Development Of Biocontrol Strategies Research Articles

3-(Methylthio)Propionic Acid from Bacillus thuringiensis Berliner Exhibits High Nematicidal Activity against the Root Knot Nematode Meloidogyne incognita (Kofoid and White) Chitwood.

Root knot nematodes cause serious damage to global agricultural production annually. Given that traditional chemical fumigant nematicides are harmful to non-target organisms and the environment, the development of biocontrol strategies has attracted significant attention in recent years. In this study, it was found that the Bacillus thuringiensis Berliner strain NBIN-863 exhibits strong fumigant nematicidal activity and has a high attraction effect on Meloidogyne incognita (Kofoid and White) Chitwood. Four volatile organic compounds (VOCs) produced by NBIN-863 were identified using solid-phase microextraction and gas chromatography-mass spectrometry. The nematicidal activity of four VOCs, namely, N-methylformamide, propenamide, 3-(methylthio)propionic acid, and phenylmalonic acid, was detected. Among these compounds, 3-(methylthio)propionic acid exhibited the highest direct contact nematicidal activity against M. incognita, with an LC50 value of 6.27 μg/mL at 24 h. In the fumigant bioassay, the mortality rate of M. incognita treated with 1 mg/mL of 3-(methylthio)propionic acid for 24 h increased to 69.93%. Furthermore, 3-(methylthio)propionic acid also exhibited an inhibitory effect on the egg-hatching of M. incognita. Using chemotaxis assays, it was determined that 3-(methylthio)propionic acid was highly attractive to M. incognita. In pot experiments, the application of 3-(methylthio)propionic acid resulted in a reduction in gall numbers, decreasing the number of galls per gram of tomato root from 97.58 to 6.97. Additionally, the root length and plant height of the treated plants showed significant increases in comparison with the control group. The current study suggests that 3-(methylthio)propionic acid is a novel nematicidal virulence factor of B. thuringiensis. Our research provides evidence for the potential use of NBIN-863 or its VOCs in biocontrol against root knot nematodes.

Bacillus sp. G2112 Detoxifies Phenazine-1-carboxylic Acid by N5 Glucosylation.

Microbial symbionts of plants constitute promising sources of biocontrol organisms to fight plant pathogens. Bacillus sp. G2112 and Pseudomonas sp. G124 isolated from cucumber (Cucumis sativus) leaves inhibited the plant pathogens Erwinia and Fusarium. When Bacillus sp. G2112 and Pseudomonas sp. G124 were co-cultivated, a red halo appeared around Bacillus sp. G2112 colonies. Metabolite profiling using liquid chromatography coupled to UV and mass spectrometry revealed that the antibiotic phenazine-1-carboxylic acid (PCA) released by Pseudomonas sp. G124 was transformed by Bacillus sp. G2112 to red pigments. In the presence of PCA (>40 µg/mL), Bacillus sp. G2112 could not grow. However, already-grown Bacillus sp. G2112 (OD600 > 1.0) survived PCA treatment, converting it to red pigments. These pigments were purified by reverse-phase chromatography, and identified by high-resolution mass spectrometry, NMR, and chemical degradation as unprecedented 5N-glucosylated phenazine derivatives: 7-imino-5N-(1'β-D-glucopyranosyl)-5,7-dihydrophenazine-1-carboxylic acid and 3-imino-5N-(1'β-D-glucopyranosyl)-3,5-dihydrophenazine-1-carboxylic acid. 3-imino-5N-(1'β-D-glucopyranosyl)-3,5-dihydrophenazine-1-carboxylic acid did not inhibit Bacillus sp. G2112, proving that the observed modification constitutes a resistance mechanism. The coexistence of microorganisms-especially under natural/field conditions-calls for such adaptations, such as PCA inactivation, but these can weaken the potential of the producing organism against pathogens and should be considered during the development of biocontrol strategies.

Molecular Characterization of Rotifers and Their Potential Use in the Biological Control of Biomphalaria.

BackgroundSchistosomiasis is one of the most important tropical parasitic diseases worldwide. Biomphalaria straminea, the intermediate host of Schistosoma mansoni, has invaded and spread to Southern China since 1974 and may pose enormous threats to public health. Controlling intermediate host snails is an effective strategy in schistosomiasis intervention. However, the only effective chemical molluscicide, niclosamide, currently recommended by WHO may cause environmental pollution, loss of biodiversity, and high costs. Thus, to counter intermediate hosts, a sustainable and environmentally friendly tool is urgently needed. Here, we conducted field investigations to collect and identify a potential snail competitor rotifer and evaluated its molluscicide effect.ResultsIn this study, we collected two samples of rotifers from Shenzhen. We found both red and black phenotypic B. straminea snails at the sampling sites. We identified the rotifer population as a species of the genus Philodina according to the amplification and phylogenetic analysis results of coxI gene. We found that rotifer exposure did not significantly affect the hatching rate of B. straminea eggs but promoted the killing of juvenile snails. Meanwhile, rotifer exposure did not significantly alter the fecundity of B. straminea quantified by the number of eggs per egg mass, the number of egg masses per snail, and the number of eggs per snail; but the snails exposed to rotifers showed lower fecundity performance than the control snails. Importantly, rotifer exposure could significantly affect the development of juvenile B. straminea, showing a smaller shell diameter of the exposed snails than that of the control snails. In addition, rotifer exposure affected the life span of B. straminea snails, showing a 16.61% decline in the average life span. After rotifer exposure, the S. mansoni-infected B. straminea snails died significantly faster than those without rotifer exposure. Similar findings were observed in S. mansoni-infected Biomphalaria glabrata snails. These results implied that rotifer exposure significantly promoted the mortality of S. mansoni-infected B. straminea and B. glabrata.ConclusionsOur study demonstrated the potential molluscicide effect of rotifers on intermediate hosts under laboratory conditions. Our findings may provide new insights into the development of biocontrol strategies for snail-borne disease transmission.

Diverse novel resident Wolbachia strains in Culicine mosquitoes from Madagascar

Wolbachia endosymbiotic bacteria are widespread throughout insect species and Wolbachia transinfected in Aedes mosquito species has formed the basis for biocontrol programs as Wolbachia strains inhibit arboviral replication and can spread through populations. Resident strains in wild Culicine mosquito populations (the vectors of most arboviruses) requires further investigation given resident strains can also affect arboviral transmission. As Madagascar has a large diversity of both Culicine species and has had recent arboviral outbreaks, an entomology survey was undertaken, in five ecologically diverse sites, to determine the Wolbachia prevalence. We detected diverse novel resident Wolbachia strains within the Aedeomyia, Culex, Ficalbia, Mansonia and Uranotaenia genera. Wolbachia prevalence rates and strain characterisation through Sanger sequencing with multilocus sequence typing (MLST) and phylogenetic analysis revealed significant diversity and we detected co-infections with the environmentally acquired bacteria Asaia. Mosquitoes were screened for major arboviruses to investigate if any evidence could be provided for their potential role in transmission and we report the presence of Rift Valley fever virus in three Culex species: Culex tritaeniorhynchus, Culex antennatus and Culex decens. The implications of the presence of resident Wolbachia strains are discussed and how the discovery of novel strains can be utilized for applications in the development of biocontrol strategies.

Use of predatory mites in commercial biocontrol: current status and future prospects

Predatory mites play the leading role in commercial augmentative biological control. They are mainly used in protected vegetable and ornamental cultivation systems to control phytophagous mites, thrips and whiteflies. Use in open-field systems and in animal husbandry is still limited. Phytoseiidae species are by far the most important group of commercially available mite biocontrol agents with about 20 species offered worldwide. Out of these, Amblyseius swirskii, Phytoseiulus persimilis, Neoseiulus cucumeris and Neoseiulus californicus are the most important ones, covering together about two thirds of the entire arthropod biocontrol agent market. The widespread use of these leaf-inhabiting predatory mites has stimulated research into their biology and we now have substantial knowledge on, for instance, the interaction between different predatory mite species, that helps to improve biocontrol programmes. Soil predatory mites, for example Stratiolaelaps scimitus (Laelapidae) or Macrocheles robustulus (Macrochelidae) for the control of sciarid fly larvae and thrips pupae are much less frequently used and also much less researched. This makes further development of biocontrol strategies using these mites more difficult. Currently, there appears to be no reliable method to quantify the abundance of these mites in soil samples. In studies at our laboratory, the frequently used Berlese-Tullgren funnels gave very variable results. We observed that soil predatory mites can even multiply during the extraction process. In addition to the control of plant pests, predatory mites can also be used to control parasites of animals like the poultry red mite, Dermanyssus gallinae. Good results have been obtained applying a combination of the predatory mites Androlaelaps casalis (Laelapidae) and Cheyletus eruditus (Cheyletidae) in laying hen stables. This paper provides an overview on the current status of commercial biological control using predatory mites and identifies research needs to make the currently available mite biocontrol agents even more successful and extend biological control with mites to other areas.

Seasonal yeast compositions in Forcipomyia taiwana (Diptera: Ceratopogonidae)

Forcipomyia taiwana, a biting midge, is one of the most annoying blood-sucking pests in Taiwan. The larvae of Forcipomyia species feed primarily on algae, and the adults feed on nectar for nutrition. After mating with male adults, females bite humans and digest blood for the formation and development of their eggs. The bites often cause human itching, swelling, skin lesion and even fatal shock. Harassment from this biting pest has become a serious problem and has influenced the quality of outdoor recreational activities. Thus, it is necessary to understand the ecology of F. taiwana to develop an effective control strategy. This study showed the seasonal variation of yeast compositions in the interior of F. taiwana. Furthermore, we found that Aureobasidium spp. appeared the most during collection times and these yeasts are able to decompose the cellulose, a major component in the cell wall of algae and Oomycete fungi. These fungi infect a broad range of host and have adverse effect on fitness of the biting midges. Thus, Aureobasidium spp. play a crucial role in the defense system of F. taiwana against pathogens. The study provides useful information that could be used in the development of biocontrol strategy in the future.

Effects of initial inoculation density of Paenibacillus polymyxa on colony formation and starch‐hydrolytic activity in relation to root rot in ginseng

To examine the relationships between population growth and biological characters of the plant-growth-promoting rhizobacterium Paenibacillus polymyxa GBR-1. Population growth, colony formation, starch-hydrolytic activity, and ginseng root rot caused by P. polymyxa GBR-1 isolated from a rotten ginseng root were examined in vitro and in vivo at high [1 x 10(8) colony-forming units (CFU) ml(-1)] and low (1 x 10(6) CFU ml(-1)) initial inoculum densities. Paenibacillus polymyxa GBR-1 showed strong starch-hydrolytic activity on modified starch agar with relatively low starch content, but only at certain incubation temperatures (18 and 23 degrees C); the high-density inoculum produced bacterial colonies about nine times thicker than those formed from the lower inoculum density. Light, scanning electron, and transmission electron microscopy showed that the thick colonies from the high-density inoculum were filled with extracellular polymeric substances (EPS), in which a relatively small number of ovoid-rod-shaped bacterial cells (mostly endospore-bearing cells) were distributed. In contrast, the thin colonies from the low-density inoculum were composed of massive vegetative cells with a rectangular rod shape and minimum EPS. Fluorescent in situ hybridization (FISH) revealed that the beta-amylase gene was expressed only in bacterial cells from the thick colonies formed from the high-density inoculum, but not in those from the low-density inoculum. The culture filtrate from the thick colonies produced a hydrolytic clear zone on modified starch agar, degraded starch granules in various manners, and produced rot symptoms on ginseng root tissues. The biological properties of colony formation, starch hydrolysis, and ginseng tissue rotting by P. polymyxa GBR-1 are interrelated; they are influenced by the initial bacterial population density but not by the in situ and the final population densities. Knowledge of disease-inducing characters of P. polymyxa GBR-1 can be used in the development of biocontrol strategies.