TY - JOUR

T1 - Formation and exudation of biphenyl and dibenzofuran phytoalexins by roots of the apple rootstock M26 grown in apple replant disease soil

AU - Busnena, Belnaser A.

AU - Beuerle, Till

AU - Mahnkopp-Dirks, Felix

AU - Winkelmann, Traud

AU - Beerhues, Ludger

AU - Liu, Benye

N1 - Funding Information: This study was supported by the German Research Foundation (DFG, BE 1174/19-1) and the Federal Ministry of Research and Education (BMBF) via the project BonaRes-ORDIAmur (031B0512D and 031B0512A). Belnaser Busnena thanks the German Academic Exchange Service (DAAD) for providing him with a scholarship. The authors acknowledge the help of the technicians Ewa Schneider, Friederike Schröder, Bärbel Ernst and Johanna Buse for the in vitro multiplication of apple plants. They also thank Dr. Stefan Weiβ and Dr. Annmarie-Deetia Rohr for setting up experiments and harvesting materials.

PY - 2021/12

Y1 - 2021/12

N2 - Apple replant disease (ARD) is a severe soil-borne disease frequently observed in apple tree nurseries and orchards worldwide. One of the responses of apple trees to ARD is the formation of biphenyl and dibenzofuran phytoalexins in their roots. However, there is no information on whether or not these phytoalexins are exuded into the soil. To answer this open question, a model system was established using the ARD-sensitive apple rootstock M26 (Malus × domestica Borkh. Rosaceae) and GC-MS analysis in combination with an in-house GC-MS database including retention indices. We have detected a total of 35 phytoalexins, i.e. 10 biphenyls and 25 dibenzofurans in root samples, thereby adding eight compounds to the previously reported 27 phytoalexins of Malinae species. When in vitro cultured M26 plantlets were treated with yeast extract, all the 35 phytoalexins were formed in the roots and 85.2% of the total phytoalexin amount was exuded into the culture medium. In roots of M26 plants grown in ARD soil in pot, 26 phytoalexins were detected and their exudation was demonstrated using two independent approaches of collecting root exudates. In a modified dipping experiment and a soil-hydroponic hybrid setup, the exudation rate was 39.5% and 20.6%, respectively. The exudation rates for individual phytoalexins differed, indicating controlled exudation processes. The exuded phytoalexins may play an important role in shaping the soil microbiome, which appears to greatly influence the development and severity of ARD.

AB - Apple replant disease (ARD) is a severe soil-borne disease frequently observed in apple tree nurseries and orchards worldwide. One of the responses of apple trees to ARD is the formation of biphenyl and dibenzofuran phytoalexins in their roots. However, there is no information on whether or not these phytoalexins are exuded into the soil. To answer this open question, a model system was established using the ARD-sensitive apple rootstock M26 (Malus × domestica Borkh. Rosaceae) and GC-MS analysis in combination with an in-house GC-MS database including retention indices. We have detected a total of 35 phytoalexins, i.e. 10 biphenyls and 25 dibenzofurans in root samples, thereby adding eight compounds to the previously reported 27 phytoalexins of Malinae species. When in vitro cultured M26 plantlets were treated with yeast extract, all the 35 phytoalexins were formed in the roots and 85.2% of the total phytoalexin amount was exuded into the culture medium. In roots of M26 plants grown in ARD soil in pot, 26 phytoalexins were detected and their exudation was demonstrated using two independent approaches of collecting root exudates. In a modified dipping experiment and a soil-hydroponic hybrid setup, the exudation rate was 39.5% and 20.6%, respectively. The exudation rates for individual phytoalexins differed, indicating controlled exudation processes. The exuded phytoalexins may play an important role in shaping the soil microbiome, which appears to greatly influence the development and severity of ARD.

KW - Apple replant disease

KW - Apple rootstock M26

KW - Biphenyl

KW - Dibenzofuran

KW - Exudation

KW - Malus × domestica borkh.

KW - Phytoalexin

KW - Rosaceae

UR - http://www.scopus.com/inward/record.url?scp=85116270940&partnerID=8YFLogxK

U2 - 10.1016/j.phytochem.2021.112972

DO - 10.1016/j.phytochem.2021.112972

M3 - Article

AN - SCOPUS:85116270940

VL - 192

JO - Phytochemistry

JF - Phytochemistry

SN - 0031-9422

M1 - 112972

ER -