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Orchidaceae is a highly dependent group on the Rhizoctonia complex that includes Ceratorhiza, Moniliopsis, Epulorhiza and Rhizoctonia, for seed germination and the development of new orchid plants. Thus, the isolation and identification of orchid mycorrhizal fungi are important to understand the orchid-fungus relationship, which can lead to the development of efficient conservation strategies by in vivo germination of seeds from endangered orchid plants. The aim of our work was to isolate and characterize the different mycorrhizal fungi found in roots of terrestrial orchids from Córdoba (Argentina), and, to learn about the natural habit and fungal associations in the Chaco Serrano woodland pristine region. In this study, bloomed orchid root and rhizosphere soil samples were obtained in two times from Valle de Punilla during spring of 2007; samples were kept in plastic bags until processed within 48 hours, and mycorrhizal condition confirmed assessing peloton presence. A total of 23 isolates of the orchideous mycorrhizal Rhizoctonia complex were obtained. The isolates were studied based on morphological characters and ITS-rDNA sequences. Morphological characteristics as color of colonies, texture, growth rate, hyphal diameter and length and presence of sclerotia were observed on culture media. To define the number of nuclei per cell, the isolates were grown in Petri dishes containing water-agar (WA) for three days at 25°C and stained with Safranine-O solution. The mycorrhizal fungi were grouped into binucleate (MSGib, 10 isolates) and multinucleate (MSGim, 13 isolates) based on morphological characteristics of the colonies. We obtained the ITS1-5.8s-ITS4 region that was amplified using primers ITS1 and ITS4. Based on DNA sequencing, isolates Q23 and Q29 were found to be related to species of Ceratobasidium. Isolates Q24 and Q4 were related to the binucleated anastomosis group AG-C of Rhizoctonia sp. The rest of the isolates grouped in the Ceratobasidium clade without grouping. From our knowledge this is the first report of the association of the AG-C testers with terrestrial orchids. A high specificity was observed in the symbiotic relationship. As the mycorrhizal fungal isolates were obtained from native orchids, they could be incorporated in conservation programes of endangered orchids in Argentina.

Se evaluó el efecto de los hongos micorri - zógenos arbusculares (HMA) autóctonos Glomus sp. 1, Glomus sp. 2, Glomus clarum y Glomus intraradices en el cultivo de tomate ( Solanum lycopersicum L. Var., amalia ) en condiciones controladas, mediante las variables de crecimien - to altura, diámetro del tallo, cantidad de hojas, flores y frutos, fitomasa seca aérea y subterrá - nea y masa fresca de los frutos asimismo las variables micorrízicas que incluyen colonización, densidad visual, cuantificación de endófito, mice - lio externo y esporas. Las cepas Glomus sp. 1 y Glomus intraradices fueron las más eficientes, con valores del índice de cosecha de 65 y 56,3% y masa fresca de los frutos de 166,7 y 131,8 g, respectivamente. Se destaca que la cepa Glomus sp. 1 siempre presentó valores fúngicos menores que G. intraradices.

The effect of native arbuscular mycorrhizal fungi (AMF) Glomus sp. 1, Glomus sp. 2, Glomus clarum and Glomus intraradices on tomato (Solanum lycopersicum L. Var., amalia) was evaluated under controlled conditions by means of growth variables (height, stem diameter, number of leaves, flowers and fruits, dry aerial and underground biomass and fresh mass of fruits) and the mycorrhizal variables (colonization, visual density, quantification of endophyte, external mycelium and spores). The strains Glomus sp. 1 and Glomus intraradices were the most efficient, with harvest index values of 65 and 56.3% and fruit fresh weight of 166.7 and 131.8 g, respectively. It is emphasized that the fungal strain Glomus sp. 1 always presented lower values than strain Glomus intraradices.

Se evaluó la efectividad de la coinoculación micorrizas-rizobacterias en el crecimiento, desarrollo, rendimiento y colonización del tomate. Los experimentos se llevaron a cabo en el Instituto Nacional de Ciencias Agrícolas, Cuba, en un suelo Ferralítico Rojo lixiviado (Udic Rhodustalfs); los tratamientos consistieron en inoculación y/o coinoculación de la micorriza y la rizobacteria, bajo diferentes dosis de fertilización nitrogenada. Los resultados mostraron un efecto positivo de la coinoculación en el crecimiento de las plántulas, siendo la altura superior en un 23%; también se logró una eficiencia del 40% respecto a la fertilización nitrogenada, lo cual no afectó el estado nutricional de las plantas ni el rendimiento agrícola. La coinoculación potenció además la población de ambos microorganismos en la rizosfera del cultivo.

Orchidaceae is a highly dependent group on the Rhizoctonia complex that includes Ceratorhiza, Moniliopsis, Epulorhiza and Rhizoctonia, for seed germination and the development of new orchid plants. Thus, the isolation and identification of orchid mycorrhizal fungi are important to understand the orchid-fungus relationship, which can lead to the development of efficient conservation strategies by in vivo germination of seeds from endangered orchid plants. The aim of our work was to isolate and characterize the different mycorrhizal fungi found in roots of terrestrial orchids from Córdoba (Argentina), and, to learn about the natural habit and fungal associations in the Chaco Serrano woodland pristine region. In this study, bloomed orchid root and rhizosphere soil samples were obtained in two times from Valle de Punilla during spring of 2007; samples were kept in plastic bags until processed within 48 hours, and mycorrhizal condition confirmed assessing peloton presence. A total of 23 isolates of the orchideous mycorrhizal Rhizoctonia complex were obtained. The isolates were studied based on morphological characters and ITS-rDNA sequences. Morphological characteristics as color of colonies, texture, growth rate, hyphal diameter and length and presence of sclerotia were observed on culture media. To define the number of nuclei per cell, the isolates were grown in Petri dishes containing water-agar (WA) for three days at 25℃ and stained with Safranine-O solution. The mycorrhizal fungi were grouped into binucleate (MSGib, 10 isolates) and multinucleate (MSGim, 13 isolates) based on morphological characteristics of the colonies. We obtained the ITS1-5.8s-ITS4 region that was amplified using primers ITS1 and ITS4. Based on DNA sequencing, isolates Q23 and Q29 were found to be related to species of Ceratobasidium. Isolates Q24 and Q4 were related to the binucleated anastomosis group AG-C of Rhizoctonia sp. The rest of the isolates grouped in the Ceratobasidium clade without grouping. From our knowledge this is the first report of the association of the AG-C testers with terrestrial orchids. A high specificity was observed in the symbiotic relationship. As the mycorrhizal fungal isolates were obtained from native orchids, they could be incorporated in conservation programes of endangered orchids in Argentina. [ABSTRACT FROM AUTHOR]