Adoption of nature-based solutions and orchard sustainable management to face kiwifruit vine decline syndrome (KVDS)

Italy, the third largest producers of kiwifruit in the world, lost 10% of its production in recent years because of the spread of the kiwifruit vine decline syndrome (KVDS) (Bardi, 2020). Although the etiology of KVDS is still not clear, it is often associated with water excess and stagnation. We hypothesize that soil compaction and hypoxia could have a priming effect in the emergence of KVDS. To investigate the causal factors and potential solutions to counter KVDS, a multi-disciplinary experimental trial was undertaken in a kiwifruit orchard (Actinidia chinensis var. chinensis ‘Zesy002’) affected by KVDS in Latina (Italy). Soils from two areas were sampled: a) vines showing severe symptoms of KVDS, and b) healthy vines as control (CTRL). Soils showed different levels of compaction, clay/silt content and water content, with higher values in KVDS field, compared to CTRL. The topsoil (0-30 cm) redox potential was significantly lower in KVDS field than in the CTRL (256 vs 327 mV), so indicating low soil oxygen content. Higher soil CO2 and CH4, two greenhouse gases that also are indicators of hypoxic conditions, were found in KVDS field (Sofo et al., 2022). The analysis of topsoil (0-30 cm) thin sections showed KVDS soils had fewer macropores than CTRL (8.5 vs 11.5%, v/v). Macroscopically, the roots affected by KVDS were rotting, showing a loss of rhizodermis and cortical parenchyma. Microscope analysis revealed damage to the root system, with tissue breakdown and decomposition (D'Ippolito et al., 2022). Genomic analysis identified some abundant fungal species in KVDS roots (Ilyonectria vredenhoekensis, Fusarium oxysporum and Paraphaeosphaeria michotii), but further investigation is required to determine the eventual role of these fungi in KVDS emergence. A metagenomic/metatranscriptomic analysis of rhizosphere-associated microorganisms was carried out for detecting a) eventual beneficial microorganisms and biocontrol microbial agents for KVDS control isolated from healthy plants, and b) the hypothetical role of pathogenic microorganisms detected in KVDS plants, able to compromise roots functionality. Nature-based solutions were applied, such as planting decompacting crops (e.g., Rafanus spp.) for increasing water permeability and agroecosystem diversification, the application of compost and bio-fertilizers containing plant-growth-promoting microorganisms and mycorrhiza (Saccharomyces cerevisiae, Bacillus megaterium, Bacillus pumilus, Pseudomonas striata, Azospirillum brasilense, Candida tropicalis, Glomus intraradices, and Trichoderma harzianum), the amelioration of water drainage into the soil, and root pruning for improving root regeneration. Implementing novel management strategies can improve kiwifruit growth and vine productivity, also reducing KVDS symptoms in impacted vineyards, contributing to the socio-economic sustainability of farms, and increasing the ecosystem services, according to a sustainable, modern and multifactorial concept of agriculture.