Latifa Askarne

Gray mold rot, caused by Botrytis cinerea, is considered as one of the most harmful fungal diseases affecting postharvest tomato fruits. In the current work, we explore the biocontrol potential of 174 bacterial strains isolated from tomato rhizosphere, argan rhizosphere and a vermicompost to control this fungal pathogen. The in vitro dual culture study of isolated bacterial strains and the fungus-causing pathogen revealed that 31 isolates exhibited a substantial antifungal activity against B. cinerea mycelial growth. The inhibition rates ranged from 55.36 to 85.07%. Twelve bacterial strains which showed the highest antifungal properties (more than 79.6%) were subsequently investigated for their ability to produce compounds with antifungal activity, including diffusible substances, volatile compounds and hydrocyanic acid. These strains were then evaluated in vivo for their ability to reduce fruit decay caused by the fungus. Indeed, isolates VC-B1 (from vermicompost), RS-TB3, and RS-T6 (from the rhizosphere of tomato root), and RH-TB11 (from the tomato rhizoplane) released the most active diffusible substances, which totally inhibited the mycelial growth of B. cinerea. In addition, bacterial strains RS-TB1 and RS-T6 isolated both from the tomato rhizospheric soil were among the isolates that produced the most effective volatile compounds. They reduced the mycelial growth of the fungal pathogen by 75.36% ± 7.24% and 72.94 ± 4.129% respectively. Moreover, RS-TB3, RS-TB4, RH-TB1, and VC-B1 exhibited the highest production of hydrocyanic acid, followed by RS-TB1, VC-3, and VC-13. In vivo bioassays showed disease reduction ranging from 37.92% to 93.14%, with VC-1, VC-5, and RS-T4 showing the highest efficacy. This study identifies several bacterial strains with high potential for biocontrol of B. cinerea in postharvest tomatoes, presenting a promising alternative to chemical fungicides for managing gray mold rot.

Apple production holds a prominent position in Morocco’s Rosaceae family. However, annual production can fluctuate due to substantial losses caused by fungal diseases affecting stored apples. Our findings emphasize that the pre-storage treatment of apples, disinfection of storage facilities, box type, and fruit sorting are pivotal factors affecting apple losses during storage. Additionally, the adopted preservation technique was significantly correlated with the percentage of damage caused by fungal infections. Blue mold accounts for nearly three-quarters of the diseases detected, followed by gray rot with a relatively significant incidence. This study has revealed several fungal diseases affecting stored apples caused by pathogens such as Penicillium expansum, Botrytis cinerea, Alternaria alternata, Trichothecium roseum, Fusarium avenaceum, Cadophora malorum, and Neofabraea vagabunda. Notably, these last two fungal species have been reported for the first time in Morocco as pathogens of stored apples. These data affirm that the high losses of apples in Morocco, attributed primarily to P. expansum and B. cinerea, pose a significant threat in terms of reduced production and diminished fruit quality. Hence, adopting controlled atmosphere storage chambers and implementing good practices before apple storage is crucial.

The aim of this study was to find an alternative to chemical products used in the control of fire blight disease of rosaceous plants. In this work, essential oils of two Moroccan Artemisia species: Artemisia mesatlantica and Artemisia absinthium were screened for their antibacterial activity against Erwinia amylovora the causal agent of this disease. The EOs extraction was carried out by water distillation method in Clevenger- type apparatus and analyzed by gas Chromatography-Flame Ionization Detector (GC/FID) and by Gas Chromatography-Mass Spectrometry (GC/MS). The antibacterial activity of extracted EOs was tested in vitro based on the agar diffusion method and broth microdilution method and in vivo on detached immature pear fruits. The results revealed that the yields of extracted EOs were 1.25 and 0.58% respectively for A. mesatlantica and A. absinthium. The chemical composition analysis showed that investigated EOs were characterized with a high amount of β-Thujone (40.42% for A. mesatlantica and 36.25% for A. absinthium). Both EOs have a similar MIC value (2.08%). A. absinthium EOs were found to be more effective than A. mesatlantica EOs since they show the lowest MBC. These results indicate that EOs of A. absinthium and A. mesatlantica contained compounds with antibacterial potential against Erwinia amylovora. In the bioassay test, the application of A. absinthium EOs on detached immature pear fruits infected by E. amylovora resulted in total suppression of disease severity. Such natural products may represent a sustainable alternative to the use of chemical pesticides.

Antioxidant and Antifungal Activity of Some Moroccan Seaweeds Against Three Postharvest Fungal Pathogens

Seaweeds are rich sources of natural bioactive products. Their interesting biological activities contributed to the investigation of natural therapeutic compounds used in biomedical and pharmaceutical applications. In this study, methanolic extracts of four seaweeds collected from the Moroccan Atlantic coastline (Agadir) Bifurcaria bifurcata, Corallina elongata, Corallina officinalis and Ulva fasciata were investigated for antimicrobial activities using the disc diffusion and broth microdilution methods. The extract bioactivity was expressed as minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against four human pathogenic bacteria Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Pseudomonas aeruginosa. The results indicated that among the algal samples screened, the methanolic extract of B. bifurcata and U. fasciata exhibited the highest potency against all pathogens tested, with MIC ranged from 0.11 to 3.75 mg/ml depending on the bacterial species. The lowest MIC and MBC values were recorded for methanolic extract of B. bifurcata against Bacillus subtilis (0.11 mg/ml, 7.50 mg/ml) and E. coli (0.23 mg/ml, 7.50 mg/ml). Therefore, the present findings suggest that local seaweeds, chiefly B. bifurcata may be considered as an interesting biological source of bioactive compounds and should be investigated for natural antibiotics to control some pathogenic bacteria strains such as E. coli and B. subtilis.