Concentration Of Spore Suspension Research Articles

Isolation, identification, biological characteristics, and pathogenicity of an entomogenous fungus against the Egyptian mealybug, Icerya aegyptiaca (J.) (Hemiptera: Monophlebidae)

BackgroundIn this study, an entomogenous, fungus was isolated from the Egyptian mealybug, Icerya aegyptiaca (J.) (Hemiptera: Monophlebidae) on the parasol leaf tree, Macaranga tanarius, in China where evaluated as a biocontrol fungus to reduce the population of the target insect. The strain was identified as Aspergillus parasiticus by morphological and phylogenetic analysisand named ZHKUAP1. The biological characteristics, pathogenicity, and field control effect of the strain were determined.ResultsThe most suitable medium for the mycelial growth of strain ZHKUAP1 was PPDA medium, with an optimum temperature of 30 °C and pH 7, in addition to glucose and peptone as carbon and nitrogen sources. The optimum sporulation conditions were the PPDA medium at 30 °C and pH 6, using the soluble starch and beef extract as carbon and nitrogen sources. The mycelial growth and spore production of strain ZHKUAP1 were stopped at 70 °C and above, indicating that it was not resistant to high temperatures. High concentrations of spore suspension, against young insect age, resulted high corrected mortality, as well as decreased the median lethal time. When the spore concentration was 1 × 108 cfu/ml, the corrected mortality of the second nymph was 88.33%, and the LT50 was 0.66 day. After 10 days of inoculation, the LC50 of the second instar nymph was the smallest, reaching 4.07 × 104 cfu/ml. On the 10th day of the field experiment, the corrected mortality was 76.45%, indicating that the A. parasiticus strain ZHKUAP1 had strong pathogenicity on I. aegyptiaca population.ConclusionsThe indoor toxicity of the strain to I. aegyptiaca was determined, and the field control effect of the pathogen was explored on this basis. The results have important application prospects in the biological control of I. aegyptiaca.

Identification of an Entomopathogenic Fungus, Pseudozyma flocculosa (Traquair, Shaw & Jarvis), and Its Efficacy against Tetranychus urticae Koch

The two-spotted spider mite, Tetranychus urticae Koch, is one of the most important agricultural pests worldwide, with chemical application being the primary control method. However, frequent heavy use or misuse of insecticides has accelerated the development of varying degrees of resistance in T. urticae. This makes the chemical control of this mite more challenging. Biocontrol methods have attracted much attention due to their safety and environment-friendly impact. Based on previous observations that the population of T. urticae was infected by unknown pathogenic fungi, we isolated, identified, and evaluated the pathogenicity of the fungi from infected mites. Through available morphological and molecular identification, the fungus was identified as Pseudozyma flocculosa. The virulence activity of the strain was evaluated at different concentrations of spore suspension (106–109 conidia/mL) using a spraying method. The strain showed pathogenic activity against the T. urticae in adult females that varied with different concentrations and temperatures. Meanwhile, the P. flocculosa also had a significant toxic effect on the developmental stages of T. urticae. In the laboratory bioassay, the mortality rate of the tested mites reached 100% at 9 d after P. flocculosa treatment. Additionally, a wettable powder processed with P. flocculosa conidia was applied on the T. urticae in the greenhouse and the control efficacy reached up to 90% at 7 d after treatment. The results showed a high insecticidal activity of P. flocculosa against T. urticae, indicating that this fungus possesses great potential for use as a bio-insecticidal agent.

Laboratory Evaluation of the Efficiency of The Entomopathogenic Fungus Beauvaria bassiana as a Biological Control Factor Against the Cucurbit Fly, Dacus ciliates

Al-Shweily, B.M., J.B. El-Zidawi and M.J. Hinnawi. 2024. Laboratory Evaluation of the Efficiency of The Entomopathogenic Fungus Beauvaria bassiana as a Biological Control Factor Against the Cucurbit Fly, Dacus ciliates. Arab Journal of Plant Protection, 42(3): 335-339. https://doi.org/10.22268/AJPP-001260 The cucurbit fly, Dacus ciliatus is a major pest which attack a wide range of crops and causes significant losses in agricultural production. Due to the high toxicity of chemical pesticides on human health and the environment, scientists focused on developing alternative safe methods to control this insect, including the use of biocontrol agents. Beauveria bassiana is one of the common fungi used as a bio-control agent. This entomopathogenic fungus was cultivated on Petri dishes containing PDA. The spore suspension of this fungus was prepared using sterilized distilled water, and three concentrations were used: 20×106 , 10×106 and 5×106 spores/ml. The effectiveness of these three concentrations was tested on larvae and pupae of the studied insect. The larval mortality rate ranged from 73.33% at the highest concentration to 33.33% at the lowest concentration used. Pupal mortality reached 66.66% at the highest concentration and 16.66% at the lowest concentration of spore suspension. Mortality rate was directly proportional to the spore suspension concentration of the entomopathogenic fungus. Keywords: Cucurbit fly, agricultural pest, biological control, Dacus ciliates, Beauveria bassiana, entomopathogenic fungi.

First Report of Root rot Caused by Mucor circinelloides on Fructus forsythiae in Hubei，China.

Fructus forsythiae is a typical traditional Chinese medicinal herb with antibacterial and anti-inflammatory effects. Surveys for root rot of F. forsythiae were conducted from 2021 to 2022 in China's major planting areas (Daweiyuan Village, Sanguandong Forest Area, Yunxi County, Shiyan City, Hubei Province, 32°52'52"N, 110°19'29"E). The disease has occurred in several plantations. A total of 200 F. forsythiae were investigated, among which 112 were diseased, the incidence rate was more than 50%, and all the plants in the plantation were over 3 years old. The roots of diseased plants were fully covered by white mycelia. When the disease was severe, leaves curled and fell, roots withered, and some eventually died. A total of 22 isolates were isolated from the 18 infected tissues ofF. forsythiae and purified by single spore cultures on PDA medium. The 22 isolates similared in morphology to isolate Lianmao (The name is one of the five sequenced samples in the lab) were selected to be representative of the group. The results showed that these samples belonged to the same pathogen. The isolates were characterized by yellowish colonies composed of tall and short sporangiophores 6 to 11 μm in width, terminal and globose sporangia, ellipsoidal sporangiospores with dimensions of 5 to 8 μm in length and 4 to 5 μm in width, and obovoid columellae. It was identified as Mucor circinelloides, based on morphological characteristics (Schipper 1976). The ITS and LSU sequences of the fungus were amplified, and sequenced with the primers ITS1/ITS4 and LROR/LR5 (White et al. 1990; Rehner et al. 1994). Sequences from isolate Lianmao were deposited in GenBank (accession nos. OQ359158 for ITS, OQ359157 forLSU). Analysis using the BLAST algorithm of the two amplified sequences showed 99.69 to 100% similarity with the sequences (KY933391 and MH868051) ofM. circinelloides.The isolated M. circinelloides was prepared into 150ml spore suspension (The method was to filter the PDB after 10 days of culture using gauze to get spore suspension. Then the concentration of spore suspension was diluted to 1.0×106 spores/ml using sterile water). The spore suspension was subsequently inoculated into healthy potted F. forsythiae plants. Uninoculated potted F. forsythiae plants served as controls. All the potted F. forsythiae plants were incubated at 25°C under 12h light and 12h dark conditions. The symptoms of the infected plants were similar to those observed in the field; The control plants were symptomless. The pathogen reisolated from symptomatic roots and morphologically identified as M. circinelloides. M. circinelloides has been reported as a pathogen of Morinda citrifolia, Aconitum carmichaelii and so on (Cui et al. 2021; Nishijima et al. 2011), but it has never been reported on F. forsythiae before. This is the first report of root rot caused by M.circinelloides on F. forsythiae. This pathogen may present a threat to the production of F. forsythiae in China.

Effect of Temperature on Efficacy of the Entomopathogenic Fungi Beauveria bassiana and Metarhizum anisopliae Against the Sunn Pest, Eurygaster integriceps Puton

El-Mukhlef, A.A., Sh.A. Kharouf and A. Al-Khalaf. 2023. Effect of Temperature on Efficacy of the Entomopathogenic Fungi Beauveria bassiana and Metarhizum anisopliae Against the Sunn Pest, Eurygaster integriceps Puton. Arab Journal of Plant Protection, 41(2): 134-139. https://doi.org/10.22268/AJPP-41.2.134139 An experiment was conducted in the plant protection laboratory of the Directorate of Agriculture and Agrarian Reform in Raqqa Province during 2013, to assess the effect of temperature and four spores suspension concentrations (1.5×102 , 103 , 104 and 105 spores/insect) on the efficacy of Beauveria bassiana and Metarhizum anisopliae against the Sunn pest (Eurygaster inegriceps Puton). Insect adults dorsal side were inoculated with 1.5×103 spores/insect of B. bassiana and caused insects mortality at a temperature range of 22-31°C, with optimum effect at 25°C, with a LT50 of 5.3 days after inoculation. In contrast, M. anisopliae had a wider temperature range up to 37°C, with optimal effect at 28- 31°C with LT50 of 5 days. No significant differences were observed between the fungal concentrations of 1.5×103 and 1.5×105 . Results obtained for using the four fungal spore suspension concentrations (1.5×102 , 1.5×103 , 1.5×104 , 1.5×105 spores/insect) under optimum conditions for each fungus indicated that the LT50 was close among concentrations, whereas, there was significant difference between the fungal two concentrations 1.5×102 and 1.5×104 , and B. bassiana was most effective at 1.5×104 spores/insect, in contrast to M. anisopliae which was most effective at 1.5×102 spores/insect. Keywords: Beauveria bassiana, Metarhizum anisopliae, Eurygaster inegriceps, Sunn Pest, biological control.

Attenuated Isolate Gibellulopsis nigrescens Vn-1 Enhances Resistance against Verticillium dahliae in Potato

Potatoes are among the four most important staple crops worldwide. Verticillium wilt in potatoes caused by Verticillium dahliae is a devastating disease that is difficult to control. To identify potential avenues for disease control, the pathogenicity of 72 V. dahliae isolates was tested here. We also tested the resistance to the most virulent isolate (Vd-36) induced by the attenuated isolate Gibellulopsis nigrescens Vn-1 in potatoes. Induction of Verticillium wilt resistance in potatoes was strongest when using attenuated isolate Vn-1 to inoculate potatoes with a spore suspension concentration of 1 × 106 conidia mL−1, followed by infection with isolate Vd-36 at 5 d intervals. After incubation of potatoes with the attenuated isolate Vn-1 followed by isolate Vd-36, reactive oxygen species (ROS) and hydrogen peroxide (H2O2) were produced and accumulated in potato leaves 12 h post-inoculation. The changes in respective defense enzymes, except phenylalanine ammonia-lyase, were consistent with the changes in ROS and H2O2 levels. Furthermore, the content of salicylic acid (SA) in inoculated plants was higher than that in the control, and biosynthesis-related genes StNPR1, StPR1b, StPR2, StPR5 were activated. However, there was no significant difference in the jasmonic acid and ethylene (JA/ET) content between the treatment and control groups. These results demonstrated that the attenuated isolate Vn-1 enhanced resistance to Verticillium wilt by inducing the SA signalling pathway and weakly activating the JA/ET signalling pathways in potatoes.

First Report of Rice Brown Spot Caused by Exserohilum rostratum in Mali.

Rice brown spot is an emerging disease of concern in many rice-growing countries. Different fungal species of the genera Bipolaris and Exserohilum were reported as the causal agents of this disease. These fungal pathogens cause similar necrotic lesions on leaves and infect grains with a significant effect on seed germination. In 2018, samples of rice seed and leaves with typical brown spot symptoms were collected from irrigated (Manikoura and Niono) and lowlands (M'pegnesso and Loulouni) rice fields in Mali and incubated for 5 to 7 days on wet filter paper at 25°C with 12 h photoperiod. Conidia observed under microscope were straight or slightly curved and light-brown or dark. They were also rostrate or obclavate and measured 31.4 to 275.6 x 7.3 to 18 µm (n=40). These morphological characteristics are identical to those of Exserohilum rostratum (Hernández-Restrepo et al. 2018). DNA from eight single-spored isolates was extracted by a CTAB-based protocol (Doyle and Doyle, 1987). Internal transcribed spacer (ITS) rDNA region, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and translation elongation factor 1 alpha (TEF1-α) genes were amplified by PCR with the primers ITS5/ITS4 (White et al. 1990), GPD1/GPD2 (Berbee et al. 1999) and EF1 983/EF1 2218 (Rehner et al. 2005), respectively. The amplicons were sequenced and deposited in NCBI GenBank. Sequence similarity between Malian strain was 100% for ITS and GAPDH, and 99.8-100% for TEF1. Sequence similarity between Malian strains and reference E. rostratum sequences BRIP 11417 (GenBank acc. no. LT837836, LT882553 and LT896656) and CBS 128061 (GenBank acc. no. KT265240, LT715900 and LT896658) were 99.6-100%. The maximum-likelihood phylogenetic tree generated with ITS, GAPDH and TEF1-α concatenated sequences, using MEGA-X 10.1.7 grouped all eight strains from Mali in the E. rostratum clade with a bootstrap value of 100%. For pathogenicity test, four strains from leaves and seed were grown on rabbit food agar (50 g/liter steeped filtrate of rabbit food pellets, Kaytee Products, Inc. Chilton, WI, USA, and 15 g agar) for 14 days at 25°C with a 12 h photoperiod (Hau and Rush 1980). Spores were collected and the concentration of spore suspension adjusted to 1.5 x 105 conidia/ml with 0.5% gelatin. The rice varieties ADNY 11, ARICA 9 and Shwetasoké were grown in pots with peat soil and NPK 13-5-18 at 3.5 g/liter of soil for 21 days. Four pots of each variety (5 seedlings/pot) were placed in a tray (60 plants per tray) and the leaves were sprayed with 30 ml of the conidial suspension or water at 0.5% gelatin (negative control). Plants were kept at maximum humidity (100%) at 21°C for one night and then transferred to a phytotron at 27°C. Seven days after inoculation, circular or oval foliar lesions of less than 5 mm long, either brown or dark, sometimes whitish in their centers were observed . These lesions were identical to those observed in the field. E. rostratum was reisolated from these lesions. E. rostratum affects a wide range of plant species, particularly grasses and has been observed on rice in many countries (Cardona and Gonzàlez 2007; Majeed et al. 2016; Silva et al. 2016; Toher et al. 2016). However, to our knowledge, this is the first report of E. rostratum causing brown spot in rice in Mali.

Inoculation conditions improved the pectinase productivity in Aspergillus niger LB-02-SF solid-state cultivation

In this work, the pectinase production by Aspergillus niger LB-02-SF was evaluated in relation to the inoculation conditions of solid-state cultivations carried out in Becher flasks and in rotating drum bioreactor. From the inoculation by spore suspension in the concentration of 7 × 107 spore/100 g of wet medium (gwm), which is standard inoculum condition, were evaluated: different concentrations of spore suspension (from 7 × 104 to 7 × 108 spore/100 gwm), solid vegetative inoculum using 50 and 100 gwm of fermented solid medium (obtained from 48 h of A. niger cultivation in Becher flasks, in a humidified atmosphere, 30 °C) and liquid vegetative inoculum in the proportions of 5 and 10% (v/w) (obtained from 18 h of A. niger cultivation at 300 rpm, 28 °C). In comparison to the standard condition, with the use of the lowest spore concentration (7 × 104 spore/100 gwm), 100 gwm of solid vegetative inoculum and 10% (v/w) of liquid vegetative inoculum, higher pectinases productivities were observed, around 48, 42 and 85%, respectively. The results obtained indicate that the three inoculation strategies defined are alternatives to increase the enzyme productivity and to facilitate the inoculum preparation stage aimed at applying this process on an industrial scale.

Effects of two Streptomyces strains on growth and physiological properties of Gerbera jamesonii

We applied different concentrations of spore suspension of Streptomyces exfoliatus FT05W and S. cyaneus ZEA17I to inoculate Gerbera jamesonii to screen for the most effective application concentration. We aimed to explore the effects of two Streptomyces strains on growth and physiological properties of G. jamesonii, and to provide scientific evidence for the application of Streptomyces in G. jamesonii production. The results showed that different concentrations of S. exfoliatus FT05W and S. cyaneus ZEA17I spore suspension could effectively promote the growth of G. jamesonii. In general, S. exfoliatus FT05W performed better than S. cyaneus ZEA17I. S. exfoliatus FT05W (1×109 CFU·mL-1) could significantly increase the height and crown width of G. jamesonii respectively by 30.2% and 41.5%. Meanwhile, it increased the length and width of the stem. When treated by S. exfoliatus FT05W (1×109 CFU·mL-1), the content of chlorophyll in G. jamesonii was significantly increased by 65.2%, root activity was significantly increased by 103.3%, and the superoxide dismutase activity was increased by 84.4%. The malondialdehyde content in G. jamesonii was maintained at a low level when treated with the two Streptomyces strains. In summary, S. exfoliatus FT05W and S. cyaneus ZEA17I could effectively promote the growth and physiological properties of G. jamesonii, which could further contribute to its resistance to stress. Therefore, S. exfoliatus FT05W had the potential as a bio-fertilizer for G. jamesonii to solve cultivation obstacles.

Fusarium pallidoroseum: A potential entomopathogenic agent for the biological management of Aphis gossypii

With rising need of switching over to sustainable agricultural practices, utilization of entomopathogenic fungi (EPF) as biocontrol agents, provides better substitute against chemical pesticides- having several side-effects. Therefore, an attempt have been made to explore the potential EPF fungi that could be incorporated into IPM practices for control of Helicoverpa armigera Hubner and Aphis gossypii Glover. Regarding this, an entomopathogenic fungus, Fusarium pallidoroseum (Cooke) Sacc, was isolated from natural population of H. armigera infesting chickpea (Cicer arietinum L.) and explored efficacy under in-vitro & field conditions. The findings of present investigation shows efficacy of F. pallidoroseum as potential biocontrol agent against okra aphid (A. gossypii), as it inflicted initial mortality of 43.33% nymphs on 2nd day and lead to complete annihilation (93.33%) of nymph population on 8th day of spore suspension application at 1x1010 spores/mL concentration. The observations against adult okra aphid clearly demonstrated that spraying of 1 x 1010 spores/mL of F. pallidoroseum resulted 66.67% mortality after 8th days of spraying. Increased mortality was recorded with increase in spore suspension concentrations. The LC50 & LC90 value for F. pallidoroseum against nymphs of A. gossypii was recorded 3.79 x 105 and 2.74 x 108, respectively. The findings were used to develop formulations (1 × 104 to 1 × 1010 spore suspension/mL conc), and tested at field-level. The results showed that formulation at 1 x 1010 spores/mL conc was most effective against A. gossypii, recorded 93.33% mortality of nymphs & 66.67% mortality of adults; could be used under IPM practices.

Biocontrol and growth-promoting effect of Trichoderma asperellum TaspHu1 isolate from Juglans mandshurica rhizosphere soil

To better apply the biocontrol agent Trichoderma spp. in Northeast China, collecting and screening more suitable native Trichoderma strains is necessary. In the present study, 10 isolates were obtained from Juglans mandshurica rhizosphere soils in Heilongjiang Province, and were identified as T. asperellum (four isolates), T. harzianum (four), T. hamatum (one), T. atroviride (one). The fastest-growing isolate per species on potato dextrose agar medium were further evaluated in stress tolerance tests (salt, alkali, nutritional stress, and low temperature) and confrontation assays (eight pathogens), which showed that T. asperellum TaspHu1 possessed the best adaptation and biological control ability. Then, Solanum lycopersicum (tomato) seeds were sown and treated with a series of concentrations of TaspHu1 spore suspension, as was unsown soil. Tomato seedlings treated by TaspHu1 had a significantly greater height, stem diameter, soluble protein content and soluble sugar content. Furthermore, their nitrate reductase activity and catalase activity were significantly increased, and these promoting effects depended on the concentration of the spore suspension. Meanwhile, a decrease in chlorophyll content was observed in the tomato seedlings treated with TaspHu1. In addition, strain TaspHu1 enhanced the tomato seedlings’ absorption of available nitrogen, but did not influence the soil available nitrogen content. Furthermore, the resistance of tomato seedlings against Alternaria alternata was enhanced by TaspHu1 (smaller, fewer leaf spots), the seedlings’ hormone signal transduction genes JAR1, MYC2, NPR1, PR1, and GH3.2 were highly expressed. Thus, TaspHu1 is a promising biocontrol candidate for use in agriculture and forestry.

Effect of Beauveria bassiana Fungal Infection on Survival and Feeding Behavior of Pine-Tree Lappet Moth (Dendrolimus pini L.)

Research highlights: The pine-tree lappet moth, Dendrolimus pini, can cause serious needle defoliation on pines with outbreaks occurring over large geographical areas. Under laboratory conditions, the promising potential of the naturally occurring entomopathogenic fungus Beauveria bassiana was tested against D. pini larvae as a biological control method. Background and objectives: The aim of this study was to investigate the most effective concentration and treatment dose of B. bassiana conidial suspension and how it affected the survival and feeding behavior of the pest. Materials and methods: The first experiment applied the fungal suspension directly on the back of selected larvae, and in the second experiment, sporulating cadavers obtained in the first experiment were placed into Petri dishes with healthy individuals. Different doses per larvae [µL] and spore suspension concentration [spores/µL]) were used. The second experiment was designed to investigate the horizontal transmission of fungi by exposing individual caterpillars to a cadaver covered in B. bassiana mycelia. Mortality rates were analyzed by Chi-squared tests using absolute values for total mortality and B. bassiana- attributed mortality. The lethal time and feeding-disruption speed were analyzed with parametric and non-parametric tests with the aim to determine whether statistically significant differences were observed between treatments. Results: Analysis of lethal time revealed that the 20 µL dose and 7.9 × 104 concentration yielded highest mortality, but also the average dieback rate of 9.4 days was significantly faster compared to all other treatments. In order to see whether insects stopped feeding after infection with B. bassiana, larvae weight loss was examined. Results showed that effective treatments induced change in the feeding behavior of infected larvae. The feeding disruption caused by the 20 µL treatment occurred on average 5.5 days after exposure or 3.9 days before the final dieback of larvae.

Isolation, Molecular Identification and Host Range Evalution of Metarhizium anisopliae Egyptian Isolate

Metarhizium anisopliae is the most popular entomopathogenic fungi used successfully in microbial control. Isolation, identification, and estimation of M. anisopliae Egyptian isolate host range has been done in this study. Our isolate was identified molecularly by amplification of Internal transcribed spacer (ITS) region using polymerase chain reaction technique (PCR). The sequence of ITS was compared with other M. anisopliae isolates published in gene bank and our isolate showed 98% homology with most published M. anisopliae isolates so submitted in gene bank database as a new Egyptian isolate with accession no MT102079.The pathogenicity was evaluated by applying five spore suspension concentrations against four insect pests, Spodoptera littoralis (2nd and 4th instar larvae), Galleria mellonella (3rd and 5th instar larvae), Tetranychus urticae (nymph) and Rhynchophorus ferrugineus (3rd and 5th instar larvae), and our results revealed that M. anisopliae was highly effective against all tested insects. The highest concentration used (109) caused a high mortality rate after 10 days post-treatment reached 96% for T. urticae nymph which appears to be highly sensitive insect tested in this study followed by S, littoralis 2nd and 4th instar larvae which showed 96 and 90% mortality rate respectively. High pathogenicity of the tested isolate also noticed in G. mellonella in which the highest concentration used (109) induced 93 and 86% for 3rd and 5th instar larvae respectively, while the same instars of R. ferrugineus were moderately affected and 73 and 66% mortality rate was achieved by the same concentration after 10 days post-treatment.

Rapid Quantification of Fungicide Effectiveness on Inhibiting Wheat Stripe Rust Pathogen (Puccinia striiformis f. sp. tritici).

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important and devastating diseases of wheat; therefore, it is necessary to rapidly and accurately quantify fungicide effectiveness to monitor Pst sensitivity and manage the disease. In this study, a rapid method of quantifying the fungicide effectiveness with detached leaves was developed. The results showed that 0.5% water agar containing 75 μg/ml of 6-benzylaminopurine and filter paper worked the best for maintaining wheat leaves. The disease incidences of different concentrations of spore suspension were compared. When the spore concentrations were 5 and 10 mg/ml, the disease incidences had no significant differences at 12 and 15 days after inoculation (P < 0.05). Fungicide treatment tests revealed that there were no significant differences in the efficacies of triadimefon on rust suppression between detached leaves in the culture dishes and direct spray on seedlings. We also developed a Photoshop software method that can replace the current classification method and accurately measure the proportion of sporulation area on infected leaves. The sensitivity baseline of Pst to triadimefon was estimated as 0.1453 ± 0.0081 μg/ml, and all the values of EC50 were tested for normal distribution using the Shapiro-Wilk test (W = 0.204). The baseline can be used to test the sensitivity of different Pst isolates to triadimefon.

Biological effects of two Trichoderma harzianum isolates and mint oil on some postharvest fungal pathogens of sugar beet

Abstract Sugarbeet (Beta vulgaris L.) stored in outdoor piles prior to processing, during this storage period the crop is subject to multiple postharvest rots. Some fungal pathogens (A. niger, A. flavus, Fusarium sp. and Rhizopus sp.) were isolated and identified from rotted sugarbeet. Pathogenicity test of the isolated fungi had different pathogenicity rates using different concentrations of spore suspension at different incubation periods. A. flavus showed little number of lesions and negative effect on sugarbeet when tested for pathogenicity. Two antagonists of Trichoderma harzianum were tested for their effectiveness on sugarbeet rot fungal pathogens and compared with mint oil. In dual culture, size of clear zone is not correlated with the occurrence of pathogen overgrowth by antagonists. The antagonistic action of the two tested isolates of T. harzianum against the isolated phytopathogens indicated different degrees of antagonism. The non-volatile and gaseous volatile organic compounds by the antagonists inhibited growth of phytopathogens on agar plates, and no inhibition was investigated for Rhizopus sp. and Fusarium spp. by the tested volatile and non-volatile compounds, respectively. Moreover, mint oil showed inhibition degrees as well as volatile compounds of antagonists for all of the tested pathogens except against Rhizopus. Sugarbeet treated with mint oil as well as culture filtrate of T. harzianum suppressed pathogen spore germination on the surface of sugarbeet root resulted in decreasing rot incidence. This work provides strong evidence that T. harzianum and mint oil are competitors to control sugarbeet rot.

Endophytic Fungi with Potential as Biological Control Agents for Black Pod Rot Disease [Phytophthora palmivora (Butler) Butler

Production and cocoa plantation area in Indonesia decline every year, major causes is the outbreak of the cocoa black pod disease. Results showed that the antagonistic fungi found based on the DNA sequences are Lasiodiplodia euphorbicola, Diaporthe tectonae, Colletotrichum siamense, Aspergillus flavus, Candida parapsilogis, and Aspergillus sydowii. The results of the best inhibition shown by the endophytic fungus L. euphorbicola, thus passed field trials which showed that the higher the concentration of spore suspension the better the power suppress fungal antagonists against P. palmivora. The best concentration that colonies of the Petri dish was dissolved in 150 ml of sugar solution (10%).

Effects of Phenolic Compounds on Growth of Colletotrichum spp. In Vitro.

Colletotrichum acutatum is responsible for anthracnose fruit rot, one of the most devastating diseases in strawberry. Phenolic compounds have been described as contributors to anthracnose resistance in strawberry (Fragaria x ananassa, Duch.). Six isolates of Colletotrichum acutatum and four isolates of three other Colletotrichum species, C. gloeosporioides, C. fragariae, and C. graminicola, associated with disease symptoms were investigated in this study. The potential inhibitory effect of phenolic acids (gallic acid, caffeic acid, chlorogenic acid, ferulic acid, trans-cinnamic acid, p-coumaric acid, salicylic acid), flavonoids (catechin, quercetin, naringenin), and ellagic acid, which are naturally found in strawberry, were screened against two different spore suspension concentrations of the Colletotrichum isolates at 5, 10, 50mM in vitro. Among the phenolic acids and flavonoids tested in this study, only trans-cinnamic acid, ferulic acid, and p-coumaric acid inhibited fungal growth. The inhibitory effects were concentration-dependent but also varied with the spore suspension concentration of the isolates. The results demonstrated that trans-cinnamic acid had the greatest inhibitory effect on all Colletotrichum spp. isolates tested.

&lt;p class="HeadingRunIn"&gt;&lt;strong&gt;A novel use of predatory mites for dissemination of fungal pathogen for insect biocontrol: The case of &lt;em&gt;Amblyseius swirskii&lt;/em&gt; and &lt;em&gt;Neoseiulus cucumeris &lt;/em&gt;(Phytoseiidae) as vectors of &lt;em&gt;Beauveria bassiana&lt;/em&gt; against &lt;em&gt;Diaphorina citri&lt;/em&gt; (Psyllidae)&lt;/strong&gt;&lt;/p&gt;

This study tests the novel use of predatory mites for dissemination of a fungal pathogen for insect biocontrol in the laboratory. We first evaluated the pathogenicity of Beauveria bassiana at several spore suspension concentrations against the nymphs of both the Asian citrus psyllid ( Diaphorina citri ) and two predatory mite species ( Amblyseius swirskii and Neoseiulus cucumeris ). The B. bassiana spores at suspension concentrations greater than 10 4 spores · ml -1 were highly effective against D. citri nymphs, resulting in a mortality approaching 100% after 7 days, but caused only low mortality rates of A. swirskii and N. cucumeris nymphs (15 and 10%, respectively) after 7 days. We then observed whether these two predatory mites, when dusted with B. bassiana spores, could disseminate the pathogen to D. citri residing on small twigs of potted Murraya paniculata (Rutaceae) plants under high humidity conditions. Several days after the release of “dusted” A. swirskii and N. cucumeris females, most D. citri had been killed by B. bassiana . As these phytoseiid predators exhibit a relatively high tolerance to this pathogen and are attracted to D. citri , we believe that this method might represent a new technique for using the Beauveria to control this pest insect. This method should be further explored for dissemination of entomophagous fungi to various insect pests in greenhouse and field conditions.

Intraspecific variation in susceptibility to dothistroma needle blight within native Scottish Pinus sylvestris

Dothistroma needle blight (DNB), caused by Dothistroma septosporum, is the most important disease currently affecting pine plantations in Britain. Intraspecific variation in susceptibility to DNB has been observed in several pine species, but it is not clear if similar variation occurs in Pinus sylvestris (Scots pine), Britain's only native pine. In three separate experiments 2‐ and 3‐year‐old Scots pine saplings from six native Scottish populations were artificially inoculated with D. septosporum conidial suspensions and incubated under conditions optimal for disease development. Conidial suspensions were produced using a single isolate from northeast Scotland. In one experiment, plants were also treated with various spore suspension concentrations to assess the impact of inoculum load on disease severity. There were no significant interactions between host population, plant height, and experiment/inoculum load (anova, P &gt; 0·05), but population, height and inoculum load all significantly affected disease severity (anova, P &lt; 0·05). Among the 2‐year‐old trees, those from Amat were less susceptible than those from Glen Loyne and Glen Cannich (anova, P &lt; 0·05). Among the 3‐year‐old trees, those from Beinn Eighe were less susceptible than those from Abernethy. Plant height and DNB susceptibility had a slightly negative relationship. The use of a spore suspension with a concentration of 1·6 × 106 spores mL−1 was optimum for disease development. In an in vitro experiment, production of conidia was greater when cultures were incubated in darkness. This paper is the first to report intraspecific variation in DNB susceptibility within Scots pine.

First Report on the Increased Distribution of Pathotype 704 of Plasmopara halstedii in Hungary.

Downy mildew of sunflower caused by Plasmopara halstedii (Farlow) Berlese et de Toni is a devastating disease worldwide. The treatment of seeds with fungicides and the use of resistant cultivars are widely employed control measures against this oomycete. Effective protection, however, may be hindered by the high genetic variability of the pathogen. There are 14 pathotypes of P. halstedii in Europe and as many as six of these were identified in Hungary before 2010 (1,4). In 2010, a new race, 704, was isolated in the eastern region of Hungary (3). Although the new pathotype was identified in two sunflower fields (near Vészto and Kondoros), it was expected to spread all over the country because of a lack of resistance against this race. The aim of our study, therefore, was to monitor the distribution of pathotype 704 in Hungary. Infected sunflower plants (2 to 5 samples/site) showing typical symptoms of downy mildew (leaf chlorosis, severe stunting) from four different sites (Árpádhalom, Rákóczifalva, Tiszasüly, and Újiráz) in the eastern region of the country were collected in mid-June 2012. Examination of isolates was carried out using a set of sunflower differential lines based on the internationally standardized method for race identification of P. halstedii (2). Inoculum of 17 isolates was increased on a susceptible cultivar (cv. Iregi Szürke Csíkos). Leaves containing zoosporangia were washed off in distilled water. The concentration of spore suspension for each isolate was adjusted to 20,000 to 30,000 viable zoosporangia per ml using a hemacytometer. Pre-germinated seeds of sunflower differential lines (20 seeds/line) with an optimal radicle length were selected and placed in separate petri dishes. They were filled with freshly prepared zoosporangial suspension of the isolates and incubated in the dark at 16°C for 6 h. Inoculated seeds were planted in trays. After 8 to 9 days when the first true leaves were ~0.5 to 1 cm long, the trays containing the plants were covered with transparent plastic bags overnight. Distilled water was sprayed into the bags to ensure a humid environment for stimulating sporulation. First disease assessment was performed immediately after incubation based on the appearance of characteristic white sporulation on cotyledons. A second evaluation was made of true leaves of 21-day-old plants. Twelve out of 17 isolates were pathotype 704, infecting either one of two commercial sunflower hybrids (NK Neoma and NK Brio) or volunteer sunflower plants. The remaining five isolates were races 700, 710, and 730, which are known to be widespread in Hungary (1). The presence of race 704 was proven in all sampling sites representing the eastern part of the country. This finding underscores the need to develop and grow improved sunflower hybrids with effective genes against this pathotype. To our knowledge, this is the first report of the wider distribution of pathotype 704 of P. halstedii in both Hungary and Central Europe.