Nomuraea Rileyi Research Articles

Performance of phytosanitary products for control of soybean caterpillar.

The present work evaluated the efficiency of applied biological control and chemical control of Chrysodeixis includens, and the management of this looper caterpillar in the field soybean crop. The experimental design was a randomized complete block design, consisting of six treatments applied only once: two different doses of Bacillus thuringiensis (Bt), 0.2 and 0.35 L ha-1; Metarhizium rileyi strain UFMS 02 (Mr), 2.0 and 5.0 kg ha-1; insecticide Flubendiamide (Fd) 20 mL ha-1; and the control. The reduction of the pest and the percentage of efficiency of the products along the development of the soybean, besides some phytotechnical parameters, were evaluated thirteen days after the application. In general, there was a decrease in the number of caterpillars after thirteen days of spraying, with the Bt treatment being 350 mL ha-1, which provided the greatest reduction in the population (96.2%) when compared to the control (6.7 %). Regarding efficiency, treatments containing biological products Bt (two doses) and Mr 5.0 kg ha-1 provided the best results: 95.88, 84.69 and 92.35%, respectively. Among the phytotechnical parameters evaluated, the biological treatments were superior to the chemical treatments in relation to the productivity and the number of pods per plant, not differing statistically among them.

Efficacy of Biosynthesised Silver Nanoparticles From Entomopathogenic Fungi Metarhizium Rileyi Against Spodoptera Litura on Cabbage

There is lot of scope for applications of nanotechnology in agriculture. Nanobased insecticide formulations show less toxicity against non-target organisms due to absence of organic solvents. Hence, in this study silver nanoparticles were biosynthesized from Metarhizium rileyi Farl. and the synthesis confirmed initially by colour change from pale yellow to dark brown after seven days. Further, these were characterized using UV-visible spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and EDAX analysis. The surface plasmon resonance peaks were observed at 311 nm and 315 nm in 1.75 and 2.00 mM concentration, respectively. The particle size ranged from 64.11 to 99.08 nm in 1.75 mM and 64.11 to 128.2 nm in 2.00 mM concentration under SEM. In TEM analysis the particle size ranged from 12.80 to 22.20 nm in 1.75 mM and 11.00 to 19.00 nm in 2.00 mM concentration. The presence of elemental silver was confirmed by signals that ranged from 0 to 10 keV in EDAX analysis. The synthesized nanoparticles were effective in suppressing the Spodoptera litura F. both under laboratory and pot culture experiments. The maximum mortality of80.00 and 53.33% was observed at 1.75 and 2.00 mM under laboratory condition, in the 2nd and 3rd instar larvae, respectively. Whereas, in pot culture the mortality was 73.75 and 78.75% with 1.75- and 2.00-mM concentrations, respectively, as compared to the commercial formulation of M. rileyi and NSKE 4%.

Studies on mycosis of Metarhizium (Nomuraea) rileyi on Spodoptera frugiperda infesting maize in Andhra Pradesh, India

BackgroundMycosis on the fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), infecting maize was observed in research farm of Regional Agricultural Research Station, Anakapalli from October 2019 to February 2020.Main bodyHigh relative humidity (94.87%), low temperature (24.11 °C), and high rainfall (376.1 mm) received during the month of September 2019 predisposed the larval instars for fungal infection and subsequent high relative humidity and low temperatures sustained the infection till February 2020. An entomopathogenic fungus (EPF) was isolated from the infected larval instars as per standard protocol on Sabouraud’s maltose yeast extract agar and characterized based on morphological and molecular analysis. The fungus was identified as Metarhizium (Nomuraea) rileyi based on ITS sequence homology and the strain was designated as AKP-Nr-1. The pathogenicity of M. rileyi AKP-Nr-1 on S. frugiperda was visualized, using a light and electron microscopy at the host-pathogen interface. Microscopic studies revealed that all the body parts of larval instars were completely overgrown by white mycelial threads of M. rileyi, except the head capsule, thoracic shield, setae, and crotchets. The cadavers of larval instars of S. frugiperda turned green on sporulation and mummified with progress in infection. In vitro pathogenicity tests revealed the potential of AKP-Nr-1 strain of M. rileyi in management of S. frugiperda.Short conclusionThe results indicated the potential of M. rileyi AKP-Nr-1 as biocontrol agent for management of the fall armyworm. This AKP-Nr-1 strain of M. rileyi needs further evaluation under field conditions to evaluate its efficacy against S. frugiperda and its effects on other hosts.

Metarhizium (=Nomuraea) rileyi (Farlow) Samson from Spodoptera exigua (Hübner) Cross Infects Fall Armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) Larvae

Mycobiocontrol is a promising management strategy in mitigating the fall armyworm Spodoptera frugiperda (J.E. Smith) infestation in the Philippines. An isolate of Metarhizium (=Nomuraea) rileyi (Farlow) Samson from onion or beet armyworm, S. exigua, which induced high mortality to this pest, was assessed against different larval instars of S. frugiperda. Surface-sterilized corn leaves were treated with different conidial concentrations and fed to S. frugiperda larvae. Cross infection of this entomopathogenic fungus to S. frugiperda was confirmed with a fungal infection that was initiated at 1–2 d post-treatment depending on the age of the larvae. Larval mortality significantly increased at 4–5 d post-treatment. Up to 100% larval mortality was recorded at 7 d post-treatment. Early larval instars (1st–3rd) were more susceptible than late larval instars (4th–6th). Higher conidial concentrations caused a higher and faster rate of larval mortality than lower conidial concentrations. The inflicted mycoses due to M. rileyi resulted in a slightly lower lethal dose (LD50) (1.44 x 105 to 9.36 x 108 conidia ∙ mL–1) and shorter mean time to death (4.51–8.89 d). Mummification of the cadaver confirmed fungal infection with white fungal growth that later changed to green during sporulation. Our findings suggest the infectivity of M. rileyi and can be explored as a biological control agent against S. frugiperda.

Selectivity of Entomopathogenic Fungi to Chrysoperla externa (Neuroptera: Chrysopidae).

Simple SummaryAgricultural crop systems have adopted integrated management as a model of success in pest control; however, chemical control is still prioritized. The use of pesticides incorrectly and excessively has provided a reduction in natural enemies, selection of resistant populations and resurgence of pests. Chrysoperla externa is a predator found in several regions in Brazil that preys on different pest insects. Entomopathogenic fungi Beauveria and Metarhizium also stand out for causing epizootics on pests. Both predators and entomopathogens can simultaneously act as pest control; thus, verifying the selectivity of entomopathogenic fungi to predators increases the potential for biological control through synergism and conservation of natural enemies in the agroecosystem. Considering the control potential of these different biological control agents, in this study we evaluated the selectivity of Beauveria bassiana, Metarhizium anisopliae and Metarhizium rileyi to the larvae of this predator. The results provide evidence that the biological development of larvae of C. externa is not influenced by the entomopathogenic fungus. These species of fungi can be recommended, aiming at a management of populations of arthropod pests, with low effect on C. externa when it is present in the agrosystem.We aimed to evaluate the selectivity of entomopathogenic fungi to larvae of Chrysoperla externa (Neuroptera: Chrysopidae). For this purpose, Beauveria bassiana (strain ESALQ PL63), Metarhizium anisopliae (strain ESALQ E9) and Metarhizium rileyi (strain UFMS 03) were assessed at different concentrations (1 × 107, 1 × 108 and 1 × 109 conidia mL−1). The control treatment consisted of distilled water and Tween80 0.01. The treatments were applied with a Potter spray tower using two different methodologies: direct application (DA) and dry film (DF). Up to 96 h after application, no treatment provided a larval mortality above 3%. After 120 h, only B. bassiana induced significant mortality in all instars, with rates of 26%, 17% and 10% for first, second and third instar larval periods, respectively. There was no difference regarding to the application method or concentration of conidia. The percentage of individuals that revealed changes in the length of the larval and pupal periods varied among different treatments with entomopathogenic fungi and control treatments, application methodologies and concentrations. Despite B. bassiana revealing a higher mortality than M. anisopliae and M. rileyi on larvae of C. externa, these three entomopathogenic fungi may be used in association with C. externa for sustainable pest management.

NATURAL INCIDENCE OF ENTOMOPATHOGENIC FUNGUS Nomuraea rileyi ON Spodoptera frugiperda INFESTING CORN IN BENGKULU

Natural incidence of entomopathogenic fungus Nomuraea rileyi on Spodoptera frugiperda infesting corn in Bengkulu. Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is a new invasive pest in corn. The intensive use of synthetic insecticides for pest control causing various problems such as resistance, pest resurgence, and environmental damage. To solve these problems, entomopathogenic fungi could be used as an alternative in pest management. Therefore, this study was aimed to determine the natural incidence of Nomuraea rileyi (Farlow) Samson (Hypocreales: Clavicipitaceae) entomopathogenic fungus on S. frugiperda in Bengkulu. The research was carried out by exploring the corn producing areas in Bengkulu for N. rileyi incidence. The results showed that the N. rileyi was occurred naturally infected S. frugiperda larvae reached 79.0%. Meanwhile, the percentage of crops damage due to S. frugiperda was ranged from 40.0 to 96.0%. The highest natural incidence of N. rileyi were found in the Village of Bukit Barisan and Tugu Rejo (79.0%), followed by Pulo Geto Baru (25.0%), and Taba Mulan (5.3%) while the lowest incidence was in Sidomulyo (1.0%). The infected larvae were not found in the Napal, Beringin Raya 1, and Beringin Raya 2, despite the percentage of S. frugiperda attacks was reached 50.0; 50.0 and 74.0%, respectively.

Comparative genomic analysis of C-type lectin-domain genes in seven holometabolous insect species

C-type lectins (CTLs) recognize various glycoconjugates through carbohydrate recognition domains (CRDs) and they play important roles in immune responses. In this study, comparative genomic analysis of CTLs were performed in 7 holometabolous species. CTL-S1 to S8 and CTL-X1 to X4 orthologous groups existed in the 7 species, while CTL-X5 group with dual-CRD, CTL-S11 group with triple-CRD, CTL-S9 group with a long C-terminus and Lepidopteran specific CTL-S10 group were not conserved. SliCTL-S12 to S14 cluster was only present in Spodoptera litura, and CTL-S genes were expanded on chromosomes 2 L and 2 R in Drosophila melanogaster. Most IMLs were clustered into three groups and the numbers of IMLs vary among species due to gene duplications. D. melanogaster specific CTLs and Lepidopteran IMLs within each of the three groups evolved more rapidly with higher dN/dS ratios. Two CRDs in IMLs clustered into two clades, with conserved Cys4-Cys5 and Cys1-Cys2 bonds in the first and second CRDs, respectively. The CTL-S and CTL-X family members in S. litura were mainly expressed in the fat body of 5th but not 6th instar larvae, and responded differently to S. litura nucleopolyhedrovirus (SpltNPV) and Nomuraea rileyi infection. The transcription levels of SliCTLs that expressed in fat body but not highly expressed in hemocytes were decreased at the middle and late stages of SpltNPV infection, and the mRNA levels of SliCTLs highly or specifically expressed in hemocytes were mainly decreased by SpltlNPV, N. rileyi and Bacillus thuringiensis infection. These results provide valuable information for further exploration of CTL functions in host-pathogen interaction.

New potential strains for controlling Spodoptera frugiperda in China: Cordyceps cateniannulata and Metarhizium rileyi

Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), an invasive pest, was identified in China in early 2019. This pest is a serious threat to food, especially maize production. Consequently, it is necessary to use biological control to reduce the damage caused by S. frugiperda. Furthermore, it is important to find new entomopathogenic fungi or a local wild parasitic isolate to control this pest. Here, one fungus was found infecting S. frugiperda larvae in China. Isolated colonies were identified as Metarhizium rileyi (Farlow) Kepler, S.A. Rehner & Humber (Hypocreales: Clavicipitaceae) using morphological and molecular methods. Bioassay studies with purified conidial suspensions further confirmed the infectivity to 4th instar S. frugiperda larvae. The results showed that no S. frugiperda larvae survived after being treated with a spore suspension of M. rileyi GZUIFR-LS01 or Cordyceps cateniannulata (Z.Q. Liang) Kepler, B. Shrestha & Spatafora (Hypocreales: Cordycipitaceae) GZUIFR-S22 for seven days at 90% RH. However, at 75% RH, 13% and 48% of larvae survived after seven days of exposure to M. rileyi GZUIFR-LS01 and C. cateniannulata GZUIFR-S22, respectively. Additionally, C. cateniannulata strain GZUIFR-S22 led to a survival rate of less than 50% in S. frugiperda larvae after two days of treatment at 90% RH. This is the first report of the pathogenicity of C. cateniannulata against S. frugiperda.

Efficacy of an oil‐based formulation combining Metarhizium rileyi and nucleopolyhedroviruses against lepidopteran pests of soybean

AbstractA biopesticide that combines Metarhizium rileyi and nucleopolyhedrovirus (NPV) in an oil dispersion (OD) was developed. Its efficacy against Anticarsia gemmatalis and Chrysodeixis includens was evaluated under laboratory and field conditions. First, each of the two selected fungal strains, combined or not in OD preparations with AgMNPV or ChinNPV, was tested in the laboratory against A. gemmatalis and C. includens, respectively. AgMNPV–fungus combinations had similar effect on overall mortality of A. gemmatalis compared to each pathogen used alone. C. includens was less susceptible to infection by M. rileyi strains, and ChinNPV became the major cause of larval death. The OD formulations with M. rileyi and/or NPV were applied in infested soybean fields. ChinNPV + M. rileyi caused 50.8% of overall mortality six days after spraying in a soybean crop infested by both pests, whereas for treatments with the fungus or the virus alone the percentages were 41.2% and 8.8%, respectively. In another field infested solely by A. gemmatalis, insect mortality was similar for the AgMNPV–fungus combination and the virus used alone. Larval parasitism by wasps and dipterans was not affected following biopesticide spraying. Our results suggest that the performance of a dual‐action biopesticide is related to the NPV and fungal strains that are combined and the proportion of host populations simultaneously infesting the crop.

Natural mortality of invasive fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) in maize agroecosystems of northeast India

Invasive fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is a pest of American origin that has recently invaded Asian countries, including India. After causing huge losses in the Africa and Asia, the FAW is now affecting large areas of India. Indigenous natural enemies of related pest species are the first defense against invasive pests and understanding their role in population suppression of invasive pests is a first step towards the development of a comprehensive management program. Therefore, we studied the natural enemy complex responsible for natural mortality of FAW in northeast India. Various locations were surveyed across five major districts of Meghalaya state, where more than 26 species of natural enemies were found attacking FAW. A total of 56.6% to 73.1% of larvae were found to be either parasitized or infected with naturally occurring entomopathogens. Species richness and diversity of predators were determined in maize fields at different locations. Values of Menhinick's species richness index (DMn) varied from 0.23 to 0.31 and Shannon-Wiener index (H) ranged from 2.16 to 2.6 across various locations. The Simpson Index (D) indicated high predator diversity in maize fields. The entomopathogenic fungus, Metarhizium rileyi (Farlow) Samson and the baculovirus, SpfrNPV were observed to be the dominant mortality factors throughout the season, responsible for >50% mortality of FAW larvae. This investigation demonstrated that indigenous natural enemies of related noctuid species can widen their host range and successfully adopt the invasive FAW as a novel host/prey in invaded regions. Therefore, conservation of such biocontrol agents could be vital for mitigating FAW damage in maize agroecosystems.

GATA-type transcription factor MrNsdD regulates dimorphic transition, conidiation, virulence and microsclerotium formation in the entomopathogenic fungus Metarhizium rileyi.

SummaryThe GATA‐type sexual development transcription factor NsdD has been implicated in virulence, secondary metabolism and asexual development in filamentous fungi. However, little is known about its function in the yeast‐to‐hypha transition and in microsclerotium formation. In the current study, the orthologous NsdD gene MrNsdD in the entomopathogenic fungus Metarhizium rileyi was characterized. Transcriptional analysis indicated that MrNsdD was involved in yeast‐to‐hypha transition, conidiation and microsclerotium formation. After targeted deletion of MrNsdD, dimorphic transition, conidiation, fungal virulence and microsclerotium formation were all impaired. Compared with the wild‐type strain, the ΔMrNsdD mutants were hypersensitive to thermal stress. Furthermore, transcriptome sequencing analysis revealed that MrNsdD regulated a distinct signalling pathway in M. rileyi during the yeast‐to‐hypha transition or microsclerotium formation, but exhibited overlapping regulation of genes during the two distinct developmental stages. Taken together, characterization of the MrNsdD targets in this study will aid in the dissection of the molecular mechanisms of dimorphic transition and microsclerotium development.

Novel formulations of Bacillus thuringiensis var. kurstaki: an eco-friendly approach for management of lepidopteran pests.

Bacillus thuringiensis (Bt) and entomopathogenic fungi (EPF) are in use for management of insect pests. Continuous use of Bt can lead to problem of resistance development in insect pests. Hence use of combination formulations (CF) of microbials with diverse modes of action has been attempted to slow down the process of resistance development. Suspension concentrate (SC) formulations of a local strain of Bt var. kurstaki DOR Bt-127 were developed singly and in combination with conidia of the EPF Nomuraea rileyi (Nr) and Beauveria bassiana (Bb). Electron microscopy of Bt + Bb CF treated larvae of Helicoverpa armigera revealed simultaneous infection by both microbials indicating their compatibility. Endotoxin contents in Bt-SC, Bt + Bb and Bt + Nr CFs were 5.0, 4.7 and 4.7%, respectively. These formulations were effective against larvae of Spodoptera litura, H. armigera and Achaea janata coupled with a lowering of the effective requirement of Bt and EPF. In multi-location field trials, Bt-SC and Bt + Nr CF were highly effective against S. litura and A. janata on castor as well as H. armigera and Thysanoplusia orichalcea on sunflower. However, Bt + Bb CF was highly effective only on sunflower against H. armigera and T. orichalcea. All formulations had 24months shelf-life at room temperature. DOR Bt-127 based SC formulations developed singly and in combination with Nr and Bb were effective against major lepidopteran pests of castor and sunflower and did not lose viability under storage at room temperature. The CFs of Bt with EPF could prove promising for mitigating resistance development to Bt.

PERFORMANCE OF Metarhizium rileyi APPLIED ON Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae)

This study aimed to evaluate the efficiency of different strains of the entomopathogenic fungus Metarhizium rileyi in the control of Helicoverpa armigera caterpillars in laboratory conditions. Caterpillars between the 2nd and 3rd instar were used, ranging in size from 0.7 to 1.2 cm length. The experimental design used was completely randomized, composed of five treatments and five replications, each one consisting of 50 insects. The treatments T1 - Control (sterile distilled water), T2 - M. rileyi UFMS 02 strain, T3 - M. rileyi UFMS 03 strain, T4 - M. rileyi UFMS 06 strain, and T5 - M. rileyi UFMS 07 strain were evaluated. All treatments were applied (2 mL/insect) in suspensions of the order of 1.0 × 109 conidia mL-1, and Tween 80® was added in all treatments. Evaluations were performed daily to verify mortality and sublethal effects. For emerging adults, Filial Generation (FG), the biological cycle was evaluated. The data referring to larval mortality for the Parental Generation (PG) and GF and pupal for GF were submitted to analysis of variance, and the Scott-Knott test grouped the averages at 5% probability. The strains tested did not provide pathogenicity in the larval phase of H. armigera for PG and FG. However, there was a reduction in oviposition in all treatments regarding the control. There was an effect on the reproductive phase of GF caterpillars exposed to M. rileyi.

Complete mitogenome of the entomopathogenic fungus Metarhizium rileyi

In this study, the complete mitogenome of an entomopathogenic fungus Metarhizium rileyi was assembled and annotated. This circular mitogenome was 62,514 bp in length and consisted of 2 rRNA genes, 25 tRNA genes, 14 standard protein-coding genes of the oxidative phosphorylation system, and seven intergenic ORFs. Seven genes were invaded by a total of 22 introns, including atp9 (1), cob (4), cox1 (8), cox3 (2), nad1 (1), nad5 (3), and rnl (3 introns). These introns all belonged to the group I intron family but fell into four specific subgroups. Phylogenetic analysis based on mitochondrial nucleotide sequences confirmed M. rileyi in the family Clavicipitaceae, being most close to Metarhizium anisopliae.

Diversity of fall armyworm, Spodoptera frugiperda and their gut bacterial community in Kenya.

BackgroundThe invasive fall armyworm, Spodoptera frugiperda (J.E. Smith) is a polyphagous pest that causes widespread damage particularly to maize and sorghum in Africa. The microbiome associated with S. frugiperda could play a role in the insects’ success and adaptability. However, bacterial communities in S. frugiperda remain poorly studied.MethodsWe investigated the composition, abundance and diversity of microbiomes associated with larval and adult specimens of S. frugiperda collected from four maize growing regions in Kenya through high throughput sequencing of the bacterial 16S rRNA gene. The population structure of S. frugiperda in Kenya was assessed through amplification of the mitochondrial cytochrome oxidase subunit I gene.ResultsWe identified Proteobacteria and Firmicutes as the most dominant bacterial phyla and lesser proportions of Bacteroidetes and Actinobacteria. We also observed differences in bacterial microbiome diversity between larvae and adults that are a likely indication that some prominent larval bacterial groups are lost during metamorphosis. However, several bacterial groups were found in both adults and larvae suggesting that they are transmitted across developmental stages. Reads corresponding to several known entomopathogenic bacterial clades as well as the fungal entomopathogen, Metarhizium rileyi, were observed. Mitochondrial DNA haplotyping of the S. frugiperda population in Kenya indicated the presence of both “Rice” and “Corn” strains, with a higher prevalence of the “Rice” strain.

First record of fall armyworm (Spodoptera frugiperda) in Indonesia and its occurence in three provinces

The occurrence of a new invasive pest species of corn, the fall armyworms Spodoptera frugiperda (Lepidoptera: Noctuidae) in Indonesia is reported. Survey in 3 provinces in Indonesia: West Sumatera, Banten and West Java were conducted from March to June 2019. The first record of this pest was in 26 March 2019 in West Sumatera. Larvae were collected from each of those locations and field symptoms of damage on corn in the field were observed. Larvae were brought to and reared individually in Insect Biosystematics Laboratory of Plant Protection Department, Faculty of Agriculture, IPB University. Identification of fall armyworm employed morphological and molecular analysis. Identification of the larva based on morphological characters of larvae from 3 provinces confirmed the identity of the pest. The pest as fall armyworms, while the molecular analysis indicated that Banten samples belonged to the ‘rice strain’. Collected larvae from Banten were infected by Metarhizium rileyi. The infested plants in the field showed the typical damage symptoms caused by the fall armyworm.

Susceptibility of Spodoptera frugiperda and Chrysodeixis includens (Lepidoptera: Noctuidae) to infections caused by Metarhizium rileyi

ABSTRACT Due to the reduced host spectrum of the entomopathogenic fungus Metarhizium rileyi, its pathogenicity against different target insects must be assessed to develop biopesticides capable of controlling more than one pest species. This study aimed to evaluate the susceptibility of the pest species Chrysodeixis includens and Spodoptera frugiperda to different isolates of M. rileyi and, thus, determine a possible influence of the host of origin on the pathogenic activity of these isolates. Three isolates [CG1312 (C. includens as original host), CG381 (S. frugiperda as original host) and a new wild isolate (C. includens as original host)] were tested against larvae of C. includens and S. frugiperda, in third instar age, by treatment of surfaces with conidial suspension, under laboratory conditions. Both species were susceptible to the isolates of M. rileyi, with mortality rates of 53-58 % for C. includens and 74-84 % for S. frugiperda. The results suggest that the host of origin may not be determinant in the selection of pathogenic isolates of M. rileyi against these two pest insects.

Bioefficacy of different biopesticides against major foliage feeders on soybean [Glycine max (L.) Merrill

Field experiments were conducted to evaluate the efficacy of different biopesticides, viz., Nomuraea rileyi @ 1x10 8 conidia/lit, Beauveria bassiana @ 1x10 9 CFU/ml minimum @ 5 ml/lit, Metarhizium anisopliae @ 1x10 9 CFU/ml minimum @ 5 ml/lit, dipel @ 1 kg/ha, spinosad 45 SC @ 0.5 ml/lit, neem seed kernel extract (NSKE) @ 5% and neem oil @ 2% against foliage feeders of soybean namely, semi looper ( Chrysodeixis acuta ) and tobacco caterpillar ( Spodoptera litura ) during Kharif, 2016. The result revealed that all treatments were significantly superior over control. The mean larval population of C. acuta and S. litura ranged from 1.29 to 9.37 and 0.92 to 6.98 larvae per meter row length (mrl) at 3, 7 and 10 days respectively after the application of treatments. The treatments comprising Spinosad 45 SC @ 0.5 ml/lit proved highly effective in reducing the population of C. acuta and S. litura with lowest overall mean larval population of 4.71 and 3.02 larvae per mrl, respectively. Against C. acuta NSKE @ 5% was least effective and against S. litura neem oil was observed as least effective with maximum over all mean larval populations of 7.75 and 4.97, respectively.

Fungal Extracts as Biocontrol of Growth, Biofilm Formation, and Motility of Xanthomonas citri subsp. Citri

For the present work, Metarhizium rileyi, a common entomopathogenic fungus, was grown in batch conditions in the absence and presence of its host, Spodoptera frugiperda, to obtain secondary metabolites with potential antimicrobial effect. The extraction of secondary metabolites was carried out by using two solvent systems for the biomass (ethyl acetate and methanol), while secondary metabolites present in the supernatant were extracted by using ethyl acetate as extraction solvent. These extracts were evaluated for their inhibitory effect on the growth, biofilm formation, and motility of three Xanthomonas citri subsp. citri strains (Xcc20, Xcc29, and Xcc42). The in vivo effect of these extracts to prevent the development of cankers on grapefruit leaves was also evaluated. M. rileyi biomass ethyl acetate extracts in the presence and absence of its host had a strong inhibitory effect on Xcc strains growth. On the other hand, the presence of S. frugiperda as an elicitor significantly increased M. rileyi’s inhibitory capacity to form a biofilm. A different behavior was observed for the copper resistant strain, Xcc42, for its biofilm formation and swimming capacity since the most active samples were the supernatant extracts in the presence and absence of S. frugiperda. Our results suggest that the most important factor for in vivo canker development is the inhibition of Xcc’s motility since all the extracts that inhibited canker development in vivo were also able to inhibit Xcc20’s motility in vitro. The fact that the extracts can prevent cankers development in vivo indicates they are promising sources of metabolites to prevent the development of this citrus disease.

MrMid2, encoding a cell wall stress sensor protein, is required for conidium production, stress tolerance, microsclerotium formation and virulence in the entomopathogenic fungus Metarhizium rileyi

Transmembrane proteins as sensors encoded by fungal genes activate specific intracellular signal pathways in response to stress cues to help the fungus survive in a changing environment. To better understand the role of the cell wall integrity (CWI) pathway in the entomopathogenic fungus Metarhizium rileyi, an ortholog encoding the transmembrane protein Mid2, MrMid2, was identified and characterized functionally. Transcriptional analysis indicated that MrMid2 was involved in dimorphic transition, conidiation, and microsclerotium formation. After a targeted deletion of MrMid2, all three traits were impaired. Compared with the wild-type strain, the △MrMid2 mutants were hypersensitive to thermal stress, and cell wall and oxidative stress. Insect bioassays revealed that △MrMid2 mutants had decreased virulence levels following topical (22.5%) and injection bioassays (38.7%). Furthermore, transcription analysis showed that other genes of the CWI pathway, with the exception of another major sensor protein encoding gene, MrWsc1, were down-regulated in △MrMid2 mutants. These results suggest that MrMid2 plays important roles in dimorphic transition, conidiation, the stress response, virulence, and microsclerotium development in M. rileyi.