فصلنامه گیاه پزشکی
سال چهل و ششم شماره 1 (بهار 1402)

Wheat ground beetle Zabrus tenebrioides (Goeze) (Coleoptera: Carabidae) is an important wheat pest in Iran and some regions of the world. This pest causes damage to wheat by feeding on the root, stalk, and leaves. Farmers try to control this pest by the foliar application of different insecticides, but this method causes damage to the environment. To find an effective method to control this pest, the thiamethoxam insecticide (Cruiser®) efficiency was evaluated using seed treatment in this study. An experiment based on a randomized complete block design with four treatments and four replications was conducted in a field in Ramhormoz city, Khuzestan province (Iran). The treatments were 150 and 200 ml of thiamethoxam plus 2350 ml of water for seed treatment, 2,000 ppm of diazinon by field spraying at the wheat tillering stage, and a control. The results indicated that the average plant density in 150 and 200 ml of thiamethoxam (333.58 and 333.28 plant/m2, respectively) was more than those of diazinon (258.28 plant/m2) and the control (182.12 plant/m2). The average ear density in 150 and 200 ml of thiamethoxam (513.78 and 506.12 plant/m2, respectively) was more than those of diazinon (321.22 plant/m2) and the control (260.86 plant/m2). According to the present results, farmers can use 150 ml of thiamethoxam plus 2350 ml of water for 100 kg of seeds to control this pest by seed treatment.

Beet necrotic yellow vein virus (BNYVV) and Beet black scorch virus (BBSV) have been observed in infected sugar beet roots from Iranian fields. This study aimed to detect the two viruses simultaneously to save time and energy during the infection detection process.

Three methods were utilized in this study. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect two viruses following total RNA extraction from the farm sample. In the first method (the standard method), the mentioned viruses were identified by amplifying 545 bp fragments from the TGB region of the RNA2 genome of the BNYVV virus and 305 bp fragments from the 3'UTR region of the BBSV virus using specific primers. Viruses on an infected root were identified using RT-PCR with primers specific to each virus and performed independently. In the second and third methods, we employed simplex and duplex RT-PCR gradient methods to simultaneously identify two viruses at annealing temperatures of 52, 54, and 56 °C. To this end, virus-specific primers (designed from a part of the gene encoding the coat protein) were used separately but simultaneously with a common PCR program in a thermocycler. These specific primers amplified 391 and 453 bp fragments of the BNYVV and BBSV coat proteins, respectively.

The study's findings show that by performing simplex and duplexRT-PCR simultaneously and optimizing the annealing temperature of primers from the gene encoding the protein coat, target fragments of 453 and 391 bp from BBSV and BNYVV, respectively, are amplified. This study found that an annealing temperature of 56 °C is the optimal temperature for duplex RT-PCR to separate the two viruses. Consequently, simultaneous identification of the BNYVV and BBSV was achieved through this method.

The present study demonstrates that simplex and duplexRT-PCR are suitable for simultaneous detection and are cost-effective in terms of saving time and energy. They can also be used to prepare distribution maps in sugar beet cultivation areas and to evaluate and identify resistant sugar beet lines in breeding programs under greenhouse conditions.

Elm leaf beetle (ELB), Xanthogaleruca luteola (Chrysomelidae), is one of the most serious and destructive pests of elm which is mainly suppressed by chemical pesticides. Concerning the prevalence of elm trees in urban green spaces and chemical control of elm and the consequent urban environmental pollution and natural enemy suppression, safe and eco-friendly tactics like biological control should be substituted for chemical control. Research carried out on biological control of ELB has suggested entomopathogenic nematodes (EPNs) as suitable and favorable candidate for the control of ELB. Regarding ELB integrated pest management, the combined use of EPNs and the bacteria Bacillus thuringiensis has been recommended. In the current study, the effect of different concentrations of the native isolate of Steinernema carpocapsae and the bacteria B. thuringiensis subsp. galleriae (Btg) either individually or in combination on ELB 2nd instar larvae and adult mortalities was tested under laboratory conditions.

Field-collected adults and larvae of ELB were exposed to in vivo-reared S. carpocapsae at 400 and 500 IJs/ml through leaf-bioassay. The elm leaves were floated for 30 sec. in 5‰ or 10‰ suspensions of Btg and air-dried before the assays. A replicate of either twenty 2nd instar larvae or twenty adults was introduced into small polystyrene boxes containing the treated leaves. The combination assays included these treatments: (a) S. carpocapsae 400 IJs/ml + Btg 5‰ (b) S. carpocapsae 500 IJs/ml + Btg 5‰ (c) S. carpocapsae 400 IJs/ml + Btg 10‰ (d) S. carpocapsae 500 IJs/ml + Btg 10‰. The corrected mortality rates were calculated by Abbott’s formula. Data were analyzed using General Linear Model, ANOVA in IBM SPSS and compared by Duncan’s test. Interaction between the nematode and bacterium was quantified through the formula of Robertson and Preisler.

Pathogenicity of the native isolate of S. carpocapsae and Btg on 2nd instar larvae and adults of ELB was verified and mortalities, in general, were recorded in the range of 51.87-88.33%. Both the nematode- and bacteria-infected larvae and adults showed different pre- and post-mortem symptoms and signs. The results showed that there was no significant difference between the incurred mortalities of the studied nematodes and bacteria within each stage group of ELB except for one treatment (df=11, P<0.05). ELB larvae were more susceptible to the nematode and the bacteria in most treatments compared with the adults. Interaction between the tested bacterium and nematode was additive at all concentrations, and neither synergistic nor antagonistic effect was observed in the combined use of S. carpocapsae and Btg.

Considering the higher susceptibility of ELB larvae to the studied nematode and bacterium compared with adults, their field application is recommended at the larval stages of ELB. The additive effect of B. thuringiensis and S. carpocapsae facilitates their combined use against ELB. Either of these entomopathogens could be simultaneously used as effective and safe management tools in the context of integrated pest management of ELB larvae.

Bacterial canker of tomato caused by Clavibacter michiganensis subsp. michiganensis, Cmm, is one of the limiting diseases of tomato cultivation. Because of the chemical control problems, biological control methods are used to control this disease in the recent investigation. Basil (Ocimum basilicum L.) is an annual herbaceous plant from the Lamiaceae family, and various endophytic bacteria have been reported from this plant. Also, many studies have shown that endophytic bacteria have the ability to stimulate growth and control many plant diseases. Therefore, in recent research, it was tried for the first time to test endophytic bacteria isolated from basil plant against tomato bacterial canker.

In this research, 16 endophytic bacteria isolated from basil. They were tested for their antibacterial properties against tomato bacterial canker in laboratory conditions using chloroform vapor method. Also, the effect of these bacteria on increasing total phenol and growth factors, including fresh weight, dry weight and seedling height were investigated. In the next step, the best bacteria in terms of growth factors were used to control bacterial canker, on tomato seedlings, under greenhouse conditions. Next, the physiological changes related to total phenol, catalase and peroxidase were investigated. Finally, molecular identification was done by PCR using universal 16SrRNA gene-specific primers ,27f and 1492r, DNA sequencing and BlastN in NCBI Genebank.

None of the endophytic bacteria showed antibacterial properties against bacterial canker under laboratory conditions. ReA1 isolate showed the highest growth stimulation and total phenol increasing compared to other bacteria therefore, it was used against tomato bacterial canker and reduced the disease by nearly fifty percent. Also, the growth factors were increased compared to the infected and healthy controls after inoculation with ReA1. In addition, the amount of peroxidase, catalase and total phenol increased in plants treated with ReA1 isolate compared to the control. So that the amount of total phenol, peroxidase and catalase, respectively from the highest to the lowest, was related to the application of ReA1 and Cmm, ReA1 alone, Cmm alone and the control without bacteria. ReA1 isolate was detected as Enterobacter sp. by DNA sequencing results.

Recent research showed that Enterobacter sp. strain ReA1 isolated from a plant belonging to the Lamiaceae family (basil) was tested on tomato plants from the Solanaceae family, which was able to reduce tomato bacterial canker disease without direct antibacterial effect. The main possible effects of this bacterium are related to the phenomenon of induced resistance in the plant and the increase of defensive and antimicrobial compounds in the plant. This control effect on the different plant species belonging to Solanaceae, the possibility that this bacterium could be used as a biocontrol agent on many kinds of plants and against a wide range of diseases. It also stimulated the growth of the plant, which makes possible the simultaneous use of this bacterium as a fertilizer and biocontrol agent.

Fusarium wilt disease is one of the most important diseases of melon, which causes damage between 20 and 80% in melon fields. In favorable conditions, the spread of the disease can reach 100%. In the improvement programs, achieving resistant cultivars is considered one of the most important methods of controlling this disease.

In this research, 46 melon landraces were collected from different parts of Razavi, Northern and Southern Khorasan provinces, along with two separate lines, Isabel and Charente T respectively as resistant and sensitive control cultivars to identify new sources of wilt disease resistance to Fusarium oxysporum f. sp. melonis. The experiments were carried out in a randomized complete block design with three replications in the greenhouse of the agricultural campus of Tarbiat Modares University. The seeds were grown in trays containing cocopeat and perlite in a ratio of 2:1; fourteen days after cultivation, the roots of the young seedlings were removed from the culture tray and inoculated for two minutes with the isolate Mt13-3a of F. oxysporum f. sp. melonis race 1.2 spore suspension solution, with a concentration of 106 conidium per milliliter. The symptom was evaluated nine days after inoculation. The spread of symptoms on the plants was recorded every day for 30 days until the complete death of the plant. Evaluation of resistance was calculated using the indices of the area under the disease progress curve (AUDPC), latent period (LP), disease severity index (DSI), and standardized area under the disease progress curve (SAUDPC) in landraces. Investigating the variation of the resistance of the studied landraces based on the mentioned indices was done using analysis of variance and cluster analysis.

The results of the analysis of variance of the data indicated the existence of a significant difference of 1% between the landraces for all four studied indices. Based on the heat map results, there is resistance to race 1.2 of F. oxysporum f. sp. melonis in the genotype Isabel and Tude Qaenat. Also, the cluster analysis of landraces based on Ward's method led to identifying six resistance groups from the 46 landraces studied, along with two differential control lines.

The results of the present research showed that for all four indices of LP, AUDPC, DSI and SAUDPC, there is resistance to race 1.2 of F. oxysporum f. sp. melonis in Isabel genotype as a resistant control and the landraces of Qaenat, Till Magasi, Till Zard, Till Torgh, Laki 1 and Till Keshideh compared to the sensitive control (Charente T).

In this study, the life history characteristics of Trichogramma euproctidis (Girault), an established egg parasitoid species in southwestern Iran, parasitizing Helicoverpa armigera (Hubner) were examined at 18, 21, 24, 27, 30, and 33 °C. The results showed that different constant temperatures significantly affected the number of parasitized eggs, development time, sex ratio, tibial length, number of parasitoids per host egg, progeny longevity, and fecundity. T. euproctidis failed to complete development at 18 °C, the lowest temperature tested. The mean developmental duration from egg to adult female decreased from 15.33 days at 21 °C to 7.25 days at 33 °C. An average of 188-degree days was required to complete development above the lower threshold temperature (7.2 °C). Survivorship was 96.20, 97.20, 98.33, 85.46, and 82.22 % at 21, 24, 27, 30, and 33 °C, respectively. The mean longevity of T. euproctidis ranged from 11.60 days at 21 °C to 4.57 days at 33 °C. Mean total progeny ranged from 19.50 / female at 33 °C to 168.70 / female at 21 °C. Data analysis demonstrated that different constant temperatures had a significant effect on the net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), and generation time (T). The intrinsic rate of increase (r) improved with temperature from 0.240/day at 21°C to 0.370/day at 27 °C and then decreased at higher temperatures. Generation time decreased from 16.90 days to 7.53 days with increasing temperature. The optimal temperature for development and reproduction of T. euproctidis was 27 °C. The results of this study showed that this strain of T. euproctidis appears to have the potential to be utilized in integrated management programs targeting H. armigera.

Wheat stem rust, caused by Puccinia graminis f.sp. tritici, which has caused heavy damage to wheat in the past, is a potential threat to the production of this crop. Considering the history of this disease in the south warm agro-climate zone of Iran and the possibility of the disease epidemics if the environmental conditions are provided, the examination of wheat cultivars and breeding lines to stem rust is a part of the south warm wheat breeding program at Cereal Research Department, Seed and Plant Improvement Institute (SPII). In this way, it is tried to increase the resistance of wheat cultivars that are going to be introduced in this zone.

The present study was carried out to determine the reaction of 56 elite wheat lines of the south warm breeding program including 28 lines obtained from the program in 2015 (named ERWYT-S-94) and 28 other lines from 2016 (named ERWYT-S-95) to stem rust at seedling and adult-plant stages. Investigating the seedling stage resistance was carried out by determining the reaction of experimental lines to three common races of Kelardasht, Mazandaran, and one Ug99 race collected from Shavour, Khouzestan in the greenhouse in Karaj. Investigating the adult-plant resistance was carried out under artificial inoculations in the field in Kelardasht during two cropping years of 2015-16 and 2016-2017 for the ERWYT-S-94 materials and two cropping years of 2016-2017 and 2017-2018 for the ERWYT-S-95 materials.

Based on the results of the present study, the line S-94-25, being resistant to four races of P. graminis f.sp. tritici at seedling stage, showed high resistance to stem rust at adult-plant stage so that the maximum disease rate of 20MR was observed for this line during the two years of experiment. The line S-94-16 also showed high resistance against two races of Kelardasht at seedling stage, and the disease rate at adult-plant stage was a maximum of 20MR. In addition, the line S-94-22 having resistance to three races from Kelardasht and the line S-94-27 with resistance against two races from Kelardasht and the race collected from Shavour at seedling stage, were less susceptible to the disease at adult-plant stage with a maximum disease rate of 30MS. Furthermore, the line S-95-22 with resistance to two races of Kelardasht and the Shavor race and the line S-95-12 with resistance to one race of Kelardasht and the Shavour race at seedling stage, showed less susceptibility to the disease at adult-plant stage with the maximum disease of 40MRMS. Due to importance of wheat stem rust in the south warm agro-climate zone, it is necessary to transfer disease resistance genes to new wheat lines and introduce disease resistant cultivars in this climate.

Aphis gossypii Glover is a polyphagous pest that infects a wide range of host plants in temperate, tropical and subtropical regions. Therefore, it has a great ability to maintain its population in different environmental conditions. Quantitative and qualitative damages of this pest are through feeding on plant sap, transmission of viral diseases, reduction of photosynthesis and secretion of honeydew. Various factors such as excessive use of chemical insecticides, the destruction of natural enemies and the emergence of resistant pest populations have increased the population of aphids and turned it into a damaging pest. However, the most common method of controlling aphids, despite its negative effects, is usage of chemical insecticides. The high potential of this pest in resistance to chemical compounds requires investigating and using of newer insecticides with different modes of action. Insect reproductive parameters as an ecological and indicator tools, can indicate the behavior and physiology of different types of pests after pesticides using. Studies have also been conducted on the effect of sub lethal concentrations of insecticides on behavior, biological characteristics and growth of insect population, which provides a more realistic estimate of the effect of insecticides on pests and natural enemies. Therefore, in this study, the lethal and sub lethal effects of the new combined insecticide Emamectin benzoate 4.8% + Acetamiprid 6.4% which has contact and oral function, was evaluated on the aphids biological and population growth parameters in greenhouse conditions.

The colony of cotton aphid used in the experiment was obtained from pinto beans fields in Urmia, West Azerbaijan (Iran), during September 2021. The aphid population was reared on pinto beans var. Khomein in plastic pots (12 × 6 cm) under controlled greenhouse conditions (21 ± 1°C, 50% ± 10% RH, and a photoperiod of 16: 8 [L: D] h). The LC50 concentration of Emamectin benzoate + Acetamiprid for cotton aphid adults was 23.84 ppm 24 hours after treatment. The values of LC10, LC20 and LC30 were estimated at 1.76, 4.31 and 8.22 ppm, respectively. The insecticide spraying method on leaves containing aphids was used in bioassay and life table studies against adults of aphid insects. The age stage, two-sex life table method was used to analyze the collected data. We used the bootstrap technique with 100,000 iterations to estimate the variance and standard errors of the biological and population parameters and used Sigma Plot software to draw graphs. The growth of the pest population in a period of 60 days was done with Timing-MsChart software.

According to the results, the adult lifespan/longevity was significantly different from the control by LC20 and LC30 concentrations. The shortest lifespan of adult aphid in LC30 treatment was recorded as 5.90 days. Fertility and the duration of Nymphal period were significantly reduced in sub lethal concentrations of the insecticide compared to the control. The highest value of pre adult period in LC30 concentration was recorded 8.88 days and the lowest value in control treatment was 5.06 days. All biological table parameters of cotton aphid treated with sub-lethal concentrations were significantly affected by the insecticide compared to the control. The highest value of intrinsic rate of increase (r) was 0.39 per day in control. The net reproductive rate (R0) decreased from 28.37 nymphs per female/generation in control to 6.90 in LC30 concentration. The lowest value of finite rate of increase (λ) was observed in LC30 concentration, which was 1.18 per day. The gross reproductive rate (GRR) in sub lethal concentrations was significantly lower than the control. The highest and lowest values of mean generation time (T) were estimated in LC30 (11.28 days) and control (9.11 days), respectively.

Based on the findings of the present study, considering the necessity of using chemical insecticides for aphid management, and the significant effect of this pesticide on the aphid Emamectin benzoate + Acetamiprid insecticide can be used to control and reduce population of cotton aphids and it can be a suitable alternative to old insecticides. In order to confirm the greenhouse results, it is necessary to conduct similar experiments in field conditions, and conduct laboratory and field studies on the effects of this compound on the natural enemies of A. gossypii especially bees and coccinellids.

Considering the adverse effects of storage insect pests and their resistance to chemical insecticides, identifying safe, cost-effective, and durable methods to control and reduce storage pest-induced damage appears essential. Utilizing diatomaceous earth is one alternative to chemical pesticides for controlling stored-product insect pests.  This study evaluated the insecticidal activity of diatomaceous earth at a concentration of 0.2 mg/cm2 against two stored-products insect pests, Rhyzopertha dominica F. and Tribolium confusum Jacqulin Duval, on concrete, mosaic, and galvanized steel surfaces. To this end, the surfaces were treated with different diatomaceous earth formulations, including a commercial formulation, SilicoSec®, an Iranian formulation, Dryasil, Dryasil + 0.05% Mentha longifolia L. extract, and talcum powder + 0.05% M. longifolia extract. Mortality was measured 1, 3, 5, and 7 days after treatment. The experiment was conducted at 27 ± 1 °C, 60 ± 5% relative humidity, and dark conditions. The experiments were performed in nine replications (10 adults in each replication). The mortality percentage of R. dominica 7 days after treatment with Silicosec®, Dryasil alone, Dryasil + 0.05% M. longifolia extract, and talcum powder + 0.05% M. longifolia extract on galvanized steel were 43.33, 54.44, 33.33, and 25.55%, respectively. The results indicated that the mortality percentage of T. confusum on galvanized steel was 35.55, 45.55, 26.66, and 23.33%, respectively. The mortality of T. confusum was lower than that of R. dominica adults. Results indicated that the insecticidal effect of diatomaceous earth increased over time. Diatomaceous earth alone had a more significant insecticidal effect than combining them with M. longifolia extract. The highest percentage of mortality in all treatments was found on the galvanized steel, mosaic, followed by concrete surfaces, respectively. Therefore, Dryasil formulation can be used to control stored-products pests in grain silos, although its insecticidal efficacy varies based on surface type.

Legumes are one of the primary protein sources in human and livestock diets worldwide. There are five different types of legumes (i.e., beans, peas, peanuts, lentils, and lupines), with beans as the most important. Fusarium root rot (FRR) is among the most challenging diseases of common beans (Phaseolus vulgaris). While soil-borne diseases are difficult to control, resistant bean cultivars significantly help reduce the losses caused by the disease. This study was conducted in a greenhouse to investigate the susceptibility of different bean cultivars to FRR caused by the F. solani species complex (FSSC).

Several bean fields in Fars, Kohgilouyeh and Boyer-Ahmad, Chaharmahaal and Bakhtiari, Hamdan, Lorestan, Markazi, Qazvin, Zanjan, East Azerbaijan, and Mazandaran provinces were explored during summer from 2017 to 2019. Infected plants were sampled, and the fungi were isolated in the laboratory. Once appeared on the culture medium, the fungal isolates were purified using single-spore isolation or hyphal tip methods. Fungal DNA extraction was performed using Doyle and Doyle’s method for molecular identification of the isolates. A part of the internal transcribed spacer (ITS) region of the ribosomal RNA (rRNA) gene and a translation elongation factor 1-alpha (EF-1α) were amplified from the polymerase chain reaction (PCR). PCR-amplified fragments were sent to the Cardiogenetics Department of Rajaie Cardiovascular, Medical and Research Center (Tehran, Iran) for sequence analysis. After editing, the Basic Local Alignment Search Tool (BLAST) was applied to ITS and EF-1α sequences of the isolates in the GenBank data set in the National Center for Biotechnology Information (NCBI) database. A preliminary pathogenicity test was performed on the Sadri bean cultivar-pathogenicity tests were fulfilled in 400ml plastic pots. An inoculum was prepared by pooling the isolates in a pot experiment utilizing Bilgi et al.’s (2008) method to evaluate bean cultivars. Ten representative isolates of F. solani with the highest pathogenicity were selected from different regions. The cultivar susceptibility was assessed in 3-liter pots as described in the preliminary pathogenicity test. Saleh, Sadri and Koosha chiti (pinto) bean cultivars, Akhtar, Goli and Sayyad red bean cultivars, Dorsa, Shekoofa white bean cultivars, and Valentino and Sanri green bean cultivars were compared based on disease severity and yield correlates (shoot/root fresh and dry weight).

Fusarium isolates from the sampled provinces were identified using authentic scientific sources and Fusarium identification keys based on morphological properties. A Blast search of ITS and EF-1α sequences in GenBank yielded 100% nucleotide identity with the sequences of strains of FSSC. In the preliminary pathogenicity test, leaf yellowing and falling symptoms appeared on the Sadri cultivar in the greenhouse three weeks after inoculation. All FSSC isolates caused root rot on the tested bean cultivar. To evaluate the susceptibility of bean cultivars to the selected isolates, the plants were carefully removed from the 3-liter pots two months after inoculation. The results showed statistically significant differences (p=0.01) among the cultivars. Koosha chiti bean, green Sanri and Valentino cultivars with the lowest root rot severity (19.5%, 22.62% and 23.81%, respectively) and red Goli and Dorsa white bean cultivars with the highest root rot severity (66.67% and 70.24%, respectively) were the least and most susceptible bean cultivars to the pooled FSSC isolates, respectively. The results also indicated relatively significant differences in yield correlates (shoot/root fresh and dry weight) among the cultivars. Besides, the Koosha cultivar was shown to be the most resistant to the disease, followed by Akhtar, Sanri, Valentino and Saleh cultivars. Dorsa white bean and Goli red bean cultivars were demonstrated to be the most susceptible to the disease. This study identified several cultivars with low susceptibility to bean root rot caused by FSSC isolates. A good variation was observed in the spectrum of bean plant responses to the disease. Koosha, Akhtar, Valentino, Sanri and Saleh cultivars with low susceptibility to the selected FSSC isolates may be considered for further studies. Proper soil management with cultivating resistant cultivars is an integral part of any disease management program for FRR.