the potential for hyper-parasites of the pathogens. They also showed a significant inhibitory effect on colony growth of pathogens from 26.4 to 73.03 percent in dual-culture. Then, ability of five superior isolates of T. harzianum was tested in controlling cucumber damping-off disease caused by the hyper-virulent isolates of the pathogens in greenhouse. All isolate of            T. harzianum were able to significantly reduce the disease severity, and two isolates controlled the disease without significant differences with healthy control. The efficacy of Iranian isolates T. harzianum in the biological control of this disease is reported for the first time.

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.

Zagros Mountains in the west of Iran and some areas in the north of Iran are covered by oak trees. Four important diseases of Iranian oak trees are charcoal rot, chestnut blight, sudden death and powdery mildew. The symptoms of these diseases and the characteristics of pathogens as well as their prevalence are described in this article. Some strategies for protecting the oak trees from these diseases are also proposed here.

Aspergillus species are saprophytic fungi which can live on plant debris in the soil and water and also on some plant products, stored fruits and grains. They can be identified by studying the features of colonies, conidiophores, vesicles, phialids and conidia, on selective culture media. The biocontrol potential of some isolates of A. flavus, A. fumigatus, A. niger, A. piperis, A. repens, A. tamarii, A. terrus and A. tubingensis, against some plant diseases such as cocoa black pod, root galls and Fusarium root rot of tomato, Alternaria leaf spot, Fusarium dry rot, potato pink and soft rot of tubers has been proven. They also can act as plant growth promoter and aflatoxin reducer agent in seeds and nuts. Key morphological characteristics of these eight species of Aspergillus is described in this paper. Most of these species are reported from Iran, thus identification and application of their efficient isolates can be suggested in plant diseases management as well as the plant growth enhancement programs.

Blight, caused by Mycosphaerella rabiei is the most important disease of chickpea in Iran. In order to find a method for the biological control of the disease, the inhibitory effect of 36 isolates of three species, Trichoderma harzianum, T. virens and T. atroviride, on a most virulent isolate of the pathogen, in hyperparasitism, dual culture, and production of volatile antibiotic compounds were investigated in vitro. Then the impact of the nine selected isolates of Trichoderma on the disease severity and growth of chickpea were tested in greenhouse. The results showed that the inhibitory ability of mycelium growth of the pathogen by isolates of T. harzianum, up to 52.42%, were greater than the others in plate assay. Also they had greater ability in reducing of disease severity in greenhouse condition. Some isolates of T. harzianum and T. atroviride had ability to promote the growth of chickpea in the presence of the pathogen with no significant difference as compared with the healthy control. It is the first report of the ability of these Trichoderma species in the biological control of this disease on chickpea.

Penicillium species have saprophytic live on plants debris, in the soil and also on some plant products, fresh and juicy damaged fruits as well as the storage fruit and grains. They can characterized by studying the features of their colony, conidiophores, phialids and conidia on selective culture media. The ability of some isolates of P. aurantiogriseum, P. bilaiae, P. chrysogenum, P. citrinum, P. funiculosus, P. glabrum, P. griseofulvum, P. oxalicum, P. purpurogenum and P. simplicissimum to control plants diseases such as Fusarium and Verticillium wilt of tomato, pulse white and gray molds, brown rot and blight twig of peach, late blight and cyst of potato has been proved. They also can act as plant growth promoter. Key morphological characteristics of these ten species of Penicillium is described in this paper. Most of these species are reported from Iran, thus identification and use of the efficient isolates of them can be suggested in management of plants diseases or in enhancement of plants growth programs.

Bean, pea, lentil, vetch and broad bean grains are rich in protein. Kohgiluyeh and Boyer-Ahmad (a province in the southwest Iran) is one of the cultivation area of the pulses. In this province, five important fungal diseases included Fusarium wilt, Fusarium root rot, Ascochyta blight, Alternaria blight, and charcoal rot, are common on these plants. Symptoms of these diseases, key morphological characteristics of the pathogens and their distribution areas in Iran and the world is described.

Most crops are propagated by seed. A large number of pathogenic fungi can transmitted by seed and cause epidemy of destructive plant diseases. Treatment of seeds has been shown to prevent plant disease epidemics caused by seedborne fungal pathogens. In this paper، morphological characteristics of ten pathogenic fungi belong to the genera، Alternaria، Aspergillus and Bipolaris، which can decay or reduce the germination of seeds or cause the brown leaf spot disease of cereals، has been described.

Endomycorrhizae or arbuscular mycorrhizal fungi، play an important role in the life of field crops، flower and fruit gardens and vegetables. They increase nutrient uptake and yield of plants and resistance to soil-borne pathogens of plants as well. As these beneficial fungi، are obligate root symbiotic، mass production of their inoculum is only possible on the living tissue of root. The first method for this purpose was pot culturing، then the hydroponic، aeroponic and root organ culture have been devised. Methods and factors affecting the mass production of these beneficial fungi are described and discussed here.

To evaluate the effect of Metarhizium anisopliae and Trichoderma harzianum on root knot nematode (Meloidogyne javanica) in tomato, experiments was performed under controlled as well as greenhouse conditions. Volatile and non-volatile tests showed that there is no inhibitory effect against every one of each biocontrol agents. On the larval mortality and inhibition of egg hatching, a laboratory test was performed in a completely randomized design with eight treatments in four replicates. It has been shown that whole treatments have significantly different with control. The best treatment that caused maximum larval mortality was T. harzianum culture filtrate, and most effective treatment in egg hatch inhibition was M. anisopliae culture filtrate. There was no significant effect of mixture of suspensions and culture filtrates of both biocontrol agents. A greenhouse test was performed in a completely randomized design with five treatments in four replicates. In this test, T. harzianum increased growth of plants in comparison to uninoculated and inoculated controls. M. anisopliae improved the growth factors in comparison to negative control, but not in positive control. Both of bioagents considerably decreased the nematode-related factors including root gall. M. anisopliae had more effect on nematode-related factors than T. harzianum. Under greenhouse condition, there was no significant effect of the mixture of both fungi against the tested nematode.

Downy mildew, caused by Pseudoperonospora cubensis, is the most important disease of cucumber production in humid areas and greenhouses in Iran. The yield loss of cucumber due to downy mildew may reach to 100%. Because the chemical control is the main method of disease control, especially in susceptible cultivars, establishing a forecasting program which is based on estimation of pathogen population, recording the temperature and relative humidity of field and greenhouse, can reduce the risk of disease epidemic. So by proper application of a protective or systemic fungicide can reduce the disease incidence, production costs and the most important, the amount of fungicide residue.

Yellow rust is a major disease of wheat in Iran. Airborne spores of the fungal pathogen are the primary source of contamination. Temperature, humidity, intensity and direction of wind, cultivars response to disease, existence of volunteer wheat in summer, planting time and level of nutrition, are main factors which affect the disease epidemic. In forecasting model based on the disease tracing and its severity in a particular year, some effective agents such as climatic factors, cultivars response and plant growth stage, are determining the numbers of fungicide application. In this review, the importance of disease in the world and Iran as well, disease symptoms, causal agent, effective factors in disease spread, forecasting model and its executive steps and also the suitable fungicides for disease control have been described.

Arbuscularfungi are root symbiontsof 80% of plants, such as most field crops and fruit trees. They establish in root tissue, arbuscule in endodermis cells, and an extramatrical fine hyphal net. These fungi byincreasing absorption of water and nutrient elements for plants, making changes in chemical constituents of plant tissues, competition with pathogens for nutrients and establishment site, structural changes in roots, alleviation of environmental stresses, and increasing population of useful bacteria in soil, help management of diseases caused by fungi, fungal like organisms, nematodes, bacteria, phytoplasmas and physiological disorders. Collection, identification, purification, propagation, and inoculation of these useful fungi to plants, can decrease usage of chemical fertilizers and pesticides that are harmful to consumers of agricultural products as well as to the environment.