Ana Teresa Mosquera-Espinosa

The natural vanilla crop faces serious phytosanitary problems. Phosphate-solubilizing bacteria (PSB) in the plant rhizosphere offer potential for enhancing crop productivity by improving nutrient availability for plants and resistance to biotic and abiotic stresses. In order to explore the rhizosphere microbiome in wild vanilla relatives, phosphate-solubilizing bacteria were isolated using three different selective media from six Vanilla taxa in circa situm conditions. 612 bacterial isolates with phosphate-solubilizing activity were obtained. 51 representative morphotypes were identified to 24 bacterial species in 15 genera. Predominant genera were Burkholderia, Paraburkholderia and Bacillus, with a microbiome distinct to that found in the vanilla crop, indicating the possible impact of the domestication process on plant microbiomes. The medium Pikovskaya Agar yielded the greatest taxonomic diversity. An effective ex situ conservation protocol was demonstrated for these valuable microbiome components, with reactivation ability after preservation for three and six months was 81 % and 77 %, respectively. This is the first study of PSB in vanilla crop wild relatives and provides a necessary base from which to continue research into the vanilla secondary gene pool and their microbiomes, currently underutilized resources for the sustainable cultivation of this valuable tropical crop.

Vanilla is an economically important crop for low‐lying humid tropical regions, but cultivated plants face serious phytosanitary problems. Fusarium wilt is a devastating disease affecting vanilla crops, caused by the fungal pathogens Fusarium oxysporum f. sp. vanillae (Fov) and F. oxysporum f. sp. radicis‐vanillae (Forv), part of the F. oxysporum species complex (FOSC). We characterized 29 fungal isolates from a vanilla crop and crop wild relatives (CWR) using molecular (EF1‐α and ITS‐rRNA loci) and morphological traits. Fusarium was the predominant genus, followed by Colletotrichum and Clonostachys . Four Fusarium species were identified: F. oxysporum (37.9%), Fusarium solani (20.7%), Fusarium pseudocircinatum (13.8%) and Fusarium concentricum (10.3%). The latter three species were isolated only from CWR and may represent latent pathogens. Fov was isolated from both the crop and CWR, while a Forv‐affiliated isolate was also found in a vanilla crop, marking the first report in the neotropical region. The EF1‐α locus provided greater genotype resolution, as well as having reference sequences for Forv. However, the fungal barcode ITS locus is widely applied. We recommend the continued use of both loci for Fusarium diagnosis in vanilla to facilitate early detection and the development of effective integrated crop management strategies.

Este artículo trata sobre microorganismos solubilizadores de fosfato - MSF, haciendo énfasis en bacterias - BSF, y compila información basada en resultados de investigación, que plantea la disponibilidad de fosforo en la rizosfera de las plantas por actividad del microbioma asociado, tomando como caso de estudio BSF en cultivos de café a nivel mundial. Se buscaron artículos científicos publicados hasta diciembre del año 2023 sobre MSF y BSF, su aislamiento y su uso en fitonutrición y fitosanidad. Se consultaron las bases de datos de Scopus, ScienceDirect, Jstore, Web of Science, Wiley Online Library usando acceso con licencia de la Pontificia Universidad Javeriana (PUJ). También, los portales de búsqueda de libre acceso ResearchGate, Scielo, Mendeley y Google Scholar. Se evidencia que son pocos los artículos publicados en los últimos cinco años de manera específica sobre disponibilidad de P por actividad microbiana en café, por lo cual toma importancia este tipo de publicación. En relación con el uso de BSF, existen avances biotecnológicos que permiten considerarlas como alternativas para la biofertilización fosfórica, sin embargo, falta investigación para el cultivo de café principalmente en Colombia, y, sobre todo, es baja la implementación de esta tecnología por parte de agricultores y técnicos.

Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. vanillae (Fov), is a disease that results in significant losses in commercial vanilla production. The genera Ceratobasidium (Ceratobasidiaceae) and Tulasnella (Tulasnellaceae), which are often reported as mutualistic symbionts in orchids, belong to the form genus Rhizoctonia, a paraphyletic group of fungi with potential for pathogen biocontrol. We assayed the antagonistic properties of the form genus Rhizoctonia from the roots of neotropical orchids: two Tulasnella spp. isolates (Bv3 and Er1) and one Ceratobasidium sp. (Er19). In a dual culture, we found that form genus Rhizoctonia isolates can generate a biocontrol effect against Fusarium through the mechanisms of antibiosis and competition for space and nutrients. On histological observations, orchid root endophytes also demonstrated potential for mutualistic symbiosis development by establishing themselves on the surface and within the root tissue of Vanilla planifolia accessions multiplied in vitro (NSF021 and NSF092). However, in plant assays, the form genus Rhizoctonia isolates did not reduce symptom expression or disease development due to infection by Fov in the host. These results contribute to the knowledge of the interactions between tropical orchids and their microbiota and demonstrate the need for multidisciplinary studies for the implementation of integrated management strategies for Fusarium disease in commercial systems.

Vanilla is an economically important crop for low-lying humid tropical regions. World demand for natural vanilla is increasing, but cultivated plants face serious phytosanitary problems. The disease known as Fusarium wilt is mainly related to the fungus Fusarium oxysporum f. sp. vanillae, and for its management, the pathogen–host relationship must be understood. Four in vitro multiplied vanilla accessions were evaluated: two Vanilla planifolia from Colombia and Mexico, one from V. odorata, and one (1) F1 hybrid (V. rivasii × V. trigonocarpa). In addition, three isolates of Fusarium from different symptomatic plants present in small-scale agroforestry systems: (1Fov) F. oxysporum f. sp. vanillae from leaf, (2Fov) F. oxysporum f. sp. vanillae from root and (3Fs) F. solani also from root. Plants with two months of growth were inoculated in vitro by immersion of roots, and the development of Fusarium wilt was recorded for 15 days, using a severity scale to describe symptoms and to calculate the area under the disease progress curve (AUDPC). No statistical differences were found when analyzing the interaction between Fusarium isolates and vanilla accessions. However, when independently analyzing the design factor Fusarium isolates, there were significant differences; the 1Fov isolate of F. oxysporum f. sp. vanillae induced the highest symptoms as well as death in some plants of all accessions, while F. solani was considered a secondary pathogen. There were no statistical differences for the vanilla accessions factor, but the values of AUDPC and symptoms observed suggest a slight resistance in all the accessions. Therefore, it is suggested to explore the vanilla gene pool to generate multiplication material with resistance genes and to contribute with genetic improvement to successfully integrate the management of Fusarium wilt in commercial systems.

La interacción biótica entre plantas y hongos endófitos fortalece la capacidad adaptativa de los hospederos frente a perturbaciones del ambiente, y confiere a los microorganismos asociados beneficios de nutrición y protección. Estudios asociados a hongos endófitos reportan su presencia en la mayor diversidad de plantas existentes. En diferentes plantas hospederas, la interacción con hongos endófitos favorece la producción de metabolitos secundarios y fitohormonas que participan en la obtención de propiedades organolépticas como los sabores y los aromas. Sin embargo, las investigaciones desarrolladas en el género Vanilla son escasas, dificultando el entendimiento de las funciones que pueden desempeñar estos microorganismos en beneficio del hospedero. Con relación a Vanilla, los frutos de especies dentro del clado aromático se distinguen por la presencia de compuestos aromáticos, que aumentan su contenido durante la maduración. Algunos estudios, han demostrado que en los frutos de esta orquídea existen hongos endófitos posiblemente asociados al proceso de maduración que se acelera mediante el curado, pero pocos de estos estudios, han evaluado la actividad de dichos hongos relacionados con la maduración del fruto de forma natural. En esta revisión se recopila literatura científica relacionada con el conocimiento de las comunidades de endófitos fúngicos y su posible aporte en la maduración y producción de compuestos aromáticos en los frutos de vainilla. Se identifican oportunidades de investigación para desarrollar futuros estudios sobre el papel de los microorganismos fungosos para la obtención de metabolitos y precursores aromáticos de los frutos en especies de Vanilla, tanto en condiciones silvestres como en cultivos comerciales.

PREMISE OF THE STUDY: Oeceoclades maculata is a naturalized, invasive, terrestrial orchid in Puerto Rico and elsewhere in the neotropics. We asked whether its success might be partly explained by its mycorrhizal associations, hypothesizing a relationship with many fungal partners or with one widely distributed partner.METHODS: Oeceoclades maculata roots were collected throughout Puerto Rico, and the degree of mycorrhizal colonization was measured. For identification of fungi, the ITS region was sequenced from pure cultures and directly from roots. Representative fungi were used for symbiotic seed germination experiments.KEY RESULTS: Colonization of O. maculata roots was very variable. The most common fungus identified by BLAST searches was Psathyrella cf. candolleana, but typical orchid mycorrhizal fungi (Ceratobasidium and Tulasnella) were also found, as were a range of saprotrophs. Seeds germinated in vitro only in the presence of Psathyrella.CONCLUSIONS: These results are surprising in two respects. First, O. maculata appears to be highly specific for fungi during seed germination, but unusually promiscuous as adult plants. Second, mycorrhizal associations with Psathyrella and with other saprotrophic fungi have been previously reported, but only from mycoheterotrophic (i.e., nonphotosynthetic) orchids, not from green orchids like Oeceoclades. This combination may partly explain the success of Oeceoclades.