TY - JOUR

T1 - Dynamics of Bacterial Root Endophytes of Malus domestica Plants Grown in Field Soils Affected by Apple Replant Disease

AU - Mahnkopp-Dirks, Felix

AU - Radl, Viviane

AU - Kublik, Susanne

AU - Gschwendtner, Silvia

AU - Schloter, Michael

AU - Winkelmann, Traud

N1 - Funding Information: The German Federal Ministry of Research and Education funded the project BonaRes ORDIAmur (FKZ 031B0512) within the framework of the BonaRes program.

PY - 2022/3/25

Y1 - 2022/3/25

N2 - Apple replant disease (ARD) is a worldwide problem for tree nurseries and orchards leading to reduced plant growth and fruit quality. The etiology of this complex phenomenon is poorly understood, but shifts of the bulk soil and rhizosphere microbiome seem to play an important role. Since roots are colonized by microbes from the rhizosphere, studies of the endophytic microbiome in relation to ARD are meaningful. In this study, culture-independent and culture-dependent approaches were used in order to unravel the endophytic root microbiome of apple plants 3, 7, and 12 months after planting in ARD-affected soil and ARD-unaffected control soil at two different field sites. Next to a high diversity of Pseudomonas in roots from all soils, molecular barcoding approaches revealed an increase in relative abundance of endophytic Actinobacteria over time in plants grown in ARD and control plots. Furthermore, several amplicon sequence variants (ASVs) linked to Streptomyces, which had been shown in a previous greenhouse ARD biotest to be negatively correlated to shoot length and fresh mass, were also detected in roots from both field sites. Especially in roots of apple plants from control soil, these Streptomyces ASVs increased in their relative abundance over time. The isolation of 150 bacterial strains in the culture-dependent approach revealed a high diversity of members of the genus Pseudomonas, confirming the data of the molecular barcoding approach. However, only partial overlaps were found between the two approaches, underlining the importance of combining these methods in order to better understand this complex disease and develop possible countermeasures. Overall, this study suggests a key role of Streptomyces in the etiology of ARD in the field.

AB - Apple replant disease (ARD) is a worldwide problem for tree nurseries and orchards leading to reduced plant growth and fruit quality. The etiology of this complex phenomenon is poorly understood, but shifts of the bulk soil and rhizosphere microbiome seem to play an important role. Since roots are colonized by microbes from the rhizosphere, studies of the endophytic microbiome in relation to ARD are meaningful. In this study, culture-independent and culture-dependent approaches were used in order to unravel the endophytic root microbiome of apple plants 3, 7, and 12 months after planting in ARD-affected soil and ARD-unaffected control soil at two different field sites. Next to a high diversity of Pseudomonas in roots from all soils, molecular barcoding approaches revealed an increase in relative abundance of endophytic Actinobacteria over time in plants grown in ARD and control plots. Furthermore, several amplicon sequence variants (ASVs) linked to Streptomyces, which had been shown in a previous greenhouse ARD biotest to be negatively correlated to shoot length and fresh mass, were also detected in roots from both field sites. Especially in roots of apple plants from control soil, these Streptomyces ASVs increased in their relative abundance over time. The isolation of 150 bacterial strains in the culture-dependent approach revealed a high diversity of members of the genus Pseudomonas, confirming the data of the molecular barcoding approach. However, only partial overlaps were found between the two approaches, underlining the importance of combining these methods in order to better understand this complex disease and develop possible countermeasures. Overall, this study suggests a key role of Streptomyces in the etiology of ARD in the field.

KW - apple replant disease (ARD)

KW - endophyte

KW - Malus domestica

KW - microbiome

KW - Pseudomonas

KW - Streptomyces

UR - http://www.scopus.com/inward/record.url?scp=85128427099&partnerID=8YFLogxK

U2 - 10.3389/fmicb.2022.841558

DO - 10.3389/fmicb.2022.841558

M3 - Article

AN - SCOPUS:85128427099

VL - 13

JO - Frontiers in microbiology

JF - Frontiers in microbiology

SN - 1664-302X

M1 - 841558

ER -