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Identification of Spodoptera frugiperda (Lepidoptera: Noctuidae) and its two host strains in China by PCR-RFLP
Jian-Zhao Jiang1, Bo-Yu Huang1, Qian Wu1
1Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology, Institute of Insect Science and Technology, School of Life Sciences, South China Normal University, Guangzhou, 510631, China.
Abstract:
The fall armyworm (FAW) Spodoptera frugiperda was first found in China in 2018. In other countries, FAW has evolved corn and rice strain biotypes. It is not possible to identify these strains based on morphology. In addition, FAW is very similar in appearance to several other common pests. These situations bring great challenges to the population management of FAW. In this study, we developed a rapid identification method based on PCR-RFLP to distinguish the two FAW strains and the FAW from other lepidopteran pests. A 697 bp mitochondrial cytochrome c oxidase I (COI) was cloned and sequenced from FAW, Spodoptera litura, Spodoptera exigua, and Mythimna separata. The COI fragments of these species revealed unique digestion patterns created by three enzymes (Tail, AlWN I, and BstY II). Thus, these four species can be distinguished from each other. The enzyme Ban I recognized a unique SNP site on a 638 bp triosephosphate isomerase (Tpi) fragment of the corn strain FAW. The Tpi fragment of the corn strain was cut into two bands. However, the rice strain could not be digested. Using this method, all 28 FAW samples collected from different host plants and locations in China were identified as the corn strain. This suggests that the rice strain has not yet invaded China. This method allows discrimination of FAW from other Lepidopteran pests and distinguishes the two FAW host strains.
Insights
A new PCR-RFLP method rapidly identifies fall armyworm (FAW) strains and distinguishes them from other pests. Current Chinese FAW populations are confirmed as the corn strain, indicating no rice strain invasion.
Area of Science:
- Agricultural Entomology
- Molecular Biology
- Pest Management
Background:
- The fall armyworm (FAW), Spodoptera frugiperda, poses significant challenges to agriculture due to its cryptic strain variation (corn and rice) and morphological similarity to other pests.
- Accurate identification of FAW strains is crucial for effective population management and preventing agricultural damage.
- Existing identification methods are insufficient for distinguishing FAW strains and other closely related lepidopteran pests.
Purpose of the Study:
- To develop a rapid and reliable identification method for distinguishing between the corn and rice strains of fall armyworm (FAW).
- To differentiate FAW from other common lepidopteran pests.
- To assess the current FAW strain composition in China.
Main Methods:
- Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was employed for identification.
- Mitochondrial cytochrome c oxidase I (COI) gene fragments were analyzed using restriction enzymes (Tail, AlWN I, BstY II) for species-level differentiation.
- Triosephosphate isomerase (Tpi) gene fragments were analyzed using the enzyme Ban I to distinguish between FAW corn and rice strains based on a single nucleotide polymorphism (SNP).
Main Results:
- Unique COI gene digestion patterns successfully differentiated FAW from Spodoptera litura, Spodoptera exigua, and Mythimna separata.
- The Tpi gene analysis using Ban I effectively distinguished the FAW corn strain (digested into two bands) from the rice strain (undigested).
- All 28 FAW samples collected in China were identified as the corn strain, indicating the absence of the rice strain.
Conclusions:
- The developed PCR-RFLP method provides a rapid and accurate tool for identifying FAW strains and differentiating them from other lepidopteran pests.
- The findings suggest that the FAW rice strain has not yet established populations in China.
- This molecular tool is vital for informed pest management strategies and monitoring FAW spread and evolution.
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