Plant Protection
Year:2019 | Volume:42 | Issue:2|Papers Count:6

Background and Objectives: Crown rot disease caused by Sclerotinia sclerotiorum, is one of the major diseases of canola worldwide. Biological control is a control method in agriculture for living organisms, especially fungi and bacteria, and is used in order to control plant damages caused by harmful factors. Materials and Methods: In this research, we evaluated the effect of seventy one isolates of Trichoderma spp. against S. sclerotiorum using various in vitro methods including dual culture and slide culture methods. Based on the obtained results of in vitro studies, six Trichoderma isolates and Tebuconazole fungicide were selected in order to study their potentials for controlling the crown rot disease in greenhouse. For this purpose, rapeseed petals were inoculated with S. sclerotiorum and inoculation of suspensions of Trichoderma isolates was done after inoculation of pathogen and also before and after its inoculation and then the severity of the disease was determined in the studied treatments. Results: Based on obtained results, in dual culture, ARCTr281 (T. harzianum) was the most effective isolate for inhibition of mycelial growth. In hyperparasitism test, all isolates of T. harzianum hade successful performance in controlling the pathogenand coiling of Trichoderma was observed around the hyphae of S. sclerotiorum. Lowest disease incidence and severity of disease was observed in the negative control (without Sclerotinia and Trichoderma). Inoculated fungi in two stages, effectively were able to reduce the incidence and severity of disease in leaves and stems that ARCTr281 (T. harzianum) was the most effective fungus under greenhouse conditions. Also, the use of Trichoderma isolates in two stages in presence of pathogen caused an increase in height, fresh and dry weight of the shoot and root under greenhouse conditions. Analysis of variance and comparing the average characters by Least Significant Difference (LSD), Duncan and nonparametric method showed significant difference between used fungi in dual culture and greenhouse studies. Discussion: According to the results of biocontrol studies under laboratory and greenhouse conditions, ARCTr281 and ARCTr272 fungal isolates belonging to T. harzianum were the most effective antagonists for control of canola's crown rot disease. The results of this study indicated that different isolates of Trichoderma can be considered as potential antagonists for the management of canola's crown rot disease.

Background and Objectives: Bracon hebetor Say is a well-known cosmopolitan ectoparasitoid that attacks the larvae of various lepidopteran pests, especially cotton boll worm, Helicoverpa armigera. Cold storage is a general technique for long-term preservation of this parasitoid in insectaries. Most parasitoids require sugar supplemental sources as a source of energy in adult stage. Because of the need to enhance cold storage efficacy in commercial insectaries, this study was carried out to assess effects of feeding frequencies and mating status on biological and reproductive characteristics of maternal wasps and their progeny (F1) stored in refrigerator (5± 1˚ C) for two durations of 7 and 14 days. Materials and Methods: B. hebetor reared on the 4-5 instars larvae of Anagasta kuehniella in a climate-controlled room, at 26 ± 2˚ C, 50± 5% RH, and a 16: 8 (L: D)h. photoperiod. The effect of feeding frequency was studied in three levels of "without feeding" (starved wasps), "one-time feeding" before cold storage, and "two-time feedings" (before and during cold storage). Mating status was investigated in two "mated" and "unmated" levels. After each treatment, adult parasitoids were stored inside a refrigerator (5± 1˚ C) for two periods of 7 and 14 days, and mortality, longevity and fecundity of maternal parasitoids were subsequently assessed. Immature’ s developmental time and mortality, percentage of adult emergence and sex ratio were also investigated for progenies in next generation. The experiment was carried out using a factorial experimental design and obtained data were analyzed using SAS software, and LSD mean comparison test. Results: Results showed that sugar feeding and mating of parasitoid before beginning of cold storage decreased mortality during storage and increased fecundity compared to starved and unmated wasps. The highest mortality of females (33. 2%) was observed in starved and unmated wasps that were stored in refrigerator for 14 days. In contrast, the lowest mortality of females (7. 71%) belonged to mated parasitoids that fed twice (before and during cold storage) on honey solution and stored for 7 days. Feeding on honey solution by maternal adult parasitoids reduced immature’ s mortality and their developmental time in progenies of next generation. Means of immature’ s mortality and developmental time in fed wasps (22. 82 percent and 11. 17 days, respectively) were significantly lower than starved ones (30. 64 percent and 11. 77 days, respectively). Discussion: According to our results, feeding on honey solution increased cold-tolerance of both male and female B. hebetor adults. So that, honey-fed adult parasitoids had lower mortality and higher fecundity than starved ones. Similar to feeding, our results showed that mated parasitoids had higher survival and fecundity than unmated ones. Also, feeding and mating of cold-stored maternal parasitoids had a positive effect on the survival and development of progenies in next generation. In conclusion, spraying honey solution on the rearing cages of B. hebetor and providing sufficient time for mating before storing in refrigerator, are recommended to improved cold-storage efficacy of this parasitoid in insectaries.

Background and objectives: The predatory bugs, Anthocoridae, are important predators of many agricultural pests in the world. Climate and agricultural manipulations may change pest populations by affecting biodiversity of biocontrol agents. In this study, fauna and biodiversity of the Anthocoridae family were investigated in two climates of Hormozgan province: Tazian and Minab. The effect of agricultural manipulations on the anthocorid biodiversity was also determined. Materials and methods: Sampling was carried out on various annual and perennial plants in both non-manipulated and manipulated (cropping and horticultural systems) ecosystems. Data were analyzed by SDR software according to various diversity and evenness indices. Results: Five species from genus Orius, Orius (Dimorphella) albidipennis (Reuter1884), O. (Dimorphella) maxidentex (Ghauri, 1972), O. minutus (Linnaeus‚ 1758), O. laevigatus (Fiber‚ 1860) and O. niger (Wolff, 1811), and three species, O. albidipennis, O. maxidentex and O. minutus, were collected from various host plants of Tazian and Minab climates, respectively. Biodiversity and species evenness index values in Tazian were significantly higher than Minab. The highest and lowest biodiversity index values were observed in spring and fall, respectively. The evenness index values were significantly higher in winter and spring than summer and fall. However, no significant difference between biodiversity of manipulated and non-manipulated ecosystems was found in each climate. Discussion: Dominant species were different according to climate condition. Moreover, our findings indicated that climate and season significantly affect biodiversity of anthocoridbugs. Agricultural manipulation had no significant effect on the biodiversity of anthocorid bugs. The results can be used in biological control program of various pests by these predators in Hormozgan province.

Background and Objectives: Leaf spot is the most important disease of sugar beet around the world. It is prevalent in areas with hot and humid weather. Damage to leaves is associated with a decrease in root and sugar content which results in lower root and white sugar yields. Materials and Methods: This study was conducted as a factorial experiment in a completely randomized design in laboratory and greenhouse of the Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardebili in 2017. Experimental factors included Leaf spot disease in two levels (control, disease) and 11 cultivars (Cesira, Lisetta, Antek, BTS 853, Merak, Yasmene, Qualita, SB16, 25447-79, 25448-79, HI 0063) of sugar beet. Results: Results showed a direct connection between the incubation period and the first day of the onset of symptoms. The first infected spot was recorded eight days after incubation equal to 12. 26 ° C for the HI 0063 cultivar. Moreover HI 0063 cultivar had the shortest incubation period (of 137. 17° C), and the shortest day of the onset of symptoms (5. 9 days). The highest number of spots (405. 33) was obtained by the 25748 Cultivar and smallest number of spots (18. 08) was recorded by the Merak cultivar. Also the Merak cultivar had the largest stain diameter (905. 1 mm), while highest percentage of plant infection (31. 75%) and lowest percentage of plant infestation (27. 93%) was observed by HI 0063, and SB16 cultivars respectively. The results of cluster analysis of resistance to disease showed that the cultivars were divided into 4 groups, HI 0063 cultivar in one group, Antek, 25448, Qualita and BTS 853 cultivars in another group, the cultivars of Cesira, Yasmene and Lisetta in the third group and SB16, 25447 and Merak cultivars were in the last group. Discussion: In this study, the sensitive cultivar of HI 0063 had the shortest time for incubation period, the day of symptom emergence, the highest number of blemishes and percentage of plant infestation. The overall results of this study showed that all of the studied traits were involved in resistance except in exceptional cases, increasing degree of resistance, increased the length of the incubation period and decreased the density of the stain per unit area, the diameter of the stain, the percentage of the infected leaves and the number of spores produced in the surface of the stain. Also there was a direct connection between resistance and disease, incubation period and other traits examined. In conclusion, the resistant varieties to disease had the longest time for incubation period, the first day of symptom emergence, the lowest number of spots and percentage of plant infections. However, sensitive varieties had the shortest time for incubation period and the day of symptom emergence and the lowest number of spots and percentage of plant contamination. Accordingly, the HI 0063 cultivar was the most sensitive cultivar and SB16, 25447 and Merak cultivars were resistant cultivars.

Background and objectives: Ground beetles as ‘ ‘ generalist predators’ ’ are one of the most common and species-rich families of arthropods in agricultural ecosystems and their role as effective bioindicators is well known. Materials and Methods: Ground beetles (Carabidae) of south east of Tehran province was studied during 2015. These beetles were collected by pitfall traps from different ecosystems such as alfalfa and barley farms as well as green lands. The species diversity was studied by Species Diversity and Richness software. Different tests in this study included: Alpha Diversity index, Shannon-Wiener Index, Simpson Index, Beta (β ) diversity, Species Evenness, Pielou J Index, Species Richness and Similarity index. Results: In this study 450 specimens belonging to 12 species were collected. The species include Acinopus picipes (Olivier, 1795), Amara ovate (Fabricius, 1792), Brachinus ejaculans Fisher von Waldheim, 1828, Calathus fuscipes (Goeze, 1777)، , Calathus melanocephalus (Linnaeus, 1758), Cylindera germanica (Linnaeus, 1758), Distichus planus (Bonelli, 1813), Harpalus griseus (Panzer, 1796), Harpalus rufipes (Degeer, 1774), Poecilus wollastoni (Wollaston, 1854), Siagona europaea Dejean, 1826 and Zabrus tenebrioides (Goeze, 1777). Based on the results, Distichus planus had the most divergence in barley fields of Pakdasht and Gharchak. Green land of Abureyhan campus and alfalfa field of Pakdasht with 8 and 5 species, respectively, had the highest number of species. Both of barley fields of Pakdasht and Gharchak with 4 species had the lowest number of species. Moreover, the alfalfa field of Pakdasht and barley field of Pakdasht had the highest and lowest evenness, respectively. Based on the similarity index, green land of Abureyhan campus and alfalfa field of Pakdasht had the most similarity (%75) and barley of Pakdasht and Gharchak with alfalfa field of Pakdasht had the lowest similarity (%33). Discussion: Carabid beetles are important biological control agents in agroecosystems and their study of biodiversity help to pest management program. The results of this study enhanced our knowledge regarding the diversity of Carabid species in central Iran.

Background and Objectives: Beet curly top Iran virus (BCTIV) and Beet curly top virus (BCTV) are the causal agents of beet curly top disease in Iran. It has been reported that both viruses are distributed in different geographical regions and host plants in Iran. Development of a simple, fast and low cost serological method such as ELISA for detection of these viruses, is a necessary demand. To do serological tests such as ELISA, an antibody is needed. Production of polyclonal antibodies against geminiviruses is a hard candidate because of low concentration and localization of their particles in the phloem tissue of their hosts. Therefore, expression and production of geminiviral recombinant proteins in bacterial system is an alternative method to obtain polyclonal antibodies. Material and Methods: Specific forward and reverse primers containing BamHI/HindIII digestion sites at the 5′ end of each primer, respectively, were designed to amplify the full-length fragment of BCTIV V1 open reading frame encoding the viral coat protein (CP). The amplified 751 bp fragment was cloned into the pTZ57R/T cloning vector. V1 gene was released from pTZ57R/T by enzymatic digestion and cloned into the expression vector pQE30. The recombinant pQE30-BCTIV V1 was transformed into Escherichia coli strain M15. The expression of protein was induced by adding 1 mM of isopropylthio-d-galactoside (IPTG) to the transformed bacterial cells and grown at 37 º C in liquid LB medium. Expression of recombinant protein was analyzed by SDS-PAGE electrophoresis and Western blot hybridization. Results: Analysis of the expressed proteins by SDS-PAGE electrophoresis, revealed a protein band with a position corresponding to molecular weight of approximately 30 kDa that was consistent with the predicted molecular weight of BCTIV CP. Time course of induction by IPTG influenced on level of the new recombinant protein expression, thus four hours induction had the highest level of expression. Western blot analysis confirmed the identity of expressed protein via using anti-His antibody to detect expressed recombinant His-BCTIV CP. Discussion: One of the most popular bacterial protein expression system is IPTG inducible system wherein IPTG regulate level of new recombinant protein expression. Our results by SDS-PAGE electrophoresis and Western blot analysis revealed a high level of expression of the fusion protein in IPTG-induced bacterial cells. However, a negligible rate of expression of recombinant protein was also observed in non-induced bacterial cells. This suggests low appearance and activity of responsible promotor even without inducing protein expression with IPTG. Expression of conserved plant viral proteins in bacterial systems following purification of the resulted recombinant proteins would facilitate production of specific polyclonal antibodies.