Effet d’osmoprotecteurs naturels sur la restauration de croissance de Streptomyces et de plantes d’intérêt agricole sur sol salé ou aride

Abstract

Seven actinomycetes strains were isolated from a fertile soil of El-Ourissia (North of Sétif). SF5 and Nocardiopsis sp. MADO3 strains produced high levels of acetic indole acid (55.58 and 39.38μg/ml respectively). They showed also an antimicrobial activity against some bacteria and fungi beside Streptomyces sp. MADO2. Streptomyces colonies can be easily identified by their opaque, rough non-spreading morphology and their earthy odor. Based on cultural and morphological characters, this isolate is designated as Streptomyces. The three actinomycete strains are moderately halophiles and their behavior towards salt stress is different depending on the degree of salinity and the culture medium. The osmoprotective effect of glycine betaine, proline and trehalose on the restoration of the growth of Streptomyces sp. and Nocardiopsis sp. is obviously in the presence of high osmolarities. However, at low osmolarities they inhibit their growth. Salsola vermiculata showed a potential osmoprotective action on the restoration of the growth of Streptomyces sp. SF5 and Streptomyces sp. MADO2.Germination of Triticum durum L. the lengths and the dry weight of roots and steams, chlorophyll a, b and carotenoids contents were strongly inhibited mainly at 200mM/NaCl. However, it should be noted that the inhibitory effect on these parameters is more pronounced in the presence of S. vermiculata combined with Streptomyces sp. Germination rates in soil at (0, 100 and 200 mM/NaCl) are respectively 46.66%, 40% et 26.6% compared to controls (100%, 80% et 53.2%). Separately application of S. vermiculata or Streptomyces sp.SF5 restores strongly germination and growth of Triticum durum L. Germination rates are respectively (86.6%, 86.6%) (100mM) and (86.6%, 93.2%) (200 mM) compared to salted controls (80% and 53.2%). The use of this halophyte and Streptomyces sp. SF5 in saline soils would be extremely useful to fight against this stress and improve crop yields.