نشریه کنترل بیولوژیک آفات و بیماری های گیاهی
سال چهارم شماره 1 (بهار و تابستان 1394)

The host plant quality not only influences on herbivorous insects but also indirectly could impact on their natural enemies’ performance. The current study was conducted to determine the effect of different nitrogen fertilization levels of canola (Brassica napus L.) on life table parameters of the predatory gall midge, Aphidoletes aphidimyza Rondani; Diptera: Cecidomyiidae, in feeding of mustard aphid, Lipaphis erysimi Kalt.; Hemiptera: Aphididae, under controlled temperature (day: 25± 2, night: 19± 2) and humidity (60± 10%) conditions. Mustard aphids were reared on canola plants grown under four nitrogen fertilization levels including 0, 0.055, 0.11, and 0.165 g N. kg soil-1 to produce different prey quality. The developmental time of the predatory gall midge growth stages were recorded daily and life table parameters were evaluated by two-sex life table procedure. The results showed that increased nitrogen fertilization of canola significantly decreased the developmental time of larva and pupa of the predatory gal midge and increased the oviposition period of females. Actually, using high and medium nitrogen fertilization levels improved the performance of the predatory gall midge. In addition, the maximum amounts of net reproduction rate (32.54 offspring per individual) and the intrinsic rate of increase (0.163 d-1) with significant differences were observed in the mediate nitrogen fertilization level (0.11 g N.kg soil-1). So, this level could introduce as the best level for the predatory midge growth.

Microbe-associated molecular patterns (MAMPs) play key roles as activators of the innate immune response in animals and, analogously, as elicitors of defense responses in plants. However, there are not much investigations concerning their real importance in plant resistance against pathogens. Here we used derivatives of flagellin and Ef-Tu as two well-known MAMPs against some important fungal and bacterial pathogens on Arabidopsis thaliana. Pretreatment of Col-0 plants with both MAMPs, significantly increased the resistance of plants against B. cinerea and A. brassicicola. Growth curve of Pseudomonas syringaepv. tomato (Pst DC3000) in Arabidopsis leaves was significantly influenced by both of the MAMPs. Moreover Xanthomonas axonopodis pv. citri (Xac 306) that is a non-pathogenic bacteria on Arabidopsis, neither grow nor decline in Col-0 leaves for 48 hours after inoculation. However the number of bacteria in the plants pretreated with elf18 was significantly decreased. Results of this study clearly showed the role of innate immunity in plant resistance against pathogens.

Plant growth-promoting rhizobacteria (PGPR) is an alternative to chemical pesticides against harmful microorganisms especially soil-borne diseases. Rhizoctonia solani is one of the most important soil-borne fungal pathogens that causes serious damages to important crops. In this study, to screen successful Pseudomonas bacterial isolates, the inhibition of pathogen growth was evaluated in-vitro. Moreover, isolates were screened based on the ability to auxin and ACC-deaminase production, phosphorus solubilization, siderophore production and possession of PhlD gene. From isolates studied for the extent of inhibition, 20 isolates were selected for further studies, among them, the isolates 33, 139 and 137 showed the highest rate of P solubility and ability to produce auxin. There was a correlation between the phosphorus solubility and pH reduction. Six isolates were selected to evaluate their capability for ACC-deaminase enzyme production based on the higher auxin production and better in-vitro inhibitory effect on the growth of Rhizoctoniasolani. All of the six strains appeared to have produce ACC-deaminase enzyme. PhlD gene that plays a key role in 2,4-diacetylphloroglucinol antibiotic biosynthesis pathway, was detected in the isolates 153, 139, 137, CHA0 and 58A. According to the characteristics, five isolates were selected for greenhouse experiments. In greenhouse experiments, all five isolates controlled disease significantly, and among them, the 137 isolate showed the highest control level

Fluorescent pseudomonads producing 2,4-diacetylphloroglucinol (DAPG) antibiotic have been well studied for use as biocontrol agents around the world. Pseudomonas fluorescens PGU0 strain was isolated from the rhizosphere of sunflower in Bushehr Province. Dual culture test showed that the strain had antagonistic activity against Rhizoctonia solani fungus on different media cultures; moreover, under growth chamber condition, the strain reduced disease severity by 52% and caused an increase in dry weight of infected bean seedlings by 80%. The polymerase chain reaction (PCR) using specific primers, demonstrated the presence of key genes (phlD, hcnBC and pltB) involved in the biosynthesis of antimicrobial metabolites Phl, Pyoluteorin (PLT) and hydrogen cyanide (HCN), respectively . Antibiotic production was examined by high-performance liquid chromatography (HPLC) and it was found that these bacteria are capable of producing DAPG and PLT antibiotics. On the other hand, production of hydrogen cyanide and siderophore by the bacterium was demonstrated under lab conditions. Phylogenetic analysis of 16S rDNA proved similarity of this strain with other world biocontrol strains capable of producing antimicrobial metabolites like Phl and Plt.

This study was carried out to evaluate the antifungal efficacy of garlic essential oil (Allium sativum L.) and two fungicides including Metalaxyl- Mancozeb and Mancozeb against Phytophthora melonis, P. drechsleri and P. capsici the causal agent of damping- off on Pepper, Melon and Cucumber, in vitro and greenhouse conditions. Fungal radial growth for each concentration of garlic oil on Phytophthora species was measured. The Median Effective Concentration (EC50) values (ppm) of garlic oil measured. The chemical composition of the essential oils was determined by gas chromatography-mass spectrometry (GC-MS). Results of in vitro studies indicated that plant extract of garlic caused a significant decrease in the mycelial growth of phytophthora species and it had Fungistatic properties. The inhibitory effect of plant essential oil was observed for P. capsici (EC50 = 43.293 ppm) and P. drechsleri (EC50 = 50.236 ppm), respectively. The profile of the extract components of Allium sativum showed that Diallyl tetra sulphide (31.32%), Allyl disulphide (26.78%), Nitrosothymol (8.64%), 1H-1,2,4-Triazole, 3-thiol-5-methyl (8.4%) and Allyl sulphide (6.15%) were the main compounds. The results of greenhouse showed that plant essential oil significantly reduced disease compared to control (P ≤ 0.05). Based on results from this research, the garlic essential oil was found to be fungistatic effect against damping –off diseae and may be used in the production of organically grown vegetables.

There are numerous problems for using essential oil due to its low solubility in water, high vapor pressure and chemical and physical instability. Use of nano-emulsions is a good idea for decreasing side effect of the essential oils and enhance their efficiency as well as delivery to hot spot. In addition, nano-emulsion system make smaller size particles and increase stability and shelf-life of the active compounds to enhance their antimicrobial activity. In this study, nano-emulsion of essential oil of cinnamon (Cinammon zeylanicum) was prepared and their physicochemical characteristics were determined. The size particle of nano-emulsions was determined 115.33±3.97 nm. Various concentrations of emulsion and nano-emulsion as well as fungicides thiabendazole were studied to control of fruit rot fungi Rhizopus stolonifer and Botrytis cinerea on PDA medium and strawberry. Generally, there was no significant difference between emulsion and nano-emulsion of oil to inhibit fungal growth in PDA medium. Both of them could completely inhibit B. cinerea and R. stolonifer at 500 and 1000 µl/l respectively. There was significant difference between emulsion and nano-emulsion to reduce fruit spoilage decay on strawberry. The nano-emulsion showed stronger antifungal properties than emulsion to suppress fungal strawberry decay. At the concentrations of the 2:1000, there was no significant difference between thiabendazole with cinammon nano-emulsion to suppress Rhizopus fruit rot. However, nano-emulsions of cinnamon at the concentration 2:1000 as well as cinnamon at 1:1000 exhibited the best impact to control gray mold caused by B. cinerea. Nano-emulsion of cinnamon recommends for making natural fungicide.

In this research, host stage preference of parasitoid wasp, Aphidius matricariae Haliday in choice and no-choice tests and functional response of the parasitoid were investigated on common wheat aphid, Schizaphis graminum Rondani on the Alvand cultivar in laboratory conditions at 20, 25 and 30 °C, RH 70 ±10 % and a photoperiod of 16 h L : 8 h D. The maximum mean parasitisms in choice and no-choice tests was on third instar nymph of the aphid and were 5.1 ± 0.43 and 10.3 ± 0.61 nymphs, respectively and the minimum mean parasitism was achieved on first instar nymph. The results of logistic regression showed that functional response of the parasitoid to different densities of the aphid was type II at 20, 25 and 30 °C. By using Rogers equation, attack rate and handling time were estimated. The maximum attack rate and minimum handling time were obtained at 20 °C.

Most essential oil extraction from medicine plant have shown the properties of antimicrobial of parasites, bacteria, fungi and viruses. The fungus from genus of Fusarium is one of the prevalent crop disease that infect a wide range of crops. Fusarium solani is one of the species of this fungus genus that various crops are host for it. A lab experiment was conducted to investigate the effect of alone and in combination applied of essential oils of medicine plants, lavender) Lavandula angustifolia) and Savory (Satureja hortensis) on control growth of the fungus. The experiment was completely randomized factorial design with two factors, different essential oils (essential oil of lavender and Savory) and various concentration of essential oils (0, 50, 75 and 100 ppm). Treatments were replicated in five. Result showed that essential oil extracted from Savory is more effective in inhibitory growth of F. solani than essential oil of lavender. Using both essential oil and applied at the various levels of their concentrations did not completely inhibit growth of the fungus F. solani. But using mixed essential oil of both plants and at the highest concentration level (100 ppm) completely inhibited the growth of F. Solani.