Effects of arbuscular mycorrhizal fungi on severity of root rot of bananas caused by Cylindrocladium spathiphylli

The interaction between four arbuscular mycorrhizal (AM) fungi, Glomus sp., G. proliferum, G. intraradices and G. versiforme, and the root-rot fungus Cylindrocladium spathiphylli, and subsequent effects on growth and phosphorus nutrition of banana (Musa acuminata, AAA, cv. Grande Naine) were investigated under glasshouse conditions. Overall, root infection by C. spathiphylli reduced the growth of banana plants, but preinoculation with AM fungi significantly attenuated this detrimental effect. Lower disease severity, stimulation of growth and increase of shoot P content were observed for the plants inoculated with one of the four AM fungi. Glomus sp. and G. proliferum induced the largest increase in growth parameters and shoot P content as compared to G. intraradices and G. versiforme, in the presence as well as in the absence of C. spathiphylli. Root damage caused by C. spathiphylli was decreased in the presence of A-M fungi, but the inoculation of mycorrhizal plants with C. spathiphylli also decreased the intensity of AM fungal root colonization, indicating a clear interaction between the two organisms.