Abstract
The main objective of this study was to evaluate the ability of both antagonistic bacteria Bacillus amyloliquefaciens (SF14) and Alcaligenes faecalis (ACBC1) used in combination with salicylic acid (SA) to effectively control brown rot disease caused by Monilinia fructigena. Four concentrations of salicylic acid (0.5%, 2%, 3.5%, and 5%) were tested under in vitro and in vivo conditions. Furthermore, the impact of biological treatments on nectarine fruit parameters’ quality, in particular, weight loss, titratable acidity, and soluble solids content, was evaluated. Regardless of the bacterium, the results indicated that all combined treatments displayed a strong inhibitory effect on the mycelial growth of M. fructigena and disease severity. Interestingly, all SA concentrations significantly improved the biocontrol activity of each antagonist. The mycelial growth inhibition rate ranged from 9.79% to 88.02% with the highest reduction rate recorded for bacterial antagonists in combination with SA at both concentrations of 0.5% and 3.5%. The in vivo results confirmed the in vitro results with a disease severity varying from 0.00% to 51.91%. A significant biocontrol improvement was obtained with both antagonistic bacteria when used in combination with SA at concentrations of 0.5% and 2%. The lowest disease severity observed with ACBC1 compared with SF14 is likely due to a rapid adaptation and increase of antagonistic bacteria population in wounded sites. The impact of all biological treatments revealed moderate significant changes in the fruit quality parameters with weight loss for several treatments. These results suggest that the improved disease control of both antagonistic bacteria was more likely directly linked to both the inhibitory effects of SA on pathogen growth and induced fruit resistance.
Highlights
Fresh nectarines are much-appreciated fruits by consumers worldwide for their high nutrition and juicy and agreeable flavor [1]
After 5 days of incubation, the highest inhibitions were recorded by the treatments SF14, 0.5 Salicylic acid (SA) + SF14, and 3.5 SA + SF14 with inhibition rates of 78.60%, 74.18%, and 72.03%, respectively (Table 1), while ACBC1 recorded the highest inhibition rate (84.80%) when combined with SA at 0.5% and 3.5% (Table 1)
This study highlights the potential use of the antagonistic bacteria A. faecalis ACBC1 and B. amyloliquefaciens SF14 in combination with SA to manage the brown rot on nectarine fruits
Summary
Fresh nectarines are much-appreciated fruits by consumers worldwide for their high nutrition and juicy and agreeable flavor [1]. They are often subjected to rapid deterioration during pre- and postharvest, especially when storage conditions are not well respected. Most of these losses are caused by spoilage fungi. Brown rot, caused by Monilinia spp., is a fungal disease that causes considerable pre- and postharvest economic losses of rosaceous fruit trees [2,3,4]. The disease can lead to 80% of postharvest fruit loss, mainly when environmental conditions are suitable for disease growth in the orchard
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