Abstract
Because weevils are the most damaging pests of sweetpotato, the development of cultivars resistant to weevil species is considered the most important aspect in sweetpotato breeding. However, the genes and the underlying molecular mechanisms related to weevil resistance are yet to be elucidated. In this study, we performed an RNA sequencing-based transcriptome analysis using the resistant Kyushu No. 166 (K166) and susceptible Tamayutaka cultivars. The weevil resistance test showed a significant difference between the two cultivars at 30 days after the inoculation, specifically in the weevil growth stage and the suppressed weevil pupation that was only observed in K166. Differential expression and gene ontology analyses revealed that the genes upregulated after inoculation in K166 were related to phosphorylation, metabolic, and cellular processes. Because the weevil resistance was considered to be related to the suppression of larval pupation, we investigated the juvenile hormone (JH)-related genes involved in the inhibition of insect metamorphosis. We found that the expression of some terpenoid-related genes, which are classified as plant-derived JHs, was significantly increased in K166. This is the first study involving a comprehensive gene expression analysis that provides new insights about the genes and mechanisms associated with weevil resistance in sweetpotato.
Highlights
The degree of damage was investigated by counting the number of eggs on the surface of tuberous roots at 3 days after inoculation and the total number of insects at 15 and 30 days after inoculation
At 30 days after inoculation, there was a large difference in the number and growth state of insects between the two cultivars. These results suggest that weevils have no preferred spawning sites between the two cultivars, and that the resistant Kyushu No 166 (K166) suppressed weevil growth, especially during pupation
The Gene ontology (GO) terms related to phosphorylation, metabolic, and cellular processes were not enriched in the upregulated differentially expressed genes (DEGs) of K166 (Figure S1). These results suggest that the upregulation of the genes involved in phosphorylation, metabolic, and cellular processes contributes to weevil resistance in K166
Summary
Sweetpotato (Ipomoea batatas (L.) Lam.) is a member of the Convolvulaceae family that is widely cultivated in the tropical and temperate zones. As a valuable source of carbohydrates, vitamins, fiber, and minerals, sweetpotato is considered one of the most important crops in the world, with an annual production of over 100 million tons globally [1]. The production of sweetpotato varieties with favorable cultivation-related traits, such as high added-value and resistance to diseases, pests, and low soil temperature, was conducted for the expansion of planting areas. Sweetpotato is a typical non-model crop species and a hexaploid (2n = 6x = 90) with a complex mode of inheritance and a large genome (2–3 Gb); breeding and genetic studies have been difficult
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