ABSTRACT Forest-to-agriculture conversion and soil management practices for soybean cropping are frequently performed in the Cerrado (Brazilian tropical savanna). However, the effects of these practices on the soil microbial communities are still unknown. We evaluated and compared the fungal community structure in soil from soybean cropland with soil under native Cerrado vegetation at different times of the year in the Tocantins State. Soil samples were collected in two periods after planting (December) and in two periods during the soybean reproductive growth stage (February). Concomitantly, soil samples were collected from an area under native Cerrado vegetation surrounding the agricultural area. The soil DNA was analyzed using a fingerprinting method termed Automated Ribosomal Intergenic Space Analysis (ARISA) to assess the fungal community structure in the soil. Differences in the fungal community structure in the soil were found when comparing soybean cropland with the native vegetation (R = 0.932 for sampling 1 and R = 0.641 for sampling 2). Changes in the fungal community structure after management practices for soybean planting in Cerrado areas were related to changes in soil properties, mainly in copper, calcium, and iron contents, cation exchange capacity, base saturation, and calcium to magnesium ratio. These results show the changes in the fungal community structure in the soil as an effect of agricultural soil management in Cerrado vegetation in the state of Tocantins.

Com objetivo de avaliar a variabilidade fenotípica e a divergência genética entre 50 clones de batata doce, foi realizado um ensaio na Estação Experimental da Universidade Federal do Tocantins - Campus de Palmas, no ano agrícola 2009/2010. A divergência genética foi avaliada pelo método de agrupamento de otimização de Tocher. As características estudadas foram produtividade, produção de matéria seca, teor de amido e rendimento de etanol. O método de otimização por Tocher separou os clones em oito grupos geneticamente distintos. As características produtividade (70,15%) e rendimento em etanol (15,06%) foram as que mais contribuíram na divergência genética entre os clones. A presença de variabilidade genética permitiu a identificação de cultivares dissimilares e com média elevada indicando a possibilidade de seleção de genótipos superiores para as características estudadas. Os cruzamentos Duda x 22.19, Marcela x 22.19, Barbara x 22.19, Duda x Barbara, Amanda x 22.19, Amanda x Marcela são promissores para obtenção de híbridos divergentes.

In order to evaluate the phenotypic variability and genetic divergence between 50 clones of the sweet potato, a test was conducted at the Experimental Station of the Federal Universidade of Tocantins, Palmas Campus, in the agricultural year of 2009/2010. The genetic diversity was assessed using the Tocher grouping optimization method. The characteristics studied were productivity, dry matter production, starch content and ethanol yield. The Tocher optimization method separated the clones into eight genetically distinct groups. The characteristics of productivity (70.15%) and ethanol yield (15.06%) were those that most affected genetic divergence among the clones. The presence of genetic variability permitted the identification of dissimilar cultivars with a high average, indicating the possibility of selecting superior genotypes for the traits studied. The Duda x 22.19, Marcela x 22.19, Barbara x 22:19, Duda x Barbara, Amanda x 22:19, Amanda x Marcela crossbreeds are those which are promising for obtaining divergent hybrids.

A época de semeadura é definida por um conjunto de fatores ambientais que reagem entre si e interagem com a planta, promovendo variações na produção e afetando outras características agronômicas. Assim, o trabalho teve como objetivo avaliar o comportamento de 21 cultivares comerciais de soja, em diferentes épocas de semeadura, visando a produção de biocombustível. Foram conduzidos cinco ensaios no ano agrícola 2008/09, sendo dois na área experimental da Universidade Federal do Tocantins - UFT, em Palmas-TO e três na Área Experimental da UFT, em Gurupi-TO. Os plantios foram efetuados em 03/12/2008, 18/12/2008 e 05/01/2009, em Gurupi, e 30/11/2009 e 16/12/2009, em Palmas. O delineamento experimental foi de blocos ao acaso com 21 tratamentos e três repetições. Os tratamentos foram constituídos pelos cultivares P98Y70, M-SOY 8766RR, M-SOY 9144RR, BR/Emgopa 314, P98R91, P98Y51, M-SOY 9988RR, P99R01, M-SOY 8867RR, M-SOY 9056RR, M-SOY 8527RR, M-SOY 8360RR, FT ESPERANÇA, FTS 4188, CM 07, CM 017, CM 136, CM 149, CM 102, NIDERA A 7002 e M-SOY 9350. Foram avaliadas as características: rendimento de grãos, teor de óleo e rendimento de óleo. Foram detectadas diferenças significativas entre cultivares, épocas e cultivares x épocas para todas as características. A primeira época de plantio em Palmas (30/11) e Gurupi (03/12) foram as mais propícias para o desenvolvimento dos cultivares. Houve associação positiva e significativa entre rendimento de óleo e produção de grãos (R = 0,97). Temperaturas mais altas e menores médias de precipitações pluviométricas durante a fase de enchimento de grãos favoreceram o acúmulo de óleo nas sementes. Os cultivares que mais se destacaram para teor de óleo e rendimento de óleo foram NIDERA A 7002, MSOY 9144RR, BR/EMGOPA 314, P98Y51 e FTS 4188.

The sowing season is defined by a set of environmental factors that react with each other and interact with the plant, thus affecting variations in production and other agronomic traits. This work was carried out to evaluate the behavior of 21 cultivars of commercial soybean, during different times, looking forward to the production of biofuel. Were conducted five essays in the 2008/09 agricultural year, being two of them in Palmas-TO and three in Gurupi-TO. The sowing in Gurupi-TO was in 03/12/08, 18/12/2008 and 05/01/2009,and in Palmas in 30/11/2009 and 16/12/2009. The experimental design was a randomized blocks with 21 treatments and three repetitions. The treatments were constituted on the cultivars P98Y70, M-SOY 8766RR, M-SOY 9144RR, BR/Emgopa 314, P98R91, P98Y51, M-SOY 9988RR, P99R01, M-SOY 8867RR, M-SOY 9056RR, M-SOY 8527RR, M-SOY 8360RR, FT ESPERANÇA, FTS 4188, CM 07, CM 017, CM 136, CM 149, CM 102, NIDERA A 7002 and M-SOY 9350. The following characteristics, were evoluated production of grains, oil content of the grain and oil yield. Significant differences were detected among cultivars, sowing season and cultivate x sowing season for all characteristics. The first planting time in Palmas (30/11) and Gurupi (03/12), were the most favorable to the development of cultivars. There was positive and significant association between oil yield and production of grains (R = 0.97). Higher temperatures and rainfall precipitation averages, during the phase of stuffing of grains, favored the oil accumulation in the grains. NIDERA A 7002, MSOY 9144RR, BR/Emgopa 314, P98Y51 and FTS 4188 were the best cultivars for oil content of the grain and oil yield.