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The objective of this work was to evaluate the influence of arbuscular mycorrhizal fungi (AMF) on the accumulation of shoot and root biomass and on the nutrient contents of Urochloa decumbens grown in soils with different densities. The experiment was carried out in a randomized complete block design, in a 4x2 factorial arrangement: four soil densities (1.0, 1.2, 1.4, and 1.6 kg dm-3) with and without inoculation of AMF, with four replicates. The biomass accumulation (dry matter weight of shoot and roots) and macro- and micronutrient contents of U. decumbens were determined at different soil densities. The mycorrhizal colonization of the plants was evaluated, and the number of mycorrhizal spores present in the soil was determined. The biomass accumulation of shoot and roots and macro- and micronutrient contents, as well as the number of mycorrhizal spores in the soil, were negatively affected by the increase in soil density. Only root biomass increased with AMF inoculation. There was no interaction between soil density and inoculation for shoot and root biomass accumulation. Arbuscular mycorrhizal fungi influence the accumulation of biomass in the roots and of N and Ca contents in the shoots of Urochloa decumbens even at the highest soil densities.

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ABSTRACT. Genetic diversity among local accessions and varieties subsidize plant breeding programs, allowing the utilization of existing variability in plants that have already adapted to local climate conditions. An alternative to studying genetic variability is the study of diversity. The aim of this research was to study genetic diversity among sugarcane accessions and varieties used for the production of craft-distilled cachaça (distilled sugarcane alcohol) in the region of Lavras, Minas Gerais, Brazil. Using a one-way design, an experiment was conducted in the municipality of Perdões, Minas Gerais to evaluate 35 regional accessions derived from germplasm collection expeditions and four varieties. Using morphological descriptions of 46 multicategorical sugarcane characteristics, dissimilarity and Tocher cluster method analyses were performed. Based on the results, it was concluded that genetic diversity exists among the accessions evaluated for the target traits.

ResumoA cultura da cana-de-açúcar desempenha um papel econômico importante na região de Lavras, Minas Gerais, onde é cultivada sem muito aporte tecnológico e com cultivares não adaptadas às condições edafoclimáticas locais. O objetivo deste trabalho foi avaliar cultivares de cana-de-açúcar quanto ao potencial produtivo agroindustrial na região sul de Minas Gerais, bem como estudar a associação entre os caracteres agronômicos e industriais no primeiro corte. O experimento foi conduzido no município de Lavras/MG, onde foram avaliadas 16 cultivares recomendadas para a indústria sucroalcooleira, em delineamento experimental látice quádruplo 4 X 4. Os resultados apresentados demonstraram que houve uma grande variabilidade genética entre as cultivares, proporcionando a formação de vários grupos de caracteres agroindustriais para os genótipos avaliados. Os genótipos que apresentaram um maior teor de fibra reduziram, ao mesmo tempo, a produção e a qualidade da matéria-prima da cana-de-açúcar. As cultivares SP891115, RB925211 e CTC9 foram as que apresentaram melhor desempenho quanto aos caracteres agroindustriais TCH, Pol, Fibra e ATR, e poderão ser indicadas para o cultivo comercial na região de Lavras. Palavras-chave: Saccharum spp. Produção. Correlação. Índice de seleção.