Management‐induced shifts in rhizosphere bacterial communities contribute to the control of pathogen causing citrus greening disease

Abstract

Introduction Citrus greening (aka Huanglongbing, HLB) caused primarily by the bacterial pathogen Candidatus Liberibacter asiaticus (CLas) has devastating effects on the global citrus industry. Agricultural management‐induced changes in microbial communities are hypothesised to contribute toward HLB resistance by reducing pathogen titre and increasing root and soil health. However, we have a limited understanding of the impacts of management practices on the soil microbiome, making the extent of HLB management uncertain. Material and Methods Here we investigated the effect of agricultural management practices on reducing CLas titer via changes in rhizosphere‐associated bacterial communities. Rhizosphere and root samples were collected from two sites in Florida where different management practices (e.g., metalized reflective mulch ground covers, compost application and microbial inoculations) are currently being implemented to prevent HLB. Management‐induced changes in the rhizosphere bacterial community were assessed using amplicon sequencing. qPCR assays were used to quantify the titer of the pathogen CLas in roots. In addition, we measured soil properties and the activities of microbial enzymes involved in soil nutrient cycling. Results Our results indicated that certain management practices lead to shifts in the community structure of rhizosphere bacterial communities that negatively interact with the HLB pathogen. Management practices improved soil quality and reduced CLas titer. Additionally, we found that Actinobacteria were frequently enriched in the successful treatment sites, suggesting that Actinobacteria taxa could be indicators for HLB suppression properties in the soil. Conclusion Our results suggest that microbiome manipulation, either through changes in the management practices or microbial amendment, can increase the suppressive potential of soils, resulting in the reduction in CLas titer and potentially leading to HLB suppression in citrus groves.

Integrated microbiome and metabolomics analysis reveal a closer relationship between soil metabolites and bacterial community than fungal community in pecan plantations

“…Tausonia was reported as a key species in the rhizosphere fungal network of Scutellaria tsinyunensis and was usually found as a soil‐borne pathogen from woody plants (Zuo et al, 2022). Additionally, Gaiellaceae (Bazany et al, 2022; Poudel et al, 2016) and Tuber (Flores et al, 2002) were demonstrated to defend against pathogenic microorganisms and were closely related to plant health. Therefore, phenylacetaldehyde in the rhizosphere soil of pecan may be produced by Gaiellaceae or Tuber against the pathogenic fungus Tausonia .…”

Host selection has a stronger impact on leaf microbiome assembly compared to land‐management practices

“…For example, land management practices such as irrigation, tillage and use of fertilizer and pesticide can influence plant growth and survival. These management practices are also known to affect soil and rhizosphere microbiome assembly (Bazany et al, 2022; Eisenhauer et al, 2022; Hartman et al, 2018; Kavamura et al, 2019; Sengupta et al, 2020; Toju et al, 2018). For example, nitrogen fertilizers were reported to reduce bacterial diversity (Yang, Zhang, et al, 2020; Zhang et al, 2018).…”

A host‐derived chimeric peptide protects citrus against Huanglongbing without threatening the native microbial community of the phyllosphere

“…Producing resistant cultivars through conventional breeding is difficult due to the lack of commercially available resistant rootstock/scion combinations (Dutt et al, 2015). Other strategies used, or in development, for HLB treatment and prevention include: (i) blocking transmission by ACP using insecticides (Boina et al, 2010; Rehberg et al, 2022; Sétamou et al, 2010; Srinivasan et al, 2008) and RNA interference targeted to ACP genes involved in transmission (Britt et al, 2020); (ii) reducing the level of C Las and maintaining plant growth by thermal, nutritional, and chemical therapy (Hoffman et al, 2013; Li et al, 2016, 2019); (iii) killing C Las by antibiotics (Hu & Wang, 2016; Zhang et al, 2011); (iv) improving soil biodiversity and harnessing beneficial bacteria (Bazany et al, 2022; Stokes et al, 2023; Zhang et al, 2017); and (v) enhancement of the HLB tolerance by transgenic technology (Dutt et al, 2015; Hao et al, 2016; Stover et al, 2013). These disease management strategies have achieved varying degrees of success (Li et al, 2020).…”