Soils collected from five locations in the argan forest (an endemic plant) in Morocco were used to form the first collection of Bacillus thuringiensis (Bt) strains from this area (58 strains). Here we found that the argan forest is a major source of Bt, as 90.62% of the samples contained Bt strains. These strains produced mainly spherical or irregular crystals that in some cases remained adhered to the spore after cell lysis. There was no strain producing bipyramidal crystals, suggesting the absence of strains bearing crv1 genes. This was confirmed by PCR analysis using eight primer pairs that can potentially detect 13 different groups of cry and cyt genes. Strains containing cry7/8 were the most abundant (25.53%), followed by strains harbouring cry9A (14.89%), cry11 (8.51%) and cry4 (4.25%). The mixtures of spores and crystals as well as culture supernatants were assayed for toxicity towards Ceratitis capitata (Medfly), showing up to 30% mortality. Our findings suggest that the argan region is a suitable target for future and wider screening programmes looking for strains bearing toxins or combinations of them to develop more efficient Bt-based formulates.

The objective of this study was to evaluate the efficiency of Moroccan Bt strains against neonate larvae, third instar larvae and emerged adults of Ceratitis capitata. This Mediterranean fruit fly causes serious damages to Argan forest and other agricultural plants. There is no successful control program of this pest fly in the endemic Argan forest in Morocco. A single-dose test was performed on neonate larvae (25 µL/g) and adult (333.33 µL/g), when three doses of Bt toxins (50 µL/g, 100 µL/g and 150 µL/g) were tested against third instar of C. capitata. Among the twenty-six Bt strains examined, local Bt13.4 and Bt A7 strains showed highest toxicity levels against larvae and adults, when compared to the reference strain, Bacillus thuringiensis subsp. israelensis HD567 “code 4Q1”, and commercial product “Skeetal”. One hundred percent mortality was observed against neonate larvae after 7 days of application by Bt 13.4 toxin. Third instar larvae were very susceptible to Bt A7 and Bt M-Ag 21.6 strains with 68% mortality (Lethal Concentration: LC50 = 1.115) at a dose of 150 µL/g. The Bt A7 strain was also highly toxic to adults with 81.66% of mortality after 7 days of application. This study demonstrated that some of our collection Bt strains can contribute to integrated C. capitata management system with strong biological control components

Le présent travail consiste à étudier l'effet de deux types de toxines (δ -endotoxines et β -exotoxines) extraites à partir d'une souche de Bacillus thuringiensis (Bt A9) isolée d'un sol au Maroc sur la mouche Ceratitis capitata Wied (Diptera ; Tephritidae). les endotoxines de Bt A9 agissent sur la mortalité des larves et la longévité des adultes. par contre, les exotoxines présentent un effet notamment sur l'émergence des adultes. Les résultats de cette étude montrent que la souche Bt A9 présente une activité insecticide importante sur C. capitata. Les toxines de cette souche pourraient être utilisées dans la lutte biologique de cet insecte ravageur de plusieurs cultures fruitières au Maroc.

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Microbial insecticides are considered as the most sustainable and ecologically acceptable means of crop protection. Here we report the ability of some Moroccan actinobacteria isolates to produce larvicidal compounds against the Medfly (Ceratitis capitata Wied.). Thus, actinobacteria isolates were tested for their insecticidal activity through biological and chemical screening. The primary biological screening using the brine shrimp bioassay showed that 12 isolates out of 210 (5.71%) have been found to be highly toxic at the concentration of 100 µg mL-1. Among these, isolates OS46, 37 and B62 were the most toxic with an LC 50 of 0.26, 0.34 and 0.84 µg mL-1 , respectively. The freeze-dried fermentation of the selected isolates showed moderate to high insecticidal activity against the first instar larvae of C. capitata, and the most important pupation reduction was obtained for isolates 37 and B89 (0 and 6% of pupation, respectively). The chemical screening on thin layer chromatography of the crude extract of the most important isolates using specific insecticide family's reagents showed a variety of compounds depending on isolate with at least one active spot for each tested specific reagent. Finally, the inhibition of acetylcholinesterase activity test was carried out in order to assess the possible nature of insecticidal activity of selected isolates. The obtained results show that, except the isolate 37 which probably acts by a different mode of action, all other isolates were active. This finding could have an applicative value for the potentiality of utilizing Moroccan actinobacteria isolates as an alternative to chemical insecticides in pest management mainly against C. capitata.