Abstract
Simple SummarySmall brown planthopper (SBPH, Laodelphax striatellus) is a serious rice sap-sucking insect pest in East Asia, especially in China. Furthermore, it is also a potential vector of rice viral diseases, such as rice stripe virus and rice black streaked dwarf virus, which cause significant yield losses. Here, a novel antimicrobial pesticide, decoyinine was applied as a seed treatment in rice in order to study life table parameters of SBPH and biochemical and physiological indices (having a role in induced systemic resistance in plants) of rice crop in response to SBPH feeding. Decoyinine significantly reduced fecundity in SBPH and also altered chemical and physiological indices of rice in response to SBPH. We conclude that the use of decoyinine in rice will contribute to integrated pest management (IPM) and may potentially provide a new idea for green technology. Induced resistance against SBPH via microbial pesticides is considered as an eco-friendly and promising management approach. In this study, the induced resistance against SBPH in rice seedling by a new potential microbial pesticide, decoyinine (DCY), a secondary metabolite produced by Streptomyces hygroscopicus, was evaluated to investigate the effects of DCY on SBPH’s biological and population parameters along with defense-related physiological and biochemical indices in rice against SBPH feeding. We found that DCY has potential to improve rice resistance and significantly reduced the fecundity of SBPH. Laboratory results revealed that DCY treated rice significantly changed SBPH’s fecundity and population life table parameters. The concentrations of hydrogen peroxide (H2O2), soluble sugars and malondialdehyde (MDA) were significantly lower in DCY treated rice plants against SBPH infestation at 24, 48 and 96 hours post infestation (hpi), respectively. The concentrations of antioxidant enzymes, catalase (CAT) was significantly higher at 72 hpi, while super oxidase dismutase (SOD) and peroxidase (POD) concentrations were recorded higher at 96 hpi. The concentrations of synthases enzymes, phenyl alanine ammonia-lyase (PAL) was higher at 48 hpi, whereas polyphenol oxidase (PPO) concentration was maximum at 72 hpi against SBPH infestation. The results imply that DCY has unique properties to enhance rice resistance against SBPH by stimulating plant defensive responses. Microbial pesticides may be developed as an alternative to chemical pest control.
Highlights
Oryza sativa L. is a major staple cereal and serves as a host for several pests that can greatly decrease rice yields [1,2]
small brown planthopper (SBPH) survivals were investigated in both the control and DCY treated rice treatments (Table 1), indicating that the number of eggs laid by SBPH fed on DCY treated rice plants was significantly lower at rice seedling stage
DCY boosted the activities of CAT and super oxidase dismutase (SOD) (Figure 3a,b), which is parallel with the findings of HarunOr-Rashid [16]; he observed that at 48 hpi against BPH, the activities of POD, phenyl alanine ammonia-lyase (PAL) and polyphenol oxidase (PPO) were considerably greater in bacteria YC7010 treated rice than in untreated control plants
Summary
Oryza sativa L. is a major staple cereal and serves as a host for several pests that can greatly decrease rice yields [1,2]. Greater photosynthesis efficiency enables beneficial microbes to convert more light energy, which allows the generation of induced systemic resistance (ISR) against phloem feeding insects, which can compensate for the losses [15] These microbes can improve plant health in other ways, which include the production of secondary metabolites, enzymes, volatile organic compounds and growth hormones. A 50 mg L−1 DCY solution was applied to the Nanning rice variety “Baixiang 139,” which improved a number of physiological indices such as germination potential, germination rate, root length, bud length, leaf age, seedling base width, plant height, root number, fresh weight and dry matter accumulation [46] Though it can affect both auxin and cytokinin regulatory pathways at the same time, it is vulnerable to mutants of auxin and cytokinin targets, suggesting that there could be new approaches to encourage growth and disease resistance [45].
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