Abnormal cell wall structure caused by boron nutrient imbalance in orchards could affect psyllid feeding behaviour, resulting in epidemic variation of Asian citrus psyllid.

Abstract

The control of Huanglongbing (HLB), one of the most destructive pests of citrus, relies heavily on the reduction of Asian citrus psyllid (ACP), Diaphorina citri Kuwayama. An in-depth understanding of ACP feeding behaviours among citrus plants is urgent for comprehensive management of orchards. An investigation was conducted in 37 citrus orchards in HLB epidemic areas, sampling shoots in the area with aggregation feeding of ACP (ACPf) and shoots in a neighbouring area without ACP feeding (CK), to study the interaction between leaf chemical composition and ACP psyllid feeding behaviours. Results of FTIR showed a strong absorption peak intensity, mainly representing functional groups originating from cell wall components in the leaf with ACP feeding. As compared with the control, cell wall components, such as alkali-soluble pectin, water-soluble pectin, total soluble pectin, cellulose, and hemicellulose, of the cell wall of ACPf increased by 134.0%, 14.0%, 18.0%, 12.5%, and 20.35%, respectively. These results suggest that cell wall mechanical properties significantly decreased in the term of decreases in pectin performance and cellulose mechanical properties. In addition, there was a remarkably lower boron (B) content in leaves and cell wall components with ACP feeding. Further analysis indicated that leaf B content significantly affected leaf cell wall components. Taken together, we provide evidence to demonstrate that the regional distribution of nutrient imbalance in orchards could affect psyllid feeding behaviour by weakening the cell wall structure, resulting in epidemic variation in ACP. This could help us to understand the management of psyllid infections in orchards with unbalanced nutrition.