نشریه کنترل بیولوژیک آفات و بیماری های گیاهی
سال دهم شماره 1 (بهار و تابستان 1400)

In this study, the effect of mycoendobiont fungi isolated from white button mushroom against Mycogone perniciosa, Lecanicillium fungicula and Trichoderma harzianum, as its important pathogens, was investigated for use in biological control and replacement of chemical compound. Isolates of mycoendobiont fungi were isolated from the cap, gills and stalk of healthy white button mushroom, collected from major mushroom growing farms in Iran. These isolates screened against aggressive strains mentioned above in dual culture tests and the most effective isolates were selected for greenhouse experiments. White button mushroom spawn was treated with the mycoendobiont fungi and disease incidence and growth parameters were measured. All mycoendobiont isolates tested were able to inhibit and compete with pathogens and controlled the incidence of wet bubble disease (M. perniciosa) from 21.42% to 97.61%, dry bubble disease (L. fungicula) from 60.63% to 96.80% and green mold disease (T. harzianum) from 64.28 to 96.93%. This test was performed in a completely randomized design with Three replications. Mycoendobiont isolates of Fusarium venenatum and Clonostachys rosea had the greatest inhibitory effect on the growth of all pathogens. In addition, Scedosporium apiospermum had a high growth inhibitory effect against M. perniciosa and T. harzianum. According to the results, mycoendobiont fungi of white button mushroom could be considered as the biocontrol agents and growth promoting with the aim of applying them in future.

Pseudomonas fluorescens bacteria are the most important rhizosphere bacteria that have a positive effect on vegetative and biochemical traits of the plant. In this study, genetic diversity of 22 Pseudomonas fluorescens strains and their effect on defense enzymes and growth factors of wheat plant were performed in three stages of greenhouse, molecular and biochemical evaluation. In molecular evaluation, 12 RAPD primers were used to evaluate the genetic diversity of strains. Biochemical evaluation was performed in 4 stages of 0, 3, 6 and 9 days after inoculation on wheat to measure the defense enzymes peroxidase and phenylalanine ammonialyase. VUPF5 strain on wheat increased shoot and biological weight. RAPD-PCR separated strains with similar geographic location and similar host. Greenhouse, molecular, and biochemical groupings identified almost the top strains. Strains 680, 738, 50, 354, 49, 58 and VUPF5, which had a positive effect on molecular evaluation in one group, were shared with the superior group of enzymes. T26-2 and F-68 in OP-I15 and OP-H8 primers amplified 1300 bp and 1200 bp bands, respectively witch these bands can evaluated after be further studies as candidate bands in the expression of these enzymes in wheat.

In this study, the interaction of Bacillus subtils, B. cereus, and Pseudomonas fluorescens CHA0 with the bacteriovorus nematode Caenorhabditis elegans was investigated in in-vitro condition. Possibilities of the survival and reproduction, the attraction and feeding of C. elegans on the bacteria, and the effect of volatile compounds and antibiotics of the bacteria on C. elegans were examined. The efficiency of the bacteria on controlling Meloidogyne javanica was studied by evaluating the number of galls and egg masses per plant, gall-diameter per plant, and the number of eggs per egg mass. Then, the most effective bacterium was used for the induction of plant defence responses. The results showed that C. elegans is not able to survive and reproduce on the colony of B. cereus and P. fluorescens CHA0. Although, in the normal condition, C. elegans did not feed on B. cereus, when the nematode was left hungry it started to eat the bacterium which, however, caused its death. Volatile compounds and antibiotics of B. cereus and P. fluorescens CHA0 caused 100% C. elegans larval mortality after 24 or 48 hours. All three bacteria caused a significant reduction (p<0.05) in all indicators of M. javanica pathogenicity while the highest efficacy in controlling the nematode was observed for P. fluorescens CHA0. Biochemical analyses showed that inoculating plants with P. fluorescens CHA0 and/or M. javanica caused a significant increase (p<0.05) of catalase in the plants.

Take-all is one of the most important wheat diseases worldwide. The present study assessed the effect of nitrogen and phosphorus fertilizers, and endophytic fungus Microdochium bolleyi on controlling this disease in wheat ‘Pishgam’ cultivar for the first time. A greenhouse experiment was conducted based on a completely randomized design (CRD) with the treatments of control, nitrogen+phosphorus fertilizers (100 and 200 mg kg-1 urea, and 50 and 100 mg kg-1 triple superphosphate) alone and their combination with pathogen Gaeumannomyces graminis and endophytic fungus M. bolleyi. Then, root dry and shoot fresh weights, plant height, and leaf chlorophyll content, as well as the percentage of root contamination were measured. Based on the results, root dry and shoot fresh weight, plant height, and leaf chlorophyll content were significantly maximized following the treatments containing urea and triple superphosphate at various levels, and endophytic fungus (p<0.05). In terms of pathogenesis control, about 46% decrease was observed in take-all disease for the treatment receiving urea+triple superphosphate alone. The disease was respectively controlled by around 58 and 75% after applying endophytic fungus M. bolleyi alone and in combination with the highest amount of urea+triple superphosphate, respectively.

Bioprotection agents, including living biocontrol agents and naturally occurring non-living substances such as diatomaceous earth, play a crucial role in controlling stored commodity pests to maintain food health. The problem with using diatomaceous earth in storage is that their recommended dose increases grains' bulk density and decreases flowability. Therefore, the present study aimed to determine the biocompatibility between two commercial formulations of Iranian diatomaceous earth, Sayan, and foreign Celite 610 with the indigenous entomopathogenic fungus isolate, Beauveria bassiana DE (Hypocreales), and to solve the problem of reducing grains' flowability using a low-lethal dose of diatomaceous earth in the mixture. For this purpose, 14-day bioassays were first performed by impregnating wheat seeds separately with the fungus and two diatomaceous earths against adults of Khapra beetle, Trogoderma granarium Everts. Then, to determine the interaction effects, five different doses of B. bassiana were mixed with LD25 of each diatomaceous earth. Based on the results, LD50 values for fungus, Sayan®, and Celite 610® were calculated at 295.3, 4439.5, and 992.3 ppm, respectively. According to the lethal dose ratio test, the insecticidal activity of Celite 610® was estimated to be 4.47 times more than Sayan®. Moreover, the interaction was synergistic in all mixtures of B. bassiana with the low-lethal dose of each diatomaceous earth except for the highest dose of the fungus, which was estimated additive. In addition, all mixtures effectively reduced progeny production during the eight-week storage period, indicating the compatibility of these two agents for co-application in the integrated T. granarium management programs.

One of the aggravating factors in the amount of frost damage, is the presence of epiphytic ice nucleation bacteria on plant philosopher. Biological control of ice nucleation bacteria seems to be a promising option to reduce this type of frost damage. In this study, the antimicrobial capacity of epiphytic bacteria and actinomycetes was evaluated through growth inhibition of ice nucleation active bacteria (Pseudomonas fragi raf3) on pistachio in Rafsanjan. For this purpose, samples were collected from healthy pistachio leaves in Rafsanjan. Among the isolated bacteria and actinomycetes, two isolates (A4 and B52) with the highest inhibitory zone were subject to different biochemical and physiological tests. Results showed that the zone of inhibition growth of ice nucleation bacterium on Petri dish, was 20 mm and 14 mm for isolates A4 and B52 respectively. Analysis of morphological and biochemical characteristics showed that isolate A4 was noted to be Gram-positive and to form white, dry colonies similar to actinomycetes. It was able to degrade glucose and sucrose as a carbon source and able to produce lipase, protease and catalase enzymes. This isolate was able to grow in conditions with pH 5 and 7, as well as, showed 2, 5,7 and 10% (w/v) salt-salt (sodium chloride) tolerance. It was tetracycline-sensitive and penicillin-resistance. The other antagonist isolate, B52, had yellow colonies on nutrient agar media Gram-negative bacterium, catalase positive, oxidase negative, facultative anaerobic and lactose fermenting.

Wheat is one of the most important agricultural products with the cultivated area covering about half of Iran's arable land. Fusarium pseudograminearum crown and root rot disease of wheat is one of the most destructive fungal agents in dry regions of Iran and the world, which affects the production of this product. By destroying the chlorophyll of the wheat plant, this disease reduces the growth of the plant and over time causes the death and complete drying of the wheat plant. The use of chemical poisons is one of the ways to control the damage caused by this disease, but due to the environmental damage caused by these poisons, scientists are looking for an alternative method. In this study, with the help of Pseudomonas fluorescens strain EB298 (UTPf298), the pathogenicity of this fungus in greenhouse conditions was significantly reduced compared to the control plant. In laboratory conditions, the bacterial isolate prevented the growth of the fungus by 70%. Also, this isolate has increased the amount of chlorophyll a, b and total chlorophyll to 1, 0.5 and 1.5 mg/g, respectively, by reducing the damage caused by the fungus. By stimulating plant growth, Pseudomonas fluorescens strain EB298 (UTPf298) increased the weight of root and stem by 0.35 and 0.9 grams and increased the length of root and stem by 15 and 28 cm. Therefore, in this research, due to the efficiency of Pseudomonas fluorescens EB298 (UTPf298), it can be used to control Fusarium pseudograminearum crown and root rot disease of wheat .