نشریه مهار زیستی در گیاه پزشکی
سال دوم شماره 1 (بهار و تابستان 1393)

Rice blast caused by Magnaporthe oryzae is the most important disease of rice worldwide. Although, application of chemical pesticides can control the disease, but they cause harmful effects on environment and human health. Nowadays, biological control is considered as an alternative and safe method in plant disease management. In this study, sampling was done from soils and rice phyllosphere of paddy fields in different regions of Mazandaran province. Trichoderma spp. were isolated following dilution plating method using McFadden & Sutton’s RB-S-F selective medium, and then purified and preserved. Eighty nine Trichoderma Rice blast caused by Magnaporthe oryzae is the most important disease of rice worldwide. Although, application of chemical pesticides can control the disease, but they cause harmful effects on environment and human health. Nowadays, biological control is considered as an alternative and safe method in plant disease management. In this study, sampling was done from soils and rice phyllosphere of paddy fields in different regions of Mazandaran province. Trichoderma spp. were isolated following dilution plating method using McFadden & Sutton’s RB-S-F selective medium, and then purified and preserved. Eighty nine Trichoderma isolates were screened against M. oryzae using various methods in vitro. In dual culture test, more than 90% of Trichoderma isolates were antagonistic against pathogen. In hyperparasitism test, no coiling of Trichoderma was observed around the hyphae of M. oryzae. However, some strains caused disintegration of M. oryzae hyphae. Volatile metabolites of RP3-4 and RP3-2 strains were the most effective in inhibiting the growth rate of pathogen by 66.6%. In addition, RP7-1 strain was reduced the growth of pathogen by 93.74% and 90.62% using 20% and 5% of culture filtrate, respectively. Based on the results of in vitro studies, 16 Trichoderma isolates were selected in order to evaluate their potentials in controlling blast disease in greenhouse. According to the results of greenhouse tests, T. harzianum RP1-6 and T.harzianum RP4-2 strains were the most effective isolates in terms of reducing the severity of leaf blast disease by 100% and 99%, respectively. Furthermore, T. harzianum RP6-1 and T. virens RS7-6 with disease reduction of 98% and 97%, respectively placed in same statistical group as chemical fungicides (Carpropamid). Evaluation of population dynamics showed that the populations of Trichoderma isolates were increased or decreased during 17d in greenhouse.T. harzianum RP6-1and T. atroviride RS4-1, showed maximum increase and decrease of opulation, respectively. There was no correlation between the populations and disease control. In addition, 16 selected Trichoderma isolates were identified by morphological and molecular methods and 14, 1 and 1 isolates belonged to T. harzianum, T. virens and T. atroviride, respectively.

The diamondback moth, Plutella xylostella (Lep.: Plutellidae) is the most destructive insect pest of crucifer plants throughout the world. In order to identify its parasitoids and study on seasonal fluctuation of parasitism, sampling was conducted in the cauliflower fields of southern Tehran from June until October 2011. One hectare cauliflower field in the middle of a large field was randomly selected in Jahan-Abad, Kahrizak, Shokr-Abadand Palayin regions. A field with the area of 600 m2' in College of Agricultural Sciences, Shahed University, Tehran was selected as control with no insecticide treatment. Each plant was presumed as a sampling unit and sample size was determined as 20 host plants. Sampling was carried out every 14_day and all larvae and pupa on the host plant were collected and reared under laboratory conditions. Also parasitoids were collected with calling method. In the present study, three species of parasitoid wasps were determined. These parasitoids were Diadegma anurum (Thomson, 1877), Cotesia plutellae (Kurdjumov, 1912) and Oomyzus sokolowskii (Kurdjumov, 1912). The highest percentage of parasitism of larval and pupal stages were recorded 47.57 (July 14th) and the lowest were 22.33 (June 19th). The highest percentage of parasitism (12.14) in Shahed field was caused by D. anurum. The highest percentage of parasitism (57.49) was observed in Jahan-Abad region and the lowest (8.22) was in Palayin region. The results of this study showed that there is significant difference between percentage of parasitism in Shahed University field and other fields.

In this study, virulence of four Beauveria bassiana isolates on aestivating and overwintering populations of Sunn pest (Eurygaster integriceps) adults was investigated. Bioassays were conducted and performed by spraying fungal spore ssuspension on adult sunn pest. Obtained data was analyzed to compare mortality in different treatments and to estimate LC50 and LT50. The results showed that overwintering adults of Sunn pest were more susceptible than the summer population. According to the results, LC50 of Fashand isolate was 1×108 and 2×105 spore/ml on aestivation and overwintering populations, respectively. LC50 of Spt-566 isolate was 3×107 spore/ml on the overwintering population. Estimated LT50 for Fashand isolate (109 spore/ml) on aestivating and overwintering populations were 13 and 7 days, respectively, whereas, estimated LT50 for Spt-566 isolate was 19 days on overwintering population. On the basis of this study, Fashand isolate was more effective than Spt-566 on two physiological stages of Sunn pest adult. The results also showed that adding oils to the suspension of the spores increase virulence of the isolates on all stages of sunn pest.

Three isolates of Trichoderma spp. (T. harzianum, T. longibrachiatum and T. viride) and two isolates of Bacillus bacteria were evaluated in biological control of Fusarium oxysporum f. sp. Meloni, the causal agent ofFusarium wilt disease of melon in the laboratory and greenhouse conditions. Dual culture, antimicrobial metabolites, and volatile metabolites were used in In vitro assay. Fungal pathogen colony area was recorded, compared with control and induced inhibition of growth was determined. A greenhouse experiments was also performed to test the efficacy of Trichoderma and Bacillus isolates in biological control of Fusarium oxysporum f. sp. melonis. This experiment displayed the antagonistic ability using dual culture simultaneous and dual culture non-simultaneous assays against fungal pathogen. Results showed that Trichoderma harzianum 6with 70% and T. viride10 with 52.9 reduction in the growth of fungal pathogen were the most efficient isolates respectively in comparison with the control. Results of dual culture assays also indicated that Bacillus 62 with 30.5%, in volatile metabolite test, Bacillus 15whit 12.37% and cell free culture test of Bacillus with 100%, were the most efficient in reducing mycelia growth of pathogenic fungus. Percent survival of the melon plants in pots treated with a mixture of both Bacillus, and Trichoderma isolates and healthy control was 100. However, the number of survived plants in other treatments varied from 65.2 to 79.38%. The above results were obtained statistically by mean comparison at 1% probability level using LSD test.

Cellular immune of insects is one of the important defense methods against foreign agents such as spore of fungi, bactria, nematodes and egg of parasitoides. Identification of immune system help to better use microbial control methods. Cellular immune of 4th instars of Utethesia pulchella L. was investigated against twe isolation of Beauveria bassiana (Fashand and 566) and one isolated of Isaria farinosae (1872c). Activity of hemocytes, nodulation and phenoloxidase activity was measured too. 105 spore/ml concentration of spores was injected to larvae in 1, 3, 6 and 12 h intervals. Control treatment was larvae in which was injected by distilled water. Total of hemocyte, plasmotocyte and granulocyte number was maximum in 3 and 6 h after injection. Plasmotocytes, granulocytes engulfed foreign particles to form nodul. Nodulation was the highest in 3 and 6 h after injection. Phenoloxidase activity was determined in the presence of L-DOPA as a substrate in intervals after injection of fungal spores. There was a direct correlation between phenoloxidase activity and total of hemocyte. Phenoloxidase activity was the highest in 3 and 6 h after injection. Results showed that larvae of U. pulchella haveimmune reaction against spores of 3 isolationes and could be remove foreign agent by nodulation.

Although some of the medicinal plants essential oils were known as fungicide, but they are hard to use and have organoleptic effects to make smell and taste in crops. Nano-emulsion is a way to reduce these side effects and enhance stability as well as antimicrobial activity by increasing cellular uptake. In this investigation, the nano-emulsion of three essential oils; Mentha piperita (peppermint), Thymus daenensis (thyme) and Satureja khuzistanica (savory) were prepared and their particles size were determined. The major compound of thyme oil was thymol (68.8%) while carvacrol (72.4%) was identified as the major compound of savory. Menthol (36.5%) and menthone (33.8%) were identified as main compounds of peppermint. Three essential oils and their nano-emulsions as well as fungicide ‘tiabendazole’ were studied at various concentrations (1, 2 and 4 per1000) to control of Rhizopus stolonifer fruit rot in strawberry. Generally, nano-emulsions of essential oils showed more antifungal activity than essential oils. The nanao-emulsion of savory oil could completely suppress the rot disease of fruits at the concentration of 4:1000 and showed stronger antifungal activity than fungicides tiabendazole (85.83%). There was no significant difference in decay control, between tiabendazole and nano-emulsions of thyme and peppermint. The nano-emulsion of savory oil at concentration of 2:1000 showed a significant effect in reducing fruit decay with 50% control. Finally, nano-emulsions of essential oils especially savory nano-emulsion are suggested for natural fungicide production.

In order to identify the natural enemies of Comstock mealybug, Pseudococcus comstocki (Kuwana) (Hem.: Pseudococcidae) samplings were made on Mulberry in Tabriz, East-Azarbaijan province. A parasitic wasp of the family Encyrtidae was reared and identified as Anagyrus novickyi (Hoffer). This species is recorded here for the first time from Iran. g=FA style='mso-ansi-font-size: 10. 0pt; font-family: "B Zar"'>، نمونه برداری هایی در شهرستان تبریز (استان آذربایجان شرقی) انجام گرفت. در این تحقیق یک گونه زنبور پارازیتویید از خانواده ی Encyrtidae جمع آوری و تحت عنوان Anagyrus novickyi (Hoffer) شناسایی گردید. این گونه برای نخستین بار از ایران گزارش می شود. i; mso-bidi-font-family: "B Zar"'> Using of sodium alginate (5 % w/w) resulted in the highest viabilities as 90 and 86% after exposure to UVB (400nm) and UVC (254 nm) irradiation, respectively. While, viability of non- microencapsulated spores under these conditions were 40 and 50%, respectively. The mortality of irradiated and non-irradiated free spore formulations on second instar larvae of Ephestia kuehniella were 15 and 93%, respectively. However, the mortality of irradiated and non-irradiated microencapsulated formulations were 70 and 80% in 10th day of the experiment, respectively. Diameters of the microcapsules were 7-20 µm and the efficiency of microencapsulation was 86%.

A sampling was carried out to determin the parasitoid complex of the cabbage white butterfly, Pieris rapae in cauliflower fields at southern area of Tehran. The Ichneumonid parasitoid, Hyposoter clausus(Brischke, 1880) (Hymenoptera: Ichneumonidae, Campopleginae) was reared from the larvae of Pieris rapae, which is a new host record for this parasitoid and expand its area of distribution in Tehran.Another species Cotesia glomerata L. (Hymenoptera: Braconidae) was also reared from the larvae of cabbage white butterfly at the same region.