نشریه کنترل بیولوژیک آفات و بیماری های گیاهی
سال هشتم شماره 1 (بهار و تابستان 1398)

In this work, the effects of two commercial bio-fungicides Biosubtil (Bacillus subtilis) and the bio-fertilizer Biophosphorus (Pseudomonas species), was assayed on the disease incidence, changes in the defensive enzyme activity, the total phenolic content and the expression level of some defense-related genes using real-time PCR method. Biochemical and molecular changes were measured at four time point: 24, 48, 72 and 96 hours post inoculation (hpi) of cucumber plantlets with Phytophthora melonis. The disease incidence decreased through applications of both antagonists. The highest disease reduction (60%) was noted for Biosubtil application compared to control plants. Biochemical analysis showed that both bio-fertilizers are able to increase total protein and phenolic compounds in infected cucumber plants. A maximum increase was observed with biophosphorus application at 72hpi. High activity of Peroxidae )PO) and β-1,3-glucanase enzymes were noted for biophosphorus application at 72 hpi while maximum increase of Polyphenol oxidase (PPO) was observed at 96 hpi for this application. Altered transcript levels of various resistance genes including cucumber pathogen-induced 4 (Cupi4), Lipoxygenase (Lox), Phenylalanine ammonia lyase (PAL) and Galactinol synthase (Gal) were recorded in both treatments. A high expression level (9.5 fold) among the treated genes was observed for Lox gene at 72 hpi and an high expression level for other genes was noted at 48 hpi when cucumber plants treated with Biophosporus. The results suggest that both bio-fertilizers are able to enhance disease resistance in cucumber through induce of resistance mechanisms and could be used as a resistance inducer in the greenhouse condition.

Bdellovibrio bacteriovorus is an obligate predator of other Gram-negative bacteria. It grows in the periplasm of the prey cell and finally lyses them, so it has high potentials to be used in biocontrol of plant pathogenic bacteria. The objective of the present study was to isolate and characterize Bdellovibrios bacteria from soil and water samples of Rafsanjan (Kerman province) in Iran. To do this, after sampling, two Bdellovibrios isolates (Sar and Pj) were isolated by using Escherichia coli strain K12 as prey on the two layers agar. The isolates were identified by phenotypic and 16S rDNA PCR amplification and sequencing. The sequencing and phylogenetic studies showed that the strains have more than 99% similarity to B. bacteriovorus. Then, the host range and specificity of the strain were evaluated on 9 different Gram negative bacterial species. The results showed that the strains have predatory effects only on E. coli as prey.

Predator species and intraguild predators can affect predation on important pest species. This predation response can influence pest consumption when multiple predators co-occur. In sour cherry orchards in Baraghan (Karaj, Iran), Zetzellia mali (Ewing) (Acari: Stigmaeidae) is a predatory mite that feeds on the plant pest Amphitetranychus viennensis (Zacher) (Acari: Tetranychidae) juveniles. Additionally, Scolothrips longicornis Priesner (Thysanoptera: Thripidae) is recorded as an intraguild predator of Z. mali juveniles. We have studied whether the oviposition behavior of predatory mites can change in the presence of intraguild predators through vertical migration within host plant. According to our results, vertical migration happened in a significant number of Z. mali females in presence of conspecific odors (P < 0.01). Odors associated with A. viennensis and the predatory mites triggered upward migration (P < 0.01) while the prey presence alone did not result in any significant movement (P > 0.05). Receiving odors related to the thrips, Z. mali showed no preference for a significant vertical movement, while the presence of thrips and A. viennensis on upwind plants led to an upward migration (P < 0.05).

Plant growth which promotes rhizobacteria (PGPR) has a potential role in controlling root-knot disease. To reach the aim of this study, we used rhizobacteria replaced by chemicals to reduce this problem in Pistachio trees. Based on the previous studies, some strains with high ability were selected to reduce root knot severity. Three different formulations were prepared, using different carriers of materials named; wheat bran, dried apple and talc powder. we have used six individual strains of P. fluorescens and one combination of two strains (Vupf506+Vupf52). These formulations were tested to control M. incognita in Pistachio seedlings in the greenhouse condition. The wheat bran based treatments was effective in reducing disease by 32.7 to 88.9%. The bacteria survived longer in wheat bran-based and talc-based formulations than in dried apple-based formulation. The results of the study indicated that organic carriers can be efficiently used to improve the stability and efficiency of biocontrol-active microorganisms in controlling the Pistachio root-knot disease

Strawberry anthracnose disease, caused by Colletotrichum nymphaeae is a major limiting factor in strawberry production in Kurdistan province of Iran. In this research, endophytic fungi were isolated from stem and crown organs of strawberry and their antifungal activity against C. nymphaeae was tested. The selected isolates were identified as Penicillium hordei and Penicillium polonicum based on morphology and molecular characteristics. Antagonistic effects of selected isolates were evaluated against C. nymphaeae, through dual culture, volatile and non-volatile compounds production mechanisms in in vitro and greenhouse conditions. In volatile compounds test, two isolates of P. hordei and P. polonicum were able to reduce C. nymphaeae growth (34.05 and 42.36%) compared with control. In addition, isolates of P. hordei and P. polonicum reduced the strawberry anthracnose disease severity significantly in greenhouse conditions (58.9 to 61.4%) compared to the control. According to the results both in vitro and greenhouse experiments, both isolates reduced the growth of pathogen. Therefore, the results of this research showed that it may be possible to manage strawberry anthracnose disease effectively by using Penicillium species as biocontrol fungus. To our best knowledge, this is the first research related to the effects of Penicillium species on strawberry anthracnose.

A study was carried out to evaluate the potential of two antagonist fungi, biofumigation, soil amendment and solarization to control M. javanica. Pots were inoculated with suspensions of Pochonia chlamydosporium var. chlamydoporium and/or Purpureocillium lilacinum to provide 1 × 104 spores/g soil and 2 × 106 spores/g soil respectively. Canola cake and green leaves of oilseed Canola Brassica napus each at 1% w/w rate were incorporated into infested soil; half of the biofumigant pots were solarized. All pots were planted with cucumber and inoculated with 5 eggs of M. javanica/ g soil of the nematode. Both fungi showed potential as biocontrol agent by infecting nearly 36% of the new eggs on roots, so decreasing nematode multiplication and increasing cucumber weight. In Pochonia treatment, number of galls and eggs were reduced to 50 and 4.2 eggs/ g soil whereas 141.1 and 12.3 were recorded in nematode control respectively. All non-chemical treatments reduced root galling by between 56 and 78% and final egg density by 35% to 83%. The effects of combined solarization and biofumigation were greater than for each one alone, as gall and final egg population were 62.4 and 6.7/ g soil in biofumigant pots, which were reduced to 31.1 and 2 in combined treatments respectively. All methods promoted the growth of cucumber. The results offer some positive measures for biocontrol agents and none-chemical methods to be considered for an integrated nematode management strategy.

The Rosaceous longhorn beetle (RLHB), Osphranteria coerulescens Redtenbacher (Coleoptera: Cerambycidae) is a significant pests of fruit orchard in Iran and it is costly to control it. During an ongoing project on natural enemies of O. coerulescens in Mashhad region, North East of Iran, two isolates of entomopathogenic fungi (EPF) were isolated as natural pathogens on the larvae. The fungal isolates were identified based on morphological characters and then ITS gene sequences were used for inferring phylogenetic relationship. These isolates were identified as Beauveria bassiana sensu lato (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae) and Metarhizium anisopliae sensu lato (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae). In the laboratory bioassay, potential virulence of entomopathogenic fungi against O. coerulescens larvae was conducted in various treatments. The larvae were susceptible to both EPF isolates, but the B. bassiana isolate caused significantly higher mortality than the M. anisopliae isolate. Application of EPF suspensions under special climatic conditions against in early life stages is thought to be promising for control of O. coerulescens.

Eurygaster integriceps Puton is an important pest of wheat and barley in Iran and the Middle East. Chemical control of the pest should be carried out by selective insecticides to conserve its natural enemies such as Trissolcus grandis (Thomson). In this research, the lethal effects of field recommended doses of two new formulations from lambda-cyhalothrin including Karate-zeon® (CS 10%) and Hef-lambda® (SC 5%) were studied on the mature and different immature stages of T. grandis under the laboratory conditions. Contact of the adult wasps with sprayed areas by both insecticides caused 100% mortality. Parasitized eggs containing first instar (at the third day of parasitism), second instar (at the fifth day of parasitism) and pupa stage (at the eighth day of parasitism) were dipped into insecticide solutions. At all immature stages and for both insecticides, the highest mean percent emergence of T. grandis female was observed in SC 5% treated eggs. Treatment of eggs with both insecticides at different immature stages of parasitoid did not show any negative effect on the parasitism activity. However, Hef-lambda®, was proved to be more selective insecticide, because it showed less negative effect on the number of adults that emerged after egg treatment. According to the results of present study, Hef-lambda® can be considered as a less hazardous selective and eco-friendly insecticide in the Sunn pest management.

In this study, 180 rhizobacteria were isolated from different fields of East and West Azarbaijan and provinces of Iran. These bacterial isolates were screened based on their antagonistic potential against Rhizoctonia solani and their ability to form robust biofilm. Out of these isolates, 49 isolates exhibited more that 30% antagonistic activity against R. solani. Different methods were used to screen the isolates with high ability of biofilm formation. Out of 180 isolates, 51 isolates were able to form considerable amount of biofilm as determined by crystal violet staining (CVS) method. Pellicle formation (PF) bioassay was performed in three different media. Most of the robust biofilm forming isolates from CVS method could also form robust biofilms in PF method, only if MSNGP (medium with glycerol and pectin) medium was used. In root colonization bioassay, isolates N168, N95 and N94 that were robust or mediocre biofilm forming isolates in MSNGP, could efficiently colonize plant roots but the population of isolates N100 and N87 (none-biofilm forming isolates) on tomato roots were lower than 6 log10 CFU g-1 root. However, results of the pathogenicity system with R. solani damping off of tomato showed that, biofilm formation and colonization ability of these isolates doesn't have significant effect on their biocontrol activity

Bdellovibrio bacteriovorus is an obligate predator of other Gram-negative bacteria. It grows in the periplasm of the prey cell and finally lyses them, so it has high potentials to be used in biocontrol of plant pathogenic bacteria. The objective of the present study was to isolate and characterize Bdellovibrios bacteria from soil and water samples of Rafsanjan (Kerman province) in Iran. To do this, after sampling, two Bdellovibrios isolates (Sar and Pj) were isolated by using Escherichia coli strain K12 as prey on the two layers agar. The isolates were identified by phenotypic and 16S rDNA PCR amplification and sequencing. The sequencing and phylogenetic studies showed that the strains have more than 99% similarity to B. bacteriovorus. Then, the host range and specificity of the strain were evaluated on 9 different Gram negative bacterial species. The results showed that the strains have predatory effects only on E. coli as prey.