Asparagus Decline Syndrome (ADS) is one of the main phytosanitary problems of asparagus crop worldwide. Diseased plants and soil samples from 41 fields from three main production areas of Spain were surveyed. Eight Fusarium species belonging to seven species complexes were identified in soils: F. oxysporum, F. proliferatum, F. redolens, F. solanisensu stricto, F. equiseti, F. culmorum, F. compactum and F. acuminatum. Fusarium oxysporum was the most prevalent species. Statistical correlation (R² = 88%) was established between F. oxysporum inoculum density and the average temperature of the warmest month. A relationship was also established between three crop factors (average temperature, crop age and F. oxysporum inoculum density) and field disease indices. Significant differences were observed between the distribution of F. oxysporum propagules in white and green asparagus fields. Thirteen Fusarium species belonging to seven species complexes were identified from roots of diseased plants, being F. oxysporum the most prevalent. F. proliferatum, F. oxysporum and F. redolens showed pathogenicity to asparagus and were the main species associated to ADS. Fusarium oxysporum was the species with the highest genetic diversity displaying 14 sequence-based haplotypes with no geographic differentiation. This work contributes to understanding the Fusarium complex associated to ADS for developing accurate integrated disease management strategies.

To avoid the use of agrochemicals in agriculture, alternative methods are emerging to control plant pathogens. Some plant growth-promoting rhizobacteria (PGPR) can be used as biocontrol agents since they can induce protection against pathogens. The aim of this study was to evaluate the protective effect of several PGPR strains against the main Fusarium species involved in asparagus decline syndrome (ADS): F. proliferatum, F. oxysporum f. sp. asparagi and F. redolens. In vitro antagonism assays showed that all the bacteria inhibited the mycelium growth of the three Fusarium species. The most effective strains (Streptomyces fradiae Hvs6, Bacillus paralicheniformis Hvs2 and Bacillus velezensis FC37) were tested to evaluate their protective effect on asparagus plants inoculated with pathogenic Fusarium isolates. Strains FC37 and Hvs2 were the most effective in controlling pathogenic F. proliferatum and F. oxysporum f. sp. asparagi, but neither could protect against F. redolens isolates. The production of hydrolytic enzymes such as β-glucosidase, amylase and protease by these bacterial strains could be involved in the structural degradation of the fungal cell wall. In addition, the production of toxic volatile compounds, such as hydrogen cyanide, may inhibit the fungal growth, and the production of phosphate solubilizers could be related to the plant growth promotion. These results suggest that strains FC37 and Hvs2 could be used as potential biocontrol agents as a sustainable and environmentally friendly control strategy for ADS-affected fields.

Asparagus decline syndrome (ADS) poses a critical challenge to the productivity and quality of asparagus (Asparagus officinalis L.), threatening the sustainability of its cultivation. This study evaluated the impact of ADS over four years in Western Europe by comparing soils with and without a history of the syndrome. The results revealed a consistent reduction in yield, with losses of 36% in 2019 and 2020 and 23% in 2021 compared to the results for the control soils. ADS also increased the proportion of non-commercial spears, peaking at 52% in 2020. Key quality parameters were significantly affected by ADS, especially in the final year of the trial, with reductions observed in spear weight, diameter, firmness, and volume. On the other hand, °Brix values increased by 10% to 16%, while juiciness decreased by 10% to 28%, depending on the year, enhancing sweetness but compromising texture, and thereby, marketable quality. The findings highlight the detrimental effects of replanting asparagus in ADS-affected soils and the need for integrated management strategies to mitigate its impacts. This research contributes valuable insights into ADS dynamics, offering a foundation for developing agronomic solutions that enhance productivity and ensure the long-term viability of asparagus cultivation in affected regions.