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Leptinotarsa decemlineata (Say) and Lasioderma serricorne F. are destructive pre-harvest and post-harvest pests of many plants in the family Solanaceae, and stored foodstuffs and non-food items, respectively. In this study, some biochemical characteristics of cellulase in the larval digestive tract of these pests were studied. Endo-β-1, 4-glucanase activity was measured against the substrate carboxyl methyl cellulose. Maximum activity of the enzyme in L. decemlineata and L. serricorne occurred at pH 7.0 and pH 6.0, respectively. The enzymes from L. decemlineata and L. serricorne were maximally stable at pH 7.0 and pH 5-6, respectively. However, the enzyme extracted from L. serricorne is more stable than that of L. decemlineata. Cellulase activity was in the highest level at 50 °C in both species. EDTA and SDS reduced cellulase activity, while the Ca²⁺, Mg²⁺ and Na⁺ ions had a significant increasing effect on cellulase activity. K⁺ did not have any significant effect on the enzyme activity. The values of Km and Vmax were 0.608 % and 0.0187 µmol min^-1 mg^-1 protein in L. decemlineata, and 0.99 %, and 0.0035 µmol min^-1 mg^-1 protein in L. serricorne, respectively. Zymogram studies revealed two bands of cellulase activity in the digestive tract of both species.  

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The diamondback moth, Plutella xylostella (L.) is a serious and economically important pest of cruciferous crops worldwide. The nutritional indices of this pest on four host plants including two canola (SLM₀₄₆ and RGS₀₀₃) and two cabbage cultivars (Green-Cornet and Glob-Master) were determined under laboratory conditions (25 ± 0.5 °C, 65 ± 5% RH and 16: 8 L: D h). The highest relative consumption rate (RCR) and relative growth rate (RGR) were recorded on RGS₀₀₃ (95.68 ± 14.52 mg/mg/day) and SLM₀₄₆(0.382 ± 0.041 mg/mg/day), respectively. The efficiency of the conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) were significantly higher on SLM₀₄₆ (2.298 ± 0.646 and 2.471 ± 0.719%, respectively). However, there was no significant difference among cultivars regarding approximate digestibility (AD) index. The highest feeding performance of the larvae of P. xylostella was found on SLM₀₄₆. The nutritional indices are appropriate tools in host plant resistance evaluation and they also could provide profound understanding of the behavioral and physiological bases of insect-host plant interactions.  

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The melon aphid, Aphis gossypii (Glover), is one of the major pests of cucurbits and an efficient vector of plant viruses such as Cucumber Mosaic Virus. Host-plant resistance is one of the management strategies that can be used to control this pest. In this study, choice test was conducted to identify antixenotic resistance against melon aphid in eight Cucumis genotypes, namely Hormozgan, Bushehr, Guilan, Girtap, Negeen, Sepehr, Pouya and Armenian cucumber. Choice tests were conducted at 25 ± 1 ºC, 60 ± 5% RH and a photoperiod of 16:8 (L: D) h. After introduction of apterous adult aphids to test arena, the number of aphids on each entry was counted at 2, 4, 6 and 24 hours of release. Total phenolic content, NPK essential elements, leaf thickness and leaf trichome density were also measured to discover any association between these factors and aphid host choice. The most antixenosis effect was observed on 'Bushehr'. Increase in antixenosis correlated with increase in leaf trichomes. Antixenosis can be important mode of resistance by reducing host selection and delaying aphid colonization. The identification of antixenotic resistance in several genotypes provides additional options for management of this pest. Moreover, the factors associated with this mode of resistance can be considered in plant breeding programs.

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Reproduction parameters for Helicoverpa armigera (Hübner) were determined and compared on 13 soybean varieties (DPX, L17, BP, Clark, JK, 356, M4, M7, M9, Gorgan3, Sahar, Zane and Williams) at 25±1ºC, 65±5% RH over a photoperiod of 16:8 (L:D) hours. Reproduction parameters were estimated for individual newly emerged moths, which had spent their immature stages on different soybean varieties. The highest rate of gross fecundity was on M4 (2,238 eggs female-1), whereas the lowest value of this parameter was on Gorgan3 (467 eggs female-1). The gross fertility rate was the highest on M7 (782 eggs female-1) and lowest on Gorgan3 (149 eggs female-1). The net fecundity rate varied from 192 (BP) to 1,275 eggs (M7). The net fertility rate was the highest on M7 (586 eggs female-1) and lowest on Sahar (56 eggs female-1). The daily number of eggs laid per female ranged from 50 to 282 eggs, the minimum on Gorgan3 and the maximum on M4. Our results demonstrated that M9, Williams, Clark, L17, M7, M4 and Zane varieties were more suitable host plants for reproduction of the studied population of H. armigera. The other varieties examined showed less suitability as host plants for H. armigera reproduction.

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The date palm fruit stalk borer is one of the most important pests of date palm in the world. Biochemical properties of digestive proteases in Oryctes elegans Prell larvae were investigated in this research and optimal total proteolytic and trypsin activities were obtained at pH 9.0 and 11.0, respectively. Activity staining of protease on SDS-PAGE showed one isoform. Also, zymogram pattern of trypsin using nitro-cellulose membrane revealed two isoforms. The inhibitory effect of PMSF, TLCK, TPCK, EDTA, iodoacetate and iodoacetamide were determined on O. elegans proteolytic activity. The iodoacetamide showed the highest inhibition on total proteolytic activity. Therefore, cysteine protease accounted for the major proteases in the gut of O. elegans. Total proteolytic activity was inhibited 22.3 and 12.15% by inhibitors extracted from Vicia faba and Lathyrus sativus, respectively. However, the inhibitors extracted from seeds of Prosopis farcta, Panecum miliaceum, and Alhagi maurorum showed negligible inhibitory effects on proteolytic activities. Trypsin activity was inhibited 91.5 and 82.3% by inhibitors extracted from V. faba and L. sativus, respectively. Electrophoretic analysis showed that inhibitors extracted from V. faba reduced the intensity of total proteolytic and trypsin activities. The inhibitor from V. faba was purified by ammonium sulfate precipitation and gel-filtration, also the molecular mass of inhibitor was determined 35 kDa. This purified inhibitor was able to inhibit trypsin activity by 72.7%. In addition, the highest inhibition of trypsin activity by inhibitor from V. faba occurred at pH 11.0. Also, the stability of inhibitor from V. faba was evaluated at different pHs and temperatures. This inhibitor was stable at pH 11.0 and 30 °C.

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The effect of eight Cucumis L. (Cucurbitaceae) genotypes, including native cucumber genotypes (Hormozgan, Bushehr and Gilan), greenhouse cucumber genotypes (Girtap, Negeen, Sepehr and Pouya) and Armenian cucumber (Cucumis melo var. flexuosus) was studied on the life table and population growth parameters of Aphis gossypii Glover to evaluate antibiosis resistance. The experiment was conducted at 25±1°C, 60±10% RH and a photoperiod of 16:8 hour (L:D). The data were analyzed by Two-Sex MSChart program. The most pre-adult mortality (22.6 %) and the shortest total life span (14.5 days) were recorded for ‘Bushehr’. The net Reproductive rate (R₀) ranged from 43.70 for ‘Bushehr’ to 92.39 nymphs per individual in the case of ‘Pouya’. The lowest value of the intrinsic rate of increase (r) and the finite rate of increase (λ) was observed in ‘Gilan’ (0.378 and 1.460 day⁻¹, respectively) and the highest in ‘Pouya’ (0.471 and 1.602 day⁻¹, respectively). The maximum and minimum mean generation Times (T) were 10.20 and 9.23 days in ‘Gilan’ and ‘Negeen’, respectively. On the basis of these parameters, ‘Gilan’ had the highest antibiosis resistance to A. gossypii. Information on life table of pests and subsequent host resistance evaluation improves IPM programs and leads us to genotype selection for crop breeding programs.

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For more than a century, chemical insecticides have been the most primary tool used by growers to control the cotton aphid, Aphis gossypii, as an important polyphagous pest worldwide. The application of insecticide mixtures through different modes of action is currently favored for resistance management of this pest. In this study, the synergistic interactions between amitraz with each of the two commonly used insecticides, i.e. imidacloprid and malathion, were studied using A. gossypii as target pest. The effects of amitraz combination on the activity of three detoxifying enzymes of cotton aphids were then evaluated using physiological assays. The synergistic effects of amitraz on imidacloprid were observed at all Lethal Concentrations (LC₁₀-LC₉₀), while, for malathion it was observed at concentrations higher than LC₃₀. The highest synergist ratio in the mixture of amitraz with malathion (LC₉₀) and imidacloprid (LC₁₀) was 1.5 and 3.09, respectively. The inhibition of Glutathione S-Transferase (GST) activity seems to be the main reason for amitraz to impose its synergistic effects.