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Effects of temperature on life-history traits of the newly invasive fall armyworm, Spodoptera frugiperda in Southeast China.

ABSTRACT: In mid-May, 2019, the fall armyworm (FAW) Spodoptera frugiperda invaded Jiangxi Province, China, and caused extensive damage to corn crops. However, little attention has been given to the life-history traits of the FAW. In the present study, we systematically investigated the life-history traits of the newly invasive FAW on corn leaves at 19, 22, 25, 28, and 31°C under a photoperiod of LD 15:9 hr. The FAW thrived on the corn leaves with short developmental periods, high survival rates of larvae and pupae, very high mating success rates, and high fecundity. The pupal developmental stage was significantly longer in males than females at all temperatures, thus resulting in a protogyny phenomenon. The pupal weight was heaviest after a relatively shorter larval development stage at a higher temperature (25°C); thus, the FAW did not follow the temperature-size rule. Females were smaller than males, indicating sexual size dimorphism. A small proportion of females delayed their pre-oviposition period and began to lay eggs on the 7th to 9th day after adult emergence. There were positive relationships between pupal weight and larval developmental time and between adult weight and fecundity. There was a negative relationship between fecundity and longevity. These findings can help us to predict the population dynamics of the FAW on corn and to develop a suitable and practical management strategy.

SUBMITTER: Huang LL

PROVIDER: S-EPMC8131782 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae) is a recent invasive pest species that has successfully established across sub-Saharan Africa where it continues to disrupt agriculture, particularly smallholder cereal production. Management of FAW in its native range in the Americas has led to the development of resistance to many commercial pesticides before its arrival in Africa. Pesticide use may therefore be ineffective for FAW control in Africa, so new and more sustainable approaches to pest management are required that can help reduce the impact of this exotic pest. Pesticidal plants provide an effective and established approach to pest management in African smallholder farming and recent research has shown that their use can be cost-beneficial and sustainable. In order to optimize the use of botanical extracts for FAW control, we initially screened ten commonly used plant species. In laboratory trials, contact toxicity and feeding bioassays showed differential effects. Some plant species had little to no effect when compared to untreated controls; thus, only the five most promising plant species were selected for more detailed study. In contact toxicity tests, the highest larval mortality was obtained from Nicotiana tabacum (66%) and Lippia javanica (66%). Similarly, in a feeding bioassay L. javanica (62%) and N. tabacum (60%) exhibited high larval mortality at the highest concentration evaluated (10% w/v). Feeding deterrence was evaluated using glass-fibre discs treated with plant extracts, which showed that Cymbopogon citratus (36%) and Azadirachta indica (20%) were the most potent feeding deterrents among the pesticidal plants evaluated. In a screenhouse experiment where living maize plants infested with fall armyworm larvae were treated with plant extracts, N. tabacum and L. javanica were the most potent species at reducing foliar damage compared to the untreated control whilst the synthetic pesticide chlorpyrifos was the most effective in reducing fall armyworm foliar damage. Further field trial evaluation is recommended, particularly involving smallholder maize fields to assess effectiveness across a range of contexts.

Project description:The fall armyworm (FAW) Spodoptera frugiperda (J. E. Smith) is a species native to the Americas. This polyphagous lepidopteran pest was first reported in Nigeria and the Democratic Republic of São Tomé and Principe in 2016, but its presence in eastern Africa has not been confirmed via molecular characterisation. In this study, FAW specimens from western and central Uganda were identified based on the partial mtDNA COI gene sequences, with mtDNA COI haplotypes matching those identified in Nigeria and São Tomé. In this study, we sequence an additional partial mtDNA Cyt b gene and also the partial mtDNA COIII gene in Ugandan FAW samples. We detected identical mitochondrial DNA haplotypes for both the mtDNA Cyt b and COI partial genes, while combining the mtDNA COI/Cyt b haplotypes and mtDNA COIII haplotypes enabled a new maternal lineage in the Ugandan corn-preferred FAW samples to be identified. Our results suggested that the African incursions of S. frugiperda involved at least three maternal lineages. Recent full genome, phylogenetic and microsatellite analyses provided evidence to support S. frugiperda as likely consisted of two sympatric sister species known as the corn-preferred and rice-preferred strains. In our Ugandan FAW populations, we identified the presence of mtDNA haplotypes representative of both sister species. It is not known if both FAW sister species were originally introduced together or separately, and whether they have since spread as a single population. Further analyses of additional specimens originally collected from São Tomé, Nigeria and throughout Africa would be required to clarify this issue. Importantly, our finding showed that the genetic diversity of the African corn-preferred FAW species is higher than previously reported. This potentially contributed to the success of FAW establishment in Africa. Furthermore, with the additional maternal lineages detected, there is likely an increase in paternal lineages, thereby increasing the diversity of the African FAW population. Knowledge of the FAW genetic diversity will be needed to assess the risks of introducing Bt-resistance traits and to understand the FAW incursion pathways into the Old World and its potential onward spread. The agricultural implications of the presence of two evolutionary divergent FAW lineages (the corn and the rice lineage) in the African continent are further considered and discussed.

Project description:Purpose: We aimed to use RNA-Seq and de novo transcriptome assembly to produce transcriptomes and analyze the changes in transcription regulation associated with cold and heat treatment in Spodoptera frugiperda. A detailed differential expression analysis revealed a number of candidate genes that may be associated with FAW cold and heat tolerance. To validate the RNA-seq results, we used qRT-PCR. We hoped to provide a foundation for the adaptive mechanism as well as a rich resource for the discovery and detection of novel genes involved in cold and heat stress responses of Spodoptera frugiperda. Methods: Spodoptera frugiperda was reared at lab condition, and incubated at 2 different temperature( 4 and 40°C) for 16 hours as temperature treatment groups. RNA was extracted using Trizol reagent and Illumina sequencing was performed at Macrogen. Illumina short reads were quality-filtered and Illumina-based de novo transcriptome assembly was performed. Differential Gene Expression Analysis was studied for different tempearture conditions. Results: A total of 211,967 unigenes were collected, at least 14,338 of which were annotated with gene descriptions, gene ontology terms, and metabolic pathways. There were 50 GO functional sub-groups and 21 EggNOG words as a result. DEGs with log2FC≥2 were identified and compared at various temperatures. In comparison to the 25°C treated group, we discovered 199 and 1248 individual DEGs co-regulated at 4 and 40°C, respectively. Comparing transcriptome profiles for differential gene expression revealed a number of DE genes, including cytochrome P450, odorant binding proteins (OBP), and immune system genes previously implicated in cold and high temperature resistance. The enrichment pathways were identified using KEGG analysis, and heatmaps of similar unigenes from both treatment groups (T4 and T40) were plotted. We used qPCR to confirm the RNA-seq data on 10 up- and down-regulated DEGs. Conclusions: In conclusion, we used RNA-Seq technology focused on high-throughput sequencing to compare the transcriptomes of Spodoptera frugiperda under high- and low-temperature stresses. This research was the first to identify a large number of genes that were significantly up-regulated at high and low temperatures. Many genes were discovered through comparative transcriptome analysis, and a significant number of improvements in metabolic pathways were discovered through GO and KEGG enrichment analysis. Our findings will help future molecular research and genomic studies. These newly found genes may be important and necessary to FAW harsh environment tolerance and its behavior for adaptation in new environment as well as quarantine area.

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Effects of temperature on life-history traits of the newly invasive fall armyworm, Spodoptera frugiperda in Southeast China.

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