Colonisation of apple roots by arbuscular mycorrhiza in specific apple replant disease affected soil

Abstract

In New Zealand specific apple replant disease (SARD) causes retarded tree growth and poor establishment in replanted apple orchards In two pot experiments arbuscular mycorrhizae (AM) colonisation of apple roots in different SARD treated soils was assessed In the first experiment AM colonisation was significantly lower in SARD soil compared with nonSARD soil In this experiment 456 of roots were AM colonised at planting and AM colonisation was increased in both soil types following chloropicrin fumigation or fungicide application The second experiment used only SARD soil and at planting only 03 of roots were colonised with AM AM colonisation was significantly greater in two commercial Trichoderma treatments (pellet and powder formulations) than untreated control uninoculated blank pellets and chemical nutrient treatments AM colonisation in fumigated soil was very low and remained similar to the initial root stock material