Assessment of Agro-Ecological Apple Replant Disease (ARD) Management Strategies: Organic Fertilisation and Inoculation with Mycorrhizal Fungi and Bacteria

Abstract

Apple replant disease (ARD) impacts the economic yield of orchards by physiological and morphological suppression of apple trees on replanted soils. The complexity of replant disease caused by a plethora of biological interactions and physical properties of the soil requires complex management strategies to mitigate these effects. Based on expert recommendations, we selected two management strategies linked to agroecological principles of (a) organic fertilisation with a specific mulch composition (MDK) and (b) biofertilisation with arbuscular mycorrhizal and bacterial strains (AMFbac), applied by a composition of existing products. For both management strategies we provide a proof-of-concept, by pot and field experiments. Both treatments have the potential to mitigate ARD effects on plant vigour. ARD effect was fully mitigated by MDK treatment in the short-term (one year) and was mitigated by up to 29% after seven years of MDK treatment (long-term). MDK provides an additional substrate for root growth. AMFbac has the potential to mitigate ARD effects on plant vigour but with non-replicable plant-beneficial effects in its current form of application. Thereby our results show a principal potential to mitigate economic effects but not to overcome replant disease inducing effects. While the MDK treatment is found resource intensive but reliable, the AMFbac treatment was found more user-friendly.

Toward a holistic view of orchard ecosystem dynamics: A comprehensive review of the multiple factors governing development or suppression of apple replant disease

“…Development of an integrated approach to the management of ARD has generally been lacking in terms of defining modes of action determining disease control as well as optimizing efficacy beyond the "try and see what happens" approach. A broad spectrum of soil amendments, including composts (Wilson et al, 2004;Yao et al, 2006;Van Schoor et al, 2008;Braun et al, 2010), fertilization programs (Traquiar, 1984;Wilson et al, 2004;Cavael et al, 2021) and use of green manure or cover crops (Edwards et al, 1994;Merwin, 1995;Mazzola and Mullinix, 2005;Yim et al, 2017;Kanfra et al, 2021) have been evaluated for the ability to ameliorate replant disease symptoms. In large part, these soil amendment strategies were unsuccessful in managing ARD (Wilson et al, 2004;Yao et al, 2006;Van Schoor et al, 2008) although a short-term benefit in terms of vegetative growth was, Left panel: relative quantity of myo-inositol as determined by LC-MS QTOF analysis (Leisso et al, 2017) in root exudates of micro-propagated G.935 and M.26 plantlets cultivated in root elongation medium (Yepes and Aldwinckle, 1994).…”

“…The tolerant rootstock G.890 consistently possessed the greatest abundance of OTUs designated as Funneliformis mosseae , a species reported to suppress apple root colonization by Pratylenchus penetrans ( Forge et al, 2001 ; Gough et al, 2020 ). Although application of mycorrhizal inoculants in controlled environment studies mitigated the growth suppressive effects of ARD ( Cavael et al, 2021 ), use of an inoculant, which commonly employs a single or few species, at the field scale is unlikely to supplant infection by the diverse mycorrhizal community resident to an orchard soil system.…”

“…Alternative soil amendment-based strategies, including pre-plant application of Brassicaceae seed meal (BSM) and use of the process termed anaerobic soil disinfestation (ASD), have demonstrated active control of ARD. In assessments of findings from previous controlled environment and field-based studies, it was either suggested that the efficacy of BSM was site and soil dependent ( Hanschen and Winkelmann, 2020 ), that it was not a reliable and transferable management strategy across different locations ( Cavael et al, 2021 ) or that it was ineffective against oomycetes ( Deakin et al, 2019 ) and was not, therefore, a suitable treatment for the control of ARD. Such statements were reasonably based upon early studies that examined a number of BSMs that were applied individually ( Mazzola and Mullinix, 2005 ) prior to determining their efficacy and modes of action in suppressing the diverse spectrum of ARD pathogens ( Mazzola et al, 2007 ).…”

Effect of Aged Cherry Orchard Soil on the Potted Seedling Growth of Malus hupehensis (Pamp.) Rehd

“…Previous studies have shown that replant diseases are caused by a combination of biological and abiotic factors. The abiotic factors include soil physicochemical imbalances and accumulation of allelochemicals [5][6][7][8]. The biotic factors include imbalance of soil microbial community structure caused by increasing harmful microbial such as fungi (Fusarium spp., Cylindrocarpon spp.)…”

Characterization of Bacillus amyloliquefaciens BA-4 and its biocontrol potential against Fusarium-related apple replant disease

“…ARD predominantly affects newly replanted apple trees, resulting in stunted growth, heightened susceptibility to diseases, root discoloration, root tip necrosis, diminished root biomass, and potential plant mortality during the initial growth season (Kanfra et al, 2022). Furthermore, even mature apple trees suffer from decreased yield and fruit quality when affected by ARD, with severe cases resulting in tree mortality (Mahnkopp et al, 2018;Cavael et al, 2021). ARD is instigated by the accumulation of phenolic compounds or phytotoxins in the roots affected by the disease, coupled with deleterious soil pathogens, notably fungi (Fusarium, Rhizoctonia and Cylindrocarpon) and oomycetes (Pythium and Phytophthora) (Kelderer et al, 2012;Manici et al, 2018;Wang et al, 2022a).…”