Analysis of Citrus Tristeza Virus Incidences within Asian Citrus Psyllid (Diaphorina citri) Populations in Florida via High-Throughput Sequencing

Abstract

The destructive citrus disease, Huanglongbing (HLB) or citrus greening, continues to devastate Florida’s citrus industry. A hemipteran insect, the Asian citrus psyllid (ACP), disperses Candidatus Liberibacter asiaticus, one of the putative bacterial pathogens of HLB. This study builds upon ongoing research utilizing high-throughput sequencing to analyze the virome of ACP populations collected from citrus groves throughout Florida. Following the widespread detection of sequences aligning to the genome of citrus tristeza virus (CTV) across consecutive years in the Florida ACP virome, we continued to detect a pervasive amount of CTV in Florida ACPs during subsequent years. Simultaneously, we also detected mixed infections of CTV strains in pooled ACPs from different Florida regions. Predating the HLB epidemic, CTV has been present in Florida for many years and our results confirm its widespread and diverse persistence in Florida citrus groves through a unique lens, the ACP. CTV presence in the ACP likely results from feeding on CTV-infected citrus trees in Florida citrus groves, which may help to understand an overlapping presence of CTV and HLB, both endemic citrus pathosystems in the state, and their role in future integrated pest management strategies.

Survey and detection for citrus tristeza virus in Florida groves with an unconventional tool: The Asian citrus psyllid

“…Using ACPs as a future bioindicator for CTV would be less labor intensive (especially in Florida weather conditions). As growers combat challenges associated with HLB, this and previous recent studies (Harper and Cowell, 2016;Britt et al, 2020;Britt et al, 2022) must remind the citrus industry of the persistence of this citrus virus throughout Florida and the threat it may pose if overlooked during citrus HLB mitigation efforts.…”

“…Curiously, CTV was detected in approximately 28% of single field ACPs ( Britt, 2021 ). The citrus virus is hypothesized to be consumed by ACPs as a part of its phloem diet, likely fragmented in the gut of the insect and awaiting further degradation with other dietary contents ( Britt et al., 2022 ). The ACP is similar to the aphid in both size and ecology, ranging between 3-4 mm and laying up to 500-800 eggs per lifetime ( Mead, 1977 ; Hall et al., 2013 ).…”

“…Cases of insecticide resistance of the ACP ( Tiwari et al., 2011 ; Kanga et al., 2016 ) emphasize a need for more diverse management options in Florida. While studying insect-specific viruses (ISVs) in Florida ACP populations to address this, we unearthed a consistent occurrence of CTV sequences in the ACP ( Britt et al., 2020 ; Britt et al., 2022 ). The incomplete genomic coverage of CTV detected in the ACP suggested that the citrus virus was likely consumed as a part of the diet when feeding on CTV-infected citrus ( Britt et al., 2022 ).…”

“…While studying insect-specific viruses (ISVs) in Florida ACP populations to address this, we unearthed a consistent occurrence of CTV sequences in the ACP ( Britt et al., 2020 ; Britt et al., 2022 ). The incomplete genomic coverage of CTV detected in the ACP suggested that the citrus virus was likely consumed as a part of the diet when feeding on CTV-infected citrus ( Britt et al., 2022 ). Phloem contents (and any microbes present) may accumulate in the gut of the insect.…”

Current Status of Citrus Tristeza Virus in Major Citrus Growing Areas of Sargodha, Pakistan

“…In Florida, declined orchards were sampled randomly and subjected to high throughput sequencing (HTS) for the detection of exact cause and CTV was found (Britt et al, 2022). CTV disease was more severe in Sargodha than Bhalwal and Kot Momin.…”