The zoophytophagous predator Pilophorus clavatus (Hemiptera: Miridae) induces plant defences in citrus

Abstract

The zoophytophagous mirid Pilophorus clavatus has been recently identified inhabiting citrus orchards in the Mediterranean region, where it feeds on several important citrus pests. In this work, we investigated whether the plant feeding by P. clavatus could induce defensive responses in citrus plants.Here, we show for the first time that the P. clavatus herbivory triggers the accumulation of the stressrelated hormones salicylic acid (SA) and jasmonic acid (JA) in citrus plants. Moreover, the SA and JA pathways enhanced plant defence mechanisms as the expression of genes encoding enzymes from both biosynthetic and responsive pathways were upregulated in P. clavatus punctured plants. We also investigated whether the induced defences could affect the plant host selection of Tetranychus urticae and the predatory mites Phytoseilus persimilis and Neouseiulus californicus. Neither T. urticae nor N. californicus preferred the odour source emitted by intact or P. clavatus-punctured plants in a Y-tube olfactometer assay. However, P. persimilis were significantly attracted to P. clavatus-induced plants.The performance of T. urticae was also compared when mites were released on control or previously P. clavatus-induced plants. Compared to the control, the infestation of T. urticae was significantly reduced up to 70% on those citrus plants previously activated by P. clavatus. Our results show for the first time that feeding of P. clavatus on citrus plants can have a dual beneficial effect due to its known predatory action and, at the same time, by inducing the plant's immune system.

Homobrassinolide Delays Huanglongbing Progression in Newly Planted Citrus Trees

“…The results obtained in the greenhouse experiment can explain the observed decrease in populations of D. citri and the damage caused by the CRM on HBr-treated plants in the field experiment. Previous research demonstrates the connection between JA signaling and herbivore resistance, showing that increased protease activity induced by JA can reduce the incidence of mites and other herbivores on plants [38][39][40][41][42][43]. These proteases interfere with protein digestion in herbivores, limiting their growth and survival in the host plant [44,45].…”

“…The increase in SAMP peptide expression underscores a broad response to stress induced by HBr treatment, suggesting that HBr activates specific defense pathways and enhances the plant's ability to handle stress, potentially improving its overall resilience to various threats. This peptide was described by Huang et al [43] with potent antimicrobial activity that directly targets CLas but also activates innate immunity in citrus trees, offering both therapeutic and preventative capabilities. In our case, the HBr treatment increased its content in the HBr-treated plants.…”