Diversity and distribution of arbuscular mycorrhizal fungi associated to Bambara groundnut (Vigna subterranea (L.) Verdcourt) in Benin

Bambara groundnut, despite its attributes in providing protein to human, is facing soil fertility and degradation problems, always leading to little performances. Arbuscular mycorrhizal fungi (AMF) constitute a microorganism group used by many researchers to improve productivity of crops in poor soils. This study aimed to evaluate the distribution and diversity of AMF associated to Bambara groundnut in different agro-ecological zones in Benin. A survey was conducted through 20 villages chosen based on Bambara groundnut yield, cropping area and its production across five agro-ecological zones (from AEZ 1 to AEZ 5). Soil and root samples were collected to assess spore density and diversity, root colonization levels and soil chemical properties. Results revealed significant difference (p <0.0001) among agro-ecological zones in terms of density of AMF, which varied from 2825 to 5713 spores per 100g of soil, depending on the AEZ. The highest density was recorded in the cotton zone in the northern Benin. The diversity of AMF also varied, depending on the AEZ. In total, 14 morphotypes belonging to five genera (Glomus, Gigaspora, Acaulospora, Scutellospora and Diversispora) were identified in the different studied zones with Glomus genus the most frequently recorded in all AEZ. Correlation tests among the different parameters have, in general, revealed that, the zones with the low rates of the different parameters had those with the highest frequencies of mycorrhization. It also appears that spore density did not correlate with diversity index, mycorrhization frequencies and intensities, but soil chemical parameters significantly did.