Trunk injection of oxytetracycline improves plant performance and alters the active bark and rhizosphere microbiomes in huanglongbing-affected citrus trees

Trunk injection of antibiotics has re-emerged as a strategy to mitigate citrus huanglongbing (HLB), a devastating disease associated with the bacterium Candidatus Liberibacter asiaticus (CLas). Despite commercial adoption in Florida, no studies have examined how oxytetracycline (OTC) injection may impact active plant-associated microbial communities. We investigated the impact of OTC trunk injection on tree physiological parameters, HLB control, and the prokaryotic and eukaryotic microbiome of the active inner bark and rhizosphere in a commercial citrus orchard under HLB-endemic conditions. OTC injection significantly increased juice quality and fruit weight. OTC was detected in leaves, bark, and roots but concentrations varied with time and across plant tissues. OTC injection reduced the abundance and diversity of the active prokaryotic microbiome in the bark and rhizosphere during the first three months post-injection. Specific prokaryotic taxa were responsive to OTC injection and their relative abundances related to increased plant performance. This study shows that OTC injection can promote the recovery of tree physiological functions impacted by HLB while also maximizing the benefits from certain prokaryotes of the bark and rhizosphere microbiomes.