-The effect of the combined inoculation of the arbuscular mycorrhizal fungus Glomus manihotis and a rhizobacteria consortium of Bacillus spp. on micropropagated banana plantlets, during the acclimatization phase under routine nursery conditions was investigated. Micropropagated banana plantlets from the 'Grande Naine' cultivar were inoculated with G. manihotis at the beginning of the nursery phase. Twenty days after fungal inoculation, a Bacillus consortium containing approximately 10 8 CFU (colonies former units) mL -1 was applied. Plants were harvested 4 ½ months after bacterial inoculation. Combined application of mycorrhizal fungus and rhizobacteria significantly increased plant growth and nutrition. Combined inoculated plants showed growth parameters, i.e. total fresh weight, aerial dry weight, shoot length and leaf area, significantly higher than non-treated control bananas. Leaf mineral content, i.e. N, P and K, was also significantly increased following combined application of both microorganisms. No adverse effect on mycorrhizal colonization due to Bacillus spp. inoculation could be detected. Our results demonstrate that the combined application of arbuscular mycorrhizal fungi and plant growth-promoting rhizobacteria highly benefits banana plants and therefore could be considered during the acclimatization stage of micropropagated banana.Glomus / Bacillus / micropropagated banana / growth / nursery phase / nutrition

Effect of the combined inoculation of arbuscular mycorrhizal fungi and plant growth-promoting rhizobacteria on papaya (Carica papaya L.) infected with the root-knot nematode Meloidogyne incognita.Abstract --Introduction. Arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR) can be considered important rhizospheric beneficial microorganisms. Their use as biocontrol strategies against soilborne pathogens such as nematodes should be taken into account. However, optimal management of soil microbiota communities is not easy because of the high specificity involved in these types of interactions. The aim of our study was to determine whether the combined inoculation of two AMF species and a Bacillus consortium based on three strains previously described as PGPR in other crops were able to reduce nematode infection and damage on papaya. Materials and methods. Papaya seedlings were inoculated with two AMF isolates (Glomus mosseae or G. manihotis) at the beginning of the nursery phase. Once the mycorrhizal symbiosis was established, a Bacillus consortium was applied. Nematode inoculum was applied 20 d after transplanting to individual pots. Plants were harvested 160 d after nematode inoculation. Results. In terms of plant development and nutrition, benefits due to AMF inoculation persisted in the presence of PGPR. However, the effect of dual inoculation was different, depending on the Glomus species. This positive effect was also evident in plants with nematode. Meloidogyne infection was significantly reduced in mycorrhizal plants. However, the addition of PGPR does not seem to improve the results of AMF single treatments in terms of nematode infection. Conclusion. Dual application of AMF and PGPR must be considered for papaya threatened by the root-knot nematode, although a previous screening should be done in order to select the best microbe combination to optimise results. Spain / Carica papaya / arbuscular mycorrhizae / Glomus / rhizobacteria / Bacillus / symbiosis / growth / plant nutrition / biological control Effet de l'inoculation combinée de champignons mycorhiziens à arbuscules et de rhizobactéries favorisant la croissance des plantes, sur le papayer (Carica papaya L.) infecté par Meloidogyne incognita, nématode des racines.Résumé --Introduction. Les champignons mycorhiziens à arbuscules (CMA) et les rhizobactéries favorisant la croissance des plantes (RFCP) peuvent être considérés comme d'importants micro-organismes bénéfiques à la rhizosphère. Leur utilisation dans une stratégie de lutte biologique contre les pathogènes du sol, contre les nématodes par exemple, devrait être envisagée. Cependant, la gestion optimale des populations de micro-organismes du sol n'est pas facile en raison de la grande spécificité de ces types d'interactions. Le but de notre étude a été de déterminer si l'inoculation combinée de deux espèces de CMA et d'un consortium de rhizobactéries Bacillus spp., basé sur trois souches précédemment décrites comme RFCP pour d'autres cultures, pouvaient limiter l'infect...

The effect of strains EPS291 and EPS817 of Pseudomonas fluorescens to improve plant growth and nutrition as well as to reduce root‐knot nematode in roots was investigated in micropropagated banana. Plantlets, cultured under commercial nursery conditions, were treated twice with bacteria after transplanting from in vitro conditions. Bacterial application was performed by drenching bacterial suspension containing approximately 108 CFU (colony‐forming units) g−1 of substrate. Both strains significantly increased aerial fresh weight, plant length and leaf area, while the effect on other growth parameters depended on the strain. N content was also significantly increased after both bacteria treatments. A second experiment was performed to determine the potential biocontrol effect against the root‐knot nematode Meloidogyne javanica. Following the same experimental conditions, Meloidogyne inoculum containing 10 500 nematodes was applied 15 days after the second bacteria treatment. At the end of the experiment, 135 days later, nematode reproduction in roots of bacterised bananas was significantly reduced. In both experiments, the inoculated bacteria colonised the root system and population levels in root, 5.5 months after transplanting were 6.8 × 103 to 1.6 × 104 CFU g−1 fresh weight of root. The potential use of this technology to improve hardening stages in banana plant production in commercial nurseries is discussed.

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