نشریه دانش بیماری شناسی گیاهی
سال نهم شماره 2 (پیاپی 18، بهار و تابستان 1399)

Chickpea blight, caused by Didymella rabiei, is the most limiting factor in chickpea production areas in the world, including the western provinces of Iran. The aim of this study was to investigate the pathogenic diversity of the isolates collected from western provinces of Iran (Ilam, Lorestan and Kermanshah) on differential lines of chickpea, as well as the relationship between pathogenic diversity of the isolates and their geographical origins.

During the 2017-18 chickpea growing season, samples of infected plants were collected from fields in western provinces and transferred to the laboratory. Then 100 pure isolates of D. rabiei were obtained. Based on the location of collection, the isolates were divided into 20 groups. Based on the morphological characteristics, one isolate from each group was selected as a representative for greenhouse experiments. The pathogenic diversity of theses 20 isolates was assessed on eight differential lines of chickpea. The factorial experiments were performed in a completely randomized block design under greenhouse conditions.

The results of analysis of variance showed that there was a significant difference between differential lines and isolates at a probability level of p<0.01. Based on the response of the differential lines, the pathogenic isolates were grouped into three pathogenic groups, including pathogenic group 1 (weakly aggressive), group 2 (aggressive or moderately aggressive), and group 3 (highly aggressive). The isolates from Kermanshah and Lorestan Province were classified into Group 1 and the Ilam isolates into Groups 1, 2 and 3. The greatest severity of the disease was found in three isolates of Ilam province. The variety ILC3996 showed the highest resistance to all isolates.

D. rabiei isolates from three western provinces of Iran are divided into three pathogenic groups: 1 (low aggressive), 2 (moderately aggressive), and 3 (highly aggressive). Highly aggressive isolates identified in Ilam province can be used in chickpea breeding programs to produce resistant cultivars to the disease.. The wild variety ILC3996 has resistant genes against these pathogenic groups and showed resistance to all of these isolates.

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.

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.

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.

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.

The production of the volatile allyl isothiocyanate compound in Indian mustard leaf inhibits the growth of S. sclerotiorum.

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.

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.

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.

Increasing the expression of genes encoding LysM-RLKs using chitin can be effective to induce systemic resistance to plant diseases and environmental stresses.

The identification of plant parasitic nematodes, which are serious damaging factors for stone fruit trees production, is important to follow the goals of the agricultural sector and increase production.

In order to identify plant parasitic nematodes associated with stone fruit trees in Khorramabad County, Iran, 72 soil samples were collected from stone fruit trees from different regions of Khorramabad County, during 2017 and 2018. After the extraction, killing and fixing of nematodes, species were identified in consideration of morphological and morphometric characteristics using a light microscope equipped with a digital camera.

Thirty species of plant-parasitic nematodes were identified from 19 genera of the suborder Tylenchina. Morphological characteristics of Aphelenchoides sp. and Ditylenchus sp. which did not match any of the reported species described.

Aphelenchoides haguei, Helicotylenchus tunisiensis, Merlinius nanus, Filenchus ditissimus and F. facultativus on stone fruit trees in Iran are reporting for the first time.

Rhizoctonia solani Kühn is a soil borne fungus that causes stem canker and black scurf and severely damages crop in various potato growing areas in Iran. The aim of this study was to investigate the pathogenicity of various fungal isolates from different potato growing areas in Iran on the Burren cultivar.

In this study, The pathogenicity of 70 isolates of Rhizoctonia solani from major potato growing areas in Iran including the provinces of Ardabil, Isfahan, Fars, Kurdistan, Kerman, Lorestan and Hamedan was investigated on the potato cultivar ‘Burren’ in completely randomized design experiment under greenhouse conditions.

The analysis of variance showed that the pathogenicity of the isolates was very different at probability level of 1% is significant, and therefore they were divided into different groups.

The isolates of Ardabil-1, Ardabil-5, Isfahan-14, Fars-26, Fars-29, Kurdistan-34, Kurdistan-39, Kurdistan-40, Kerman-47 and Hamedan-66 had the highest pathogenicity, while the  isolates Fars-21, Isfahan-20, Hamedan-65 and Isfahan-18 showed the lowest pathogenicity, respectively.

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.

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.

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.

The organic compounds used in the present study are effective to control M. javanica on tomato under greenhouse conditions.

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.

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.

Turf grass is the most important grown plant in urban green space, which functions such as temperature adjustment, increase in relative humidity, air softness and dust absorption. Fungal and fungal-like diseases are the most common lawn diseases in Iran, affecting this plant at all stages of growth, causing its decline. Pythium, Fusarium, Microdochium, Rhizoctonia, Bipolaris, Pyricularia and Colletotrichum species are known as damping-off, root and crown rot, leaf spot and anthracnose pathogens of lawns in Iran. The symptoms of these diseases, the morphological characteristics of pathogens and the methods for their management are described.

By studying the structure of the nematode community, healthy and unhealthy soils can be identified in terms of biodiversity and nutrient network. This information is useful for managing soil nutrient networks. The study of the nematode population structure as a biological indicator of soil health is based on the assessment of biodiversity indices, nutrition groups, population dynamics, soil nutrient network profile, biomass and metabolic profile. Practical applications for studying the structure of nematode populations in agricultural and natural ecosystems are described.