DIVERSITY OF ARBUSCULAR MYCORRHIZAL FUNGI ASSOCIATED WITH CAROB TREES (Ceratonia siliqua L.) IN WESTERN ALGERIA

The carob tree is a leguminous plant originating in the Mediterranean region. It is used in many reforestation and ornamentation programs. The aim of this study is to characterize the diversity of AMF associated with the carob tree and the importance of their role in the integration of a semi-arid ecosystem in Western Algeria. Samples of soil and roots in the rhizosphere of ten carob specimen were taken in different areas in the northwest of Algeria: Hassasna, Nedroma and Ouled Mimoun. Physicochemical analyses were carried out as well as enumeration and morphological and anatomical analyses of the spores. The roots were trypan blue- dyed to determine the level of mycorrhization. The results showed that the soil of Ouled Mimoun is the richest of the three sites in organic matter, and contains the largest proportion of nitrogen and available phosphorus. It also has the largest spore count: 641 per 100 g of soil. Furthermore, the study revealed the presence of 16 morphotypes of AMF spores in all three sites, Glomus and Acaulospora genera being the most abundant. Likewise, microscopic observation of the roots revealed the presence of all the structures typical of AMF including vesicles, hyphae and arbuscular structures. The level of mycorrhization in the roots sampled in Ouled Mimoun was the highest with a mycorrhization frequency of F=94%, an intensity of M=44% and an arbuscular rate of A=94%. The mycorrhizal abundance and high infectivity of the carob roots taken in the site of O.Mimoun, an old plantation site, reflect the physicochemical characteristics of a fertile and more lively soil, in particular its organic carbon and nitrogen content. Another explanation may be that indigenous AMF communities, apparently more resilient and better adapted to the edaphic conditions, have gradually replaced the fungi introduced.