Applied Entomology and Phytopathology
Year:2020 | Volume:87 | Issue:2 (109)|Papers Count:14

Contamination to Aspergillus flavus and aflatoxin is a significant and chronic threat of pistachio production, consumption and exportation in the world. The aims of the present study was evaluation of resistance of pistachio cultivars (Shahpasand, Abbasali, Kale-ghouchi, Khanjari, Akbari and Pesteh-garmeh) and relationship between total phenolic content (TPC) and total flavonoid content (TFC) of green hull and kernels, as antioxidant, to A. flavus growth and aflatoxin production. Inoculation of pistachio kernels was done by 2×106 spores of toxigenic A. flavus. Aflatoxins (B1 and B2), TPC and TFC of the green hull and their kernels were measured by HPLC, Folin-Ciocalteu and aluminum chloride method, respectively. Results showed that Pesteh-garmeh and Akbari cultivars with the lowest and Shahpasand with highest percent colonization of A. flavus and aflatoxin production in kernels were respectively resistant and susceptible and other cultivars were intermediate. TPC and TFC were higher significantly in resistant cultivars than susceptible. A negative correlation was observed between TPC, TFC and aflatoxin content in kernel and green hull of pistachio cultivars, as well as TPC, TFC and A. flavus growth. These findings show the role of TPC and TFC in resistance of pistachio cultivars with contamination to A. flavus growth and aflatoxin production.

Bakanae disease and foot rot of rice is one of the seed-borne diseases with conspicuous symptoms: elongated, narrow and pale seedlings from contaminated seeds caused by Gibberella fujikuroi (Sawada) fungal agent. The aim of the present investigation is determination of disease severity index (DSI) of the fungus G. fujikuroi and its relationship with rate of gibberllic acid production by the fungus on Sepidroud cultivar rice. Infected plants, isolation and purification of fungus were done. All of isolates cultivated in a specific medium for production of gibberellic acid. Amount of the hormone produced by isolates of pathogen was evaluated by HPLC. Plant stems were inoculated by injection of conidial suspension of pathogen at the end of booting and the beginning of panicle exertion stages on Sepidroud rice cultivar and disease severity was evaluated. According to the results of this study, significant correlation was not found between the disease severity of G. fujikuroi and the amount of gibberellic acid produced in rice Sepidroud cultivar.

Brevicoryne brassicae (L. ) is one of the important pests of canola in Iran and some countries of the world. Population growth parameters of this aphid were evaluated by two-sex life table method on different canola cultivars (Opera, SLM046, RGS000, Okapi, Delgan, Licord, H19, and Modena) at 25 ± 1 ° C, 65 ± 5% RH and a 16: 8 h (L: D) photoperiod. Net reproductive rate (R0) varied from 7. 48± 1. 11 to 26. 95± 4. 24 offsprings per generation on eight canola cultivars; the lowest value was on H19 and Okapi and the highest value was on Modena, Opera, SLM046, Delgan and Licord. The lowest intrinsic rate of increase (rm) was related to aphids that were fed on cultivars Okapi and RGS000 (0. 176± 0. 001 and 0. 209± 0. 002 day-1). However, rm value was the highest when aphids were fed on cultivars Modena, Opera, Delgan, and SLM046. The results of this study indicated that Okapi and RGS000 were relatively resistant, and Modena, Opera, Delgan, and SLM046 were susceptible cultivars to B. brassicae.

In this research, a learning vector quantization neural network (LVQ) model was developed to predict the spatial distribution of Sitona humeralis in Marvdasht. This method was evaluated on data of pest density from alfalfa field. Pest density assessments were performed following a 10 m × 10 m grid pattern on the field and a total of 100 sampling units on field. Some statistical tests, such as means comparison, variance and statistical distribution were performed between the observed point samples data and the estimated pest values to evaluate the performance of prediction of pest distribution. The results showed that in training and test phase, there were not significant differences, with the confidence level of 95%, between the statistical parameters such as average, variance, statistical distribution and also coefficient of determination in the observed and the estimated pest density. The results suggest that learning vector quantization (LVQ4) neural network can learn pest density model precisely. In addition the results also indicated that trained LVQ4 neural network had a high capability (92%) in predicting pest density for non-sampled points. The technique showed that the LVQNN could predict and map the spatial distribution of Sitona humeralis. The map showed that this pest has aggregation distribution so there is possibility potential for using site-specific pest control on this field.

Pseudomonas syringae pv. syringae (Pss) is the causative agent of the bacterial common diseases in stone fruit trees fields. In this research, samples were collected from various areas in Razavi and Northern Khorasan provinces. A total of 23 bacterial isolates were compared based on their phenotypic (physiological and biochemical) characteristics and pathogenicity tests. Identification of the strains was further confirmed by PCR using D21/D22 primers specific to P. syringae. Genetic diversity of selected strains was investigated by repetitive element palindromic PCR (rep-PCR) fingerprinting using BOXA1R, ERIC1R, ERIC2 primers and Insertion Sequence PCR (IS-PCR) fingerprinting using IS50 primers. The cluster analyses of the fingerprint data showed that in BOX-PCR with BOXA1R primer, 7 groups were developed at a similarity level of 75%. The same numbers of groups were obtained in ERIC-PCR using ERIC1R primer at a similarity level of 65%. In case of ERIC2 primer, at a similarity level of 56%, strains were divided into 8 groups, whereas, in IS-PCR with IS50 primer at a similarity level of 52%, strains were divided into 11 groups and finally by combining all four primers at a similarity level of 54%, strains can be distinguished into 7 groups. The results demonstrated the existence of a considerable genetic diversity among Pss strains causing bacterial canker in stone fruit trees in the studied provinces.

A disorder on Satsuma mandarin, Citrus unshiu (Yu. Tanaka ex Swingle) trees with bark scaling of the trunk, ring spot or mosaic pattern symptoms on mature fruits especially around the calyx and extended yellow ring spot on the old leaves observed over the recent years in Mazandaran province. The results of virus mechanical inoculation on Gomphrena globosa indicator plants and indexing on different citrus stock and biological properties of the studied isolates indicated the presence of the type B citrus psorosis virus in samples. Molecular detection of CPsV was done by using RT-PCR and specific designed primers in which a desired amplicon with a size about 600bp amplified in infected samples collected from the orchards and greenhouse. Phylogenetic analysis of the representative isolates on the basis of nucleotide sequences of the CPsV-coat protein, categorized the representative isolates into two distinct groups which the group one further divided into three subgroups. Iranian isolates were clustered in the second subgroup beside the Americans and Japanese isolates and showed the lowest identity with the isolates from Latin American and African countries.

Charcoal rot is the most important fungal disease on soybean in Iran. According to the absence of the resistant cultivars, soil inhabitant and the high pathogenicity rate of the pathogen, chemical and crop control alone is not succeed. To improve the efficiency of disease biological control on soybean in greenhouse, the wild type Trichoderma koningii NAS-K1 (non radiated) and the selective mutant NAS-K1M25 isolates were used. The induction of mutation in wild type increases the biological control efficiency of the disease. The efficiency of powder, granular and seed coating bio-formulations, were evaluated separately in greenhouse. Powder has the best effect in reducing the disease; granular bioformulation has the best effect on plant growth and its yield and seed coating, has the best effect on seed germination characteristics and vigor index. The application of these bio-formulations increased soybean growth indices compared to the control and chemical treatments. The highest yield production increase in the presence of the pathogen was observed by seed coating treated with NAS-K1M25. Study on viability of biological agent in powder and granular bio-formulations, showed that it has slight decrease and still effective for a period of 11 months at room temperature, but keeping it at 4 ° C has a positive effect on it.

Potato virus Y, is the type member of the genus Potyvirus, family Potyviridae is of the most destructive viruses of tobacco worldwide. In order to detect PVY and its distribution in Golestan province, several surveys were conducted during July to October 2017 at 15 days intervals in tobacco fields of Gorgan, Aliabad and Minoodasht. 50 plant was selected for each farm and various disease incidence (DI) and population frequency of the virus vector (MP and MPN were evaluated. Double antibody sandwich-ELISA (DAS-ELISA) using PVYspecific polyclonal antibodies was used to estimate changes in the relative concentrations of PVY. The rate of PVY infection was different among tobacco cultivars and the maximum and minimum infection rates were belonged to PVH03 (33. 6%) and Barley (6. 2%) cultivars respectively. Based on the statistical analysis of data, there was a significant difference for disease indicators and the virus vector on different tobacco cultivars, as Basma and Barley were less susceptible to PVY than Flue-cured cultivars (PVH03, NC100 and K326). Also, the K326 cultivar has the highest Myzus persicae ssp. nicotiana and Myzus persicae populations. There was a direct correlation between disease incidence (DI( and PVY relative concentration (OD) and relative humidity and rainfall changes so that DI with rainfall changes had the highest Correlation (r = 0. 98 and P = 0. 004).

Biology and economic importance of peach twig borer were investigated during 2000-2001 and 2016-2017 in almond orchards located in Saman, Chahar mahal VaBakhtiary, Iran. From the beginning of the growing season, almond orchards were visited weekly to collect infected branches and fruits transferred to laboratory to isolate and rear different developmental stages of the pest. Moreover, pest population changes were investigated by installing pheromone traps in almond orchards. Results showed that the pest spends winter in the form of first and second instar larvae within the terminal buds of the branches of host trees. Pest larvae feed on shoots and buds in the early growing season. Since mid-June, the larvae fed upon immature apricot, peach, and almond fruits, causing them to fall. The average infection rate in immature fruits of “ Mamaee” almond cultivar was 2. 95% and 1. 47% in2000 and 2001, respectively. The amount of “ Sefid” almond cultivar infection was determined18% in heavy infested orchards. The number of infested fruitand branches in peach trees were higher than almond trees. The amount of infestation in almond and peach trees in the west and south directions was statistically more than the north and east directions. In laboratory conditions, with 25± 2 ° C, 50± 10% RH and 8: 16hours (L: D) the embryonic period of the pest along withlarval and pupal stages were lasted 5-6, 12-16 and 7-12days respectively. The pest completes three generations per year. The peak of the first, second and third generation occurs in late May, the second week of July and the last week of September respectively.

This study aimed to define sampling programs for pests, Oryzaephilus surinamensis (Linnaeus), Ephestia kueheniella (Zeller) and Plodia interpunctella (Hü bner) using spectrophotometer in date Zahedi cultivar. The experiments were conducted in a completely randomized design with factorial arrangement. The first factor consisted of eggs, larvae, pupae and adult and the second including 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 densities of the above stages. Results showed that the maximum absorption wavelength for egg, larva, pupa and adult of O. surinamensis, was 1220, 1240, 1280, 1300 nm, for E. kuheniella 1210, 1270, 1320, 1360 nm and for P. interpunctella 1310, 1320, 1380, 1400 nm, respectively. The lowest number of sampling (each sample 110 g date fruits) for an accurate estimation of the egg, larva, pupa and adult of O. surinamensis were 1, 2, 1, 2, for E. kuheniella 1, 1, 3, 3 and for P. interpunctella 1, 1, 2 3, 2 samples, respectively, Relative Variation )RV( and Relative net precision )RNP( indices were used to validate the sampling accuracy. The RV for development stages of O. surinamensis were 2. 23, 3. 26, 3. 15, 2. 52, for E. kuheniella 2. 52, 1. 42, 1. 64, 1. 78, 3. 71 and for P. interpunctella 2. 23, 3. 27, 3. 15, 3. 52 respectively. The accuracy level of samplings was lower than 10 in all cases, The RNP values for O. surinamensis were 39. 79, 18. 06, 32. 29, 22. 37, for E. kuheniella 22. 54, 27. 58, 13. 15, 10. 33 and for P. interpunctella 36. 51, 23. 71, 15. 58 10. 99 respectively. Based on the results, the spectrophotometer could detect the hidden pest stages (egg and pupa) with maximum accuracy and minimum cost.

Crown and root rot are important diseases of different small-grain cereals, especially wheat and barley which are caused by soil-borne fungi Fusarium culmorum and F. pseudograminearum. For controlling such diseases, application of fungicides is inadequate, and cause hazardous effects for environment and living organisms. As an alternative strategy, screening of resistant wheat genotypes has been emphasised in the recent studies. This research was conducted to evaluate level of resistance of 66 cultivars/advanced lines of bread wheat and durum wheat to F. culmorum and F. pseudograminearum isolates in greenhouse and field conditions. These experiments were conducted based on completely randomized design with seven replications in greenhouse and randomized complete block design with 4 replications in field condition. The results showed that, 12 genotypes including C61 (C-87-18) and C62 (C-87-11), C38 (F06659G6-1), C43 (POLOVCHANKA/PEHLIVAN), C52 (McCormick/Trego), C37 (F06580G2-1), C35 (Prostor), C54 (VA01W-205/TX99D4628), C50 (GA951079-3-5/Neuse), C58 (Burbot-6), C53 (AWD99*5725/FL9547) and C34 (Gelibolu) were moderately resistant to F. culmorum and F. pseudograminearum isolates. These genotypes have potential to be incorporated into wheat breeding programs.

The objective of the current study was to isolate and identify the fungal endophytes of rice as the effective and safe alternatives to use indtead of chemical fungicides for controlling rice Bakanae disease caused by Fusarium fujikuroi. Fungal endophytes obtained from leaf, stem, sheath and root samples of rice plants in paddy fields. The fungal isolates screened against aggressive strain of F. fujikuroi F257 in dual culture tests and the most effective endophytes were selected for greenhouse experiments. Rice seedlings were treated with the fungal endophytes and F. fujikuroi F257 isolate. Disease incidence and growth parameters were measured. The lowest Bakanae incidences were recorded using Chaetomium globosum NR-R688 and C. globosum NR-SH321 strains as 2% (with 97. 4% disease control) and by NR-L243 Penicillium sp. and Fusarium sp. NR-L645 as 6% (with 92. 3% disease control). In addition, these four fungal endophytes significantly promoted the growth parameters of rice seedlings compared to the control. According to the results of this study, fungal endophytes of rice could be applied as the potential biocontrol agents of Bakanae disease and plant growth promoter, but more research is needed for developing them in the future.

Dispersal of Trichogramma brassicae Bezd. was studied in 2 rice fields by a single release of 50000 adult wasps from a central point and recapturing them using yellow sticky traps and egg cards of Sitotroga cerealella (Oliv. ) Results revealed that in rice field 1, dispersal coefficients were 3. 04 and 1. 07 m2/day at 1st and 2nd sampling turns. However, it reached to a level of 11. 28 m2/day at 3rd sampling turn. In contrast, T. brassicae dispersed with a speed of 3. 93 m2/day at 1st sampling turn and had the highest dispersal coefficient (29. 76 m2/day) at 3rd sampling turn in rice field 2. Similarly, the distances that encompassed 98% recaptured T. brassicae was highest in field 2 (53. 45 m) compared with that in field 1 (15. 11 m) at 3rd sampling turn. Number of wasps remained in fields 1 and 2 were recorded as 630. 67 and 272. 18 individuals, respectively, for total sampling turns. Moreover, the highest parasitism rates (64. 75 and 91 mean parasitized eggs/card in fields 1 and 2, respectively) were observed at 1 meter distance from release point at first sampling turn and it decreased wi th time and distance elevation. It is concluded that more release points of T. brassicae per rice field is required to achieve universal dispersal in successful rice stem borer biocontrol. It needs innovation in packing and release method of the wasp.

isolated from grapevine (Vitis vinifera), among which Grapevine virus A (GVA), Grapevine virus B (GVB) and Grapevine virus E (GVE) have been reported from Iranian vineyards (1, 2, 3). In this study, the occurrence of Grapevine virus D (GVD) has been reported from Iran. During a survey in 2017, a total number of 33 symptomatic samples were collected from grapevines showing leaf mottling, stem...