نشریه پژوهش های کاربردی در گیاه پزشکی
سال یازدهم شماره 1 (بهار 1401)

 Foliar diseases are considered among important barely diseases worldwide, causing economic crop losses in barely industry worldwide, including Iran. Present study was aimed to characterize Pyrenophora, Bipolaris, Curvularia and Exserohilum species associated with leaf spot diseases of barley in East Azerbaijan province, using consolidated species concept. Totally 462 fungal isolates were isolated and purified from barley plants representing leaf spot symptoms during 2016-2017. Based on morphological and sequence data of ITS-rDNA and Glyceraldehyde-3-Phosphate Dehydogenase gene (gpdh) regions. A considerable diversity was observed among the fungal species associated with leaf spot diseases on barley. In this study, Pyrenophora graminea, P. teres, Bipolaris sorokinana, B. salkadehensis, Curvularia inaequalis, C. spicifera, C. nicotiae and Exserohilum rostratum were identified. Pyrenophora graminea and P. teres were dominant species associated with brown leaf spot symptoms, with isolation frequencies of 68.4 and 25.54 percent, respectively. With the identification of fungal species associated with leaf spot diseases on barley, it will be possible to practice suitable management strategies for these diseases.

 Demographic toxicology is usually the best way to evaluate total effects of pesticides on a population of natural enemy. Lethal and sublethal effects of imidacloprid, pymetrozine and Dayabon® were investigated on the sexual population of Lysiphlebus fabarum at laboratory conditions. Toxicity of the insecticides on immature stages of L. fabarum was evaluated, by dipping leaves containing parasitized Aphis fabae. These insecticides significantly reduced adult emergence rate when parasitized aphids were treated with field-recommended concentrations at larval stage. Imidacloprid had more toxicity than pymetrozine and Dayabon® at pupal stage. Imidacloprid was significantly more toxic than pymetrozine at adult stage. Dayabon® did not have residual effect on adults. In order to assess sublethal effects of three insecticides on life-table parameters of L. fabarum, the concentrations that had 25% mortality threshold and field-recommended concentrations were used for larval, adult and pupal stages treatments, respectively. Adults’ longevity, mean fecundity, females' oviposition period, sex ratio and some population parameters (r,λ, R0) were negatively affected by application of imidacloprid in comparison with other insecticides and control at larval, pupal and adult stages treatments. The intrinsic rate of increase (r) values for imidacloprid treatment and control at larval, pupal and adult stages of parasitoid were 0.2035 ± 0.01, 0.2240 ± 0.01 and 0.2273 ± 0.01 (day-1) and 0.2635 ± 0.01, 0.2759 ± 0.01 and 0.2687 ± 0.01 (day-1), respectively. According to obtained results, pymetrozine and Dayabon® could be used to control A. fabae in combination with L. fabarum.

Downy mildew caused by Perenospora destructor is one of the most important onion diseases. In this research, the efficiency of Poltiglia Bordolese (Bordeaux Mixture WG 20%) at the rate of three, four and five kg/ha and Infinito SC 687.5 (flopicolide + probamocarp) at the rate of two L/h used to control downy mildew of onion disease and compared with control. The experiment was conducted in a randomized complete block design with six treatments in four replications in Jiroft and Behbahan, Iran. The results indicated that, in terms of effect on reducing the severity of the disease, Poltiglia showed a significant difference in compare with control. The comparison of effectiveness of treatments showed that it was related to those of poltiglia five kg/ha which was 63.5 %. In case of Infinito fungicide which used in Behbahan and Jiroft regions, it was 61.97% and 53.22 %, respectively. The comparison of the area under the disease progress curve (AUDPC) showed that in the control treatment with water spraying, this index recorded 21.4 and 20.1 unites per day in Behbahan and Jiroft respectively, and in the control treatment without water; this index was 20.4 and 16.9 per day, respectively. It indicates the role of free moisture in increasing the severity of the disease. The AUDPC index in Behbahan and Jiroft was 9.6 and 10 respectively, and belonged to the treatment of 5 kg/ha of Poltiglia fungicide. The Poltiglia fungicide at the rate of four Kg/h is recommended for controlling onion downy mildew disease.

 Citrus red mite, Panonychus citri is an important plant pest species in the citrus growing regions of the world. Due to the use of chemical pesticides with a wide range of effects against this pest and other pests in citrus orchards, P. citri has been become a serious pest in citrus orchards, including citrus orchards in the north of the country. In this study, the acaricidal and sublethal effects of diflovidazin on different stages of citrus red mite were investigated. The results showed that diflovidazin was highly toxic to the eggs, larvae and deutonymph stages of citrus red mite. The sublethal effects of diflovidazin on the parameters of citrus red mite life table were investigated and the results showed a significant decrease in generation length average, adult longevity, fecundity and fertility period. The net reproduction rates (R0) were 11.2 and 1.62 offspring per female mite for control and treatment of diflovidazin, respectively. The intrinsic (r) and finite (λ) rates of increase for the control were 0.133 and 1.142 per day, respectively, and for the LC30 treatment was 0.033 and 1.034 per day, respectively. In general, the sub-lethal concentration of difluvidazine showed a diminishing effect on all population growth parameters in treated deutonymphs. Overall, the results indicate the lethal and sub-lethal effects of diflovidazin on citrus red mites, and this compound can be recommended as part of a resistance management program to control this mite.

SummaryPathogenic and non-pathogenic fungi growing on insect’s body cansignificantly affect their biology and population. To identify insect-associated fungi, the life stages of the insects, including larva, pupa and adults (alive or dead and helthy), were collected from different habitats in Golestan and Khuzestan Provinces during 2017-2018 and their associated fungi were isolated after surface-sterilization. In this study, 13 various isolates were selected (based on primary morphology) and identified according to morphological and molecular analysis. For molecular identification, the sequences of ITS-nrDNA, tef1a, tub2 and gapdh were obtained, where required for identification. Accordingly, eleven species were identified as follow: Auxarthron kuehnii, Biscogniauxia sp., Cladosporium halotolerans, Curvularia mosaddeghii, Fusarium brachygibbosum, Lasiodiplodia mediterranea, Metarhizium brunneum, Nigrospora gorlenkoana, N. oryzae, N. osmanthi, Petriella guttulata and Phascolomyces articulosus. This study firstly reports the genera of Auxarthron (A. kuehnii) and Phascolomyces (P. articulosus) and the species of L. mediterranea, N. gorlenkoana and N. osmanthi for the mycobiota of Iran.

Seed priming improves germination and growth components of seedlings under biotic and abiotic stress conditions. The aim of this study was to compare the effect of seed priming with chemical fungicides and isolates of Trichoderma harzianum on germination and vigor indices of native cumin population. Also, the activity and expression of phenylalanine ammonia lyase enzyme were evaluated as main markers of phenylpropanoid signal transduction pathway and accumulation of phenolic secondary metabolites. The results of effective inhibitory concentrations showed that the lowest values of minimum inhibitory and fungicidal concentrations of chemical fungicides against Fusarium oxysporum were related to Iprodione-Carbendazim (Rovral-TS®), Carbendazim (Bavistin®) and Carboxin thiram (Vitavax thiram®), respectively. The results also showed that T. harzianum isolates had fungistatic but not fungicide activity against F. oxysporum. The results of biochemical mechanisms showed that protein content and accumulation of phenolic and flavonoid compounds increased significantly in seedlings obtained from bioprimed seeds compared to healthy control. A significant relationship was observed between gene expression and phenylalanine ammonia lyase enzyme activity with phenolic and with flavonoid compounds, as well. Moreover, the results showed that isolates of T. harzianum and chemical fungicides caused activation of the antioxidant system and by increasing protein content and inducing the expression of phenylalanine ammonia lyase gene led to the production and accumulation of phenolic secondary metabolites in cumin. The findings of this research showed that seed priming, especially with T. harzianum isolates while improving seed quality and seedling health, increase the production and accumulation of phenolic secondary metabolites.

Chickpea ascochya blight caused by the fungus Ascochyta rabiei, reduces the yield and quality of chickpea (Cicer arietinum) around the world. The biocontrol potential of 12 bacterial probiotics from genera Alcaligenes, Arthrobacter, Bacillus, Delftia, Lysinibacillus, Pseudomonas and Stenotrophomonas was investigated against A. rabiei. In dual-culture and volatile compounds production tests, all probiotic bacteria (except one Bacillus isolate) significantly inhibited the mycelial growth of pathogen. The highest inhibition in these tests was obtained by Bacillus subtilis BS (57.84%) and Alcaligenes faecalis 1624 (72.5%), respectively. Six probiotic bacteria with the best inhibitory results in the laboratory were selected and their biocontrol and growth stimulation (fresh and dry weight) effects were evaluated in the presence of the pathogen using seed application and foliar spraying methods in the greenhouse. In comparison to the disease control, all selected probiotics in both application methods significantly reduced the disease index and increased the growth factors of chickpea plants (except for the seed treatment of A. faecalis 1624 which did not increase the fresh weight of shoots). Foliar application of B. subtilis BS, with large difference to other treatments, was the most effective treatment in reducing the disease index (63.80%) and increasing the growth factors of chickpea. According to the results of this study, foliar application of B. subtilis BS had great potential in biocontrol of ascochya blight and growth promotion of chickpea. Therefore, if its effectiveness is confirmed by field studies, it could be used in integrated management of this disease in the future.

 In order to minimize the systemic infection in potato seed tubers, annually more than 300 potato seed lots are subjected to laboratory testing for potato viruses in the national potato seed certification system. The accuracy, sensitivity, specificity and speed are of the most important criteria for a diagnostic method to be employed in seed certification laboratory testing procedure. In this study the efficiency of using two methods including single sprout culture and RT-PCR as an integrated diagnostic method was investigated for detecting Potato Virus Y in potato seed samples. According to the present study, RT-PCR performance in Potato Virus Y detection was better than ELISA in terms of sensitivity, accuracy and time saving. RT-PCR successfully detected one infected sample in a combined sample consists of 50 individual samples while ELISA enabled to detect one infected sample in a much smaller combined sample consists of only five subsamples. Moreover because of ELISA retractions to detect low virus concentration and its false negative result, about six percent potato seed lots were incorrectly labeled basic seeds instead of certified seeds. Considering the maximum permissive virus infection percent in national potato seed standards (4% for the lowest seed class) and the maximum required subsamples to be tested (5 subsamples), using RT-PCR method in potato seed certification is economically recommended.

There are many epiphytic bacteria live on surface of pome fruit tree foliage, and have been proven to show antagonistic activity against Erwinia amylovora, the causal agent of fire blight disease. In order to characterize and assess antagonistic potential and genetic diversity of epiphytic bacteria associated with pome fruit trees in orchards of West Azarbaijan province samplings were carried out from foliage of apple, pear, and quince trees during spring, summer and autumn in 2014. Epiphytic bacteria were isolated and their antagonistic potential against E. amylovora were evaluated and then bacterial isolates were identified. The isolated bacteria were categorized into three group including Pantoea agglomerans, Pseudomonas fluorescens and other unknown Gram-positive bacteria. Genetic diversity among the Pseudomonas and Pantoea isolates were studied using Rep-PCR technique. Resulted data were analyzed in NTSYSpc v2.02e software and compared using UPGMA and Jaccard similarity coefficient methods. Also, the analyses of the BoxA1R primer’s band patterns separated ten groups with at least 75% similarity among the pseudomonad isolates. Similarly, nine groups with 70% similarity within the Pantoea isolates were discovered. These results showed a high genetic diversity among the epiphytic strains of Pseudomonas and Pantoea in west Azarbaijan pome fruit orchards.