Effects of water regime and inoculation with arbuscular mycorrhizal fungi on mycorrhizal communities of roots of rice and pearl millet in upland and lowland fields

Abstract

Knowledge of biodiversity of soil microorganisms, including arbuscular mycorrhizal fungal (AMF) species, is limited in agroecological contexts. We investigated the effects of the popular inoculant Dr. Kinkon R10 on AMF communities in rice and pearl millet in upland and lowland fields under different water regimes by using a metagenomic approach. Numbers of operational taxonomic units (OTUs) were much lower in lowland than in upland. In upland, alpha diversity was lowest in rice but highest in pearl millet under the nonirrigated treatment (W0); OTUs of Claroideoglomus showed the greatest differences in abundance. Three OTUs of Claroideoglomus tended to have higher abundance in pearl millet under W0, whereas that of two OTUs (Acaulospora, Diversispora) increased under the well-irrigated treatment (W100). In lowland, alpha diversity was higher under the flooded condition than alternate wetting and drying, with greater abundance of Acaulospora, Ambispora, and Scutellospora. Overall, inoculation with R10 did not change the alpha and beta diversity of AMF communities. In upland, eight OTUs showed greater abundance in pearl millet than in rice, including one OTU present in the R10 inoculant. In upland, the shallow soil layer (0-10 cm) had greater abundance of Claroideoglomus, Paraglomus, and Acaulospora, with a higher diversity index, whereas the deep layer (20-30 cm) had greater abundance of Rhizophagus and Scutellospora. This study highlighted abundance of Acaulospora in higher water regimes in both upland and lowland and of Claroideoglomus for pearl millet in lower water regimes in upland.