FIRST OBSERVATIONS OF VESICULAR-ARBUSCULA R MYCORRHIZAS AND GLOMALES IN THE RHIZOSPHERE OF SOME SPERMATOPHYTES IN THE SOUTH-WEST OF NIGER

This first study of vesiculo-arbuscular mycorrhizas in Niger concerns 41 species of Spermatophytes species collected in the most representat ive ecosystems of the South-West of the country. The prospected region is localized along a transect from ''W'' pare, 150 km south of Niamey to 150 km north of the Niger capital. The climatic gradient is consid erable since rainfall ranges from 800 mm annual precipitation in the S outh to 150 mm in the North. The rain season occurs between June and S eptember and is extremely variable from year to year. Ninety per cent of the sampled plants were mycorrhizal at different degrees in January (the mean infection level is 4.8%) and eighty five per cent in August (with 1.7% mean infection level). Six spores types, belonging to the genera Glomus, Gigaspora and Scutellospora, were observed. The number of spores extracted from 100 g of soil, varied from 96 to 716 in Janua ry and from 360 to 2120 in August. The dominant types of spores differ ed according to the season of sampling. The frequency was T3 > T2 > T4 > T5 > T1 > T6 in January and T2 > T1 > T5 > T3 > T6 > T4 in August.