مجله دانش گیاه پزشکی ایران
سال پنجاه و چهارم شماره 1 (بهار و تابستان 1402)

Macrophomina phaseolina causal agent of charcoal rot, stem, and seedling rot, causes economic losses on over 500 plant species including tomato and melon around the world every year. One of the most important and effective alternative methods for chemicals and reducing their risks is biocontrol using different agents such as endophytic fungi. In the present study, the effect of some endophytic fungi on charcoal rot disease and the growth indices of tomato and melon plants were assessed. In the dual culture test, among the 12 endophyte species, five isolates including Chaetomium globosum 2S1, Ch. globosum 3L2, Fusarium fujikuroi 37F6, F. acuminatum GO2L1, and F. incarnatum 25S3 which had the highest inhibition of pathogen mycelia growth, were selected for further tests. In the volatile compounds test, all endophytic isolates showed more than 90% inhibition of pathogen mycelia growth. In biocontrol assay under greenhouse conditions, all endophytic isolates except F. fujikori 37F6, completely prevented disease on both tomato and melon plants. In the evaluation of the growth indices and by comparing the treated plants with the infected and healthy controls, no positive effect of the selected endophytic isolates was observed on the growth indices of both plants. However, they reduced the harmful effects of the pathogen and thus reduced the charcoal rot disease severity. Recovery of endophyte isolates from both inoculated melon and tomato plants showed that the surveyed isolates can become endophytes in plant tissue.

Eriophyoidea mites are all herbivorous and are known as scabies mites or rust mites. These mites are plant pests and carriers of plant pathogens.  During the years 2020-2021, gardens, farms, and pastures of eight villages of Maku City were sampled. After identifying and counting the samples, considering the number of species and their relative abundance, species diversity indices, Shannon, Simpson, and Margalefs diversity indices were calculated at each station.In this research, a total of 35 species from 12 genera belonging to five tribes and two subfamilies were collected and identified from different Mako villages. It seems that contrary to the imagination, climate changes and low rainfall in 2019 have affected the species diversity of pasture plants, which has led to a decrease in the indicators of the diversity of the pasture ecosystem compared to other ecosystems that have a regular irrigation schedule. Handavar village had the highest value of Shannon-Wiener's index, and this village also showed the lowest Simpson's index, which means that the decrease in this index indicates high species diversity. Also, the Shannon-Wiener index of Eriophyoidea mites in the garden ecosystem is significantly higher at the probability level of 5% compared to the agricultural and pasture ecosystems. The increase in the diversity of these mites in the garden ecosystem creates this mentality resulting from previous studies that it is possible to witness a change in the behavior and preferences of eriophyoid mites over some non-productive plant species that are close to being on the side of fruitful plants

Tan spot disease caused by Pyrenophora tritici-repentis is a destructive disease in wheat production areas around the world. The disease has a high prevalence and distribution in the Golestan, Mazandaran, and northern regions of Ardabil province. Due to the lack of suitable resistant varieties in Iran, the damage caused by the disease is high. In this study, the evaluation of 50 wheat lines resistance belonging to the 9HLBSN treasury of the International Maize and Wheat Research Center (CIMMYT) was investigated using race1 of the pathogen. By inducing the fungal isolates to produce abundant conidia, the infection was established in the wheat seedlings through inoculation of the suspension of fungal conidia. The results of this study demonstrated that lines number 1, 17, 18, 22, 25, 29, 33, 34, 35, 36, 37, 38, 44, 45, and 47 had a susceptible reaction, and other lines which included 70% of investigated lines, were resistant. In addition, the mean disease index in different lines was calculated and compared. In terms of the mean disease index on the evaluated lines, 13 groups were obtained, which had 8, 8, 8, 4, 3, 5, 12, 23, 24, 28, 28, 26, and 22 members, respectively. Considering the susceptibility of most of the country's commercial cultivars to this disease, the resistant lines obtained in this study are good sources of resistance to be used in the breeding programs of wheat.

Bacterial canker of stone fruit trees caused by Pseudomonas syringae pv. syringae (Pss) interacts with several factors such as ring nematodes. The effect of infection of Mesocriconema xenoplax (Mx) and Pss and co-infection in pot conditions in the greenhouse on peach bacterial canker was investigated on GN and GF677 rootstocks, tolerant and susceptible to Mx, respectively. One-year peach seedlings (cv. Zaafarani), susceptible to Pss, grafted on these rootstocks were used. Infection treatments included nematode inoculation, bacterial inoculation, and inoculation with both pathogens. The experiment was conducted as a factorial in a completely randomized design with five replications. The results were evaluated and compared statistically based on disease severity, bud death, seedling height, root weight, total plant weight, and population of Mx in soil. The results showed a significant difference between GN and GF677 in terms of response to pathogen inoculation (s) based on evaluation indexes. In both vegetative rootstocks, canker severity and dead bud in seedlings co-inoculated with Mx and Pss were more than those only inoculated with Pss alone. In seedlings with GF677 rootstock, in infection with both pathogens, the rate of canker progression up to about 30 cm was measured and dieback was observed. In inoculation with only Mx and Pss, there was a significant difference in plant growth indexes (in both treatments) and nematode population and disease severity between the two rootstocks for inoculation with nematode and bacteria. Therefore, it can be concluded that Mx is a synergistic factor for peach trees (especially at a susceptible rootstock) to aggravate bacterial canker disease caused by Pss.

The cotton whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is one of the important pests of agricultural products that causes great economic losses. In this research, the effect of spirotetramat on three different developmental stages of the pest was studied in several populations that were collected from different provinces of Iran. Bioassay was done by leaf disk method. The results showed a higher sensitivity of the 2nd nymph stage compared to the adult stage and the egg stage; while the adult stage showed the least sensitivity to spirotetramat. The highest rate of resistance in different developmental stages was observed in the Jiroft population The LC50 ratios of adults in Karaj, Yazd, Pishwa, and Jiroft populations to sensitive one (Marand) were 7.6, 6.2, 4.2, and 9.6, respectively. For second instar nymphs, the ratios were 2.0, 2.2, 2.1, and 5.5 respectively. The investigation on detoxification enzymes indicated the higher activity of monooxygenase enzyme in the resistant population of Jiroft (3.34-fold) compared to the Marand population, which indicates the effective role of these enzymes in creating resistance. According to the results, to prevent resistance development, it is necessary to use other chemical compounds with different modes of action to prevent the occurrence of cross-resistance while affecting different developmental stages of pests.

Soybean is one of the most important oilseed crops, supplying half of the protein and vegetable oil by humans. Charcoal rot disease and soybean crown and root rot caused by Macrophomina phaseolina and Phytophthora sojae, respectively, are among the most important soybean pathogens that cause a reduction in crop yield. A biocontrol strategy using Actinobacteria, especially different species of Streptomyces, and Hypocreaceae especially different species of Trichoderma, is considered a method for the management of disease and pests. In this study, biological control of these pathogens was investigated using Streptomyces sp. isolate 23 and Trichoderma sp. isolates 1 and their volatile metabolites. The activity of Streptomyces isolates and a Trichoderma isolate taken from the soil of Kerman was evaluated against pathogenic fungi, M. phaseolin, and P. sojae. Experiments in the laboratory were conducted based on a completely randomized design with three replications. Sequence analysis of 16s rDNA and ITS region showed Streptomyces sp. isolate 23 and Trichoderma sp. isolate 1 belong to S. bacillaris and T. longibrachiatum, respectively. The results of the double culture method and volatile metabolites test showed that S. bacillaris isolate 23 and T. longibrachiatum isolate 1, significantly inhibited the growth of M. phaseolina and P. sojae. In both tests, the two biocontrol agents used showed more inhibitory effects on P. sojae compared to M. phaseolina. The results of the dual culture and volatile metabolites tests showed that S. bacillaris isolate 23 and T. longibrachiatum isolate 1 had a high inhibitory effect on M. phaseolina and P. sojae.

Citrus yellow vein clearing virus (CYVCV) is in the genus of Mandarivirus that infects some citrus cultivars and causes damage. In this study, the transmission of CYVCV by Aphis spiraecola, A. gossypii, and Toxoptera aurantii was investigated. Several 30 adult aphids of each species after a 24-hour acquisition access period (AAP) on infected Persian Lime were transferred to Citrus lemon cv. Eureka seedlings for 24 and 48 hours’ inoculation access period (IAP). Six months after inoculation, the infected plants were counted. Then their infection was confirmed by a two-step RT-PCR test. The results of the first test showed that 6 months’ post-inoculation, the mean transmission rate of CYVCV by A. spiraecola, A. gossypii, and T. aurantii was 16.67%, 13.33%, and 26.67%, respectively, for 24h AAP/24h IAP. The mean transmission rate was 23.33%, 20%, and 33.33% for 24h AAP/48h IAP, respectively. By increasing the inoculation access period of aphids on virus-infected plants from 24 h to 48 h, the transmission rate increased. In the second test, all three species of aphids with an unknown AAP were collected from infected Persian lime trees in the orchard, under natural conditions and allowed to feed for 24 and 48 hours on Eureka lemon in the greenhouse. It was found that the tested aphids were capable of transmitting this virus. The present study confirmed that the virus is transmitted from Persian lime to Eureka lemon by these citrus aphids under controlled conditions.

Accurate identification of the host species is critically important for disease detection and informing appropriate disease management decisions. Paecilomyces formosus, a causal agent of dieback and decline of oak, is an emerging threat that may cause severe risk to the Zagros forests of Iran in the future. In this study, a nested PCR assay for the identification of P. formosus was developed with the species-specific primer pairs PaMF and PaMR designed from the comparisons of nucleotide sequences of the nuclear ribosomal DNA internal transcribed space regions (ITS) from P. formosus isolates and other closely related taxa. To accomplish this, we sampled forest trees with dieback symptoms in Kermanshah and Ilam provinces. The Paecilomyces isolates were identified based on morphological characteristics, acid production on keratin sucrose agar medium, and sequencing of the ITS-rDNA region and part of the beta tubulin gene. Nested PCR was successfully amplified a 441 bp product exclusively from P. formosus genomic DNA, and no cross-reactions were observed with any other species, and also P. variotii. The nested PCR method can detect 100 fg of P. formosus genomic DNA. Sixty of symptomatic forest trees from seven locations in Zagros foreste were assayed, resulting in the discovery of Amygdalus lycioides, Cerasus avium, Cerasus microcarpa, Quercus libani, Acer spp., Acer monspessulanum, Ficus carica, Ziziphus spina-christi, Tamarix ramosissima and Ziziphus spina-christi as new host species, and all seven infested areas. To fulfill Koch’s postulates, the experiments were carried out on detached branches and attached healthy branches of trees at the forests in Kermanshah and Ilam provinces, Iran. The PCR-based method developed here can be used for a fast and reliable diagnosis of P. formosus, monitoring the epidemics, and assessing management strategies in Zagros forests.

Russian wheat aphid, Diuraphis noxia is one of the economic and polyphagous pests of cereals that are exposed to various chemicals such as phenols. In this research, to investigate the possible effect of host phenolic content on the effectiveness of chemical control, Imidacloprid susceptibility was detected for aphids reared on wheat (Shiroodi and Gascogne) and triticale (Sanabad and Juanillo 92) cultivars, under greenhouse bioassay. The LC50 values of Imidacloprid against the mentioned populations were 2.41, 3.56, 4.89, and 5.73 mg a.i. L-1, respectively. Therefore, the highest Imidacloprid susceptibility belonged to the Shiroodi population. Based on biochemical studies, the activity of alpha and beta esterases, glutathione S transferases, and cytochrome P450 for the Gascogne population was 1.32, 1.16, 1.16, and 1.5 times that of the Shiroodi population, respectively. These ratios were 1.82, 1.96, 1.4, and 2 for the Sanabad population and 2.09, 2.48, 1.51, and 2.25 for the Juanillo 92 population, respectively. Moreover, the phenol content of the mentioned cultivars was 2.19, 2.71, 3.48, and 3.87 mg per gram of leaf, respectively. The data analysis showed a positive and significant correlation between the cereals' phenolic content with the research subjects. Considering the biochemical relationships between D. noxia and its host plants, the value of plant phenolics can be suggested as a suitable index for the prediction of aphid response to Imidacloprid.

Acrosternum arabicum Wagner (Hem: Pentatomidae) is an important pest, due to its qualitative and quantitative damage in pistachio orchards. Different diets have been used to breed this insect, but it has not been possible to rear this pest permanently. In this research, using an artificial diet, the nutritional importance of the main substances in a conventional natural diet, sunflower seeds and peanuts were investigated. At first, three diets D1-D3 were tested in which the amount of sunflower seed and peanut butter was modified. After comparison of fecundity parameters in a completely random design it was found that with increasing the amount of sunflower butter in the artificial diet, the intrinsic rate of population increase (rm) changed significantly, so that this index had a significant difference between D3 and D2, which had only sunflower seed and peanut butter respectively. In the second experiment with increasing sunflower butter in D4 and feeding on the conventional diet without peanut seeds, (rm) and the net reproductive rate (Ro), reached their highest value (0.111±0.006) and (114±17.253) in the case of the sunflower seed-green bean diet respectively which showed significant difference with all diets. In addition to Acrosternum arabicum, several other bugs can also be grown with the sunflower seed-green bean diet. The highest value of rm was related to Peribalus sp. The nymphs of the Sunnpest grew well and turned into full-fledged insects by feeding on this diet. It was discussed that sunflower seeds may have special properties for this group of insects.

The cabbage aphid, Brevicoryne brassicae, is a serious pest of cruciferous plants, causing worldwide economic damage, notably due to its resistance to many commonly used insecticides. Therefore, the development of integrated pest management (IPM) approaches that include novel effective insecticides against this pest is essential. This study evaluated the toxicity of insecticides flupyradifurone, fluxametamide, and dinotefuran against adults of B. brassicae after 24 hours using the leaf-dipping method. Probit analysis revealed flupyradifurone as the most effective insecticide against the pest, with an LC50 value of 58.16 mg/L. However, the sublethal concentration (LC25) effect of this novel insecticide on population growth parameters was estimated using the age-stage, two-sex life table theory method. The sublethal concentration (LC25= 21.65 mg/L) of flupyradifurone reduced female adult longevity and fecundity compared to the control treatment. The values of the intrinsic rate of increase were 5.236 and 24.345 nymphs per female, the net reproductive rate was 0.125 and 0.277 per day, and the finite rate of increase was 1.134 and 1.319 per day with LC25 of flupyradifurone treatment and control, respectively. Dinotefuran with LC50 values of 244.50 and 1005.17 mg/L, had the highest toxicity on third instar larvae and adults of Hippodamia variegata, respectively. The selectivity ratio and hazard quotient values indicated that all three insecticides are selective and safe for the predator H. variegata. By conducting more experiments in the future, simultaneous use of insecticides flupyradifurone, dinotefuran, fluxametamide and H. variegate can be recommended in the integrated management of B. brassicae.

During the growth period, the potato crop is exposed to a combination of biotic and abiotic stresses. Rhizoctonia solani Kuhn is the causal agent of potato stem canker disease and one of the most important soil-borne plant pathogens that reduce the yield and quality of potatoes worldwide. Antagonistic bacteria seem to be a good alternative to chemicals in controlling plant pathogens. This study evaluated the biocontrol properties (hydrolyzing enzymes, siderophore, surfactant, biofilm) of 20 Bacillus isolates against R. solani AG3. In total, 23 to 64.9 % of isolates in dual culture assay, 38.2 to 85.4% in volatile compound production, and 76.9 to 90% in antibiotic production showed inhibition against the tested fungus. The isolates were variable in terms of biocontrol properties. Based on the in vitro results, five isolates including Ba1, Ba5, Ba8, Ba11, and Ba12 were selected for identification and additional investigations under greenhouse experiments. The selected isolates inhibited the germination of fungal sclerotium and caused mycelial fragmentation and cytoplasmic coagulation. Strains Ba1, Ba5, Ba8, Ba11, and Ba12 belonged to B. mojavensis, Bacillus sp., B. pumilus, Bacillus sp., and B. velezensis, respectively. In the greenhouse trials, the disease severity index was zero in treatments Ba5 (Bacillus sp.) and Ba8 (B. pumilus), similar to Rovral -TS fungicide and completely controlled stem canker disease. Therefore, they are suggested for additional investigations and preparation of optimal formulations.