Physiological stress responses in apple under replant conditions

Physiological stress responses in plants that are the key to understanding ongoing biological scenarios were observed in apple seedlings with regards to apple replant disease CARD). In this study the complexity between ARD, and the influence of the reduction of growth parameters, the influence on the synthesis of valuable, antioxidative compounds, such as phenols, and its interaction with other valuable antioxidative compounds in leaves and other parts of the plants was shown for the first time. The study showed a communication between compounds in roots and leaves which could affect a higher tolerance of plant parts (leaves) against a secondary occurring oxidative stress (in this study induced by paraquat). Seedlings were grown under controlled conditions within a growth chamber. ARD playing a major role in apple fruit production and soil fertility, respectively, was observed as a biotic stress induction factor. Parameters such as photosynthetic activity, antioxidant capacity in the leaves (AC) and total phenolic compounds within the roots were observed to alter significantly under replant conditions. Vegetative growth parameters showed a significantly inhibited development in those plants exposed to replant conditions. Plants having undergone a latent stress through ARD affected soil showed significantly less impact of a secondary oxidative stressor such as the application of paraquat. When exposed to a secondary stressor such as Paraquat the photosynthetic activity (F-v/F-m.)within the leaves of those plants did not alter under replant conditions whereas F-v/F-m values decreased in leaves of plants grown in none affected soil. The accumulation of total phenolic compounds within the root of plants grown under replant conditions increased significantly suggesting an ongoing defense mechanism within the host plant. The methodology moves towards early detection of replant disease etiology with the aim of defining first specific ARD related response patterns within apple. (C) 2015 Elsevier B.V. All rights reserved.