نشریه دانش بیماری شناسی گیاهی
سال دوازدهم شماره 1 (پیاپی 23، پاییز و زمستان 1401)

Bacterial soft rot caused by Pectobacterium species is one of the important and common diseases in Potatoes and vegetables. Disinfection of tubers or seeds with chemicals is one of the methods of disease management. Copper nanoparticles, like silver and gold nanoparticles, have a strong inhibitory effect on bacterial cells, but they are much cheaper and more accessible than them. This research was conducted to determine the effect of copper nanoparticles alone and in combination with oxytetracycline and streptomycin antibiotics on potato, carrot and onion soft rot.

The pathogen was isolated from rotten tissues of potato, carrot and onion, purified and identified by studying the phenotypic and genetic characteristics of the Pel-gene region using Pectobacterium specific primers (Y1 and Y2). The effect of copper nanoparticles, oxytetracycline and streptomycin, and their combination with copper nanoparticles on the pathogen growth was investigated in a completely randomized design experiment with three replications for each treatment in vitro.

Pectobacterium odoriferum was identified as pathogen based on phenotypic characteristics and genetic affinity. Streptomycin compared to oxytetracycline inhibited the pathogen growth more and their effect in combination with copper nanoparticles increased by 12 and 19.5%, respectively.

Copper nanoparticles can inhibit the growth of P. odoriferum, and in combination with antibiotics increase their effect.

Longidoridae is a family of plant-parasitic nematodes belonging to the order Dorylaimida, that cause damage to most agricultural crops especially fruit trees by direct damage and also transmitting some plant pathogenic viruses. Considering the lack of prior research studies on this topic in the fruit orchards of Rafsanjan region, identifying and monitoring their population is important.

In a study that was conducted to identify plant-parasitic nematodes of horticultural products in Rafsanjan city, some soil samples were collected from the rhizosphere of various fruit trees, in 2020. The nematodes were extracted from the soil samples using two methods, centrifugal flotation-sieving and tray technique, fixed and transferred to the anhydrous glycerin. After preparing permanent slides, the nematodes were studied using a light microscopy. The nematode species were identified based upon morphological and morphometric data using relevant valid references.

In this study, three species of Dorylaimida order belonging to the Longidoridae family including the two genera: Longidorus (L. africanus) and Xiphinema (X. vuittenezi and X. index) were obtained from the rhizosphere. Also, in order to confirm the traditional identification of X. vuittenezi, this species was molecularly studied using D2-D3 extension fragment of LSU rDNA. The obtained sequence of the species was 100% identical to the sequences of the other populations of X. vuittenezi in the GenBank.

This study shows that regional nematode population monitoring needs more attention.

This research was conducted with the aim of determining the reaction of 32 tomato genotypes from the plant gene bank of Iran to the root-knot nematode Meloidogyne javanica, to identify resistant genotypes during two years under greenhouse conditions.

After purifying the nematode population and planting the seeds of 32 tomato genotypes and reaching the stage of 3-4 leaves, each treatment was inoculated with 6000 eggs and larvae of M. javanica in five replicates, and 60 days after inoculation, vegetative traits and traits related to nematode population were determined in each treatment, and based on gall index (GI) and nematode reproductive factor (Rf), the reaction of genotypes to nematode was determined.

Eighteen  genotypes with Rf>1 and GI>2, 23 genotypes with Rf<1 and GI>2, and three genotypes TN-72-938, TN-72-1041 and TN-72-1012 with Rf≤1 and GI≤2, were identified as susceptible, moderately resistant, and resistant to this destructive nematode respectively.

These three resistant genotypes can be used in the M. javanica management program.

The almond tree (Prunus dulcis) and its wild relative, the mountain almond tree (Amygdalus scoparia), grew up together in the province of Fars in Iran over decades. Red leaf blotch disease caused by Polystigma amygdalinum is one of the most important almond diseases in the world. This research was conducted with the aim of investigating the evolution of this pathogen on its wild and domestic hosts.

Ascospores suspension of P. amygdalinum isolates obtained from almond in Fars province was inoculated to almond and mountain almond seedlings in a greenhouse. The progress of the disease in the diseased leaves of mountain almond compared to almond was investigated by sectioning with a freezing microtome from the spots created on the leaves.

Red leaf blotch spots appeared on the leaves of both types of almonds. Statistical analysis of test data showed that P. amygdalinum isolates from almond are able to cause disease in mountain almond with significantly lower severity, and longer incubation period.

The results of this research show that P. amygdalinum, the cause of red leaf blotch disease, have coevolved on cultivated almond through a process of host tracking.

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.

Erwinia amylovora, the cause of apple and pear fire blight disease, is one of the main factors limiting the production of these fruits in the world. Since only a limited number of copper compounds have a protective effect in controlling this disease, increasing attention has been paid to investigating the effect of plant essential oils on this pathogen.

The effect of different concentrations of carvacrol (the active ingredient of thyme, oregano, etc.) and trans-anethole (the active ingredient of fennel essential oil) on the growth of E. amylovora colony, was investigated in laboratory conditions, and their minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) were determined. The inhibitory effect of MIC of these substances alone and the mixture of one-half of their MIC and MBC concentrations was investigated by disc method on nutrient agar medium on the growth of E. amylovora colony. The effect of the three best mixing ratios of these materials on the fruit tissue of the pear Spadona variety was evaluated on the severity of fire blight disease.

Carvacrol and trans-anethole both had antibacterial effects against E. amylovora, but the effect of carvacrol was greater than the other. Mixing carvacrol with trans-anethole increased its effectiveness. Among the three mixing ratios, 47 µg/ml of carvacrol + 141 µg/ml of trans-anethole caused the greatest reduction in disease severity in pear fruit tissue.

The use of a mixture of carvacrol and trans-anethole can be considered for the management of fire blight disease.

Fusarium wilt disease is known as one of the most destructive and fatal diseases of date trees in many date-producing areas of the world, especially date-producing countries in Africa. Currently, a significant portion of date orchards in Morocco and the western and central Sahara of Algeria are affected by Fusarium wilt disease. The economic losses caused by Fusarium wilt disease of dates, especially in the incidence of severe epidemics, are significant. Over the past century, the disease has killed more than 12 million palm trees in Morocco and about three million palm trees in Algeria. Fusarium oxysporum (Schltdl.) f. sp. albedinis, a soil-borne vascular pathogen, is known to cause Fusarium wilt disease of dates. The economic losses caused by this disease are very significant, especially in the incidence of severe epidemics, and in some areas, the Fusarium wilt epidemic has destroyed more than 70% of the date fruits. Integrated disease management strategies include the use of resistant or tolerant cultivars, prevention of introduction of the disease causal agent into disease-free areas, eradication of the disease, biological control and chemical control. This disease has not been reported from date-producing areas of Iran, although similar symptoms to Fusarium wilt have been observed in some date orchards of Hormozgan province.

Saffron is one of the valuable agricultural products and its dried stigma is used as medicine and is known as a precious spice. Infection of the plant's reproductive organs plays an important role in the spread of pathogens. The saffron is reproduced via corms, and using healthy and pathogen-free corms is the best and most effective strategy to prevent the spread of soil-borne pathogens in new areas and fields. Saffron corm rot disease is caused by some fungal and bacterial pathogens. Burkholderia gladioli pv. gladioli is the causal agent of saffron leaf and corm rot disease. The bacterium survives in the soil for a long time, and it is transmitted through the infected soil, farming tools, and corms. In recent years, this disease has been reported from Khorasan Razavi province. In this article, along with introducing the bacterial disease of saffron leaves and corms rotting, strategies to prevent the occurrence and spread of the disease have been presented.

Tomato brown rugose fruit virus (ToBRFV) is an emerging pathogen that generally causes disease in greenhouses. This virus causes yellow areas, malformation and brown necrotic lesions on tomato fruits. This virus, which has a global distribution, has recently been reported using molecular methods in the greenhouses of few provinces of Iran. According to the report of this virus from Iran, the characteristics of the ToBRFV, its symptoms, host range, mode of transmission and spread, and its management methods have been described based on previous studies.

Yeasts are widely distributed on earth.They play role in industries such as bakery, fermentation, protein production, the synthesis of chemicals such as riboflavin and citric acid, agriculture and plant diseases management. They are effective in reducing plant diseases. through a variety of mechanisms, such as competition for food and space, parasitic relationship with the pathogen, induction of plant resistance, mycoparasitism, ecological niche occupation, mycotoxin detoxification and production of cell wall degradation enzymes. The superior characteristics of yeasts are greater tolerance and adaptation to thermal fluctuations at low and high temperatures, adaptation in a wide range of relative humidity, pH fluctuations, low oxygen levels, high proliferation rate, limiting the pathogen population and tolerance to UV radiation. Due these characteristics, yeasts are considered as one of the best choices to use in the process of biological control. In this paper, the positive aspects of yeasts compared to other microbial agents, their role in agriculture and management mechanisms of plant diseases are discussed.

Bacterial wilt caused by Ralstonia solanacearum is one of the major diseases of tomato in the world. Today, new methods based on the use of biological products for the management of plant diseases have been considered to reduce the consumption of chemical toxins and damage to the environment, to provide an organic product for consumers.

The effect of three biofertilizers: Nitro Kara (containing several nitrogen-fixing bacteria), effective microorganisms (EM®: containing several species of yeasts and bacteria), and compost on tomato growth indices and severity of bacterial wilt disease were evaluated in a completely randomized design in greenhouse conditions.

Analysis of variance showed that, these three bio-fertilizers had significant effect on increasing tomato growth indices, but did not significantly reduce the disease severity. Compost among them had the greatest effect on tomato growth indices even in the presence of the pathogen.

Compost can be considered as an improvement factor for tomato growth indices in the management program of bacterial wilt disease.

Plant viruses are important pathogens that cause quantitative and qualitative decline of agricultural products all over the world. Plants resistance is the most effective way to control plant viruses. Viruses as obligate parasites to complete their infection cycle, such as the processes of protein synthesis, replication, and movement, are dependent on the compatibility of cellular factors of host plants. Absence or mutation in these essential factors for the virus infection cycle or mutation in the regulator of plant defense responses may cause the host's recessive resistance to the virus. Recessive genes identified in virus-plant interactions include eukaryotic translation initiation factors eIF4E, eIF4G, and their isoforms. A number of translation factors have been identified in plants, such as eIF3, eEF1A, and eEF1B, which are essential in interacting with viral RNAs and regulating various processes in the virus infection cycle. More awareness of molecular mechanisms of these factors as well as their interaction with other host and viral factors can be used in the development of new management methods such as silencing or genome editing against viruses.