Apple Root Microbiome as Indicator of Plant Adaptation to Apple Replant Diseased Soils

Abstract

The tree fruit industry in Nova Scotia, Canada, is dominated by the apple (Malus domestica) sector. However, the sector is faced with numerous challenges, including apple replant disease (ARD), which is a well-known problem in areas with intensive apple cultivation. A study was performed using 16S rRNA/18S rRNA and 16S rRNA/ITS2 amplicon sequencing to assess soil- and root-associated microbiomes, respectively, from mature apple orchards and soil microbiomes alone from uncultivated soil. The results indicated significant (p < 0.05) differences in soil microbial community structure and composition between uncultivated soil and cultivated apple orchard soil. We identified an increase in the number of potential pathogens in the orchard soil compared to uncultivated soil. At the same time, we detected a significant (p < 0.05) increase in relative abundances of several potential plant-growth-promoting or biocontrol microorganisms and non-fungal eukaryotes capable of promoting the proliferation of bacterial biocontrol agents in orchard soils. Additionally, the apple roots accumulated several potential PGP bacteria from Proteobacteria and Actinobacteria phyla, while the relative abundances of fungal taxa with the potential to contribute to ARD, such as Nectriaceae and plant pathogenic Fusarium spp., were decreased in the apple root microbiome compared to the soil microbiome. The results suggest that the health of a mature apple tree can be ascribed to a complex interaction between potential pathogenic and plant growth-promoting microorganisms in the soil and on apple roots.

Leaf Fermentation Products of Allium sativum L. Can Alleviate Apple Replant Disease (ARD)

“…The manifestations of ARD are root damage and growth inhibition of replanted apple seedlings, fruit quality and yield decline, disease, and insect infestation aggravation, and even causing the orchard to cease production [2,3]. The causes of ARD include the imbalance of the soil microbial community, deterioration of soil physical and chemical properties, and allelopathy induced by the excessive accumulation of phenolic acids in soil [4][5][6].…”

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

“…Fusarium spp. constitute a prevalent group of soilborne pathogens, encompassing various species linked to ARD, such as F. oxysporum, F. moniliforme, F. proliferatum, and F. solani (Xiang et al, 2021b;Liu et al, 2022;Ajeethan et al, 2023).These pathogens exhibit remarkable resilience in the soil, persisting as chlamydospores capable of infecting apple tree roots for a prolonged period, up to 10 years (Xiang et al, 2021a). The germination of Fusarium conidia is stimulated by root exudates, facilitating their penetration into the root system through wounds or natural openings, leading to rotting and necrosis.…”