Arbuscular Mycorrhizal Dependency of Three Moringa Genotypes

The genus Moringa includes several multi-purpose species that are receiving increased attention worldwide because of their potential to enhance human health, nutrition, and to generate income in the tropics. Although adapted to low-input environments, fertilization of Moringa is generally required for optimum production. Inoculation with arbuscular-mycorhizal (AM) fungi is a promising strategy to enhance plant growth and P nutrition while reducing inputs in the tropics. However, there is almost no information available regarding the response of Moringa sp. to AM fungal inoculation. To bridge this knowledge gap, two genotypes of Moringa oleifera (‘PKM-2’ and ‘Hawaii’) and one accession of Moringa stenopetala (Steno) were evaluated for their response to inoculation with Glomus aggregatum under varied soil solution P concentrations in two greenhouse experiments. The response of the three genotypes varied significantly and was dependent on soil solution P concentration. Dry matter accumulation and tissue P levels of all genotypes were generally enhanced by inoculation at relatively low soil-solution P concentrations (0.009-0.02 mg L^-1). The degree to which the accessions tested depended on mycorrhizal association for growth and P uptake  was calculated to be 40-50% for ‘Hawaii’, 20-50% for ‘PKM-2’ and <20% for  ‘Steno’. We, therefore, classified M. oleifera as moderately dependent and M stenopetala as marginally dependent on mycorrhizal association. At higher soil solution P concentrations (0.02-0.20 mg L^-1), ‘PKM-2’ exhibited a sharp decreases in dry matter accumulation with AM  fungal colonization resulting in negative dependency values (-20 to -40%). The parasitic effect of G. aggragatum at the  higher soil solution P concentrations was not observed in the other genotypes.  Our work represents the first investigation on the interaction of Moringa sp. with arbuscular-mycorrhizal fungi.