The aim of this study was to determine the mycorrhizal status of four species of natural pastures of the community of Ccarhuaccpampa. The number of spores per 100 g of soil, the characterization of spores and the percentage of colonization of the roots were determined. The number of spores / 100 g of rhizospheric soil varied according to the plant species (66-732). Sixteen morphotypes of mycorrhizal fungi were located in three genera: Glomus, Acaulospora and Entrophospora, the first one was considered the most important because it had the highest number of morphotypes and was present in the different soils evaluated. A low mycorrhization of the analyzed roots was found (20 and 27%) and the presence of the arbuscular mycorrhizal association in all the species studied. A high correlation was determined between the number of spores per 100 g of soil and the percentage of mycorrhization of the roots, which indicated a similar tendency between both determinations.

La investigación se realizó con el objetivo de determinar el estado de micorrización de cuatro especies de pastos naturales de la comunidad de Ccarhuaccpampa. Se determinó el número de esporas por 100 g de suelo, la caracterización de esporas y el porcentaje de colonización de las raíces. El número de esporas/100 g de suelo rizosférico varió de acuerdo a la especie de planta (66 - 732). Destacaron 16 morfotipos de hongos micorrízicos ubicados en tres géneros: Glomus, Acaulospora y Entrophospora, el primero se consideró el más importante por poseer el mayor número de morfotipos y estar presente en los diferentes suelos evaluados. Se comprobó una baja micorrización de las raíces analizadas (20 y 27%) y la presencia de la asociación micorrízica de tipo arbuscular en todas las especies estudiadas. Se determinó alta correlación entre el número de esporas por 100 g de suelo y el porcentaje de micorrización de las raíces, lo cual indicó similar tendencia entre ambas determinaciones.

No Setor de Microbiologia do Solo, Departamento de Solos, da Universidade Federal do Rio Grande do Sul, Porto Alegre, Brasil, de janeiro de 1994 a março de 1995, quatro estirpes de Rhizobium leguminosarum bv. trifolii foram avaliadas para recomendação para a produção de inoculantes de trevo vermelho (Trifolium pratense). Em experimentos de casa de vegetação, as quatro estirpes apresentaram igual eficiência na fixação do nitrogênio. Contudo, em experimento de mistura de pares de estirpes, a estirpe SEMIA 222 foi mais competitiva na formação de nódulos. Em meio levedura manitol sacarose, a taxa de crescimento foi maior para as estirpes SEMIA 222, T107 e T154 do que a estirpe SEMIA 235. O tempo de geração da estirpe 222 foi mais baixo, seguido da T107 e T154, e maior para a estirpe 235. Em inoculante com veículo de turfa esterilizada, avaliado até seis meses de armazenamento, as estirpes 222 e T154 apresentaram boa sobrevivência, enquanto em inoculante com a mistura das estirpes, a T154 dominou a população. As duas estirpes apresentaram similar sobrevivência nas sementes tratadas por inoculação simples e por peletização.

Four strains of Rhizobium leguminosarum bv. trifolii were screened for their use in inoculants for red clover (Trifolium pratense) in the Soil Microbiology Sector, Department of Soils, University of Rio Grande do Sul, Porto Alegre, Brazil, from January 1994 to March 1995. In greenhouse experiments, all four strains presented similar efficiency in nitrogen fixation. However, when mixed strains were used, the strain SEMIA 222 was more effective in nodule formation. In a yeast manitol sucrose medium, growth rate was higher for strains SEMIA 222, T107 and T154, than for strain SEMIA 235. Generation time was lower for strain 222, followed by T107 and T154, and highest for 235. Strains 222 and T154 survived well in an inoculant with sterilized peat carrier evaluated at six months of storage, though the latter dominated the population in an inoculant with mixed strains. These two strains survived in a similar manner in inoculated seed.