نشریه مهار زیستی در گیاه پزشکی
سال نهم شماره 1 (بهار و تابستان 1400)

Today, the knowledge of agricultural and health pest management using biological control method is expanding, and among these, Bacillus thuringiensis as a bio–pesticide with high efficiency and safety have a major role in pest control. However, due to high production costs, it has not yet been able to replace chemical pesticides. In the present study, to promote pesticide and cost–effective cultivation Bt subspecies kurstaki native strain 6R, food waste and by–products including wheat bran, soybean pulp, corn powder and corn steep , fish meal, date juice, sugar beet molasses and sugarcane bagasse were evaluated as raw fermentation media. In this study, the above substances were studied as food culture medium as an extract and as a liquid for propagation. Factors of spore and crystal production were measured during the fermentation process in different cultures for 72 hours, including bioassay on Helicoverpa armigera larval stage three, dry biomass weight, spore content and the effect of pH. The results showed that Bt from wheat bran, sugarcane molasses and corn steep substrates on H. armigera larval stage three has 100% mortality. The highest dry biomass of Bt after the end of fermentation was related to corn powder, wheat bran and corn steep, as 0.903, 0.7804 and 0.559 g per 100 ml of suspension culture, respectively. The results showed that corn steep culture medium with the highest Bt production in laboratory conditions (2.8 × 1012 CFU / ml) was the most efficient. In combination of two culture media, beet molasses (carbon source) with corn steep  (nitrogen source) with 4.22 × 1012 CFU / ml and wheat bran (carbon source) with corn steep  with 3.44 × 1012 CFU / ml, each two had the best performance with 100% mortality on H. armigera larvae. Overall, our findings provided a new strategy for using food waste and by–products with less environmental impact and reduced production costs.

Plant viruses are a limiting factor in agriculture. Natural compounds, especially herbal plant metabolites, have been considered to control viruses. In this regard, the effect of aqueous–ethanolic extract (50% water) and essential oil nanoemulsion of Satureja khuzistanica were investigated to reduce the infection of cucumber mosaic virus on the local lesion test plant of cowpea (Vigna unguiculata) in greenhouse conditions. The extract and essential oil nanoemulsion were applied in four concentrations of 0.5, 1, 2 and 4 percent (g/100 mL) and three different times including simultaneously, two hours before, and after inoculation of plant leaves with virus inoculum (concentration 2 mg/ml). The lowest number of local lesions was obtained by using 2 and 4% of hydro–ethanolic extract (by 66–78% disease reduction) and nanoemulsion of essential oil with a concentration of 2% (by 59% disease reduction), and two hours after inoculation with virus inoculum. The particle size of the nanoemulsion after preparation was 119.4 nm, which reached 232.8 nm after 60 days of storage, which indicates the good physical stability of the nanoemulsion. According to GC–MS analysis, the main constituents of essential oil were carvacrol (91.5%), para–cymene (1.5%), beta–caryophyllene (1.1%) and beta–pinene (1.1%). Nanoemulsion of this essential oil improved its efficiency to inhibit the cucumber mosaic virus on cowpea. This study is the first report of the antiviral effect of phytochemical compounds of Khuzistani savory to inhibit a plant virus.

Pistachio is an important and economical crop that is attacked by Armillaria mellea which causes a significant reduction in yield and deterioration. Root rot disease caused by A. mellea is one of the fungal diseases which has been increasing in pistachio orchards in recent years. Extensive mechanisms and complex life cycle limit its control and almost impossible. In this study, the biochemical aspects of Glomus intraradices and A. mellea root symbiotic interaction on Pistachio vera root, Badami zarand cultivar, as a sensitive rootstock were investigated. This experiment was performed in a completely randomized design and factorial with four replications in greenhouse conditions. Chitinase activity enzyme was calculated based on the amount of N–acetyl glucose amine released. The results showed that colonization with symbiotic fungi changed enzymatic activities in favor of the plant, which was directly related to the percentage of colonization of symbiotic fungi with roots. The results showed an increase and maximization of chitinase activity enzyme in the roots of plants inoculated with mycorrhizal fungi.

Tomato (Lycopersicon esculentum) is one of the most important crops in the world and Iran. Verticillium wilt of tomato caused by V. dahliae is one of the most important obstacles to the cultivation of this plant in the country. Using endophytes has been introduced as a new solution to plant disease management. The aim of this study was to introduce endophytic bacteria as biological control agent for Verticillium wilt of tomato. For this purpose, plants were collected from both greenhouses and tomato fields in Tehran and Alborz provinces. Endophytic bacteria were isolated mainly from the roots, stems, leaves and fruits of tomato. Based on key tests and fluorescent pigmentation on King' B medium, 30 fluorescent Pseudomonas were selected. In dual culture tests, six isolates with biocontrol capacity of V. dahliae were screened and complementary evaluation was done under greenhouse conditions. The P. fluorescens NZ105 strain was identified as the most effective biocontrol agent with 3.7 mm inhibition zones in Petri dish and 85% disease incidence reduction in greenhouse. This strain was identified based on the key tests and 16S rDNA gene amplification. The results of the greenhouse test showed that P. fluorescens NZ105 had the best performance in increasing plant growth factors including plant dry weight, dry root weight, plant height, root length, wet root weight and wet plant weight. Furthermore, the studies showed that this strain is capable of producing protease, volatile antifungal metabolites and extracellular metabolites.

In the present study, effect of seed protein extracts of Robinia pseudoacacia, Medicago sativa, Lens culinaris and Vica villosa were studied (in vitro and in vivo) on alpha-amylase activity of boll worm, Helicoverpa armigera (Hübner). Effect of 4 concentrations (14, 13.15, 10.05 and 9.7 μg) of protein extract of the mentioned plants showed the greatest inhibitory effect. The highest inhibition of the enzyme was observed under the influence of all four inhibitors at pH value equal to 9. Zymogram analysis in confirmation of enzyme quantification showed inhibition of alpha-amylase in reducing band thickness. At the highest concentration of alfalfa seed protein extract, 49% enzyme inhibition was observed. In the presence of acacia inhibitor at a concentration of 41 μg / ml, 76% of alpha-amylase activity was reduced. Alpha-amylase was assayed at different concentrations of lentil protein extract and a concentration-dependent inhibitory process was obtained at the highest concentration of 51% enzyme inhibition. Also, four different concentrations of hairy vetch inhibitor were measured with enzymatic extract and in the highest concentration of hairy vetch, 61% of enzyme inhibition was observed. Amylase activity in digestive lumen after the second larval instar in acacia treatment showed significant reduction. Total larval longevity in acacia treatment (49.03±1.12) had significantly longer life time in comparison with other treatments. Thus, the seed extract of R. pseudoacacia had high inhibitory activity for the α-amylase of this pest.

The circulatory system is involved in the transport and storage of food and defense against microorganisms. The success rate of this system depends on the number and type of blood cells and their proper function against contaminants in the body. In the present study, the effect of Bacillus thuringiensis and temperature stress was investigated on homocyte abundance and phenol oxidase activity in fifth larvae of Plutella xylostella. In the first experiment, rapeseed leaves were treated with sub–lethal concentrations of bacteria and fifth instar larvae were bled at 12 and 24 hours after feeding on the leaves. In the second experiment, the larvae were exposed to 4 and 30 degrees Celsius for 12 hours and temperature stress was examined on their homocytes. The results showed that feeding on canola leaves infected with bacteria after 12 and 24 hours caused a significant increase in total cells, plasmotocytes and granulocytes and phenol oxidase activity compared to the control. Temperature stresses also increased the number of homocytes and phenol oxidase activity compared to the control, which was more significant in larvae that tolerated high temperature stress. Certainly, additional research is needed to be able to evaluate the possible use of microbial control methods against cabbage willow by recognizing the safety characteristics.

Induced resistance is a type of defense system in plants that is activated by a biotic agent and allows plants to resist pathogens or parasites. Strong inducers are usually quite effective and can trigger a plant resistance reaction. These molecules, also called elicitors, can be inanimate or biotic in nature, challenging the plant and reacting to it, which must be done by producing antimicrobial compounds and / or creating mechanisms is related to plant defense. Induction of resistance in plants is strongly influenced by environmental conditions, especially light and temperature during the day and growing conditions. In general, induction of resistance in plants by using live or non-live stimuli or the use of plant cultivars incompatible with the patient, are among the strategies considered by researchers in the management of diseases and plant diseases. Induced resistance to change of grape varieties infected with phytoplasma disease has been observed on different cases. This method is one of the treatment strategies in the management of phytoplasma diseases and diseases caused by fastidious vascular bacteria.

The quality of biological control agents has a main role in the success of a biological control program. It is believed that long–term mass rearing in confinement may affect the quality of them. In this study, the life table and parasitism parameters of Trichogramma embryophagum (Hartig) reared on Ephestia kuehniella Zeller eggs was studied for 32 generations (G). The initial population of wasp from the pomegranate orchards of Kuhdasht County (Lorestan Province) and the population of host from an insectary, from Hamadan (Hamadan Province), were prepared and reared at 26°C, RH of 65%. Data on the duration of different developmental stages, survival, fecundity and parasitism in G5, G10, G15, G20, G25, G28, G30 and G32 were determined separately, and were analyzed using age–stage, two–sex life table theory with use of TWOSEX–MSChart and CONSUME–MSChart programs. The adult longevity was not significantly different until the 15th generation, but declined as the generation numbers increased and reached 7.15 days in G30. The highest and lowest fecundities were observed in G5 (72.73 eggs) and G32 (28.64 eggs), respectively. The highest values of net reproductive rate (R0) were seen in G5 to G15. The values of intrinsic rate of increase (r) in G5 to G15 were significantly higher than the other generations. The r value from 0.301 day–1 in G1 reached to 0.229 day–1 in G32. Also the finite rate of parasitism (ω) with increasing the generation numbers declined and from 0.478 host/parasitoid/day in G5 reached to 0.332 host/parasitoid/day in G32. According to the findings of this study, due to the constant rearing conditions and not adding wild individuals with genetic diversity to the population, after the 15th generation, the quality of reared individual’s decreases significantly.

The olfactory responses and biological attributes of Trichogramma evanescens (Te) and T. brassicae (Tb) were studied at laboratory conditions. Odor treatments included Carob moth eggs and healthy and infested pomegranate crown and seed and healthy and artificially damaged leaves. The olfactory apparatus consisted of a Y shape glass tube with 30° angle. Ninety mated females (0–24 hrs. old) of each species were exposed to the selected odor and clean air in 3 replications (each 30 wasps as one replication). In addition, biological characteristics of wasps were determined on Carob moth eggs using two sex age–staged life table approach. Olfactory results revealed that Te wasps significantly responded to the odors of Carob moth eggs and healthy and infested pomegranate crown and seed over clean air. In contrary, Tb wasps did not respond positively toward any tested odor. Considering biological trait investigations, Te male and female immature stage took 10.70 and 10.52 days being significantly shorter compared with that of Tb male (11.20 days) and female (10.95 days), respectively. Adult female Te had 3 days longevity which was one day longer than that of Tb wasps (2 days). The net reproductive rate and intrinsic rate of population increase of Te and Tb wasps were 16.56 offspring and 0.2337 day–1 and 15.20 offspring and 0.2220 day–1, respectively. Eventually, the transformation rate of host to parasitoid egg (Qp) was equal to 1 for both species. In order to select superior natural enemy candidates for biological control programs, the possibility of using fast olfactory tests instead of time consuming biological studies is discussed.

In the summer of 2014, the outbreak of Aleuroclava jasmini sensu lato (Hem., Aleyrodidae) on white mulberry trees in the urban green spaces of Tehran caused a disturbance for the citizens in the parks and streets. By formation of the monitoring and surveillance network, while providing non–chemical strategies for mulberry whitefly management, the natural enemies of this pest were identified. Later, the trend of changes in the host and its parasitoid populations was determined during 2017–2019. Among the 19 species of natural enemies of the mulberry whitefly  collected from different orders and families of insects and mites, two species of parasitoid were identified as Encarsia strenua (Silvestri) and Eretmocerus sp. nr trialeurodis Hayat (Hym., Aphelinidae). The study of immature stages and adult whitefly population and monitoring the exact time and place of presence and activity of parasitoids of the pest, showed that during the last five years, the population of mulberry whitefly has been inhibited by forming a natural balance and 71.16 and 45.4% parasitism on mulberry and olive trees, respectively. Meanwhile, olive trees play an important role in maintaining the parasitoid population of this whitefly in autumn and winter. Therefore, in urban green space ecosystems, the avoidance of using chemical pesticides is highly emphasized for the preservation and sustainability of predators and parasitoids.

Grapevine is one of the most important agricultural products in Iran. West Azerbaijan province is considered as one of the biggest production centers of grape in Iran, due to its suitable climatic conditions. The aim of this study was to identify grape endophytic bacteria in West Azarbaijan. In this study, 67 endophytic bacteria were isolated from the stems and roots of grapevines. Then, biochemical properties such as hypersensitive reaction, fluorescent and potato soft rot test and the ability to produce proteases, amylase and gelatinase enzymes were tested. Eleven bacterial isolates were selected for molecular identification and it was found that Bacillus and Pseudomonas are the most abundant genera. According to our knowledge, three species of Stenotrophomonas sp., Bosea lathyri and Frigoribacterium faeni are reported for the first time in Iran as grapevine endophytic bacteria. Also, the antifungal effect of endophytic bacteria on three fungal species i.e. Chaetomium globosum, Cytospora chrysosperma and Fusarium sp. was done by dual culture method and three isolates of GI6 (Priestia sp.), GI43 (Pseudomonas kilonensis) and GI45 (Bacillus sp.) showed the most growth inhibitory properties. Due to the importance of endophytic bacteria, their isolation and identification from different parts of the country seems necessary, as the result, these bacteria can be used in biological control of plant diseases and can be replaced by chemical control.

Tobacco aphid (Myzus nicotianae) is an important pest affecting the quantity and quality of tobacco products which may cause pesticides application inevitable. Today, due to the emergence of pests resistant to chemical pesticides and their adverse effects on the human health and environment, it is a mandate to reduce the use of chemical compounds in pest control. In this regard, the use of botanicals such as plant extracts and essential oils are recommended as safe alternatives to the chemical pest control measures. In the present study, the effect of tobacco (Nicotiana tabacum), tombak (Nicotiana rustica) and thyme extracts were investigated on tobacco aphid. The bioassay tests were accomplished under a complete randomized design with four replications at 25 ± 1 °C, 65 ± 5% RH and a photoperiod of 16:8 hours L:D. The percentage mortality was calculated for five concentrations (6000, 8000, 10000, 15000, and 20000 ppm) of each plant extract at 24, 48 and 72 hours post application. According to the results, the pest mortality increased with the increasing concentration of plant extracts and elapsed time after treatment. The highest mortality rate (100%) belonged to tombak extract with a concentration of 20000 ppm and the lowest rate (56.75%) was observed in thyme extract at 6000 ppm concentration, respectively. The LC50 values of tobacco, tombak and thyme extracts were 12463, 10210 and 17385 ppm on the tobacco aphid tested population, respectively, showing the greater effect of the tobacco extract compared with that of other extracts.