ALVES, V. M. C.

COELHO, A. M.

GOMES, E. A.

MARRIEL, I. E.

OLIVEIRA-PAIVA, C. A.

PINTO, A. C.

RAPOSEIRAS, R.

SALES, S. H. O.

SCHAFFERT, R. E.

SOARES, E. M.

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Mycorrhizal diversity of glomaceae family from sorghum rhizosphere in cerrado soil withdifferent aluminum saturationRaposeiras, R.; Marriel, LE.'; Gomes, E.A.'; Oliveira, C.A.2; Pinto, A.C.; Alves, Y.M.C.';'Soares,E.M; Sales, S.H.O.; Coelho, A.M.'; Schaffert, R.E.''Embrapa Milho e Sorgo, Sete Lagoas, MG, Brasil; 2UFMG/ICB Departamento de Botânica, 31270-901, Belo Horizonte-MG, Brasil MG e 3PUC.Minas; imarriel@cnpms.embrapa.brIntroductionPhosphorus (P) is an essential nutrient and it is frequently limiting macronutrient for plantgrowth, especially in acid soils. ln many agricultural systems in which high application ofP tothesoil is necessary to ensure plant productivity, the recovery of applied P by crop plants is very low,because in the soil more than 80% ofthe P becomes immobile and unavailable for plant uptake dueto adsorption, precipitation, or conversion to the organic form (Raij, 1991; Holford, 1997). On theother hand, microbial associations, inc1uding mycorrhizal symbioses, are altematives of low costimportant for phosphorus supply. Arbuscular mycorrhizas (AM) are likely a primitive state for allvascular plants, and the glomalean fungi that produce them form symbiotic associations with mostterrestrial plants (Smith & Read, 1997; Brundrett, 2002). Plants benefit from these associations byimproved nutrient acquisition and protection from other biotic and abiotic factors less well defined(Schachtman et al., 1998). However, plant and soil factors can influence the benefits provided bymycorrhizal fungi to plants. Little information currently exists on species diversity in communitiesof arbuscular mycorrhizal fungi (AMF) associated with sorghum plant. Recently, progress hasoccurred in the study of plant-microorganisms interactions mainly because of the introduction ofnew molecular techniques such as polymerase chain reaction (PCR) (Smalla et al., 1993) anddenaturing gradient gel electrophoresis (DGGE) (Muyzer and Smalla, 1998). The aim ofthis workwas to characterize the genetic diversity of arbuscular mycorrhizas colonizing sorghum rhizospherein cerrado affected by genotypes and aluminum saturation.Materiais and MethodsRhizosphere soil were collected from two sorghum cultivars (G 1-tolerant and G2-sensible)growing in cerrado soil, with three levels of aluminum saturation (O, low; 30 intermediary and 50%,high) and sieved through a 2-mm sieve. For non-rhizosphere control, soil without roots was used.Soil samples of 500 mg were used for total DNA extraction using BIO 101 Kit protocols, followingthe manufacturer's recommendations. The small subunit (SSU) ribosomal RNAgene were amplifiedfrom a total soil DNA extract based on nested PCR using fungal universal primers (NS5 and ITS4)and ITS/Glomaceae specific primers attached with the sequence c1amp, GLOM1310 and ITS2(Redecker, 2000). PCR products were loaded by electrophoresis in a 6% polyacrilamide gel composedof denaturing gradients between 45 and 70% of urea- formamide gels (DGGE) and run for 16h in aBIO-RAD Dcode System, VA, USA. A routine silver staining protocol was used for detection ofDNA and the gels were documented with digital camera before analysis.Results and DiscussionBased on DGGE pattems, the dates allow the comparison of variation in the AM fungalcommunity composition among plants genotypes, between presence and absence of plants andbetween levels of aluminum saturation. As expected, diversity (measured here as the number ofamplicons) was higher on roots than in non-rhizosphere soil. There was a strong shift in themycorrhizal communities due to AI in the non-rhizosphere soil samples and in the rhizosphere soilof the sensible genotype, with reduced diversity. But, an apparent paradoxical increase in AMFrichness was noted with tolerant genotype. There was high diversity AMF at high Allevel, perhaps260 Proceedings of S'" International Symposium on Phosphorus Dynamics in the Soil-Plant Continuumreflecting association with sorghum adaptation to AI stress. Similarly, the cluster analysis identifiedtwo principal groups. Group Iwith samples of soil free of roots, and group 11,with samples ofrhizosphere, suggesting two different communities. The subgroups observed - two in the group Iand three in the group 11,show the influence aluminum saturation and genotypes in the compositionofthe studied fungi, respectively. The high diversity and variation detected due to analyzed factorsimplies that the AM fungal types are ecologically distinct and thus may have the potential to influenceadaptation of sorghum cultivars to acid soil.ConclusionsThe diversity in communities of arbuscular mycorrhizal fungi ofGlomaceae family in cerradosoil is stimulated by sorghum plants and reduced by aluminum toxicity.The arbuscular mycorrhizal community composition of Glomaceae family in cerrado soildepends of sorghum genotype.ReferencesBrundrett, M.C. Coevolution ofroots and mycorrhizas ofland plants. New Phytologist 154:275-304.2002.Holford, L C.R Soil phosphorus: its measurement, and its uptake by plants. AustJ Soil Res 35:227-239. 1997Muyzer, G.; Smalla, K. Application of denaturing gradient gel electrophoresis (DGGE) andtemperature gradient gel electrophoresis (TGGE) in microbial ecology. Antonie van Leeuwenhoek73: 127-141. 1998.Raij, B. Fertilidade do solo e adubação. São Paulo, Ceres, 1991. 343p.Redecker, D. Specific PCR prmers to identify arbuscular mycorrhizal fungi within colonized roots.Mycorrhiza, 10:73-80. 2000.Schachtman, D. P.; Reid, R. J. & Ayling S. M. Phosphorus uptake by plants: from soil to cell.Plant Physiology 116:447-453. 1998.Smith, S.E, Read D.l. 1997. Mycorrhizal symbiosis. London, UK: Academic Press.Proceedings of 3'" lnternational Symposium on Phosphorus Dynamics in the Soil-Plant Continuum 261

Mycorrhizal diversity of glomaceae family from sorghum rhizosphere in cerrado soil with different aluminum saturation.

Mycorrhizal diversity of glomaceae family from sorghum rhizosphere in cerrado soil with different aluminum saturation.

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