TY - JOUR

T1 - Impaired defense reactions in apple replant disease-Affected roots of Malus domestica 'M26'

AU - Weiß, Stefan

AU - Liu, Benye

AU - Reckwell, Dennis

AU - Beerhues, Ludger

AU - Winkelmann, Traud

N1 - Funding Information: This work was funded by the ‘Deutsche Forschungsgemeinschaft’ (DFG, Grant number: GRK 1798/1) and it was part of the GRK1798 ‘Signaling at the Plant–Soil Interface’. Publisher Copyright: © 2017 The Author. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.

PY - 2017/12

Y1 - 2017/12

N2 - A soil-And site-dependent complex of diverse microbial populations causes apple replant disease (ARD), which leads to economic losses for tree nurseries and apple producers due to reduced plant growth and diminished fruit yields. Soil fumigation has been widely used to mitigate ARD, but the application of these chemicals is restricted in the European Union. Hence, other counteractions have to be developed. Genomics-based breeding may be used to select ARD-Tolerant genotypes; however, molecular responses of ARD are not well understood. Recent studies revealed that biotic stress-Associated genes involved in typical defense reactions are activated but do not result in an adequate response to ARD. The objective of this study was to analyze selected responsive genes in a time-course experiment to test for expression kinetics. Cultivating the ARD-susceptible apple rootstock 'M26' on ARD-Affected soil resulted in significantly reduced growth as early as 7 days after planting. Genes involved in phytoalexin biosynthesis were upregulated in ARD samples as early as 3 days after planting and reached up to 26-fold changes at Day 10, which resulted in high amounts of 3-hydroxy-5-methoxybiphenyl, aucuparin, noraucuparin, 2-hydroxy-4-methoxydibenzofuran, 2′-hydroxyaucuparin and noreriobofuran. For the first time, these phytoalexins were detected, identified and quantified in apple roots. The lack of a sufficient defense response may be due to impaired sequestration and/or exudation of the potentially cytotoxic phytoalexins and perturbed formation of reactive oxygen species, leading to root damage in ARD soils. The findings provide a basis for comparative studies of the defense processes in more ARD-Tolerant rootstocks.

AB - A soil-And site-dependent complex of diverse microbial populations causes apple replant disease (ARD), which leads to economic losses for tree nurseries and apple producers due to reduced plant growth and diminished fruit yields. Soil fumigation has been widely used to mitigate ARD, but the application of these chemicals is restricted in the European Union. Hence, other counteractions have to be developed. Genomics-based breeding may be used to select ARD-Tolerant genotypes; however, molecular responses of ARD are not well understood. Recent studies revealed that biotic stress-Associated genes involved in typical defense reactions are activated but do not result in an adequate response to ARD. The objective of this study was to analyze selected responsive genes in a time-course experiment to test for expression kinetics. Cultivating the ARD-susceptible apple rootstock 'M26' on ARD-Affected soil resulted in significantly reduced growth as early as 7 days after planting. Genes involved in phytoalexin biosynthesis were upregulated in ARD samples as early as 3 days after planting and reached up to 26-fold changes at Day 10, which resulted in high amounts of 3-hydroxy-5-methoxybiphenyl, aucuparin, noraucuparin, 2-hydroxy-4-methoxydibenzofuran, 2′-hydroxyaucuparin and noreriobofuran. For the first time, these phytoalexins were detected, identified and quantified in apple roots. The lack of a sufficient defense response may be due to impaired sequestration and/or exudation of the potentially cytotoxic phytoalexins and perturbed formation of reactive oxygen species, leading to root damage in ARD soils. The findings provide a basis for comparative studies of the defense processes in more ARD-Tolerant rootstocks.

KW - Apple replant disease

KW - Biotic stress response

KW - Growth depression

KW - Malus domestica

KW - Phytoalexins

KW - Plant defense

KW - Quantitative real-Time PCR

KW - Time-dependent gene expression.

UR - http://www.scopus.com/inward/record.url?scp=85044749608&partnerID=8YFLogxK

U2 - 10.1093/treephys/tpx108

DO - 10.1093/treephys/tpx108

M3 - Article

C2 - 29036594

AN - SCOPUS:85044749608

VL - 37

SP - 1672

EP - 1685

JO - Tree Physiology

JF - Tree Physiology

SN - 0829-318X

IS - 12

ER -