The aim of our study was to screen Moroccan actinomycete isolates able to produce nonpolyenic antifungal metabolites in order to contribute to limiting the problem of fungal infections emergence in particular mycotic diseases and to discover known antifungal families, especially nonpolyenic drugs. 480 isolates were tested against 5clinically pathogenic Candida species. Several methods have been used to study the polyenic or non-polyenic nature of the antifungal molecules produced by Actinobacteria (i) The study of the antibacterial activity (the bacterial plasma membrane is devoid of sterols); (ii) The screening of the antimicrobial activity of resistant strains to polyenic antifungals essentially Candida tropicalis R2 and Pythium irregular; (iii) The inhibition of antifungal activity by exogenous ergosterol addition in the culture medium and (iv) The UV-Visible light spectrophotometric analysis of the crude extracts of the actinomycete isolates. Among all isolate tested, only 60 (29 %) showed an antifungal activity against all test microorganisms used. Six active isolates meet all the selection criteria and produced nonpolyenic antifungal metabolites. The taxonomic study of the promising isolate Z26, using morphological, physiological and molecular characters, showed that it has 99,43% of similarity with Streptomyces phytohabitans but there were some differences in morphological characteristics. In addition, the chemical study, using chromatographic and spectroscopic techniques, of the bioactive substances produced in the Z26 isolate fermentation broth in NL300 culture medium allowed the determination of two macrolide derivatives with chemical structures C 62 H 100 O 24 (m/z 1251.6504 [M+Na] +) and C 68 H 110 O 26 (m/z 1365.7174 [M+Na] +). NMR experiments revealed that the active compounds were Novonestmycin A and B. The Novonestmycins A and B are for the first time produced by an actinomycete strain purely isolated from the Moroccan ecosystems.

Three hundred and fifty‐nine isolates of actinobacteria collected from different Moroccan soils were evaluated for their in vitro antimicrobial activity against the oomycete pathogen Aphanomyces euteiches, the causal agent of damping‐off of pea and other legumes. Eighty‐seven isolates (24%) had an inhibitory in vitro effect against A. euteiches. Fourteen bioactive isolates with the greatest inhibitory effect against A. euteiches and no inhibitory effect on plant beneficial rhizobia were tested for their ability to protect pea seeds and seedlings against the damping‐off disease using culture supernatants or spore suspensions as treatments. The two most protective isolates, OB21 and BA15, significantly reduced, compared to untreated control plants, damping‐off by 33% and 47%, respectively. The two bioactive isolates were classified as species of the genus Streptomyces based on 16S rDNA analysis and morphological and chemical characteristics.

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Potato (Solanum tuberosum) as a food source and culinary ingredient varies is the fourth most produced noncereal crop in the world. Among multiple biotic stresses, late blight caused by Phytophthora infestans is the most destructive disease. Control of this pathogen is usually by the synthetic fungicides which have been fueled by the public concern about toxicity and environmental impact and development of pathogens resistance. Biological control agents (BCAs) seems the potentially alternative to these pesticides, biological disease control is now recognized and constitute an important tool in integrated pest management. BCAs strains should be able to protect the host plant from pathogens and fulfill the requirement for strong colonization. Bacteria such as Bacillus, Pseudomonas and Streptomyces and fungi such as Trichoderma and Penicillium were the most reported as a BCA against P. infestans using different direct antagonistic mode on the pathogen (via e.g. parasitism, antibiosis, or competition) or via exerting their biocontrol activity indirectly by induction in the plant of an induced systemic resistance to the pathogen. In this study, we present an overview and discussion of the use of beneficial microbes (bacteria and fungi) as novel BCAs for biocontrol of P. infestans.