BIO CONTROL IN PLANT PROTECTION
Year:2016 | Volume:4 | Issue:2 |Papers Count:8

To study the antagonistic effects of two antagonistic fungi, Talaromyces flavus and Trichoderma harzianumin the control of root knot nematode, Meloidogyne javanica in tomato, experiments were carried out in two years (2013-2014). The experiments were conducted and executed with eight treatments and five replications using pots with a completely randomized design under greenhouse conditions. To prepare treatments, 2´107 spores of T. flavus and T.harzianum (originally isolated from tomato roots) per gram soil, were added to the pots containing 3 kg pasteurized soil. After transplanting four leaves seedlings of tomato, pots were inoculated with 15000 eggs and juveniles of the nematode per pot. The uninfected control pots contained only pasteurized soil without root knot nematode and antagonistic fungi. Two months after inoculation of the nematode, the growth parameters of the plants including foliar height, root weight, and some nematode- related parameters including the number of galls and egg mass, final population and reproduction factor were measured. In the combined statistical analysis, the differences were observed in data and analysis was performed separately for two years. The results showed that the antagonistic fungi were effective in increasing the plant growth and there was significant nematode population decrease up to 80% in comparison with the infected control (a=0.05). According to the results, T. harzianum was more effective than T. flavus in increasing plant growth and decreasing the population of the nematode (78 and 67%, respectively), but differences were not significant. Furthermore, the combination of two fungi was more effective than other treatments in increasing plant growth characteristics and controlling the root knot nematode such as reduction of the galls and reproduction factor.

Many species of the family Syrphidae are predators of pests, especially aphids. To study the predacious syrphid species of rapeseed fields of Kermanshah, we assembled a sizable collection of syrphids between 2013-2015. The result showed the existence of 12 species in these fields of which the speciesEupeodes corollae F. was found to be the predominant species. The length of growth periods and feeding capability of this species was studied on cabbage aphid (Brevicoryne brassicae) at 3 different temperatures. The growth period means of this fly are 22.45, 18.82 and 15.17 days at 20, 25 and 30oC respectively. The predation rate of E. corollae on third instar nymphs of B. brassicae at 20, 25 and 30°C significantly decreased with increasing temperature with a mean value of 371.07, 283.00 and 253.13, respectively. There were significant differences between daily and total feeding rates of the first, second and third instar larvae of E. corollae at various temperatures. The results suggest that 25ºC was the optimum temperature for both survival and feeding of E. corollae. As the temperature increases of the feeding rate reduces during periods of growth. The lowest mortality rate occurred at 25°C.

One hundred seventhy seven quorum quenching bacteria were isolated from Solanaceae family using two methods of minimal medium containing synthetic acyl homoserine lactone signal 3-oxo-C6-HSL and sole common culture medium. Eleven isolates of bacteria, including Pseudomonas, Enterobacter, Acinetobacter and Bacilluswere identified as bacteria with high quorum quenching ability, especially the genus Pseudomonas showed the highest quorum quenching activity. Investigating quorum quenching mechanisms among these bacteria revealed that enzymes and non-enzymatic small compounds with quorum quenching activity were involved in this process. However, most of the bacteria showing enzymatic activity were confirmed by HPLC. Results also showed that one isolate of Acinetobacter calcoaceticus obtained by the second method, had nonenzymatic quorum quenching activity. The quorum quenching bacteria mainly reduced the biofilm and pathogenicity of Pectobacterium carotovorum subsp. carotovorum on potato and cactus. Therefore, there was a direct relationship between increasing quorum quenching activity and biocontrol ability against this pathogen. However, there were some exceptions. In addition, some isolates of Pseudomonas as the best biocontrol agents were identified, which were effective against the pathogen based on quorum quenching.

Reports have proved that Pieris rapae with 40% annual damage is the second destructive pest of cabbage after Plutella xylostella. As there are frequent chemical spray operations against the pest and due to environmental and public health hazards, an investigation was carried out to introduce a species of Trichogramma for future bio-control programs in cabbage. All experiments were carried out at 25 ± 0.5°C, 60±10% RH and 16: 8 L: D. Based on field observations and greenhouse rearing of P. rapae, it was revealed that egg incubation took 5-7 days. Five larval instars development enlonged 20-30 days and pupal stage period was about 6-9 days. Longevity of male and female butterflies was 7 and 10 days, respectively. Preliminary results demonstrated that immature stage development took 10.43±0.15 and 10.07±0.11 days and 10.48±0.099 and 10.17±0.093 days for female and male individuals of T. brassicae and T. evanescens, respectively. Moreover, female and male longevity was 2.03±0.20 and 1.40±0.24 days and 1.68±0.16 and 1.85±0.40 days for both species, respectively. Further analysis showed that gross and net fecundity and fertility for T. brassicae and T. evanescenswere 51.92 and 39.46 eggs/ female and 83.04 and 77.19 eggs/female, respectively. Similarly, mean age net fecundity and fertility in the same order species were 0.36 and 0.39 days and 0.162 and 0.162 days, respectively. Data analysis on reproductive attributes revealed the gross and net reproductive rates for T. brassicaeand T. evanescens on eggs of P. rapae obtained as 22.77 female egg/female and 12.95 female progeny/female and 66.14 female egg/female and 29.32 female progeny/female, respectively. Similarly, intrinsic (rm) and finite (l) rates of increase were calculated as 0.238 (day-1) and 1.269 female progeny/day and 0.305 (day-1) and 1.357 female progeny/day for T. brassicae and T. evanescens, respectively. Doubling times were 2.90 and 2.265 days and generation times were calculated as 10.74 and 11.04 days for the same species, respectively. Also results proved that in both parasitoids immature stages accounted for about 98% and adults for 2% of the population in the age distribution of the stable population. For final conclusion, it could be said that almost all T. evanescenslife history parameters on eggs of P. rapae were superior compared to those of T. brassicae. Therefore, it would be a potential candidate for future bio-control programs for small cabbage butterfly.

Helicoverpa armigera (Lepidoptera: Noctuidae) is one of the important pests of cotton in the world and Iran with wide host range and causes an irrecoverable damage in the agricultural system. In the past decades, researchers have been searching for a new technology to produce safe pesticides with the properties such as selective effects on target pests and less risk on non-target organisms and the environment. One of the most popular pesticides is disruptive molting (IGRs) which has been used widespread in the fields. The aim of this study was to evaluate the interactions between some phytoecdysteroids which submitted in data base, during 2013-2015, and Ecdysone receptors in order to control H. armigera with less adverse effects on Chrysoperla carneaas a natural enemy by molecular docking. Ecdysone receptor models of H. armigera and C. carnea were designed and their efficacies were estimated. According to the Z-score index, qualities of EcR receptors made for H. armigera and C. carnea were equivalent to NMR and X-ray crystallography methods, respectively. Results showed that among tested phytoecdysteroids, 11 b-Hydroxy-20-Deoxyshidasterone; 2, 3, 14, 20, 26-PentaHydroxy-6-OXO-Stigmast-7-ENE-22.26-Lactol; Callecdysterol A, B, C and Glutinosterone had the minimum inhibition constant (Ki), the most negative bonding energy and the minimum changes in RMSD in binding to target pest ecdysone receptor. In conclusion, the mentioned phytoecdysteroids, have a potential to control H. armigerawith less side effects on C. carnea life cycle.

Study on the life table and predation rate of Menochilus sexmaculatus (Fabricius) (Col.: Coccinellidae) was performed under laboratory conditions at 25±2°C and 27.5±2°C, respectively and 65±5% RH and 16: 8h L: D. To study the life table, 60 one- day-old larvae were chosen and were feed on third and fourth instars of pomegranate green aphid Aphis punicae. Daily fertility, immature development time and mortality were analyzed through age-stage, two-sex life table analysis-MSChart software. The mean and standard error of parameters of population growth were analyzed according to the bootstrap method. Based on the results, the intrinsic rate of increase (rm), finite rate of increase (l), mean generation time (T0), gross and net reproductive rate (R0) were 0.21±0.01 d-1, 1.23±0.01 d-1, 24.57±0.46 d, 236.36±33.57 and 178.15±27.83 eggs/individual, respectively. The amounts of consumed aphids by fourth larval instars of ladybird were 188.08 for males and 179.09 for females. Average predation rate (C0) at pre-mature stage was 358.9 aphids and showed that predation of the M. sexmaculatus has a high potential in natural population control of this aphid.

Sclerotinia sclerotiorumis an important plant pathogenic fungus. Biocontrol agents such as Bacillus spp. are promising candidates to manage the disease caused by this fungus. In this study, we identified 63 isolates of Bacillusspp. obtained from cucumber rhizosphere based on morphological, physiological and biochemical characteristics. The antagonistic activity of the isolates against the fungal pathogen was evaluated using dual culture method and the production of volatile metabolites. According to the obtained results, the isolates Ba17, Ba24, Ba14 and Ba29b showed the most inhibitory effects against the pathogen in dual culture method. Volatile metabolites of isolates Ba21, Ba29c, Ba10b, Ba17, Ba29b, Ba9c and Ba12a, reduced the mycelial growth of the pathogen by 87.14, 84.85, 83.42, 82.42, 79.14, 79.14 and 77.71%, respectively and had a significant difference compared with the control. In the greenhouse trails, isolates Ba17, Ba21, Ba10b, Ba29c and Ba14 decreased the disease index of Sclerotinia stem rot, significantly. The isolates Ba29c, Ba10b, Ba17, Ba29b, Ba24 were capable to show protease enzyme activity. Results also showed that isolates Ba29c, Ba10b and Ba21 were capable of producing surfactin. Molecular identification of isolates with antagonistic activities against the fungal pathogen by partial sequencing of 16S rDNA gene which amplificated with specific primers fD1 and rD1 was performed. Based on this procedure, isolates showed high homology withBacillus cereus, B. subtilis, B. licheniformis, B. endophyticusand Lysinibacillus spp..

The diamondback moth, Plutella xylostella, is a destructive pest of crucifers in different parts of the word. Cotesia vestalis (Hym.: Braconidae) is one of the best agents for application in biological control programs of this pest. In order to examine the quality control of C. vestalis including: parasitism rate, survival rate, offspring sex ratio, adult longevity and progeny fecundity in different mass-rearing conditions, an experiment was conducted with three different treatments. All experiments were conducted in the laboratory at 26±2°C, 75 ± 5 % RHand 16L: 8D h photoperiod. The treatments including (1) (SLD) a big cage (55´70´100 cm), 12 cabbage plants, 240 pest larvae and 30 female parasitoid (2) (BMD) a smaller cage (50´55´70 cm), 6 cabbage plants, 120 pest larvae and 15 female parasitoid (3) (BMU) a big cage, 12 cabbage plants and a natural population of pest larvae. Results showed that in treatments of BMD and SLD, adult's survival rate of C. vestalis were 62.8±4.2 and 69.8±3.2, adult's longevity were 13.5±0.04 and 13±0.03, progeny fecundity were 200.4±6.2 and 195.9±5.7 and production of pupae were 57.2±0.02 and 56±0.02, respectively. Results show that there was a significant difference between BMD and SLD compared to BMU for mass production of C. vestalis.