Abstract
Manioc (Manihot esculenta Crantz) is an important tropical crop that depends on arbuscular mycorrhizal (AM) association for its nutrition. However, little is known about the richness and species composition of AM fungal communities associating with manioc and possible differences across soils and manioc landraces. We studied the diversity and composition of AM fungal communities present in the roots of different manioc landraces and surrounding soils in indigenous shifting cultivation fields on different Amazonian soil types. A total of 126 AM fungal virtual taxa (VT; phylogenetically defined taxonomic units) were recovered from soil and root samples using 454 sequencing of AM fungal SSU rRNA gene amplicons. Different AM fungal communities occurred in different soil types. Minor differences occurred in the composition of AM fungal community associating with different manioc landraces, but AM fungal richness was not different among them. There was a low similarity between the AM fungal communities colonizing manioc roots and those recorded in the soil, independently of differences in soil properties or the manioc landrace evaluated. Rhizophagus manihotis and Glomus VT126 were the most abundant AM fungal species colonizing manioc roots. Contrasting with the results of earlier spore-based investigations, all the AM fungi identified as indicator species of particular manioc landraces were morphologically unknown Glomus species. In conclusion, different manioc landraces growing in common conditions associated with distinct AM fungal communities, whereby AM fungal communities in soils did not necessarily reflect the AM fungal communities colonizing manioc roots.
Highlights
IntroductionManioc (Manihot esculenta Crantz; Euphorbiaceae), known as cassava, is native to the Amazon region and is an important staple crop throughout the tropics
Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Manioc (Manihot esculenta Crantz; Euphorbiaceae), known as cassava, is native to the Amazon region and is an important staple crop throughout the tropics
Ambispora was not recorded in Podzols, Gigaspora was not recorded in Fluvisols, Scutellospora was not recorded in Ferralsols, and Racocetra was not recorded in Ferralsols and Fluvisols (Table A3 Online Resource)
Summary
Manioc (Manihot esculenta Crantz; Euphorbiaceae), known as cassava, is native to the Amazon region and is an important staple crop throughout the tropics. It is emerging as an important crop for bio-fuel production and other industrial processes (Aristizábal et al 2007; FAO 2000). Manioc is widely cultivated by subsistence farmers with limited access to inputs in marginal acidic low-fertility soils (ElSharkawy and Tafour 2010). While manioc is productive on low-fertility soils, it produces higher yields in fertile or fertilized soils (Cadavid et al 1998; El-Sharkawy 2004; Omorusi and Ayanru 2011). It is likely that much subsistence cultivation of manioc fails to realize the full yield potential of the crop. Arbuscular mycorrhiza (AM) may represent a low-cost resource that could improve plant nutrient acquisition and enhance manioc production (Cardoso and Kuyper 2006)
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