Showing papers in "Journal of Plant Protection Research in 2016"

Biocontrol mechanisms of Trichoderma harzianum against soybean charcoal rot caused by Macrophomina phaseolina

Abstract: Throughout the world, charcoal rot, caused by Macrophomina phaseolina, is one of the most destructive and widespread dis- eases of crop plants such as soybean. In this study, the biological control capability of 11 Trichoderma spp. isolates against M. phaseolina was investigated using screening tests. Among all the tested Trichoderma spp. isolates, inhibition varied from 20.22 to 58.67% in dual culture tests. Dual culture, volatile and non-volatile tests revealed that two isolates of Trichoderma harzianum (including the isolates T7 and T14) best inhibited the growth of M. phaseolina in vitro. Therefore, these isolates were selected for biocontrol of M. phaseolina in vivo. The results of greenhouse experiments revealed that disease severity in the seed treatment with T. harzianum isolates was significantly lower than that of the soil treatment. In most of the cases, though, soil treatment with T. harzianum resulted in higher plant growth parameters, such as root and shoot weight. The effects of T. harzianum isolates on the activity of peroxidase enzyme and phenolic contents of the soybean root in the presence and absence of M. phaseolina were determined in greenhouse conditions. Our results suggested that a part of the inhibitory effect of T. harzianum isolates on soybean charcoal rot might be related to the indirect influence on M. phaseolina. Plant defense responses were activated as an elicitor in addition to the direct effect on the pathogen growth.

Management of soil-borne diseases of organic vegetables

Abstract: With the rising awareness of the adverse effects of chemical pesticides, people are looking for organically grown vegetables. Consumers are increasingly choosing organic foods due to the perception that they are healthier than those conventionally grown. Vegetable crops are vulnerable to a range of pathogenic organisms that reduce yield by killing the plant or damaging the product, thus making it unmarketable. Soil-borne diseases are among the major factors contributing to low yields of organic produce. Apart from chemical pesticides there are several methods that can be used to protect crops from soil-borne pathogens. These include the introduction of biocontrol agents against soil-borne plant pathogens, plants with therapeutic effects and organic soil amendments that stimulate antagonistic activities of microorganisms to soil-borne diseases. The decomposition of organic matter in soil also results in the accumulation of specific compounds that may be antifungal or nematicidal. With the growing interest in organic vegetables, it is necessary to find non chemical means of plant disease control. This review describes the impact of soil-borne diseases on organic vegetables and methods used for their control.

Insecticidal efficacy of silica nanoparticles against Rhyzopertha dominica F. and Tribolium confusum Jacquelin du Val

Abstract: Bioassays were conducted to assess the effects of two silicon dioxide nanoparticles of Aerosil® and Nanosav against adults of Rhyzopertha dominica F. and Tribolium confusum Jacquelin du Val. Silica nanoparticles were applied at the rates of 50, 100, 200 and 300 mg · kg–1 on wheat and peeled barley. The mortality was counted after 1, 2, 3, and 7 days of exposure. Another experiment was carried out to evaluate the effect of food source on the survival of beetles after exposure to silica nanoparticles. Adults were exposed to silica nanoparticles at the rate of 0.2 mg · cm–2 for 1 and 2 days on filter paper inside plastic Petri dishes, respectively. After exposure, the initial mortality was counted and live individuals of both species were held for a week in empty glass vials or vials containing wheat and wheat flour, respectively. Silica nanoparticles have high toxicity on R. dominica and T. confusum adults. Rhyzopertha dominica was more susceptible than T. confusum. However, the mortality of both species increased with increasing concentrations and time exposed to each concentration. At low concentrations, Aerosil® was more effective than Nanosav. Silica nanoparticles were more effective in wheat grains than barley. Results indicated that the initial mortality was so high that the impact of food source on delay mortality was unclear in most cases. Silica nanoparticles were efficient against tested species and can be used effectively in a stored grain integrated pest management program.

The cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) as a new menace to cotton in Egypt and its chemical control

Abstract: The cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is a polyphagous sap sucking insect with a wide geographical and host range causing severe losses in economically important crops. This study represents the first record of P. solenopsis as a new insect attacking cotton plants (Gossypium barbadense var. Giza 86) in Kafr El-Sheikh governorate, Egypt. The insect was noticed on cotton plants for the first time during its growing season of 2014. The mealybug specimens were collected from infested cotton plants and identified as P. solenopsis. In an attempt to control this pest, eight toxic materials viz., imidacloprid, thiamethoxam, flonicamid, emamectin-benzoate, chlorpyrifos, methomyl, deltamethrin and mineral oil (KZ-oil), belonging to different chemical groups, were tested for their influence against P. solenopsis on cotton under field conditions. Methomyl, imidacloprid, thiamethoxam and chlorpyrifos showed the highest efficacy against P. solenopsis recording 92.3 to 80.4% reduction of the insect population. Flonicamid, emamectin-benzoate and KZ-oil failed to exhibit sufficient P. solenopsis control.

Basic substances under EC 1107/2009 phytochemical regulation: experience with non-biocide and food products as biorationals

Abstract: Basic Substances are a newly effective category of Plant Protection Product under EC Regulation No 1107/2009. The first approved application of Equisetum arvense L. opened Part C of Implementing Regulation (EU) No 540/2011, which lists the basic substance approved. Although E. arvense was described as a fungicide extract, subsequent applications like chitosan were related to non-biocide molecules. Consequently, plant protection product data were collected from research on alternative or traditional crop protection methods. They are notably issued or derived from foodstuffs (plants, plant by-products, plant derived products, substances and derived substances from animal origin). Applications are currently submitted by our Institute, under evaluation at different stages of the approval process or already approved. Remarkably, this Basic Substance category under pesticide EU Regulation was surprisingly designed for these non-biocidal plant protection products. In fact, components described as the “active substance” of most of the actual applications are food products like sugars and lecithin. Basic Substance applications for these foodstuffs are therefore a straightforward way of easily gaining approval for them. Here we describe the approval context and detail the agricultural uses of theses food products as Biological Control Agents (BCAs) or biorationals for crop protection. From all deposited or approved Basic Substance Application (BSA), a proof has been provided that non-biocide and food products via physical barrier or lure effects may be effective plant protection products with an acceptable low profile of concern for public and agricultural safety.

Silicon control of bacterial and viral diseases in plants

Abstract: Silicon plays an important role in providing tolerance to various abiotic stresses and augmenting plant resistance against diseases. However, there is a paucity of reports about the effect of silicon on bacterial and viral pathogens of plants. In general, the effect of silicon on plant resistance against bacterial diseases is considered to be due to either physical defense or increased biochemical defense. In this study, the interaction between silicon foliar or soil-treatments and reduced bacterial and viral severity was reviewed. The current review explains the agricultural importance of silicon in plants, refers to the control of bacterial pathogens in different crop plants by silicon application, and underlines the different mechanisms of silicon-enhanced resistance. A section about the effect of silicon in decreasing viral disease intensity was highlighted. By combining the data presented in this study, a better comprehension of the complex interaction between silicon foliaror soil-applications and bacterial and viral plant diseases could be achieved.

The role of detoxifying enzymes in the resistance of the cowpea aphid (Aphis craccivora Koch) to thiamethoxam

Abstract: The cowpea aphid (Aphis craccivora Koch) is considered a serious insect pest attacking several crops. We carried out biochemical studies to elucidate the role of the metabolising enzymes in conferring resistance to thiamethoxam, in two strains (resistant and susceptible) of the cowpea aphid. Bioassay experiments showed that the thiamethoxam selected strain developed a 48 fold resistance after consecutive selection with thiamethoxam for 12 generations. This resistant strain also exhibited cross-resistance to the tested carbamates; pirimicarb and carbosulfan, organophosphorus (malathion, fenitrothion, and chlorpyrifos-methyl), and the neonicotinoid (acetamiprid). Synergism studies have indicated that S,S,S-tributyl phosphorotrithioate (DEF), a known inhibitor for esterases, increased thiamethoxam toxicity 5.58 times in the resistant strain compared with the susceptible strain. Moreover, the biochemical determination revealed that carboxylestersae activity was 30 times greater in the resistant strain than in the susceptible strain. In addition, the enzyme activity of glutathione S-transferase (GST) and mixed function oxidases (mfo) increased only in the resistant strain 3.7 and 2.7 times, respectively, in relation to the susceptible (the control). Generally, our results suggest that the higher activity of the detoxifying enzymes, particularly carboxylesterase, in the resistant strain of the cowpea aphid, apparently have a significant role in endowing resistance to thiamethoxam, although additional mechanisms may contribute.

Improving biological control of stalk borers in sugarcane by applying silicon as a soil amendment

Abstract: The sugarcane stalk borers, Sesamia spp. (Lepidoptera: Noctuidae) are the most destructive sugarcane insect pests in Iran. The efficiency of Telenomus busseolae Gahan (Hymenoptera: Scelionidae) used alone or in combination with silicon fertilization was investigated for controlling the sugarcane stalk borers under field conditions. The treatments were: a combination of silicon plus multiple releases of 2,500 T. busseolae, and multiple releases of 5,000, 2,500 and 1,250 T. busseolae alone. Plots receiving no soil amendment or parasites were included as the controls. Three weeks after the first application of each treatment, 100 shoots were selected randomly from each plot and the percentage of dead heart was determined. Then, three months after the first application of parasites, the percentage of stalks damaged, the percentage of internodes bored, and the level of parasitism were determined. Finally, at harvest the percentage of stalks damaged, the percentage of internodes bored, and sugarcane quality characteristics were determined. Results indicated that the efficiency of parasitism increased when combined with an application of silicon fertilizer. The release of 2,500 T. busseolae followed by an application of silicon fertilizer decreased dead hearts to 4%, while 12% dead hearts was observed in the control plots. For the combination treatment, the percentages of stalk damage were 1.5% and 17.2%, at 3 weeks and 3 months after time release, respectively. However, the percentages of stalk damage were 35.2% and 51% when no treatment was applied. Cane quality was significantly higher with the application of silicon fertilizer plus the release of 2,500 T. busseolae, followed by releasing 5,000 Hymenoptera. The level of parasitism was also greater when parasites were released in combination with an application of silicon. We conclude that biological control by egg parasitoids can be enhanced with concurrent applications of silicon fertilizer as a soil amendment and thereby creating a more robust, Integrated Pest Management (IPM) program of stalk borers in Iranian sugarcane fields.

Evaluation of some microbial agents, natural and chemical compounds for controlling tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

Abstract: Solanaceous plants have a great economic impact in Egypt. These groups of plants include potatoes, tomatoes and eggplants. The new invasive pest of tomatoes, Tuta absoluta (Meyrick) causes the greatest crop losses which can range from 60 to 100%. After its detection in Egypt during the last half of 2009, it spread quickly to all provinces in the country. We aiming to propose a sustainable control program for this devastating pest. In this research we tested three groups of control agents. The first was microbial and natural, the second – plant extracts and the third – chemical insecticides. Our results showed that the impact of T. absoluta can be greatly reduced by the use of sustainable control measures represented by different insecticide groups. Bioassay experiments showed that this devastating pest can be controlled with some compounds that give high mortality rates. Of these compounds, spinosad and Beauveria bassiana, microbial control agents, followed by azadirachtin, gave the best results in controlling T. absoluta. Of the chemical insecticides, lambda-cyhalotrin was the most effective, followed by lufenuron and profenofos. In conclusion we encourage farmers to use microbial and natural control measures in combating the tomato leafminer, T. absoluta, in Integrated Pest Mangement (IPM) programs.

Antifungal activity of essential oils on Aspergillus parasiticus isolated from peanuts

Abstract: Aspergillus parasiticus is one of the most common fungi which contaminates peanuts by destroying peanut shells before they are harvested and the fungus produces aflatoxins. The aim of this study was to evaluate the antifungal activities of seventeen essential oils on the growth of the aflatoxigenic form of A. parasiticus in contaminated peanuts from commercial outlets in Georgia. The agar dilution method was used to test the antifungal activity of essential oils against this form of A. parasiticus at various concentrations: 500; 1,000; 1,500; 2,000; 2,500 ppm. Among the seventeen essential oils tested, the antifungal effect of cinnamon, lemongrass, clove and thyme resulted in complete inhibition of mycelial growth. Cinnamon oil inhibited mycelial growth at ≥ 1,000 ppm, lemongrass and clove oils at ≥ 1,500 ppm and thyme at 2,500 ppm. However, cedar wood, citronella, cumin and peppermint oils showed partial inhibition of mycelial growth. Eucalyptus oil, on the other hand, had less antifungal properties against growth of A. parasiticus, irrespective of its concentration. Our results indicate that the aflatoxigenic form of A. parasiticus is sensitive to selected essential oils, especially cinnamon. These findings clearly indicate that essential oils may find a practical application in controlling the growth of A. parasiticus in stored peanuts.

Molecular identification of pathogenic Fusarium species, the causal agents of tomato wilt in western Iran

Abstract: Fusarium species are causal agents of fungal diseases occurring frequently in numerous agriculturally important plants, including potato, garlic and are one of the common pathogens of tomato, causing root rot in the west part of Iran. Therefore, the objectives of this study were to isolate and identify disease-causing Fusarium species from infected tomatoes based on the morphological and molecular characteristics. Twenty-five isolates of Fusarium were obtained from infected root of tomato plants collected from the fields in different regions of western Iran. Based on morphological features, the strains were classified into four following Fusarium species: F. oxysporum, F. redolens, F. proliferatum and F. verticillioides. The phylogenetic trees based on tef1 and tub2 dataset clearly distinguished closely related species. All of the isolates were evaluated for their pathogenicity on healthy tomato seedlings in the greenhouse. This is the first report on molecular identification of Fusarium species isolated from tomato plants cultivated in Iran.

Evaluation of Streptomyces spp. against Fusarium oxysporum f. sp. ciceris for the management of chickpea wilt

Abstract: In this study, about 112 isolates of Streptomyces were isolated from chickpea rhizospheric soils. Among the isolated strains, five showed strong inhibitory effects against chickpea Fusarium wilt caused by Fusarium oxysporum f. sp. ciceris in vitro using plate assay and selected for further studies. The selected strains were identified as Streptomyces spp. based on morphological and biochemical characterization as well as 16S rDNA sequences analysis. Our results assigned them to strains related to genus of Streptomyces. In vitro, antagonistic effects of Streptomyces strains against the disease were evaluated through the dual-culture method, volatile and non-volatile metabolites, siderophore, protease and chitinase production. All bacterial strains inhibited mycelial growth of the pathogen ranging from 26 to 44.2% in dual culture assay. The non-volatile extract of five of the Streptomyces strains inhibited more than 50% growth of the pathogen, whereas volatile compounds were less effective on mycelial growth inhibition (20.2 to 33.4%). The ability of the biocontrol agents to produce siderophore and protease were varied, whereas, production of chitinase was detected for all strains. Results of the greenhouse assay indicated that all biocontrol agents reduced disease severity (ranging from 38.7 to 54.8%). Accordingly, strain KS62 showed higher control efficacy (54.8%). In addition, the biomass of chickpea plants (plant height and dry weight) significantly increased in plants treated with Streptomyces strains compared to non-bacterized control. The results of this study showed that it may be possible to manage chickpea Fusarium wilt disease effectively by using Streptomyces species, as biocontrol agents. Therefore, evaluating their efficiency under field conditions is needed.

Unconventional alternatives for control of tomato root rot caused by Rhizoctonia solani under greenhouse conditions

Abstract: This study was done to assess the antifungal effect of some biocontrol agents effective microorganisms (EMs1), Pseudomonas fluorescens, and Bacillus pumilus, titanium dioxide (TiO2) nanoparticles, black cumin and wheat germ oils as well as the recommended fungicide (flutolanil) against root rot of tomato. Moreover, gas chromatography-mass spectrometry (GC-MS) examination was completed to identify the bioactive compounds in plant oils (dark cumin and wheat germ). Also the impact of these medicines on some biochemical and growth parameters of tomato was examined. Flutolanil was the best treatment followed by dark cumin, TiO2, EMs1, Pseudomonas fluorescens, Bacillus pumilus and wheat germ oil, individually in both test seasons. The outcomes demonstrated a marked increase in each biochemical character (chlorophyll substance, peroxidase and polyphenoloxidase) and plant development (height and fresh and dry weight) under all the tried treatments in comparison to the controls.

Changes of antioxidant enzymes of mung bean [Vigna radiata (L.) R. Wilczek] in response to host and non-host bacterial pathogens.

Abstract: The natural resistance against the majority of potential pathogens that exist in most plant species is known as non-host resistance. Several reports suggest the role of antioxidant enzymes in non-host resistance. We assayed the expression or activity of four scavenging enzymes during non-host pathogen-plant interaction (Xanthomonas hortorum pv. pelargonii/mung bean) and host pathogen-plant interaction (Xanthomonas axonopodis pv. phaseoli/mung bean). The expression of superoxide dismutase (SOD) and ascorbate peroxidase (APX) and the enzyme activity of catalase (CAT) and peroxidase (POX) were investigated. The activities of CAT and POX were higher during non-host pathogen invasion vs. host pathogen attack. The expression of SOD and APX were also differ- ent between compatible and incompatible interactions. The expression of SOD and APX were higher in the incompatible compared to the compatible interaction. Additionally, induction of the antioxidant enzymes in response to non-host pathogen was earlier than induction in response to host pathogen. Such information is important for plant breeders, and useful when looking for alternative control strategies as well.

Fenton reagent and titanium dioxide nanoparticles as antifungal agents to control leaf spot of sugar beet under field conditions

Abstract: In this study, foliar sprays of Fenton solutions (Fenton reaction, Fenton-like reaction and Fenton complex), titanium dioxide (TiO2) and the recommended fungicide (chlorothalonil) were estimated in the control of sugar beet leaf spot caused by Cercospora beticola under field conditions in two growing seasons. In addition, the impacts of these treatments on some crop characters (leaf dry weight, root fresh weight, soluble solid content, sucrose content and purity of sugar) were examined. Biochemical and histological changes in the livers and kidneys of treated rats compared to an untreated control were utilized to assess the toxicity of the examined curative agents. Overall, chlorothalonil and Fenton complex were the most effective treatments for disease suppression in both tested seasons followed by Fenton-like reagent, Fenton’s reagent and TiO2, respectively. Growth and yield characters of treated sugar beet significantly increased in comparison to an untreated control. There were mild or no (biochemical and histological) changes in the livers and kidneys of treated rats compared to the control. Fenton solutions and TiO2 may offer a new alternative for leaf spot control in sugar beet.

Chemical constituents and ovicidal effects of mahlab, Prunus mahaleb L. kernels oil on cotton leafworm, Spodoptera littoralis (Boisd.) eggs

Abstract: The carried out investigations evaluated ovicidal activity of mahlab, Prunus mahaleb L. kernel oil against cotton leafworm, Spodoptera littoralis (Boisd.). The chemical constituents of the fixed oil of mahlab were analyzed using gas-liquid chromatography (GLC). Timnodonic (33.07%), oleic (28.71%) and linoleic (24.35%) were the basic fatty acids, while the major hydrocarbon and sterol were found to be heneicosane (62.57%) and β-sitosterol (10.57%). The LC₅₀ values for the one-day-old egg masses were found to be more susceptible than 3-day-old ones. Moreover, the leaf dip technique occurred to be more efficient than spraying technique. The results also showed abnormalities in the external morphology of egg shell, chorion surface, shell imprints and aeropyles of S. littoralis eggs treated with mahlab and KZ oils as compared to a control by using scanning electron microscope. Generally, the tested oils significantly reduced the activities of transaminase enzymes (AST and ALT), acid and alkaline phosphatases and total soluble protein except mahlab oil on acid phosphatase as compared to a control. Additionally, the oils of both mahlab and KZ oil affected some biological aspects such as incubation period, larval duration, larval mortality and pupal weight comparing to a control.

Identification and diversity of Fusarium species isolated from tomato fruits

Abstract: Fruit rot of tomato is a serious disease caused by Fusarium species. Sampling was conducted throughout Selangor, Malaysia and fungal species identification was conducted based on morphological and gene encoding translation elongation factor 1-α (tef1-α) sequence analysis. Five species of Fusarium were discovered namely F. oxysporum (including F. oxysporum f. sp. lycopersici), F. solani, F. equiseti, F. proliferatum and F. verticillioides. Our results provide additional information regarding the diversity of Fusarium species associated with fruit rot disease of tomato.

Detoxifying enzyme studies on cotton leafhopper, Amrasca biguttula biguttula (Ishida), resistance to neonicotinoid insecticides in field populations in Karnataka, India

Abstract: The cotton leafhopper (Amrasca biguttula biguttula Ishida) is considered to be an alarming insect pest causing both quantitative and qualitative loss in cotton. In situ bioassay studies were done and the role of detoxifying enzymes in conferring resistance to neonicotinoid groups of insecticides in low (MUD), medium (DVG), high (HVR) and very high (GLB) pesticide usage areas of Karnataka were determined. Bioassay studies showed that imidacloprid, thiamethoxam, acetamiprid, thiacloprid and clothianidin registered varying levels of resistance for all the locations studied. The resistance ratio was high in imidacloprid (3.35, 8.57, 9.15 and 12.27 fold respectively) and the lowest in dinoferuran (1.86, 5.13, 6.71 and 9.88 fold respectively). Furthermore, the enzyme activity ratio (glutathione-S-transferase) was relatively greater, and corresponded to the higher LC50 values of neonicotinoids for very high, high, medium and low pesticide usage areas. Our study suggested that the higher activity of the detoxifying enzyme in the resistance population of cotton leafhopper apparently has a significant role in endowing resistance to neonicotinoid groups of insecticides. However, this study recommends using neonicotinoids in cotton growing areas with caution.

Original Article. Topical treatment of LdMNPV-infected gypsy moth caterpillars with 18 nucleotides long antisense fragment from LdMNPV IAP3 gene triggers higher levels of apoptosis in infected cells and mortality of the pest

Abstract: Th e high effi ciency of baculovirus infection is partially explained by the ability of the virus to suppress host defense machinery connected with the apoptosis pathway. Members of the baculovirus gene family, inhibitors of apoptosis (vIAPs), have been shown to inhibit apoptosis in baculovirus-infected cells. Here we showed that treatment of the LdMNPV-infected 1st instar gypsy moth (Lymantria dispar) caterpillars with sense (oligoBIR) and antisense (oligoRING) DNA oligonucleotides from the LdMNPV IAP3 gene induced elevated mortality of the insects. Apoptotic DNA ladder assay showed that the leading role in this phenomenon is played by the antisense oligoRING fragment of the vIAP3 gene. Th ese results imply that the application of both antisense DNA oligonucleotides from vIAP genes and baculovirus preparations (one following the other) may be a potential method for plant protection against insect pests.

Isolation and evaluation of biocontrol agents in controlling anthracnose disease of mango in Thailand

Abstract: The agricultural based economy is a core business in Thailand and food export is one of the main sources of income for the Thai population. However, pesticides are overused and misused. As a result there is an urgent need to reduce the use of synthetic chemicals. Biological control offers an alternative to the use of pesticides. Mango (Mangifera indica L.) is widely planted in Thailand and is one of the major cash crops for international export. However, mango suffers from various diseases especially anthracnose, a fungal disease caused by Colletotrichum gloeosporioides. One hundred and twelve isolates of epiphytic microbes were isolated from healthy leaves and fruits of mangoes; this included 93 and 19 isolates of epiphytic bacteria and yeasts, respectively. They were screened for bioactivity against a pathogenic strain of C. gloeosporioides isolated from diseased mangoes using a dual culture technique. Out of 112 isolates, eight isolates exhibited at least 60% inhibition. These isolates were further screened for their inhibition on mango using fruit inoculation. Two isolates reduced the lesion sizes caused by C. gloeosporioides compared to control treatment. These two isolates, based on phenotypical and biochemical tests, were identified as Bacillus sp. MB61 and Bacillus sp. LB72.

Inhibitory effects of antagonistic bacteria inhabiting the rhizosphere of the sugarbeet plants, on Cercospora beticola Sacc., the causal agent of Cercospora leaf spot disease on sugarbeet

Abstract: In the present study, the antagonistic capability of bacterial agents inhabiting the rhizosphere of sugarbeet plants were evaluated against Cercospora beticola Sacc. under laboratory and greenhouse conditions. After preliminary screening using the dual culture method, 14 strains with higher antagonistic capability were selected for further inhibitory assays against C. beticola. Bacterial strains were identified based on the sequence data of the small subunit-rDNA (SSU-rDNA) gene. Based on the SSU sequence data, the identity of bacterial strains were determined as Bacillus (10 strains: RB1, RB2, RB3, RB4, RB5, RB6, RB7, RB8, RB9, RB10), Paenibacillus (two strains: RP1, RP2), Enterobacter (one strain: RE), and Pseudomonas (one strain: RPs). The results obtained in this study showed that in all of the assays (dual culture, volatile and non-volatile metabolites) bacterial antagonists significantly inhibited the growth of C. beticola compared to the control. Bacillus (RB2) showed the highest inhibition rate on C. beticola in all of the assays. Based on the results of the laboratory assays, three bacterial strains RB2 (Bacillus), RPs (Pseudomonas), and RE (Paenibacillus) were selected for greenhouse assays. The experiment was designed based on a completely randomised design (CRD) with the application of antagonists prior to, simultaneously, and after inoculation with C. beticola on sugarbeet leaves. The reduction in disease severity was evaluated seven days after inoculation. The results of greenhouse assays were consistent with the results of laboratory studies. The obtained results showed that bacterial antagonists significantly reduced the disease severity when compared to the control.

Original Article. Geographic distribution of Fusarium culmorum chemotypes associated with wheat crown rot in Iraq

Abstract: Fusarium crown rot (FCR) is an important disease of wheat and other grains that has had a signifi cant impact on cereal crop production worldwide. Fusarium species associated with FCR can also produce powerful trichothecenes mycotoxins that pose a considerable health risk to humans and animals that consume infected grains. In this study we examined Fusarium species of wheat from diff erent regions of Iraq that showed FCR symptoms. Twenty-nine isolates were collected overall, and the marker gene translation elongation factor 1 alpha (TEF-1α) was sequenced in order to determine their taxonomic identities. All isolates were determined to be F. culmorum, and primers targeting tri-cluster genes were used in order to further characterize isolates into specifi c trichothecene chemotype strains. Five of the 29 isolates were determined to be the nivalenol (NIV) chemotype, while the rest of the isolates recovered were the deoxynivalenol (DON) chemotype. All DON-type isolates produced 3Ac-DON, while the 15Ac-DON-type was not detected. Th e majority of the NIV-type isolates originated from wheat growing regions in the mid-latitudes of Iraq, while the DON-type isolates were recovered from areas distributed broadly across the country. To the best of our knowledge, this study is the fi rst to report on the distribution of specifi c F. culmorum chemotypes from FCR diseased wheat in Iraq.

PCR-RFLP method to distinguish Frankliniella occidentalis, Frankliniella intonsa, Frankliniella pallida and Frankliniella tenuicornis

Abstract: Thrips from the genus Frankliniella (Thysanoptera, Thripidae) are phytophagous on crops and wild plants. Some of them cause slight economic damage, however, others including F. occidentalis and F. intonsa are responsible for considerable losses in crop production. Moreover, they constitute a double threat for host plants by not only feeding on them but also vectoring viruses, some of which are on the quarantined list of the European Plant Protection Organization. The rapid detection and differentiation between more and less harmful Frankliniella species is, therefore, important in order to combat the pests at the time of their appearance. In this study, we have undertaken to develop a method of detecting F. occidentalis, F. intonsa, F. pallida, and F. tenuicornis. The protocol is based on PCR amplification of ITS1 rDNA fragments of these insects using universal primers pair giving products of slightly distinct length for studied insects. Restriction enzymes digestion which is easy to interpret, allows for visible differentiation of all these Frankliniella species. The method was shown to be species-specific and sensitive. Even single specimens in either the larvae or adult stage could be distinguished.

Co-occurrence of pathogenic and non-pathogenic Fusarium decemcellulare and Lasiodiplodia theobromae isolates in cushion galls disease of cacao (Theobroma cacao L.)

Abstract: Flowery cushion gall of cacao is a disease complex with six types. Fusarium decemcellulare have been isolated from both flowery and green point galls and recognized as the etiological agent of the disease. In the present work we: i) identified by ITS-rDNA sequencing and/or taxonomy the cultivable fungal species or Operative Taxonomic Units (OTUs) associated with the five symptoms of cushion galls in cacao from Venezuela, and ii) determined the gall inducing capacity on cacao peeled seeds after 45 days of inoculation with suspensions of mycelia/spores from distinct isolate types. The whole isolate collection rendered an abundance of 113 isolates with a richness of 39 OTUs (27) and eight identified at the species or genera levels, respectively, and in unidentified fungi. The dominant recovered species (≈36%) were F. decemcellulare and Lasiodiplodia theobromae. Some isolates of F. decemcellulare, L. theobromae, F. equiseti, Fusarium spp., F. solani, F. incarnatum, Rhizocthonia solani and Penicillium sp. were pathogenic. Some other isolates of the first six mentioned taxa behave as non-pathogenic. Furthermore, pathogenic and non-pathogenic isolates can also co-occur within a single plant and gall type. Moreover, 2–5 species within a single gall symptom in a single tree were identified (not necessarily at the same point in the tree), indicating a broad diversity of co-occurring taxa.

Effectiveness of the chemical stabilizers of Talaromyces flavus in biological control of tomato and greenhouse cucumber vascular wilt disease

Abstract: Fungal antagonist, Talaromyces flavus, is one of the most important biological agents of soil-borne fungal diseases including Verticillium and Fusarium wilt. In this study, to increase the effectiveness of T. flavus isolates obtained from greenhouse cucumbers and field grown tomatoes five chemical stabilizers were evaluated. Based on the results of previous studies, the most effective substrate for the growth, sporulation and stability of T. flavus isolates related to the above-mentioned plants was a mix of rice bran and peatmoss. Different chemical stabilizers were mixed with the above-mentioned substrate containing spore suspensions of various T. flavus isolates. For each plant, a completely randomized experiment was conducted under greenhouse conditions with seven treatments and three replications. The results of this study indicated that treatments containing sodium nitrate and D-cycloserine were more effective than those containing other stabilizers. The overall results of this study suggest that the use of some chemical stabilizers may enhance the biocontrol potential of fungal antagonists in controlling different plant diseases including Verticillium and Fusarium wilt.

Occurrence and distribution of nematodes in rice fields in Guilan province, Iran and the first record of Mylonchulus polonicus (Stefanski, 1915) Cobb, 1917 (Nematoda: Mononchina)

Abstract: The distribution of nematodes was studied in rice fields in Guilan province, Iran, from 2014 to 2016. Nematode biodiversity of 250 soil and root samples was examined. Thirty nematode species were identified morphologically, including plant parasites, microbivores and mycetophagous and predator species. Molecular techniques were also used for further identification of three plant parasitic species. Indicators of population were also estimated. Spiral nematodes (Helicotylenchus crenacauda Sher, 1966 and H. digitiformis Ivanova, 1967) and stunt nematode (Tylenchorhynchus agri) were the predominant parasitic species identified. Among other species, three mononchid species were identified namely Mononchus aquaticus, Mylonchulus sigmaturus and M. polonicus. The species M. polonicus was found and reported in Iran for the first time. The two plant parasitic species T. agri and Xiphinema index were reported in association with rice in Iran for the first time. To evaluate the distribution and incidence of Aphelenchoides besseyi (rice white-tip nematode) in different regions of Guilan province, a total of 255 fresh seed samples were collected/inspected, of which, about 40% of them were infested with A. besseyi. Of the 16 studied counties, the highest percentage of infected seeds came from fields around the city of Astara (69.2%) and the second highest infection was observed near the city of Anzali (60%).

Selective toxicity of diafenthiuron to non-target organisms: honey bees, coccinellids, chelonus, earthworms, silkworms and fish

Abstract: Diafenthiuron, an insecticide widely used in the management of pests of cardamom and cotton, was assessed for its toxicity- effect on beneficials commonly found in these ecosystems. Diafenthiuron was found to be toxic to honey bees, the prime pollinators of crop plants. Diafenthiuron at the highest tested dose caused 40% mortality to the coccinelid grubs at 48 h after treatment so, diafenthi- uron was found to be slightly harmful. Monocrotophos, on the other hand has been found to be a highly toxic pesticide. Diafenthiuron is moderately harmful to the adults of Chelonus blackburni L. The testing was done using the insecticide diafenthiuron. An insecticide- coated vial (scintillation) bioassay was performed. It was found that there was 86.67% mortality in 48 h, at the recommended dose. Diafenthiuron is highly toxic to the silkworm, killing more than 80% of the caterpillars in 24 h, at all the doses tested. Diafenthiuron, even in the highest dose tested, is non-toxic to the earthworm, Perionyx excavatus, which was found to have a 3.33% mortality. As far as fish are concerned, the common carp, Cyprinus carpio L., is found to be highly susceptible to diafenthiuron and even doses 10 times lower than the field dose can kill the fish within 6 h.

Rapid evolutionary dynamics of the Pepino mosaic virus – status and future perspectives

Abstract: Pepino mosaic virus (PepMV) has emerged as an important pathogen of greenhouse tomato crops and is currently distributed worldwide. Population genetic studies have revealed a shift in the dominant PepMV genotype from European (EU) to Chilean 2 (CH2) in North America and several European countries. New genetic variants are constantly being created by mutation and recombination events. Single nucleotide substitutions in different parts of the genome were found to affect on development of symptoms resulting in new pathotypes and accumulation of viral RNA. The variability of the PepMV population has a great impact on designing specific diagnostic tools and developing efficient and durable strategies of disease control. In this paper we review the current knowledge about the PepMV population, the evolutionary dynamics of this highly infective virus, methods for its detection and plant protection strategies.