نشریه دانش بیماری شناسی گیاهی
سال دهم شماره 2 (پیاپی 20، بهار و تابستان 1400)

Truffles are edible fungi belonging to the phylum Ascomycota. These valuable fungi can be divided into two categories: desert and forest truffles. They are obligatory mycorrhiza forming with some trees, shrubs, annual and perennial plants. These fungi belong to 38 genera of six families of the order Pezizales, class Pezizomycetes. The forest truffles are classified in the Tuberaceae family and the desert truffles in the other families. The existence of Tuber aestivum from the family Tuberaceae, Terfezia claveryi, Terfezia boudieri, Tirmania pinoyi, and Tirmania nivea from the family Pezizaceae, Picoa juniperi, Picoa lefebvrei, Geopora cooperi and Geopora cooperi, from the family Pyronemataceae, has been morphologically and molecularly proven by researches in Iran. The morphological characteristics, symbiotic plants, and distribution areas of these fungi are described here.

Bacterial canker caused by Pseudomonas syringae is one of the most damaging diseases in apricots. This experiment was conducted to evaluate relative resistance to the disease in 22 selected local apricot hybrids including AD507, AD405, and HS731 which were recently released as Jalil, Parsi and Shanli.

Evaluation methods included artificial inoculation of two-year-old seedlings in an orchard and of cut shoots in the laboratory. Initially, the pathovar identity of localP. syringae strains were determined using LOPAT and GATTa tests and three isolates were used as inoculum. The inoculation was done in the seedling stem and after one year and 1.5 years, canker length was recorded.

The pathovar of all isolates was identified as P. syringae pv. syringae. The longest and shortest cankers were observed in AD1033 and AC113 with averages of 34.76 mm and 8.35 mm, respectively. The cut shoot bioassay was not practical for apricots. The hybrids were classified into four groups including highly resistant, resistant, moderately resistant, and susceptible.

AD1033, AD1042, AD940, AD811, HS210, DM101, HS203 have been classified as susceptible and should not be used in breeding programs and orchard establishment/replacement. Jalil, Parsi, and Shanli were rated as resistant, and moderately resistant, respectively.

Cumin is the second most popular spice worldwide after black pepper. It is planted with a large acreage each year in Iran, especially in the Khorasan-Razavi province (northeastern Iran). Fungal diseases have caused great loss to this precious plant every year. This study aimed to investigate and identify the causal fungi of chlorosis and wilting of cumin in the Khorasan-Razavi province.

Yellowed and wilted cumin plants were sampled from Torbat-Heydarieh, Kashmar, and Roshtkhar suburban’s farms, and fungi were isolated, purified, and identified, from their diseased tissues. The pathogenicity test of isolated fungi was carried out on a local cultivar under greenhouse conditions.

Two Fusarium species, including F. oxysporum with the highest frequency and F. equiseti with the lowest frequency, were isolated from diseased cumin plants. Between 43 isolates of these fungi in the pathogenicity test, twenty-four isolates of F. oxysporum caused wilt, and nine isolates of  F. equiseti caused chlorosis and leaf fall, in the plant.

F. oxysporum, and F. equiseti are known as the causal agents of cumin wilt and chlorosis in the Khorasan-Razavi province of Iran.

Soil-borne fungus Sclerotinia sclerotiorum or white mold is the cause of the destructive disease of root and stem rot of many plants. Chemical control due to the lack of highly resistant cultivars is the most important method in the pathogen management program in various plants. However, the repeated use of fungicides leads to the development of resistant strains in pathogen populations. The use of fungicides with different modes of action, especially those with a synergistic effect, is one the most important anti-resistance methods.

In this research, the effect of different mixing ratios in pairs of carbendazim, iprodione, and tebuconazole fungicides and their possible synergistic activity on four S. sclerotiorum isolates were investigated in vitro conditions. For this purpose, the isolates were cultured on potato dextrose agar, containing different concentrations of fungicides mixtures, and EC50 values and the synergy factors were then determined for different mixtures ratios.

Tebuconazole: carbendazim mixture in 1:7 ratio, with a synergistic activity, inhibited all the isolates growth, and carbendazim: iprodione mixture in 1:9 ratio showed a synergistic effect on three isolates.

The mixture of tabuconazole: carbendazim in 1:7 ratio had the best synergistic activity, and inhibitory effect on the growth of all the pathogen isolates, so it has the potential to be used in the management program of S. sclerotiorum.

The soil-borne root-knot nematode (Meloidogyne javanica) causes heavy losses in tomato plants every year. Their management by chemical nematicides is difficult, expensive, and may also kill soil beneficial microorganisms, so other safer methods should be used to replace them. Purpureocillium lilacinum is an important biological control agent against root-knot and cyst nematodes. This study was carried out to determine the appropriate substrate and carrier of this fungus and its effect on these nematodes in tomatoes.

P. lilacinum was propagated in vitro on seeds of millet, corn, alfalfa, and clover substrates and their spore production was assessed 10, 20, and 30 days after inoculation. The survival of the fungal spores was then examined in talc, kaolin, and corn cob powder as carriers for 12 months. The effect of the fungus in the mentioned carriers against Meloidogyne javanica on tomato was investigated in the greenhouse by means of a completely randomized design experiment.

The highest number of spores in one gram of substrate was produced on millet seed on day 30. The highest number of survived spores was detected in the corncob powder carrier at all 12 months of the experiment. The fungus on corn cob powder was able to control M. javanica to 95% was similar to the nematicide Flopyram. This formulation also had a superior effect in establishing the fungus in the rhizosphere and on roots, suppressing the growth parameters of nematode and increasing plant growth.

The fungus reproduced well on millet seeds and could last longer if formulated on corn cobs powder. Therefore, corn cobs powder can be a suitable base to produce an effective powdered product against M. javanica.

The Root-knot nematodes (Meloidogyne spp.) are one of the most damaging plant pathogens with a wide host range and cause major losses to agricultural crops. The use of resistant cultivars is considered a safe, economical, and effective method to control these nematodes.

In the present study, eight melon cultivars namely Ahlam, 105, Tracey, Ronak, Deltagrin, Mac, Holar, and Veno were evaluated for their response to M. javanica. The seeds were planted in 2 kg pots and maintained under natural conditions in Khormuj city, Bushehr province. Seedlings at the four-leaf stage were inoculated with 5000 eggs and second-stage juveniles. The factorial experiment was conducted in a completely randomized design with five replicates. Sixty days after nematode inoculation, the plants were harvested and the plant growth and nematode population indices were evaluated.

The results showed that the nematode reproduction factor was significantly lower in Ronak, Deltagrin, and Veno than in the other cultivars. No significant difference was observed in shoot fresh weight of nematode inoculated and non-inoculated plants of Ronak cultivar.

Ronak, Delta-green and Veno cultivars are less susceptible to M. javanica.

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.

Blight caused by Ascochyta rabiei is the most destructive disease of chickpea worldwide. Identification of agronomic and morphological properties of disease-resistant cultivars is necessary to set up a suitable chickpea breeding program.

Twelve agronomic and morphological properties of 21 resistant, semi-resistant, and susceptible chickpea genotypes were investigated in a field experiment in a randomized complete block design with six replications in one agronomic year in western Iran.

All genotypes were divided into three main clusters based on the UPGMA dendrogram. The lowest yielding genotypes were located in cluster II and IDDMAR-2012-32 genotype was susceptible to disease and desi-type in this cluster. The genotypes with the highest yield were placed in cluster III, and the genotype Gebres 419-2 was resistant to the disease and the desi-type in this cluster. Among the Kabuli-type genotypes, ILC482 was included in cluster III as a high-yielding and semi-disease-resistant cultivar, and low-yielding FLIp-02-65C and FLIp-01-164C lines along with disease resistance were included in cluster I.

Gebres 419-2 can be crossed with FLIp-02-65C or FLIp-01-164C to produce robust, high-yielding Kabuli chickpea varieties with large seeds.

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.

Rose is the most important cut flower in the world. Dieback is one of the most devastating rose diseases in greenhouses. The main symptom of the disease is dryness of the branch tips and lack of flower formation. The disease causal agents are Coniothyrium fuckelii, Botryodiplodia theobromae, Botrytis cinerea, Trichothecium roseum, Acremonium sclerotigenum, Diplodia rosarum, Lasiodiplodia pseudotheobromae, Phomopsis sp., and Pestalotia funereal. Disease management methods include cutting the top of the knot at an angle with the least remaining of the deadwood tissue to accelerate the formation of callus tissue, chemical protection of pruning wounds with fungicides, disinfection of the garden knife after each cut, avoiding wounds on the stems and compliance with greenhouse sanitation are described in this article.

Agrobacterium tumefaciens is capable of causing distractive disease of crown gall in a wide range of dicotyledonous plants and causes great economic impact in its hosts. This soil-dwelling bacterium can survive as a saprophyte in soil and plant debris for a long time. When the host plant is present, the bacterium is absorbed into the plant through the root secretions from the wounds and enters the plant through it. The pathogenic bacteria introduce a part of its Ti plasmid, called T-DNA, into the plant cell. Integration of the T-DNA to plant cell genome results in expression of the encoded oncogenes and an increasing the production of phytohormones in cells. Overproduction of auxin and cytokinin leads to cells hyperplasia and hypertrophy, which results in the gall formation on the root, crown, and branches of infected plants. As regards the wide host range, high economic impact, and difficult control of this disease, in this article phenotypic, genetic and pathogenicity characteristics of bacteria have been studied, as well as biology and effective strategies of integrated disease management are presented.

Fungi lack chlorophyll and are not able to photosynthesize and obtain the required energy from the decomposition of organic matter in the environment. In general, for the industrial production of biological agents, the choice of cheap and accessible food sources is very important. In this paper, the main nutritional requirements of fungi in liquid fermentation are discussed, which include carbon sources, nitrogen sources, minerals and oxygen in aerobic fungi. Carbon sources in the liquid fermentation industry are carbohydrates, animal fats, vegetable oils, hydrocarbons and alcohols, of which the major carbon sources are carbohydrates. Eight to fourteen percent of the dry weight of fungi is nitrogen, and a large number of mineral and organic compounds can be used to meet the fungus's need for nitrogen. Fungi, like other microorganisms, need certain minerals for their growth and cellular metabolism. Most commercially produced and consumed biological fungi are aerobic microorganisms and in some cases, facultative anaerobes. In the mass production of filamentous fungi, the presence of sufficient dissolved oxygen is an important and limiting factor for proper growth and sporulation.