Resistant cassava cultivars inhibit the papaya mealybug Paracoccus marginatus population based on their interaction: from physiological and biochemical perspectives

Abstract

Dangerous Paracoccus marginatus papaya mealybugs cause considerable threats and challenges to cassava production and processing. The deployment of resistant cultivars offers effective, economical and eco-friendly management strategies for pest management. We utilized P. marginatus mortality, development and reproduction to evaluate the resistance of fteen cassava cultivars and conducted physiological and biochemical analyses when P. marginatus was fed on two resistant cultivars (Myanmar, C1115) and three susceptible cultivars (BRA900, Bread, SC205). Signi cantly lower digestive (amylase, sucrase, lipase), detoxi cation (glutathione-S-transferase and carboxylesterase) and antioxidant, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and polyphenol oxidase (PPO), enzyme activities were observed in P. marginatus feeding on resistant cultivars compared to susceptible cultivars. For resistant cultivars, a signi cant reduction was found in nutritional components containing free amino acids, nitrogen, soluble sugars and the secondary metabolite malondialdehyde. Additionally, signi cantly higher enzymatic activity (SOD, CAT, POD and PPO) levels and secondary metabolite quantities (total phenol and tannins) were found in resistant cultivars induced by P. marginatus compared with susceptible ones. Additionally, RT-qPCR tests showed that the transcripts of ten genes involved in nutrition, secondary metabolites and antioxidant activities were consistent with their physiology and biochemistry changes. Thus, resistant cultivars prevented P. marginatus populations from suffering lower P. marginatus damage by elevating secondary metabolite contents and antioxidant activities, reducing nutrition levels and decreasing enzymatic activities. This study will be bene cial in determining the important indexes for developing standard regulations to evaluate P. marginatus-resistant cassavas, helping the development of effective strategies for pest management. Key MessageWe identi ed and characterized the resistance of fteen cassava cultivars to P. marginatus.The activities of digestive, detoxi cation and antioxidant enzymes of P. marginatus were signi cantly inhibited after they were fed on resistant cultivars.Lower contents of nutritional components and malondialdehyde, and higher levels of toxic secondary metabolites together with antioxidant enzyme activities were observed in resistant cassava cultivars infested with P. marginatus.The resistant cultivars prevented P. marginatus populations from suffering lower P. marginatus damage by elevating secondary metabolite contents and antioxidant activities, reducing nutrition levels and decreasing enzymatic activities.

Not just candy: A herbivore‐induced defence‐related plant protein in honeydew enhances natural enemy fitness

“…Although the defensive mechanisms activated in plants to defend against mealybugs are poorly known, a previous study showed that several cassava cultivars increased the activity of antioxidant enzymes when they were infested by the papaya mealybug Paracoccus marginatus (Chen et al, 2022). These enzymes protect the cells from oxidative stress (Alscher et al, 2002;Wang et al, 2018) and play a significant role in controlling the level of ROS from all organisms that live in the presence of oxygen.…”

“…Although honeydew reportedly contains a high diversity of proteins (Sabri et al, 2013;Urbaneja-Bernat et al, 2023;Zhu et al, 2020), to our knowledge, the effects of herbivore-induced plant proteins in honeydew on the fitness of natural enemies remain unknown. Some of these plant proteins could be antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), glutathione Stransferase (GST) and polyphenol oxidase (PPO), among others, which are upregulated in plants when attacked by phloem feeders (Chen et al, 2022). If such proteins would contribute to enhanced fitness of natural enemies feeding on honeydew, this could be viewed as an indirect plant defence mechanism mediated by herbivore-induced plant proteins excreted in honeydew, although herbivores would be expected to be under selection to minimize excretion of such proteins in the honeydew.…”

Identification of cassava germplasms resistant to two-spotted spider mite in China: From greenhouse large-scale screening to field validation

“…Similar results mentioned above can also be found in several pest–crop interaction studies, i . e ., cotton genotype and silverleaf whitefly ( Miyazaki et al., 2013 ), cassava varieties and papaya mealybug ( Paracoccus marginatus ) ( Chen et al., 2022b ) or T. cinnabarinus ( Lu et al., 2017 ), rubber tree germplasms, and Eotetranychus sexmaculatus ( Lu et al., 2016 ).…”