جستجوی مقالات مرتبط با کلیدواژه "جمعیت" در نشریات گروه "گیاهپزشکی"

The codling moth, Cydia pomonella (Linnaeus), is the most important pest in apple orchards. In order to successfully control of the pest, using phenological forecasting models is necessary. Phenological forecasting models are basically provided using temperature-dependent phenology of the pests. Estimation of the most important eco-physiological indices of pests is essential for the preparation and use of a high-performance, accurate forecasting model. Therefore, current study was conducted to determine temperature-dependent development trend and to estimate the most important thermal indices of three established populations of the codling moth in Tehran, West Azerbaijan, and Esfahan provinces. Results showed differences among the values of the estimated thermal index in studied populations. Estimated values of the low temperature threshold were 8.32, 8.19, and 9.85°C for total immature stages of Tehran, West Azerbaijan, and Esfahan provinces, respectively. Additionally, estimated values of the thermal requirement were 622.74, 633.20, and 695.84 Degree-Days for the total immature stages of the mentioned populations, respectively. The results of this study showed differences in thermal adaptations of different populations of codling moth located in different regions of Iran. This information is necessary to develop a precise forecasting model based on the heat requirement (GDD or GDH) of key pests in each geographical locations.

Colonization and population of antagonistic bacteria on rhizosphere have a definite role on their antagonistic effect. In this study in order to determine optimal population density of antagonistic bacteria, in a way that they would be able to induce maximal defensive power in plant, and also in order to investigate effect of initial inoculated population and amount of plant defense enzymes, microelements uptake, chlorophyll and carotenoids; level of peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, total phenolic compounds, total protein, Zn, Fe, Mn, chlorophyll a, chlorophyll b, total chlorophyll and carotenoids in population of 104, 106 and 108 of four antagonistic bacteria Pseudomonas fluorescens VUPF5, P. fluorescens T-17, Bacillus subtilis V1 and B. subtilis 96 in Sarakhs cultivar of pistachio was measured. Experiments were done in randomized complete block design with three replications per each treatment. Studies showed in the measured factors despite of diverse results in bacterial populational treatments, all populational treatments follow a constant pattern in a way that along with increasing in bacterial population, amount of measured enzymes, total phenol content, microelements, chlorophyll and carotenoids increases.

Carob moth, Ectomyelois ceratoniae, is the most important pest of pomegranate in Iran and is one of the most effective threats to the export of this product, but only a few studies have been done on the diversity and genetic structure of its populations.Therefore, in order to increase knowledge about the structure and genetic diversity of this pest populations, infested pomegranates were collected from 12 provinces of the country during 2016 and 2017 and genetic diversity components were investigated using a part of the mitochondrial DNA gene, cytochrome oxidase I (COI). Also, the haplotypic network and the phylogenetic tree was drawn using the maximum likelihood method. In the present study, six haplotypes were obtained. The first haplotype (H1) was common in all populations, which can be considered as the ancestral haplotype so that other haplotypes have been evolved from it. This haplotype is connected to other haplotypes with a mutation and forms a star-like shape in the haplotypic network. Results of the grouping populations indicate that the northern part of Iran has the most diversity of haplotypes in comparison to the central and southern parts, which can be related to native cultivars, genetic diversity of cultivars, and natural habitat of Pomegranates in this area. The adaptation of pomegranates to different micro-climates, development of commercial cultivation of traditional varieties, and the role of the human in product transformation lead to high gene flow and genetic differences reduction even at wide geographical distances.

Wheat thrips, Haplothrips tritici (Kurdjumov) (Thysanoptera: Phlaeothripidae) is one of the most important pests in wheat fields in Ilam Province. In order to study the population fluctuations and spatial distribution of wheat thrips in wheat fields of Eyvan city, sampling was weekly carried out during different growing stages of wheat from April to the end of June 2016. Spatial distribution of immature as well as adults of wheat thrips was estimated using Taylor’s power law and Iwao’s patchiness regression methods. The population peaks in both of the irrigated and rainfed wheat fields occurred in middle of May. Based on R2 and F values of regression analysis, in irrigated wheat fields, Iwao's patchiness provided a more adequate description of spatial distribution than Taylor’s power law for wheat thrips. The spatial distribution for adults was randomized but for larval stages and the total stages (larvae and adults) was aggregated. Whereas, in rainfed fields, Taylor’s power law provided a more adequate description of spatial distribution than Iwao's patchiness. The spatial distribution for both larval and adult stages was clumped and for the total was randomized.

Epiphytic bacteria are common inhabitants of plant leaflet surfaces and can have important influences on the plants on which they live. Accurate estimates of epiphytic bacterial population sizes are needed to detect their roles in several important biological phenomena. For example, reliable disease forecasts and anticipate of frost damage depend on the exact estimation of bacterial population in their habitant. Frostbite is one of the major agricultural problems in Iran and is one of the most important environmental stresses which influences plant growth and crops productivity. Chilling and freezing limit the geographical distribution and growing season of many crops and cause significant crops losses. Apical meristem and upper leaves show the first symptoms of frostbite. Without bacteria involved, freezing damage on actively growing shoots is usually limited to the tip or outer branches, and the plant will recover. Freezing is not the sole reason of severe damage to such plants and if such damage or dieback occurs there must be synergistic effects between frost and bacterial infection. Ice nucleation epiphytic bacteria are one of the casual agents of frost and canker in stone fruit trees. In order to identify ice nucleation active (INA) bacteria, 248 samples from twigs of sour cherry, sweet cherry, apricot, prune, peach, nectarine, almond and plum from the main areas of stone fruit tree orchards in Khorasan-Razavi province were collected in spring of 2013. In each area, 2 orchards and in each orchard 4 trees were randomly selected. The samples were placed in paper bags and were kept in a refrigerator until use. The weight of tissues was measured and bacteria were washed from the surface of plant parts in distilled water treated with 0.2 percent. The samples were homogenized for 1 hour at 100 rpm rotary shaker. One milliliter of this suspension was serially diluted to 10−9, 10−8, 10−7 and 10−6 cfu/ml. Twenty-five micro liter of each dilution was cultured on King’s medium B. Among bacterial colonies grown after 48 h, 820 isolates were randomly selected (10 colony of each types that observed on petri dishes). Bacterial population in different areas and hosts, were estimated by counting of the bacterial colonies in each gram of fresh weight. To discover INA bacteria, bacterial suspensions in distilled water were incubated at -5 to -7 °C. After 30 min freezed bacterial suspensions were selected. The population of INA bacteria were estimated by the formula -. The ice nucleation active bacteria were purified and identified by different tests including Gram reaction, catalase, fluorescent pigment production on KB or casamino acid medium, levan, oxidase, arginine dihydrolase, potato rot and hypersensitive reaction on tobacco. The growth with 5% and 7% NaCl, anaerobic condition, at 37 °C, were also tested. The yellow bacteria were cultured on YDC, and the production of xanthomonadin was tested. Among these 820 isolates that analyzed, 110 isolates were determined as INA. These bacteria were identified by phenotypic and biochemical tests. According to our data 56, 27, 8, 6 and 3 percent isolates were identified as Pseudomonas syringae, P. fluorescens, P. viridiflava, Pantoea agglomerans and Xanthomonas sp., respectively. The population of INA bacteria in chenaran and Mashhad was higher than other cities. There was no correlation between plant species and the population of INA bacteria. Although our data indicated the positive correlation between canker symptoms and the population of INA bacteria. This study indicated that plant species cause significant differences in bacterial population size. Effects of plant species on epiphytic bacterial population sizes may also reflect physiological differences. It is fascinating that, for some species, different plants of the same genotype grown in the same area and under similar environmental conditions would exhibit significant differences in mean bacterial population size. It is possible that diversity in soil and water content, soil nutrient availability, release nutrient deposition, nutrient leakage from plants, presence of unseen wounds through which leakage occurs, or exposure to immigrants contribute to the generation of significant differences in bacterial population sizes among plants. Perhaps bacterial population sizes on plant species in which resources required for epiphytic colonization are abundant and are less susceptible to influenced by exogenous factors, therefore fewer variables among plants. We found that bacterial population sizes were varied in relation to plant host, and the physical environment. The ice formation and frost damage in plants are normally depend on the logarithm of the ice nuclei number in freezing time. Therefore, population estimation of the epiphytic INA microorganisms is very important for frost forecasting. Our results, for the first time, demonstrated the population dynamics and the presence of different species of ice nucleation active bacteria in Khorasan-Razavi province.

Sitobion avenae (F.) is an important species infesting wheat spikes in region Dehloran, Iran. To evaluate the spatial distribution of O. avenae on wheat, weekly samplings were carried out from five winter wheat fields around Dehloran throughout 2010-2011. Spatial distribution of different developmental stages and morphs of the aphid were described by fitting data to Poisson (random) and negative binomial (clumped) distributions. Based on R2 and F of regression analysis, Taylor’s power law provided a more adequate description of variance/mean relationships than Iwao’s patchiness regression model, and the b values ranged from 1.102 (alate adults) to 1.463 (apterous adults). Other distribution indexes and spatial distribution models showed the cumulative distribution of aphid population on clusters and fitting to negative binominal distribution in many section of season. Mature winged aphids were more likely to show a random distribution compared to other developmental stages.

Populations of honeybees from 5 provinces of Iran were compared using morphometric tecnques. Five workers from each of 10 hives from 3 apicultures belonging to each province were selected randomly. Eight characters of the forewing consisted of length, width, A4 angle, D7angle, G18, cubital index, anal length and ratio of forewing length to width of honeybees were measured and analysed. Results showed that populations of Markazi and Khuzestan provinces were distincthy located in two different places Ι and ΙΙ respectively and populations of Esfahan, Kordestan and Fars provinces had the most similar wing characters and located in place ΙΙΙ.

Effect of different rice varieties، as the first link of the food chain، on age specific life table and population growth parameters of the egg parasitoid wasp، Trichogramma brassicae Bezdenko، as the third link of the food chain was studied. Four commonly planted rice varieties، including two early maturity cultivars namely، Tarom-Mahalli and Tarom-Hashemi and two late maturity cultivars namely، Fajr and Neda were considered as the hosts of stripped stem borer، Chilo supressalis Walker. Stripped stem borer was reared on each variety for two generations. The eggs of the 2nd generation from each rice variety exposed to egg parasitoid wasps inside test tubes for experiments. Based on the collected data، the most important life table parameters، survival rate (lx)، age specific fertility (mx)، probability of surviving (px)، probability of dying (qx)، difference in survivorship (dx)، life expectancy (ex) and population growth parameters، net reproductive rate (R0)، intrinsic rate of increase (rm)، finite rate of increase (λ)، mean generation time (T)، and doubling time (DT) of were estimated.

tomato pests, such as tomato fruitworm, Helicoverpa armigera Hünber (Hym.Eurytomidae), cause high reduction in tomato production, but no sampling program for population estimate and management of them has been developed. Spatial distribution of immature stages of the tomato Fruit-worm was determined by fitting data to either taylor’s, iwao’s, mean_variance ratio, k and morisita calculating dispersion indices, during 2008 and 2009 growing seasons in tomato fields of Gorgan, Spatial distribution immature (egg and larvae) is a random. Based on R2 and p-values of regression analysis, for most of the natural enemy groups, Taylor’s power law generally provided a more adequate description of variance/mean relationships than Iwao’s patchiness regression model. The median part of plant were fitted most value of Taylor’s b index. Percentage fit of immature stages the dispersion more random ratio bionominal value of morisita, k and mean-variance.

Grape berry moth, Lobesia botrana (Denis et Schiffermuller) is the main pest of Iran and most vineyards of the world. The pest larva causes yield reduction by feeding on inflorescences and berries. The pest reduces the quality of grape by favoring the growth condition of rot fungus such as Botrytis cinerea as well. The seasonal population abundance and related damage of the pest were investigated for 3 years in 3 main vine growing districts of Orumieh, Iran. The population dynamics and density of the moth were monitored by sex pheromone traps and the damage of inflorescence clusters and fruit bunches were determined by sampling from experimental vineyards in different years and generations. Results showed that the grape berry moth has 3 complete flight periods with an average of 37, 26 and 54 days for 3 generations, respectively. Population abundance was varied between years, districts and generations from 51 to 1647 male moths /trap/generation. There was no significant relationship between population abundance and damaged clusters at different districts and generations during 2 years study. Infestation rate of flower clusters at the first generation varied form 68 to 90 percent with a severity of 1 to 15 larval nests per cluster. In the second and third generations, the infestation rate of fruit bunches varied from 43 to 100 percent and the damaged berries per clusters were from 1 to 63 percent.

Herbivory is observed in different forms, one of these forms leading to gall production. Among gall–inducing insects, oak gall wasps (Hymenoptera: Cynipidae) are found on the oak trees producing galls on certain parts of the host. In this survey, oak gall wasps were collected from oak forests in West Azerbaijan in spring (2010). The occurred galls on oak trees (in spring) were collected from such locations as Ghabre-hosein, Mirabad, Vavan, Shalmash, Rabat and Dar-ghabr (a number of 40 trees in each site). In each tree, as a unit of sampling, all the occurred galls on 4 branches (each branch of 40 cm length, and each in any of the 4 geographical directions) were counted. Species richness was evaluated through Rarefaction and Jackknife methods and four similarity indexes calculated. During the survey, 7 oak gall wasp species (sexual generation) were indentified on oaks (Quercus infectoria, Q. brantii and Q. libani) in West Azerbaijan. Most of the galls occurred on Q. brantii. All collected oak gall wasps belonged to 3 genera, namely: Andricus, Chilaspis and Biorhiza. The highest number of expected species’ richness as determined through Rarefaction and Jackknife methods was estimated at 4.68 and 5.2 species respectively, in Mirabad region. The highest similarity indexes of Morisita, Horn, Renkonen and Sorensen were recorded between Ghabre-hosein and Mirabad in the sexual generation of oak gall wasp species. Difference in the local distribution of oak species (Quercus sp.) and subspecies shall be considered as one main factor involved in species diversity, and as well in the oak gall wasp species’ distribution in different locations under study.

Abundance of Thrips tabaci Lind., an important pest of vegetables, was investigated on upper and lower leaves of different genotypes of eggplant, including Siah-Mashhad, Borazjan, Black beauty, Siah-Neyshabour, Zabul indigenous, Imami-905, Juybar-Mazandaran, Sarkhoun-Hormozgan and Galami-Varamin, during 2000-2001 in Varamin region. Eggplant seedlings were cultivated in May in a randomized complete block design with three replications. Each replication consisted of four rows of 10 plants. Five leaves were randomly sampled at weekly intervals until October to estimate the incidence and population fluctuation of T. tabaci. The number of thrips was counted on the surface of four square centimeters of leaves using a binocular microscope. All analyses and comparisons were carried out using statistical package SAS. The results showed that there was a significant difference between the number of thrips on upper and lower leaves, so that the number of thrips on lower leaves were several times higher than that of on upper leaves. Borazjan and Juybar-Mazandaran with the mean number of 1.55 and 0.86 had the highest population in 2000 and 2001, respectively. In complex analysis, there was no significant difference between the thrips abundance on lower and upper leaves. Incidence of thrips faced with increase from June, and the maximum number was recorded in early until late July in both years. The results indicated that, a trend of increase initiated from late June in Varamin. Borazjan had more thrips than other genotypes and the thrips abundance in the first year was two times of the second year.

To study the genetic structure of the Mycosphaerella graminicola, cause of septoria leaf blotch of wheat in Iran, fifty eight isolates of the fungus were collected randomly from wheat fields of Golestan, Mazandaran, Ardebil, Ilam, Khozestan, Kermanshah and Fars provinces. SSR and SCAR markers were used to estimate genetic diversity of the population. Frequencies of alleles of each locus were detected. Genetic diversity values ranged from 0.25 to 0.62 with an average of 0.44. Partitioning the total genetic variability into within-and among-location components revealed that 77% of the genetic variability occurred within locations but relatively little variability (23%) occurred among locations. Using ERIC 1AR and BOX 2 primers, totally, 158 reproducible fragments were amplified ranging from 100 bp to 1000bp. Similarity of the isolates were determined using Dice's coefficient and UPGMA clustering method. The results showed that isolates St20 from Kermanshah and St29 from Ilam provinces had the highest (100%) similarity suggesting that they might have been originated from the same clonal lineage. Other isolates were less similar (less than 50% similarity).

Spatial distribution of different natural enemies of the cotton aphid, Aphis gossypii Glover, was determined by fitting data to either Poisson (random) or negative binomial (aggregated) distributions and calculating dispersion indices, during 2002 and 2003 growing seasons in cotton fields of Gorgan, northern Iran. Based on R2 and p-values of regression analysis, for most of the natural enemy groups, Taylor’s power law generally provided a more adequate description of variance/mean relationships than Iwao’s patchiness regression model. Natural enemy populations, especially parasitoids, cecidomyiid species and coccinellid eggs, were aggregated during most of the growing season, and negative binomial models generally fitted the data sets better than the Poisson series in cotton fields. Percentage fit for some species such as larva and adult stages of chrysopids, adult stages of Coccinella septempunctata L. and Scymnus spp., and spider species, showed a distinct tendency to the Poisson distribution and low values of Taylor’s b index. There were no significant relationships between k (a measure of the amount of clumping in negative binomial distribution) and mean values, indicating the existence of a common k for the most of the natural enemy groups. These results can provide a reliable basis to develop proper sampling plans for estimating or classifying natural enemy populations in cotton fields of Gorgan.