Abstract
Constitutive resistance of plant can be divided into physical and chemical barriers. Cassava (Manihot esculenta Crantz) is susceptible to mites, especially Tetranychus cinnabarinus. Although significant differences in the resistance to T. cinnabarinus are observed in different cassava cultivars, limited research has been done on the mechanism accounting for the resistance. The aim of this study was to explore the mechanism of resistance to T. cinnabarinus by comparing morphology, secondary metabolites and proteins in different cassava cultivars. The anatomical structure of leaves showed that the cassava cultivar Xinxuan 048 (XX048), which showed a stronger resistance to T. cinnabarinus in both greenhouse testing and three years field evaluation tests (2016–2018), had thicker palisade tissue, spongy tissue, lower epidermis and leaf midrib tissue compared to cultivar Guire 4 (GR4). Greenhouse evaluation demonstrated that originally these cultivars were different, leading to differences in constitutive levels of metabolites. The proteomic analysis of protected leaves in XX048 and GR4 revealed that up-regulated differentially expressed proteins (DEPs) were highly enriched in secondary metabolic pathways, especially in the biosynthesis of flavonoids. This study not only provides a comprehensive data set for overall proteomic changes of leaves in resistant and susceptible cassava, but also sheds light on the morphological characteristics of cassava-mite interaction, secondary metabolite defense responses, and molecular breeding of mite-resistant cassava for effective pest control.
Highlights
Constitutive resistance of plant can be divided into physical and chemical barriers
The down-regulated proteins were significantly enriched in glutathione metabolism, phenylpropanoid biosynthesis, arginine and proline metabolism. These results indicate that the differentially expressed proteins (DEPs) from XX048 and Guire 4 (GR4) were highly associated with the flavonoid biosynthesis
Morphological structure indicated that lower epidermis and palisade tissue may be the key physical barriers leading to XX048 being more resistant to T. cinnabarinus than GR4
Summary
Constitutive resistance of plant can be divided into physical and chemical barriers. Cassava (Manihot esculenta Crantz) is susceptible to mites, especially Tetranychus cinnabarinus. The aim of this study was to explore the mechanism of resistance to T. cinnabarinus by comparing morphology, secondary metabolites and proteins in different cassava cultivars. Cassava (Manihot esculenta Crantz) is the most important energy-producing root crop in the tropics It belongs to the Euphorbiaceae family and has high carbohydrate production potential and adaptability to diverse environments. Tetranychus cinnabarinus has a short life cycle, rapid development, high fecundity, wide host range and became an important pest. It mainly resides in the underside of cassava leaves and sucks nutrient ts from the leaves, causing them to turn yellow prematurely. Mainly toxins and secondary metabolites, reduce palatability and affect pest’s growth, development and digestion. Other studies showed that the content of secondary metabolites increased remarkably in plant leaves infested by mites[13,14,15,16]
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