Effect of the combined inoculation of arbuscular mycorrhizal fungi and plant growth-promoting rhizobacteria on papaya (Carica papayaL.) infected with the root-knot nematodeMeloidogyne incognita

Abstract

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...

Pre-inoculation with arbuscular mycorrhizal fungi suppresses root knot nematode (Meloidogyne incognita) on cucumber (Cucumis sativus)

“…Since AM fungi and RKN are all indigenous soil organisms and therefore co-exist in plant roots, the potential role of AM fungi as biocontrol agents and their protective effects on plants against RKN have been well documented Diedhiou et al 2003). Studies have shown that inoculation with AM fungi can significantly reduce RKN infestation and reproduction in some plant-nematode systems (Hol and Cook 2005) such as papaya with Meloidogyne incognita (Jaizme- Vega et al 2006), olive planting stocks with M. incognita and Meloidogyne javanica (Castillo et al 2006), tomato with M. incognita (Talavera et al 2001;Siddiqui and Akhtar 2007), pyrethrum with Meloidogyne hapla (Waceke et al 2001), Prunus rootstocks with M. javanica (Calvet et al 2001), and banana with M. javanica (Rodriguez and JaizmeVega 2005). In addition to enhancement of plant nutrition, especially P nutrition, establishment of arbuscular mycorrhizae may exert beneficial effects on plant growth though direct competition with RKN for infection sites and space, alteration of the composition of root exudates, or through activation of plant defense reactions and other mechanisms (Smith et al 1986;Azcón-Aguilar and Barea 1996;Harrier and Watson 2004;Li et al 2006).…”

Evaluation of some fungicides on mycorrhizal symbiosis between two Glomus species from commercial inocula and Allium porrum L. seedlings

“…Considering the role of AMF in plant growth stimulation and protection (Pinochet et al, 1996;Calvet et al, 2001;Hernández-Dorrego, 2002;Sorensen et al, 2005;Jaizme-Vega et al, 2006;Barea et al, 2008), the objective of this work was to test the effect of twenty-five commercial fungicides which are among the most active chemicals currently applied in horticultural crops on the mycorrhizal symbiosis established by Glomus intraradices and Glomus mosseae isolates from commercial inocula, in leek (Allium porrum L.) seedlings under controlled conditions.…”

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“…De otro lado, la incorporación de micorrizas aumenta el crecimiento y favorece muchos cambios a nivel morfológico en el sistema radicular, estimulando la proliferación de raíces, lo que hace que las plantas sean más tolerantes al ataque de los nematodos 16,29,30 . En cuanto al porcentaje de colonización por HMA, existieron diferencias altamente significativas entre tratamientos.…”

“…En los últimos años se ha encontrado que cuando se inoculan las raíces de las plantas con hongos micorrizo arbusculares (HMA), se disminuye significativamente la incidencia de nematodos patógenos 14 . Existen ejemplos en especies frutales como el kiwi 15 , papaya 16 , y tomate 17 donde los HMA han disminuido el efecto negativo de los nematos patógenos. Debido a ésto, sería de gran utilidad conocer sí los HMA disminuyen estos efectos en plántulas de granadilla.…”