Boron deficiency mediates plant–insect (Diaphorima citri) interaction by disturbing leaf volatile organic compounds and cell wall functions

Nutritional enhancement has been reported to effectively relieve infected symptoms of Huanglongbing, one of the most destructive diseases of citrus. However, few studies focused on the role of plant nutrition in citrus plant-vector (Asian citrus psyllid; Diaphorina citri Kuwayama) interactions, which is regarded as an important part to develop an effective management strategy.In the present study, a hydroponic culture was carried out to evaluate the effects of boron deficiency on psyllid feeding process to decode the molecular/biochemical basis of host-psyllid interaction.Boron deficiency was observed to play a major role in accelerating the release of volatile organic compounds, especially methyl salicylate, affecting the shikimic acid pathway through an elevated synthesis of shikimic acid, l-phenylalanine, 3-phenylpyruvic acid and salicylic acid. These changes made citrus leaf more attractive to psyllid adults. Meanwhile, boron deficiency evidently decreased the boron concentration of leaf cell wall fractions, thereby, weakened the structural stability by affecting pectin and cellulose formations. A significant decrease of cell wall mechanical strength was observed in boron-deficiency leaf, which could be the critical reasons to reduce piercing and to increase phloem ingestion during psyllid feeding.Our study demonstrated that boron deficiency facilitated the feeding behavior of psyllid adults through elevated release of methyl salicylate, coupled with weakened mechanical properties of cell wall.