Citrus Root and Rhizosphere Dynamics in the Age of HLB

Abstract Huanglongbing (HLB; also known as citrus greening) is severely reducing global citrus production. HLB is a bacterial disorder caused by the vector‐transmitted pathogen Candidatus Liberibacter asiaticus ( C Las), and, as of today, it is one of the most destructive diseases facing the citrus industry of Florida and beyond. HLB in Florida was first detected in 2005 and is now widely distributed throughout the commercial citrus‐growing regions in the state. Preliminary studies have found that root systems of HLB‐tolerant rootstocks show less damage in response to C Las infection, whereas marked injury is evident soon after infection of susceptible material. An HLB‐damaged root system has poor nutrient uptake capacity, which leads to nutrient deficiencies and impairs tree performance. As of today, plant mechanisms of HLB‐tolerance are still unclear and there is no cure for HLB and root structure–function relationships remain an understudied component of the responses and may play a key role in tolerance. This review summarised all the recent studies on soil and root health of HLB‐affected citrus. Better understanding of how roots and soils are affected by HLB can potentially lead to improved management practices.