Improving the Biocontrol Potential of Bacterial Antagonists with Salicylic Acid against Brown Rot Disease and Impact on Nectarine Fruits Quality

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.

Combination of Sodium Bicarbonate (SBC) with Bacterial Antagonists for the Control of Brown Rot Disease of Fruit

“…M. fructigena (VPBG) was originally isolated from sweet cherry showing typical brown rot symptoms in Serbia in 2010 [ 29 , 30 ]. The pathogen was then stored at 4 °C in PDA (Potato Dextrose Agar) media plates, containing 200 mL extract of boiled potatoes, 20 g dextrose, and 20 g agar in 1000 mL distilled water.…”

“…Before their use in the different in vivo experiments, fruits without wounds or rot were selected based on uniformity of size and absence of physical injury or disease infection. All fruit surfaces were disinfected with 2% ( v / v ) sodium hypochlorite for 3 min, then rinsed twice with SDW and air-dried for 1 h under a laminar flow cabinet [ 30 ].…”

“…These bacteria have been isolated from the soil and flowers of apple trees in Morocco. They have been identified for their antagonistic potential against Erwinia amylovora [ 28 ], M. fructigena on postharvest apples [ 29 ], and in combination with salicylic acid [ 30 ]. The combined effect of these antagonistic bacteria with SBC on postharvest diseases of fruit is however still unknown and not fully investigated.…”

Biological Control of Plant Pathogens: A Global Perspective

“…Based on the ability or behavior of the crops and biocontrol agents, PGPRs also act as biopesticides [ 33 ]. PGPRs are bacterial species including Alcaligenes , Azospirillum , Arthrobacter , Acinetobacter , Bradyrhizobium , Bacillus , Burkholderia , Enterobacter , Erwinia , Flavobacterium , Pseudomonas , Rhizobium , Azorhizobium , Bradyrhizobium , Allorhizobium , Sinorhizobium , Frankia , Mesorhizob , Azoarcus , Exiguobacterium , Methylobacterium , Paenibacillus , and Pantoea [ 29 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ]. In reaction to diverse chemicals found in root exudates, beneficial bacterial communities in the soil are chemoattracted towards plant roots.…”

Temporal Patterns and Inter-Correlations among Physical and Antioxidant Attributes and Enzyme Activities of Apricot Fruit Inoculated with Monilinia laxa under Salicylic Acid and Methyl Jasmonate Treatments under Shelf-Life Conditions

“…For instance, postharvest damages were effectively controlled by SA treatments in the case of Colletotrichum gloeosporioides on mango [45,46], Penicillium expansum on sweet cherry [24,34,47] and peach [48,49], Botrytis cinerea on peach [50], and Monilinia spp. on sweet cherry [34], apricot [51], apple [52] and nectarine [53].…”