Diversity of arbuscular mycorrhizal fungi (AMF) in the rhizosphere of soybean in Cameroon

Abstract

Understanding the diversity and dynamics of arbuscular mycorrhizal fungi (AMF) in their natural environment is useful for a given crop, particularly when aiming to introduce AMF for soil fertilisation and disease control. The aim of this study was to assess the diversity of AMF associated with the soybean rhizosphere, in the different agro- ecological zones (AEZ) of Cameroon. Samples of soybean rhizosphere were collected from 25 sites across the five AEZ. The chemical properties of soil were determined as well as the abundance of the spores after 3 months of spore trapping and their extraction from the soil by passing the samples through 710, 250, 125 and 45 µm mesh sieves. The diversity of AMF was assessed. Root samples were used to determine frequency of mycorrhization. The results showed that the abundance, colour and diameter of soybean rhizosphere spores varied with AEZ. The highest spore densities were 173 spores per 100 g of soil in AEZ III and the lowest (23 spores per 100 g of soil) in AEZ V. Nine genera were identified (Gigaspora, Entrophopora, Scutellospora, Dentiscutata, Rhizophagus, Paraglomus, Clarodeoglomus, Racocetra and Diversipora); Gigaspora and Entrophopora were the most abundant genera. AEZ II (0.35) had a higher diversity index than AEZ I (0.18). High frequencies of mycorrhization occurred in AEZ I and II (46 and 44% respectively) but this was low in AEZ IV (14%). The abundance of spores showed a positive and higher correlation between the organic matter content and the density of the spores (r = 0.84), meaning that, the higher the content of the organic matter, the more abundant the density of the spore will be. This study reveals that there is a great diversity of AMF in the soybean rhizosphere in Cameroon.