Identification of a fall armyworm (Spodoptera frugiperda)-specific gene and development of a rapid and sensitive loop-mediated isothermal amplification assay.

The fall armyworm [FAW, Spodoptera frugiperda (J E Smith)], a moth native to America, has spread throughout the world since it was first discovered in Africa in 2016. The FAW is a polyphagous migratory pest that can travel over long distances using seasonal winds or typhoons because of its excellent flying ability, causing serious damage to many crops. For effective FAW control, accurate species identification is essential at the beginning of the invasion. In this study, the FAW-specific gene Sf00067 was discovered by performing bioinformatics to develop a fast and accurate tool for the species-specific diagnosis of this pest. An Sf00067 loop-mediated isothermal amplification (LAMP) assay was developed, and optimal conditions were established. The Sf00067 6 primer LAMP (Sf6p-LAMP) assay established in this study was able to diagnose various genotype-based strains of FAW captured in Korea and FAWs collected from Benin, Africa. Our FAW diagnostic protocol can be completed within 30 min, from the process of extracting genomic DNA from an egg or a 1st instar larva to species determination.

Insecticidal activities of cinnamic acid esters isolated from Ocimum gratissimum L. and Vitellaria paradoxa Gaertn leaves against Tribolium castaneum Hebst (Coleoptera: Tenebrionidae).

BACKGROUND: Pest management using botanicals has been widely practiced in sub-Saharan Africa and other parts of the world in recent times. The natural compounds present in these botanicals are known to be responsible for the protection they offer against insect pests. Some of these compounds may act as single compounds to produce an effect or they may be synergistically effective. In the present study using a bioassay guided approach, two cinnamic acid derivatives, methyl cinnamate and sitosterol cinnamate, were isolated from the leaves of Ocimum gratissimum and Vitellaria paradoxa, respectively. RESULTS: The two cinnamic acid derivatives were found to show higher levels of insecticidal, larvicidal and larval growth inhibition activities against Tribolium castaneum. The LC50 of methyl cinnamate was determined to be 26.92 mg mL-1 (95% CL: 1.18.66-38.84 mg mL-1 ; slope ± SE: 2.84 ± 0.81) for the adult 8.31 mg mL-1 (95% CL: 2.39-28.83 mg mL-1 ; slope ± SE: 0.66 ± 0.28) for the larvae while the LC50 of sitosterol cinnamate was determined to be 6.92 mg mL-1 (95% CL: 3.97-12.06 mg mL-1 ; slope ± SE: 1.59 ± 0.12) the adult and 3.91 mg mL-1 (95% CL: 2.21-6.93 mg mL-1 ; slope ± SE: 1.52 ± 0.13) for the larvae. CONCLUSION: Generally, the susceptibility of adult T. castaneum to these cinnamic acid esters can be directly associated with the concentration as well as time of exposure to the compounds. The isolated compounds support the use of O. gratissimum and V. paradoxa as important botanicals for the management of storage pests. © 2019 Society of Chemical Industry.

Native SAG1 in Toxoplasma gondii lysates is superior to recombinant SAG1 for serodiagnosis of T. gondii infections in chickens.

Toxoplasma gondii can infect almost all mammals and birds, including chickens. The aim of this study was to identify an appropriate immunogenic antigen for serodiagnosis of T. gondii infections in chickens. We examined serum samples from chickens that were intravenously or intraperitoneally infected with 106-108 tachyzoites of T. gondii strains PLK, RH, CTG, ME49 or TgCatJpGi1/TaJ using enzyme-linked immunosorbent assays (ELISAs), latex agglutination tests (LATs) and western blotting. Regardless of parasite strain or infection dose and route, the commercial LAT was positive for almost all sera collected 1 week post-infection. However, at 2 weeks post-infection, LATs were negative in the same birds. ELISAs using the Escherichia coli-produced recombinant T. gondii antigens SAG1 and GRA7 showed strong signals at 1-2 weeks post infection, but thereafter diminished for the majority of serum samples. In contrast, western blotting against crude tachyzoite antigens showed a persistent band up to 4 weeks post-infection. Sera from these chickens reacted much more strongly with SAG1 from crude tachyzoite antigens than with recombinant SAG1. Even in experimentally-infected birds whose parasite burdens in tissue were undetectable, sera still reacted with native SAG1. We tested sera from free-range chickens on a small farm in Ghana, Africa, using western blotting and found that the serum of one bird reacted with a single band of approximately 27 kDa, the putative molecular weight of SAG1. Thus we conclude that native SAG1, but not E. coli-produced recombinant SAG1, is suitable for serodiagnosis of T. gondii infections in chickens.