Iranian Journal of Plant Protection Science
Year:2018 | Volume:48 | Issue:2 |Papers Count:10

Alternaria brown spot and postharvest black rot of fruit are serious diseases of citrus trees. These diseases are caused by Alternaria spp. and can be economically destructive on susceptible citrus trees. The aim of this study was to identify the pathogenic species of this fungus and to introduce orange cultivars resistant to this disease. For this purpose, samples suspected to Alternaria infection were collected from orchards of Golestan and Mazandaran provinces and were cultured on PDA and PCA media in the laboratory. Then, the fungi were identified according to the morphological key to Alternaria spp. In order to verify the morphological, molecular identification was done using universal primers ITS1, ITS4 and PCR product sequencing. From 45 isolates collected, the identified species were A. alternata (28 isolates), A. dumosa (12 isolates) and A. atra (5 isolates). For investigating pathogenicity of the isolates, 4 orange cultivars including Thomson Navel, Jaffa Sweet, Sanguinelli Blood, and Valencia were used. The pathogenicity test was done by using spore suspension with 105 spores per ml on the leaf, fruit and, seedling. The results revealed that the isolates of these three species showed serious symptoms on the Thomson, Jaffa, and Valencia cultivars. However, the Sanguinelli was relatively resistant in three pathogenicity tests on the leaf, fruit, and the seedling and the mentioned species were not able to create disease symptoms at this cultivar. Thus, Sanguinelli was introduced as a resistant cultivar against Alternaria spp. in orange.

The common pistachio psyllid, Agonoscena pistaciae Burckhardt & Lauterer (Hem.: Aphalaridae), is one of the most important pests of pistachio trees in Iran and Middle East. Little is known about the morphological variation of the geographic populations of the common pistachio psyllid in Iran, especially in Kerman province as the main pistachio production province. In order to prepare more information on the morphological variation of this pest, different populations were collected from some main producing areas of pistachio in Iran, including Kerman and Khorasan Razavi provinces in 2016; and wing shape geometry of them was investigated using the geometric morphometric method. The results showed a significant difference in wing shape between the population of Khorasan Razavi Province and all of the populations from Kerman province. The results indicated a significant difference in the centroid size among the populations. Also, wing size was smaller in psyllid population from Ravar compared to other populations. Furthermore, narrower wing shape was found in psyllid populations from Khorasan Razavi province. In the studied populations, in spite of the allometric growth, significant shape differences still remain in constant size which may indicate the genetic basis of the variation rather than environmental factors. Moreover, links between morphological (in the present study) and molecular data (in the other studies) revealed.

This research was carried out to study the effect of host switching on the biological characteristics of the Colorado potato beetle, Leptinotarsa decemlineata, under greenhouse conditions. One generation of the pest was reared on potato. Then, biological characteristics of the Colorado potato beetle was studied on three solanaceous species including tomato, eggplant, and pepper along with Agria (potato cultivar as control treatment). Studied species were planted in pots and on each pot, sleeve cages were set up, in which 15 first instar larvae were released and reared. Larval weight on the 12th day after releasing, mortality percentages of larvae and pupae and durations for these stages were determined on four studied species. In another experiment, durations of pre-oviposition, oviposition, and post-oviposition of the pest were investigated on four studied species. Also, daily and total fecundities of the pest were determined on them. Analysis of variance of data showed that the differences between species were significant for all studied traits excep for egg hatching and duration of eggs incubation of (P<0. 05). The highest mortality rate of developmental stage (77. 00± 1. 91%) and the longest developmental period of the pest (73. 00± 0. 89 day) were observed on pepper and eggplant, respectively. The longest (89. 20± 3. 06 day) and shortest (34. 46± 0. 62 day) duration of oviposition were observed on the pepper and eggplant, respectively. The lowest (247. 60± 25. 54) and highest (437. 80± 33. 71) total fecundities of the pest were on the pepper and potato, respectively.

Tomato spotted wilt virus is a member of the genus Tospovirus, and family Bunyaviridae. TSWV has a wide range of hosts and is one of the most destructive viruses. In order to detect TSWV in South Khorasan province, a total of, 161 saffron and 44 tomato symptomatic samples were collected from Ghaen, Khosf, Darmyan and Ferdows counties, during fall 2016. Infection ratios on tomato and saffron were evaluated as 11. 4 and 8. 7 percent, respectively, by DAS-ELISA. Mechanical inoculation of ELISA-positive samples on Nicotiana benthamiana, N. tabacum cv Samsun and Chenopodium quinoa caused mosaic, mottle, local lesion and rogues. The nucleoprotein gene of five saffron and two potato isolates of TSWV was amplified, cloned, and sequenced. In the Phylogenetic tree based on nucleotide sequence of N protein gene, TSWV isolates dirived into three groups. Three Iranian isolates of saffron grouped into clusters one and three and two Iranian isolates of tomato were placed in group two. Results showed that isolates from different geographical and host plants were separated into different groups. According to our knowledge this is the first report on molecular characterization of TSWV on saffron in the world.

Induced defense responses of a plant to herbivory can influence interactions of that plant with subsequent organisms that use it as a food source. In this study, we conducted several experiments in order to understand whether preference and performance of Trialeurodes vaporariorum, Tetranychus urticae, and Aphis gossypii are affected by the previous herbivory of conspecific on the cucumber plant; and whether these effects are local or systemic. Longevity, fecundity, and pre-imaginal development period were measured as performance criteria. About A. gossypii; longevity and fecundity, about of T. urticae; fecundity and pre-imaginal development period, and about T. vaporariorum fecundity negatively affected by the previous herbivory of conspecifics. Results indicated that herbivory of these pests can induce resistance in cucumber, and can affect preference and performance of conspecifics. Results of performance experiments varied from negative to neutral depending on the performance criteria and the studied level (local or systemic). No positive effect was observed in studied interactions. According to results, all three herbivores tested here were able to induce resistance in cucumber and affect the preference of conspecifics. However, whitefly was unable to detect the previous herbivory of conspecifics, although these plants negatively affected whiteflies. According to results of preference experiments, it can be concluded that T. urticae was much more accurate than others at detection of the induced plants. Effect of induced defense on herbivore performance is not always aligned with the preference of the herbivore. Conducting both performance and preference experiments not only revealed the effect of induction of plant defense, but also showed the sensitivity of the herbivore at detection of changes in plant and ability to choose the appropriate host.

Tomato leaf miner moth, Tuta absoluta (Meyrick) is a key pest of tomato in the world, which has recently entered Iran and become a serious threat to tomato production. It has several generations per year which increases the risk of insecticidal resistance. A relatively low-cost and low-risk method to control this pest is a light trap for capturing adults. The goal of this research was to find a proper light source for light traps in the laboratory and greenhouse. To collect the adult, infested tomato plants were collected from the greenhouses of the Varamin region and were brought to the growth chamber. In the growth chamber, a completely randomized design with four light traps (green, blue, red, and yellow) was set up, in four treatments and seven replications. For greenhouse comparisons, the sticky light traps (with four lights of blue SMD, blue LED, green, and UV) were evaluated in a completely randomized design with four replications. The highest and lowest mean captures were recorded for the blue light (69. 2± 0. 2) and red light (0. 28± 0. 2) in growth chamber. In the greenhouse, the highest capture was recorded for UV light trap (14. 8± 0. 2), while the mean captures of the moths in the other light traps with SMD, LED, and green light were 4. 4± 0. 16, 5. 5± 1. 14, and 7. 16± 1. 2, respectively. The sex ratio of the captured moths in the growth chamber was equal (1: 1), whereas the rate of the females was higher in the greenhouses. In conclusion, the traps with UV light can capture a high number of moths; and could be used to reduce the pest population and the pest damages in the greenhouse.

Organophosphorus compounds are widely used, and their presence in different components of the ecosystem has led to harmful effects on the environment. The use of microorganisms in detoxification of xenobiotic compounds and measurement of pesticide residues is considered as an environmental-friendly and appropriate method. Organophosphorus hydrolase (opd), is a phosphotriester hydrolase enzyme which is discovered in some soil microorganisms such as Flavobacterium sp. and has a wide range of substrates and is able to hydrolyze many organophosphorus compounds. In the present study, codon optimization was done to express the protein in Escherichia coli. Following omission of the signal peptide sequence and substitution of serine by methionine as the start codon, this fragment was cloned under the control of lac promoter in a promoter-probe vector (pTH1705) as a transcriptional fusion and was used for transformation in two Escherichia coli strains DH5α and XL1-blue. To measure the performance of the transgenic bacteria expressing opd gene (as in trans), they were cultured in M9 mineral medium containing 10 and 50 mg/L diazinon and appropriate available carbon and nitrogen sources. Studying the growth curve of V103 strain revealed that bacterial growth in the presence of 50 mg/L diazinon had been affected while this effect in the presence of 10 mg/L diazinon was minor. Results obtained from high-performance liquid chromatography as a standard method to compare with the performance of obtained transgenic strain showed that after 24 hours, diazinon concentration (initially 10mg/L ) in the bacterial culture medium of V100, V101, V102 and V103 strains reached to 6. 38, 7. 19, 7. 09 and 5. 74, respectively. These results reflected the successful transfer and expression of target gene in the bacterium and this genetically engineered bacterium was able to degrade organophosphorus compounds directly.

In this research, some life table parameters of Schizaphis graminum on Yavaras, Bahar, Akbari, Pishtaz and Omid and wheat lines of R1-10, R3-16, R3-17, and R2-9 were investigated under laboratory conditions in 2016. The daily survival and fertility of aphids were studied in leaf cages. Also tolerance of these cultivars and lines to aphids was calculated based on the amount of some growth parameters such as hight reduction, chlorophyll content, the fresh and dry weight of the plant in contaminated plants compared to healthy plants. Experiments were conducted in a completely randomized design. Survival of the aphids in the early of life was 100%. The highest and lowest life expectancy in the first days of life was on Pishtaz and R1-10 respectively. The lowest intrinsic rate of increase was observed on Yavares (0. 262 d-1) and the highest was observed on Pishtaz and R2-9 (0. 346 and 0. 340 d-1, respectively). Based on the results of tolerance, the lowest percentage of fresh and dry weight reduction were on Yavaras, Bahar, R1-10 and R3-16 and the most were on R2-9 and Pishtaz. Furthermore, the lowest percentage of chlorophyll reduction were observed in Yavaras and R1-10 and the highest in Omid and R2-9. The results showed that Pishtaz and R2-9 were the most susceptible and Yavaras and R1-10 were the most resistant wheat cultivars and lines to S. graminum.

To evaluate the effects of the fungus Trichoderma viride, the bacterium Pseudomonas fleurescens CHA0 and salicylic acid against root-knot nematode (Meloidogyne incognita race 2) on the defense enzyme production process of tomato, a pot experiment was conducted under greenhouse conditions. The nematode populations were reproduced on tomato Rutgers cultivar and the test plants were inoculated at four-leaf stage. The peroxidase, phenylalanine ammonia lyase and catalase activities were measured in the first, fourth and seventh days after nematode inoculation. The results showed that all three application modes of fungi, bacteria, and salicylic acid, increased nematode control and significant decreases occurred in the number of gall and egg mass. The infected plants inoculation with fungi, bacteria and salicylic acid, in the cultivars Gina VF, Falat CH, Falat 111 and Karoon reduced the percentage of gall (81, 68, 80, and 83), the number of egg mass (87, 78, 83, and 88) and reproductive factors (83, 69, 82, and 84), respectively. The highest numbers of galls were observed in Karoon, Flat 111, Gina VF and Flat CH in the absence of control agents, respectively. The three agents not only reduced the amount of disease but also increased the activity of catalase peroxidase, and phenylalanine ammonia lyase enzymes in plants, respectively. The enzymes activity reached a maximum on the 4th day after inoculation.

Pistachio die-back disease is an important disease in Iranian pistachio orchards. One of the most important fungal agents of the disease is Paecilomyces which has been recently identified as P. formosus based on phylogenetic and physiologic studies. In this study, four pairs of primers designed using mating type idiomorph sequences of P. variotii deposited in GenBank (NCBI). Designed primers were tested in some isolates of P. formosus and finally two primer pairs including; Mat1-1f224 and Mat1-1r224 for amplification of Mat1-1 and Mat1-2f165 and Mat1-2r165 primers for amplification of Mat1-2 idiomorphs were selected. Mating type idiomorphs were amplified in 124 isolates of P. formosus which have been obtained from pistachio trees and eight other species including; Pistacia mutica, Punica granatum, Prunus amygdalus, Caesalpinia gilliesii, Nerium oleander, Tamarix aphylla, Tamarix hispida, Haloxylon sp. and air of pistachio orchards. In 50 isolates (40. 3%) Mat1-1, in 59 isolates (47. 6%) Mat1-2 and in 15 isolates (12. 1%) both idiomorphs were identified. 16 isolates from each mating type and three isolates which had both idiomorphs were selected and crossed in all of the possible combinations on PDA culture medium and cultures were incubated at 25 ° C in continuous dark condition. After eight months, sexual reproduction was not observed in crosses.