TY - JOUR

T1 - Diagnosis of apple replant disease (ARD)

T2 - Microscopic evidence of early symptoms in fine roots of different apple rootstock genotypes

AU - Grunewaldt-Stöcker, Gisela

AU - Mahnkopp, Felix

AU - Popp, C.

AU - Maiß, Edgar

AU - Winkelmann, Traud

N1 - Funding Information: The authors are grateful to Mrs. Ewa Schneider and to Ms. Jenny Rebentisch for technical assistance and to Dr. W. Jarausch, RLP AgroScience GmbH, D-67435 Neustadt, for providing clone material of rootstock B63. Annmarie-Deetja Rohr made fresh biomass data of B63 available. Simon Margaux and Stefan Pätzold, INRES-Soil Science, University of Bonn, kindly determined the soil types of the reference sites. The authors owe many thanks to Dr. Christine Dieckhoff who made a significant contribution to the improvement of the English language in this manuscript. The German Federal Ministry of Research and Education funded this work in the project ORDIAmur (FKZ 031B0025A ) within the framework of the BonaRes program.

PY - 2019/1/3

Y1 - 2019/1/3

N2 - Apple replant disease (ARD) is a problem of high economic relevance in tree nurseries and apple orchards worldwide. After replanting, plants show growth reduction, reduced yield, and damaged root systems. The disease's decade-long persistence in soil exacerbates the situation where alternative cultivation areas and ecologically safe soil decontamination measures are lacking. The etiology is still unclear and there are neither clear causal factors nor reliable parameters (except growth data from plant bioassays) for the early detection of the disease in plants or from samples from potentially affected soils. We report on greenhouse pot trials with the susceptible rootstock Malus domestica ‘M26’ grown in soils of ARD-affected as well as grass plots from three different field sites. Both gamma-irradiated ARD soils and grass soils served as control soils. The aim was to develop a diagnostic tool for the early detection of ARD. In fine roots of first to third order, we assessed the root structure, the root hair density, the cellular damages in the outer layers, and the cell vitality. After only two weeks in ARD soil, ‘M26’ reacted with cell necroses and blackening in a characteristic pattern, impaired root hair development, and low cell vitality. These symptoms were confirmed in Malus domestica ‘Bittenfelder’ and Malus-hybrid B63. Root systems grown in gamma-irradiated soils were almost symptom-free while those from grass soils showed different and only minor alterations. Thus, we suggest selected fine root symptoms to be used for an early diagnosis of ARD, e.g. in plant breeding selections and soil surveys.

AB - Apple replant disease (ARD) is a problem of high economic relevance in tree nurseries and apple orchards worldwide. After replanting, plants show growth reduction, reduced yield, and damaged root systems. The disease's decade-long persistence in soil exacerbates the situation where alternative cultivation areas and ecologically safe soil decontamination measures are lacking. The etiology is still unclear and there are neither clear causal factors nor reliable parameters (except growth data from plant bioassays) for the early detection of the disease in plants or from samples from potentially affected soils. We report on greenhouse pot trials with the susceptible rootstock Malus domestica ‘M26’ grown in soils of ARD-affected as well as grass plots from three different field sites. Both gamma-irradiated ARD soils and grass soils served as control soils. The aim was to develop a diagnostic tool for the early detection of ARD. In fine roots of first to third order, we assessed the root structure, the root hair density, the cellular damages in the outer layers, and the cell vitality. After only two weeks in ARD soil, ‘M26’ reacted with cell necroses and blackening in a characteristic pattern, impaired root hair development, and low cell vitality. These symptoms were confirmed in Malus domestica ‘Bittenfelder’ and Malus-hybrid B63. Root systems grown in gamma-irradiated soils were almost symptom-free while those from grass soils showed different and only minor alterations. Thus, we suggest selected fine root symptoms to be used for an early diagnosis of ARD, e.g. in plant breeding selections and soil surveys.

KW - Bioassay

KW - Blackening

KW - Cell damage

KW - Cell vitality

KW - Malus domestica

KW - Root hair status

UR - http://www.scopus.com/inward/record.url?scp=85053419446&partnerID=8YFLogxK

U2 - 10.1016/j.scienta.2018.09.014

DO - 10.1016/j.scienta.2018.09.014

M3 - Article

AN - SCOPUS:85053419446

VL - 243

SP - 583

EP - 594

JO - Scientia horticulturae

JF - Scientia horticulturae

SN - 0304-4238

ER -