BIO CONTROL IN PLANT PROTECTION
Year:2017 | Volume:5 | Issue:1 |Papers Count:9

Endophytic bacteria are important group of bacteria that produce phytohormones, antifungal and antibacterial agents, siderophore, nutrient competition and induced systemic resistance in the host, causing the biocontrol of plant pathogens. The aim of this study was to obtain endophytic isolates with antagonistic effects against the alfalfa wilt agent, Clavibacter michiganensis subsp. insidiosus in the laboratory and greenhouse. In order to conduct this research study, samples and isolation of bacteria from alfalfa fields in Hamedan province were performed. Then, in the laboratory conditions, their antagonistic effects against Cmi were investigated. The experiments were conducted in laboratory on NA (Nutrient Agar) culture medium in a completely randomized design with three replications by determining the pathogenic bacterium growth inhibition. The obtained data were analyzed by Statistical Analysis System (SAS) software and the means were compared by Duncan's multiple range test. Based on the laboratory studies results, eight antagonistic strains with inhibition diameter higher than 6 mm were selected for the greenhouse studies. In the greenhouse conditions, the strains were evaluated for their effects on increasing growth factors of alfalfa. The results showed that isolates 8 and 56 showed higher biocontrol efficacy. These isolates increased plant growth factors at 1% level statistical probability. The 16srRNA encoding genes of strains were amplified and sequenced. Result showed that they were belonged to the genera Bacillus subtilis, Pseudomonas sp., Escherichia coli, Sphingomonas paucimobilis and Paenibacillus glycanilyticus. These isolates have been effective in biocontrol of wilt bacterial agents in the laboratory and greenhouse conditions, and increasing plant growth factors. Endophytic bacteria including Bacillus subtilis and Sphingomonas paucimobilis showed effective performance against pathogenic bacteria. In addition they had great impact on plant growth characteristics such as fresh weight, dry weight and plant height. These effects may be due to the production of antibiotics and induced systemic resistance to biological control of bacterial wilt disease in the laboratory and greenhouse and increasing plant growth factors. These results are promising and may be used in the biocontrol and the management of soil-borne diseases.

Wheat take-all is one of the most important soil-borne fungal diseases that causes significant annual damage to this strategic crop in the world including Iran. In this study, potential of 27 antagonistic bacterial strains of Bacillus subtilis was evaluated in the biocontrol of Gaeumannomyces graminis var. tritici, the causal agent of wheat take-all in the laboratory and greenhouse conditions. In dual culture experiment, all studied strains had inhibition zone against growth of the pathogenic fungus and they prevented fungal growth between 39. 48-96. 29%. In antifungal volatile metabolites production, some strains reduced fungal growth up to 87. 62%, while this for some others was less than 20%. In extracellular liquids secretion at three concentrations of 5, 15 and 25%, the most effective concentration was 25%. Results of biosurfactant production and biofilm formation showed that all the studied strains produced biosurfactant and biofilm with high variation. Correlation between production of biosurfactant and biofilm in in vitro was 0. 83. Eleven strains with different potential in antagonistic effects and biofilm formation were selected for the possibility of disease biocontrol in the greenhouse conditions. All strains decreased the disease between 20-100%. About 72% of the trains reduced disease more than 50% comparing to the control. Correlation of 0. 71 and 0. 85 was obtained between biofilm formations and biosurfactant production in the laboratory and the greenhouse in the biological control of the disease.

Ephestia kuehniella eggs are among protein rich sources for mass production of the predator Nesidiocoris tenuis. It has been used as an alternative prey for the predator establishment in the tomato greenhouses. Comparing the predation rate of N. tenuis on E. kuehniella and Tuta absoluta eggs, a factorial experiment based on completely randomized design (CRD) was conducted and performed under laboratory conditions. Results indicated that predator sex and prey species significantly affected the rate of predation. The predation values of the female predatory on E. kuehniella and T. absoluta eggs were 58± 4. 83 and 77. 50± 4. 83, respectively, showing a significant difference (P < 0. 0001). The predation rates of the male predatory on the E. kuehniella and T. absoluta eggs were 27. 50± 4. 83 and 61. 44± 5. 09 respectively, showing a significant difference (P < 0. 0001). In the prey preference test, predation of the female on the E. kuehniella and T. absoluta eggs were 41. 3± 3. 63 and 29. 8± 3. 20 respectively. Mean consumption of the male individuals from E. kuehniella eggs was 14. 33± 1. 53 and from T. absoluta eggs was 20. 33± 2. 39. The Manley’ s preference indices (􀟚 ) female were 0. 64± 0. 07 and 0. 36± 0. 08 for the E. kuehniella (prey I) and T. absoluta eggs (prey II), respectively. While Manley’ s indices (􀟚 ) for male were 0. 38± 0. 02 and 0. 62± 0. 04 for the E. kuehniella and T. absoluta eggs, respectively. According to our data, the male predatory showed preference towards the T. absoluta eggs than the E. kuehniella eggs. Therefore, based on the Manley’ s preference indices (􀟚 ), females of N. tenuis need more E. kuehniella eggs to provide their dietary requirements for fecundity. In conclusion, E. kuehniella eggs can be used as an alternative food source in tomato greenhouses, especially when the main prey is insufficient or absent.

The biology of Lixus fasciculatus Boheman, was studied on Artemisia vulgaris L. (Asteraceae) in the fields and field margins of Urmia region. The results revealed that, the weevil completes a single generation per year and overwinters as mature larvae inside the dried stems of host plant. Adults emerge from the dead stems, in early May. After emerging, they start to feed on the leaf tissues of the host plants and mate from time to time. Females then chew holes into the stem, and lay eggs singly in the each hole. The eggs were covered with plant fibers by females for protection. Female's fecundity was calculated as 23. 4± 4. 6 (range: 17-32). In the natural conditions, the incubation period takes 8. 3± 1. 8 (range: 6-11) days. Upon hatching, the young larvae bore into the stem where they feed on the tissue. The fully developed larvae make pupal cell in the stem and eventually pupate in it. Larval stage takes more than 10 months to complete inside the stem. The mature larvae stay inside the stem until late-April of the following year. The pupal stage begins in mid-April and depending on the environmental conditions lasts 13. 2± 4. 5 (range: 11-19) days. The new generation of adults appears in the late April. The larvae of L. fasciculatus were parasitized by Rhaconotus aciculatus Ruthe, 1854 (Hym.: Braconidae), Schizoprymnus telengai Tobias, 1976 (Hym.: Braconidae) and Eurytoma ussuriensis Zeova (1995) (Hym.: Eurytomidae) in Urmia region. The association of L. fasciculatus with mentioned parasitoids are new findings. To our knowledge, this is the first report of S. telengai and E. ussuriensis from Iran.

Bacteria use a unique sophisticated mechanism named as Quorum Sensing (QS) for regulation of diverse physiological processes in consent with their population activities and gene expression. This phenomenon depends on the synthesis and perception of small signal molecules such as acyl-homoserine lactones (AHLs) which regulates the important functions including motility, antibiotic and pigment production, biofilm formation, and production of virulence determinants in many bacteria. The presence of Anti-QS activity in methanolic extract of 25 plants was assessed through inhibition of violacein pigmentation in Chromobacterium violaceum CV026 growing on LB agar plates at the presence of 5 mg/l C6-homoserin lactone. The results revealed that the QS inhibition activity was observed in the leaves and stem extracts of coriander (Coriandrum sativum), licorice (Glycyrrhiza glabra), rocket (Eruca sativa), hollyhock (Althea officinalis) and mountainous celery (Kelussia odoratissma) which repress violacein production in C. violaceum CV026 via formation of clear hallo with colorless bacterial colonies around the plant extracts. In addition, the methanolic extracts of Glycyrrhiza glabra and Eruca sativa were also able to inhibit QS-regulated virulence in Pectobacterium carotovorum and severely decreased soft rot symptoms on potato tubers. Both LuxI and LuxR activity were affected by crude extracts of rocket and mountainous celery suggesting that the phytochemicals target both QS signal and receptor. The overall results suggest that plants have mimic quorum-sensing signals, which could be serving as potential sources to disrupt quorum sensing in associated bacteria and inhibited secretion of pectolytic enzymes in Pectobacterium.

Soybean is considered as the most important oilseed crop in the world. One of the common diseases of soybean is charcoal rot which is caused by Macrophomina phaseolina. Chemical control of this disease is not effective and its integrated management using different methods is important. In this research study, in order to obtain suitable antagonist isolates for the disease biological control, effect of 126 Trichoderma isolates on the causal pathogen, M. phaseolina was studied using dual culture and the effect of volatile compounds tests in the laboratory and 12 most effective isolates were selected for the greenhouse studies. Identification of the isolates was done based on the morphological characteristics using valid keys showed that three isolates recognized as Trichoderma reesei, seven as T. harzianum and two as T. atroviride. Effects of the above-mentioned isolates with two control treatments (positive and negative) were investigated on soybean charcoal rot in the greenhouse. After soil pasteurization in the pots, pathogen was added and Trichoderma isolates were used at soybean planting time. In order to create suitable conditions for the pathogen infection, drought stress applied in the pots at early flowering. At the end of infection period, decreasing the disease incidence on soybean and decreasing the population of pathogen microsclerotia in the soil were observed and there were significant differences among different treatments (P<0. 01) regarding both factors. The highest decrease of disease incidence and microsclerotia population were observed in the negative control (without Macrophomina and Trichoderma). Isolates ARCTr144 (T. reesei), ARCTr102 (T. harzianum), ARCTr184 (T. reesei) and ARCTr105 (T. atroviride) showing the highest decrease of disease incidence (62-75 percent) and microsclerotia population (73-85 percent) after the negative control were the best and most effective isolates.

Tea root lesion nematode, (Pratylenchus loosi) is currently considered as the most important damagecausing agent in the most tea-producing countries including Iran. In order to use antagonistic fungi for biological control of this nematode, samples of soil and tea roots were collected during the spring and summer of 2013 in tea plantation of Guilan and Mazandaran provinces. Different fungi were isolated and identified from collected soil samples and or parasitic nematodes. These isolates included Paecilomyces lilacinus (isolates T1, N1, N3), Fusarium culmorum, F. graminearum, Cladosporium sp. and Trichoderma harzianum (isolates T1, T2, T3). Pathogenicity tests of these fungi on nematode were conducted on 1. 5% water agar and mortality rate of Juvenile and adult nematodes were determined at three different periods of 48, 72 and 168 hours. Among the 11 tested isolates, the isolate of P. lilacinus (T1) with causing 64% mortality of juveniles and 29% the adults and also the isolate of P. lilacinus (N1) with having 47% mortality rate in juveniles and 24% in adults after 168 hours, had the highest mortality rate compared with other fungi. Also in this study, T. harzianum fungus was a very weak biocontrol agent compared with other isolates. The overall results showed that P. lilacinus have high potential to control tea root lesion nematode.

Predator ladybird, Cryptolaemus montrouzieri and the armored-scale ladybeetle, Chilocorus bipustulatus (L. ) are important predators of Diaspididae and Eriococcidae families in Iran. Application of mineral oils are among chemical methods to control mealybugs which are more compatible with the environment and relatively quickly are destroyed in the environment and the risk of secondary pest resistance in regards with these compounds is very low. In this study, the effect of Volk oil® on adult and different larval stages of C. montrouzieri and C. bipustulatus was evaluated on citrus leaves in orchard conditions. Ladybeetles were released and then sprayed with Volk oil at the concentrations of 0. 5, 1, 1. 5 percent and water (control) was carried out and after 24 hours the number of dead and alive insects were determined. . The results showed that there were significant differences between the effects of different concentrations on life stages of both ladybirds at 5% level. The concentration 1. 5% had the highest mortality rate, as 92. 16± 1. 11 and 96. 83± 1. 24 percent on the 1st larval stage of C. montrouzieri and C. bipustulatus ladybirds, respectively. Based on the results and compared with the evaluation criteria of the International Organization for Biological Control (IOBC), mortality rate caused by 1 and 0. 5% concentrations of Volk oil in most age stages for both predators were placed in the second group of side effect ranking (Moderately Harmful).

The common reed wasp, Tetramesa phragmitis (Erdö s, 1952), is newly recorded from Iran. It was collected during surveys on biocontrol agents of common reed, Pharagmites australis (Cav. ) (Poaceae), in the West Azarbaidjan province, Urmia. The species is belonged to Trans-Palaearctic region.