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

Abstract

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.

Fall armyworm from a maize multi-peril pest risk perspective

“…Here we refreshed the modeled evidence, motivated, in part, by reports that FAW is now overwintering in subtropical ranges both in the U.S and China (47,48), and, concordant with these in-field findings, results from the phenological experiments conducted by Valdez-Torres et al (49) regarding the minimum thermal threshold for FAW on maize. To accommodate these new lab and in-field findings, as described below we lowered the minimum threshold temperature parametrization in our CLIMEX model, which in conjunction with the expanded set of occurrence data used to calibrate our model, enabled us to update the spatial climate suitability extent of the pest relative to the prior modeled evidence.…”

“…In calibrating their CLIMEX models, du Plessis et al ( 9 ) Ramirez-Cabral et al ( 39 ), and Timilsena et al ( 43 ) set their DV0 values equal to 12.0°C. Based on the recent field occurrence observations gleaned from Osabutey et al ( 48 ) for the U.S. and Yang et al ( 47 ) where the temperature is as low as 9°C, coupled with Valdez-Torres et al ( 49 ), lab findings that the minimum thermal threshold for FAW on maize was 8.7°C, we opted to set our DV0 value at 8.7°C. Thus, our lower limit was used to capture these subtropical ranges and ensure we did not underestimate the current risk coverage.…”

Development of a Rapid, Accurate, and On-Site Detection Protocol for Red Imported Fire Ants, Solenopsis invicta (Hymenoptera: Formicidae)

“…We identified two genes that could be Si -specific by performing transcriptome analysis followed by bioinformatics as in a previous study [ 4 ]. In addition to Si , we have also developed LAMP assays for the detection of Bursaphelenchus xylophilus [ 24 ], Drosophila suzukii [ 25 ], and Spodoptera frugiperda [ 26 ], using species-specific genes or a specific insecticide-resistant allele [ 27 ]. Although the development of LAMP assays for species-specific genes requires more research effort than using COX1 or ITS regions, given that the sequences of COX1 or ITS regions are known to often show large differences both within and between species [ 28 ], it is possible that invading insects could develop new mutations in COX1 or ITS regions as they adapt and spread.…”

Major biotic stresses affecting maize production in Kenya and their implications for food security

“…An assay based on loop‑mediated isothermal amplification (LAMP) has been reported for the species specific diagnosis of FAW ( Osabutey et al, 2022 ). However, for the small scale farmer, scouting protocols which looks for the signs of egg hatch and feeding by egg larvae instar have been developed to allow early detection of FAW for better management ( Prasanna et al, 2018 ).…”