Arbuscular Mycorrhizal Fungi Inoculation and Intercropping Combine to Control Nematodes in Bananas

Aims: To investigate the combined effect of Arbuscular Mycorrhizal Fungi (AMF) and intercropping on the control of the nematode Radopholus similis in banana.

Study Design: The study involved an experiment in which banana-banana monocrops alongside banana-groundnut and banana-sweet potato intercrops were inoculated with AMF Rhizophagus irregularis MUCL 41833 to control the nematode R. similis.

Place and Duration of Study: Centre Africain de Recherches sur les Bananiers et Plantains (CARBAP), from September 2016 to April 2017.

Methodology: An experiment was conducted under greenhouse conditions (photoperiod 12 h. average temperature 24 - 28°C and 70 - 80% relative humidity) and R. irregularis were tested against R. similis with banana intercropped with either groundnut, sweet potato or banana itself. The plants were cultivated in boxes (30 x 15 x 10 cm) containing sterilized (2x1hour at 121°C) sand/coffee ash substrate (proportion 1:2 v/v), as an intercropping system with the following plant combinations: Banana-banana, banana-groundnut and banana-sweet potato. The experimental set-up was a completely randomized design comprising four treatments and six replicates: (1): Nematode (Nem), (2) AMF, (3) AMF + Nema and (4) control without nematode and without AMF. The ratio of banana: intercrop was 1:1 in the intercropping treatments. A total of 72 boxes was considered in the experimental set-up.

Results: AMF root colonization of banana was clearly affected by intercropping with about 25% increment observed in banana co-cultivated with groundnut or sweet potato compared to banana-banana combination. Positive effects of AMF expressed as an increase in banana biomass compared to the control treatment was observed in root fresh as well as shoot dry weights. However, the impact of AMF colonization in intercropping systems on R. similis did not confirm its bioprotective effect. Intercropping had a significant (P < .05) effect on R. similis and sweet potato has been shown to be more effective in controlling R. similis with 62% reduction compared to groundnut (24% reduction). Contrarily, banana plant growth decreased in the banana / sweet potato combination.

Conclusion: Findings in this study indicate that R. similis biological control in the banana intercropping system is more dependent on the intercrop species than on AMF.