Expression of anthocyanins in a citrus genotype reduces host preference and performance by a phytopathogen vector

Citrus greening, or Huanglongbing (HLB), one of the most devastating citrus diseases worldwide, is caused by the phloem-limited bacterium 'Candidatus Liberibacter asiaticus' and transmitted by the Asian citrus psyllid (Diaphorina citri). Current disease control strategies rely primarily on insecticide applications to suppress vector populations, leading to environmental concerns and limited efficacy. Anthocyanins are plant secondary metabolites known for their protective roles against biotic and abiotic stresses. This study explores the impact of anthocyanin overexpression on the host preference and performance of D. citri by introducing the transcription factor VvmybA1, cloned from red grape, into Mexican lime (Citrus aurantifolia).

Transgenic VvmybA1-expressing citrus trees developed purple leaves because of anthocyanin accumulation, particularly in young shoots. Comparative analysis of volatile organic compounds revealed minimal differences between wild-type and transgenic trees, suggesting that olfactory cues play a limited role in psyllid preference. Behavioral assays showed that D. citri preferred to land and settle on wild-type trees when visual cues were available. However, in the absence of light, psyllids exhibited no preference between wild-type and transgenic trees. Survival and lifespan of D. citri were significantly reduced on VvmybA1-expressing plants compared with wild-type trees. In addition, psyllid mortality increased when fed on phloem sap extracted from transgenic plants, suggesting a direct toxic effect. A similar increase in mortality was observed in psyllids fed synthetic cyanidin 3-malonyl glucoside, a major anthocyanin compound found in the transgenic citrus.

Our findings indicate that anthocyanin overexpression in citrus reduces D. citri host preference and negatively impacts psyllid survival. These effects appear to be primarily mediated through visual deterrence and direct toxicity rather than olfactory cues. The genetic modification of citrus to overproduce anthocyanins presents a promising strategy for HLB management by reducing vector populations and limiting pathogen transmission. Further research is needed to assess long-term stability, agronomic feasibility, and integration with existing pest management strategies. © 2025 Society of Chemical Industry.