In vitro association of banana plantlets to arbuscular mycorrhizal fungi : application to the interactions study with a plant parasitic nematode and the mass-production of mycorrhized plantlets

Today, one major practice to control diseases and pests in banana fields is the use of in vitro plantlets. However, nematodes, in particular Radopholus similis, remain a major problem. The restriction on the use of nematicides has encouraged the development of alternative strategies, among which the use of biological control organisms (BCO) such as arbuscular mycorrhizal fungi (AMF). Their beneficial effects on the control of nematodes have been demonstrated but their application in the field remains rare. In the recent decade the association of BCO to plants at the in vitro stage, has been proposed to produce plants more resistant to pathogens and to transplant stresses. The in vitro association of AMF to banana plantlets may thus represent an adequate system to investigate the interaction with nematodes and for the mass-production of mycorrhized plantlets. Here we developed an in vitro culture system for the mycorrhization of banana plantlets. It was used to study the interactions with the nematode R. similis and to evaluate the effects of the in vitro mycorrhization on plant acclimatization. Regarding the interaction with the nematode, the total R. similis population as well as the root necrosis was significantly reduced in the mycorrhizal plantlets. By contrast, nematodes had no visible impact on the AMF. Regarding the acclimatization of the banana plantlets, the mycorrhized plantlets had a significantly higher vegetative growth as compared to the non mycorrhized plantlets proliferated on the Murashige-Skoog and Modified Strullu-Romand medium. The introduction of AMF in the in vitro micropropagation process may thus represent an innovative alternative to mass-produce banana plantlets, potentially more resistant against nematodes.