Iranian Journal of Plant Protection Science
Year:2017 | Volume:48 | Issue:1 |Papers Count:15

In this study, the reproductive activity and olfactory response of the parasitoid wasp Lysiphlebus fabarum to the presence of an intraguild predator, the ladybird Hippodamia variegata, was investigated on the cotton aphid Aphis gossypii on cucumber plants. For this purpose, in addition to comparing the predator feeding of healthy and parasitized adult aphids, reproductive characteristics of the parasitoid wasp (percent parasitism, percent emergence, and sex ratio) were investigated in three different host patches, including those of only aphids alone, aphids with a female ladybird, and aphids with aphid carcasses. Moreover, the preference of the female wasps to these patches was determined using a Y-tube olfactometer. Ladybirds significantly preferred healthy aphids to previously parasitized ones (F2, 27=12. 53, P<0. 001), and the proportion of parasitism by parasitoid wasps were lower in the patch containing a female ladybird (G2, 42=6. 99, P=0. 03). According to olfactometer test results, the parasitoid wasp significantly avoided the patch containing the intraguild predator ladybird (χ 2=6. 40, df=19, P=0. 01). In conclusion, based upon the findings of the avoidance of ladybirds by female wasps and also preference of healthy aphids by ladybirds, it is expected that female wasps forage more in patches lacking the intraguild predator ladybirds, and that ladybirds prefer feeding on healthy aphids, resulting in a reduction in the intraguild predation and improving the cotton aphid control.

In order to determine the most efficient chemical compound in fluctuation of plant defense enzymes level and causing resistance to Phytophthora drechsleri in two pistachio cultivars (Sarakhs and Badami-riz-Zarand), a factorial experiment was carried out based on complete randomized design (CRD) with chemical compounds (potassium phosphite, fosetyl-aluminium, potassium silicate, complex amino acid, and siderophore). The results indicated that chemicals used for this experiment were able to reduce the percentage of death in pistachio seedlings as plants treated with potassium phosphite and amino acid complex with 100% and fosetyl-aluminium with 25% had the most and the least effects in these reduction of disease incidence, respectively. These compounds increased plants height, roots, and shoot fresh and dry weights in comparison to the control and inoculated plants with P. drechsleri. The results indicated that chemical compounds used for this experiment were able to reduce the percentage of death in seedling. Plants treated with pottasium phosphite Chemical compounds also enhanced enzymatic levels and phenolic compound content, which phenomenon was more obvious in simultaneous inoculation with disease agent and lead to enhancing the peroxidase, poly phenol oxidase, phenylalanin aminolyase enzymatic level, and total phenolic compound content.

Annual aggressions of Italian locust, Calliptamus italicus (Linnaeus) (Orthoptera: Acrididae) at the gregary phase cause serious damages and reduce yields in crop production systems in Khodafarin region. Despite a long history of the pest in the region, no sampling program has been developed for its population estimate and management. During growing season 2011, the spatial distribution of the post-embryonic stages of this insect was studied as a major component of a sampling program. The discrepancy of sampling data from both poisson and negative binomial distributions was investigated using Pearson's Chi square test. Moreover, different crowding and contagiousness indices including dispersion index (ID), index of clumping of David & Moore (lDM), green index (Cx), mean crowding of Lloyd (x*), patchiness index of Lloyd (Ip), Arbous and Kerich's λ , Morisita index (lδ ) were used to strengthen the analyses. Taylor's power law and Iwao's regression techniques also were used to create a relation between means and variances. Results revealed that all stages have an aggregation tendency. Arbous and Kerrich's λ index was>2 in all samples and according to Blackith, it may suggest a combination of a behavioral cause of aggregation as well as an environmental one.

In an investigation of endophytic fungi associated with cherry (Prunus avium L. ) in Iran, healthy plant samples including twigs and leaves were collected during autumn of 2013 and spring and summer seasons of 2014. In this study, 10 fungal species including Acremonium sclerotigenum, Aureobasidium microstictum, Chaetomium globosum, Chalastospora gossypii, Clonostachys rosea, Dendrothyrium variisporum, Fusarium sambucinum, Fusarium verticillioides, Trichothecium roseum and Trichurus spiralis were identified as endophytic fungi of cherry trees in Iran. All identified species are reported for the first time as endophytic fungi of cherry trees in the world. The two species including Aureobasidium microstictum and Dendrothyrium variisporum are new taxa for Iran mycoflora.

Application of fertilizers in the plant growth medium can affect plant-herbivore interactions by changing plant growth and physiology. In this research, the effect, of solid and aqueous extract (tea compost) of vermicompost application in tomato potting media on host preference, survival and fertility life table parameters of tomato leaf miner, Tuta absoluta, were investigated. Five treatments including control (without vermicompost), 30% and 60% solid vermicompost fertilizer, 40% and 20% tea compost were used. Results of host preference test, results showed that the lowest number of eggs per leaf and the highest mortality in the larval stages were observed in 60% solid vermicompost treatment. In the life fertility table investigation, female adult longevity (≈ 2days), the number of eggs laid per female (≈ 16 eggs), intrinsic rate of increase (≈ 0. 013 day-1), net reproductive rate (≈ 8 nymphs), and finite rate of increase (≈ 0. 01 day-1) of tomato leaf miner reared on plants treated with vermicompost were significantly decreased especially in 60% solid vermicompost treatment. The negative effect of vermicompost application on the tomato leaf miner population can be mentioned in integrated pest management.

Yellow or stripe rust, Puccinia striiformis f. sp. tritici, the most damaging wheat disease that has been widely distributed around the world including most parts of our country. Yellow rust can cause heavy damage during the epidemic to wheat production. Producing new resistant varieties is the most effective way to control yellow rust disease. In this study, hot race of yellow rust which was collected from Sari and according to reactions standard and differential varieties, 198E150A+, Yr 27 was named to evaluate the resistance of 64 doubled haploid lines, produced by chromosome elimination method crosses between wheat and maize along with resistant (Morvarid, Parsi and Sivand) and susceptible (Bolani and Morocco) control varieties in form of completely randomized design. To assess the resistance of doubled haploid lines of wheat, the first or second leaves of the seedling grown in the greenhouse were inoculated with spores of pathogen. Resistance was measured by infection type, latent period, pustule size and density. The analysis of variance showed a significant difference among the genotypes. The results indicated that there is a high correlation between the measured traits. Besides the result of data analysis indicated that 21 DH lines were the most highly resistant lines and other lines were semi-resistant to highly susceptible. These lines can be used as resistance resources relative to pathogen in improvement wheat programs.

The tomato leafminer moth, Tuta absoluta, Myrick. (Lep.: Gelechiidae) is an important pest of cultivated tomato, Solanum lycopersicum in Iran and other countries throughout the world. This pest damages on tomato and other crops economically due to high fecundity and short generation period. Nowadays, semiochemicallybased management strategies are developing. We aimed to screen and characterize new deterrent compounds to T. absoluta. therefor, the stimulating potential of 15 botanical repellent compounds was assayed on antennal receptors of virgin and mated of both sexes using Electroantennogarame (EAG). In this test, each compound was tested in highest concentration level, 100 μ g/μ l, on the right antennae of both sexes, 2-4 days old in two reproductive statues, mated and virgin, with 10 replications. Electrophysiological responses showed that all of tested compounds could bind to antennal receptors of tomato leaf miner mothds. (-)-Carvone, Salicylic acid, and Methyl jasmonate were the three compounds that elicited maximum responses on mated females. As a result, these compounds can be introduced as suitable candidates for the behavioral control of T. absoluta females as well sex pheromone on males in control strategies and IPM.

Potato virus Y is one of the most important damaging viruses with a broad host range. In this research due to detection and isolation of Potato virus Y in turnip fields of Khuzestan province during 2014 growing season, characteristics of three selected isolates (7Tu, 9Tu and 10Tu) from Dezful, Shushtar and Shush cities were investigated. To analyze the host range of the isolates, three selected isolates were mechanically inoculated on some members of Solanaceae, Chenopodiaceae, and Amaranthaceae. All three isolates induced local and systemic symptoms on the leaves of potato, tomato, pepper, datura, and gomphrena plants, but no symptoms were observed on Chenopodium quinoa. Analysis of the PVY partially purified preparations indicated that molecular weight of two protein bands obtained by SDS-PAGE was estimated to be about 33 and 31 KDa. To determine the strain of selective isolates the specific primer pairs CF/OR, NF/NR, OF/OR, and NF/OR were used. Using OF/OR and PVY3TIM/PVNIBIP primers, two fragments with 609 and 1200 bp length respectively were amplified. The CP region in the all three isolates was amplified, cloned and sequenced. The results of all aforementioned tests showed that 7Tu, 9Tu, and 10Tu isolates are probably a member of NTN or W strain groups. According to our knowledge, this is the first report on occurrence of PVY in turnip fields.

Nutritional indices and digestive enzymatic activity of Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) was studied on eight potato cultivars including Agria, Dayfla, Ceasar, Labadia, Lady Rozeta, Lotta, Marfona, and Santae under laboratory conditions (25± 1 ° C, 65± 5% R. H. and a photoperiod of 16L: 8D h). L. decemlineata third instar larvae reared on cultivar Ceasar had the lowest values of consumed food and larval weight gain. Approximate digestibility values were highest and lowest on cultivars Agria and Marfona, respectively. The larvae reared on cultivar Santae showed the highest efficiency of conversion of digested food and efficiency of conversion of ingested food. Those larvae that fed on cultivar Agria had the highest relative consumption rate. In contrast, the larvae fed on Labadia and Ceasar cultivars had the lowest relative consumption rate. Furthermore, the larvae fed on Santae and Agria cultivars had the highest relative growth rate. Amylolytic activity in the 4th instar larvae was the lowest on Ceasar and Labadia and the highest activity was observed in the larvae fed on cultivars Lotta and Santae. The highest larval proteolytic activity was recorded in Agria, Santae and Lotta cultivars. According to the results, Labadia and Ceasar were the most unsuitable cultivars for feeding of L. decemlineata.

Today, describing the distribution patterns of insects using interpolation and estimation methods in order to explore the possibility of proportional control where they has gained the attention of many researchers. This study was performed to evaluate the MLP neural network algorithms and interpolation of population estimates of B. tabaci in areas not sampled and mapped its distribution. Information density of this pest was obtained by sampling in cucumber field of Behbahan. For evaluating ability of different neural network algorithms we used, mean square error and coefficient of determination and to evaluat the network with optimal algorithm we utilized a comparisson of parameters such as mean, variance, statistical distribution and the determination coefficients of linear regression between predicted values by the neural network and actual values. Results showed optimum performance of neural network white Levenberg-Marquardt algorithms was in Learning rate 0. 26, Momentum Factor 0. 75 and 11 neuron in hidden layer and no significant difference between the values of statistical characteristics (mean, variance) and differences in the statistical distribution of predict and the actual pest density. In other words, an artificial neural network with Levenberg-Marquardt could well learn whitefly density data model. Map of interpolation showed that the pest had cumulative distribution and proved possibility of site-specific pest control on this field.

Responses of twenty four selected wheat genotypes including commercial cultivars and isogenic lines against the yellow rust (Puccinia striiformis f. sp. tritici; 6E158A+ pathotype) were evaluated in Kermanshah province, Iran. Infection type and disease severity as the resistance characteristics were studied in greenhouse and field conditions for seedlings and adult plants respectively. Cluster analysis of seedling stages based on infection type indicated that 8% of the genotypes had probably resistant genes with minor while major effects and other genotypes were controlled by major effect genes. Area under disease progress curve (AUDPC) and relative area under disease progress curve (rAUDPC) criteria were calculated for wheat genotypes in adult plants stages. Cluster analysis using infection type of the first leaf data showed that 29% of the genotypes were susceptible in seedling and adult plant stages; 8% of genotypes were sensitive in the seedling stage but resistant in the adult stage. Additionally, it was found that 25% of the genotypes were resistant in whole periods of growth. High significant correlation (P≤ 0. 01) was calculated for the infection type of the first leaf and two other parameters included AUDPC of flag leaf and infection coefficient.

The large cabbage white, Pieris brassicae (L. ), is a pest of Brassicaceae family which overwinters as a pupa on different host plants or other shelters. Little information is available on the physiological changes during overwintering of this pest and its cold tolerance. In the current study, the cryoprotectants were identified by LC/MS and their changes were examined by HPLC in specimens collected during the months of autumn and winter, as well as lab-reared pupae which treated one week at 27, 15, 10, 7, and 4 ° C. The changes of glycogen content were investigated as the main source of cryoprotectants. Four compounds of trehalose, sorbitol, glucose, and inositol were identified and trehalose and sorbitol showed the highest increase in the winter months and these changes were accompanied by a significant decrease in the glycogen content. In lab-reared pupae treated in 7 and 4 ° C, trehalose and sorbitol significantly increased. Therefore, it seems that trehalose and sorbitol, as the most important cryoprotectants, play a significant role in tolerating of low temperatures of winter and tolerating temperatures below 10 ° C can induce the production of such compounds in this species.

In this research, genetic diversity and pathogenicity of Paecilomyces formosus isolates, causal agent of die-back disease of pistachio trees in Yazd and Khorasan Razavi provinces were investigated. Genetic diversity of 50 selected isolates using SSR markers, showed a high degree of polymorphism between isolates. Cluster analysis based on UPGMA algorithm and Jaccard's similarity coefficient, divided the isolates into 11 groups with 75% similarity level. Shannon index, Principal coordinates analysis (PCoA) and analysis of molecular variance (AMOVA) revealed that the highest genetic variation (81%) was disturbed among isolates and genetic variation within isolates was determined as 19%. Between used primers, PVar15 was more appropriate than others to study of genetic diversity of isolates. Study of pathogenicity test and mean comparison mean of data showed that isolates of Mehriz and Abarkoh regions in Yazd province had the most and lowest aggressive isolates, respectively. Our results indicated that there is a specific relationship between the isolates of each region whereas no relationship was identified between related isolates belongs to two provinces and their genetic diversity.

Trichogramma brassicae Bezdenko (Hym.: Trichogrammatidae) is one of the most widely used parasitoids of lepidopteran key pests around the world. This species has two reproductive modes, arrhenotoky and thelytoky, the second one is caused by an endosymbiont bacterium which is called Wolbachia. Colors have been mentioned as one of the factors which influence the oviposition of parasitoids. The present study examined the effect of the color patch and quality on oviposition of Wolbachia-infected and uninfected T. brassicae population. At the first, sterile eggs of Ephestia kuehniella Zeller (Lep.: Pyralidae) as laboratory host of both populations were glued on colorful patches included; blue, green, yellow, orange, red, and white, with 30 repetitions for each populations. Colorful papers and cellophanes were used as patches. Both cardboard and cellophane patches were placed in an equal distance from each other in cylindrical containers. All females were separated from E. kuehniella eggs after 24 h. The results showed significant differences in the oviposition rate of infected and uninfected T. brassicae on colorful papers while there were not any significant differences in the oviposition rate of both populations on colorful cellophanes. The results showed that asexual and sexual populations responded differently to colorful papers although females of both populations were able to discriminate between the color of paper patches.

The early blight disease of potato caused by Alternaria alternata and A. solani is one of the most important epidemic diseases of potato crop in Iran, out of which A. alternata is the dominant one. For resistance sources, 24 potato cultivars which are grown throughout Iran were assessed at greenhouse and field conditions. The infection percentages, severity, and disease scoring scales means showed that the cultivars Markies, Kennebeck, Premiere, Atlantic, Sante, Sonate, and Agria were the most susceptible ones under greenhouse conditions. However, the cultivars Granula, Diamont, Picasso, Maradona, and Kayzer were the most resistant ones and were ranged in the significant and respective groups of statistical analysis. The other cultivars reacted intermediately with a moderately resistance, tolerance, and moderately susceptible reactions with significant effects. The field results also showed almost the same results as for greenhouse experiments with significant statistical groups and distinct on the basis of the disease developments. The disease expansion in advanced stages of the crop growth showed an ascending level of developments in a varying degree with high significant effects, indicating that, the cultivars reacted independently and were distinct from each other on the basis of disease severity and scoring scale.