Intergenotypic competition in the analysis of forest tree progeny trials.

No presente trabalho buscou-se introduzir o efeito da competição entre plantas nas análises dos testes de progênie/procedências em essências florestais, com o fim de identificar os seus efeitos e as distorções devidas à sua não observância. Para tanto, foram utilizados ensaios com níveis de precisão e mortalidades diferentes, de cinco espécies, a saber: Gallesia gorarema Vell. Moq., Eucaliptus grandis Hill ex Maider, Eucaliptus citridora Hook, Pinus elliottii Engl. var. elliottii e Araucaria angustifolia (Bert.) O. Ktze. Obtiveram-se as esperanças dos quadrados médios das fontes de variação da análise de variância nos delineamentos aqui utilizados. Com base nestas derivações, foi demonstrado explicitamente o viés nas estimativas de parâmetros genéticos quantitativos. Este viés está diretamente relacionado com a magnitude do coeficiente de regressão b e com a grandeza relativa das somas de quadrados de diferentes efeitos contidos na análise de variância da variável competição. Caso ignorado o efeito de competição, quando este influencia a variável resposta Y, os ponderadores b, que compõem o índice de seleção terão estimativas viesadas, gerando erro na seleção dos indivíduos superiores. Na análise de dados observou-se que a inclusão da competição, de maneira geral, reduziu as estimativas das componentes de variância, e por conseqüência, outras estimativas de parâmetros que são função destes, quando comparado com as estimativas feitas por via das análises sem o ajuste para a competição. A análise com a variável competição não mostrou diferenças significativas para o efeito de progênies. Isto demostra que a competição comportou-se de forma aleatória, o que corrobora para que seja colocada na análise como uma covariável; caso contrário esta teria que ser considerada uma componente da performance e introduzida numa análise multicaracterística. Utilizando as análises com e sem ajuste para a competição, para estimar os valores genéticos e o ganho com a seleção, observou-se que os indivíduos selecionados não são concordantes. Isto indica que os equívocos na seleção podem ser comuns, haja vista que o fato de se ajustar os dados faz com que o posto dos indivíduos tidos por superiores seja alterado. É recomendável considerar os efeitos da competição na análise de dados em que os indivíduos estão sujeitos a competir uns com os outros, no seu desenvolvimento.The aim of this work was to introduce competition effects in the model underlying the analysis of forest tree experiments. Results were compared with analyses in which effects were neglected. Progeny trails with different levels of precision and mortality were used, including the following species: Gallesia gorarema Vell. Moq., Eucaliptus grandis Hill ex Maider, Eucaliptus citridora Hook, Pinus elliottii Engl. var. elliottii and Araucaria angustifolia (Bert.) O. Ktze. Mathematical expectation of mean squares values were derived and the bias of estimates was explicitly shown. Competition effects were found significant in all experiments, but were primarily of random nature. Bias was shown to be directly proportional to the magnitude of the regression parameter b and to the relative magnitude of sums of squares of the competition variable. Including the variable in general lead to a reduction of estimates of variance components and to smaller expected progress from selection. The b coefficients of multi-effect selection index are also biased if competition is ignored. Results indicated that different sets of genotypes could be selected if the analyses of data were carried out with or without the competition effects. Including a competition variable in the analysis of trials in which plants are exposed to competing with each other is recommendable

Enraizamento de pecíolos de folhas de espécies silvestres e híbridos de Arachis

O gênero Arachis possui 69 espécies, sendo a maioria nativa do Brasil. Ápices radiculares de plântulas têm sido usados para a obtenção de células em divisão. Diversas espécies silvestres produzem pouca quantidade de sementes, o que dificulta a obtenção de meristemas para preparações citológicas. O objetivo deste trabalho foi avaliar a capacidade de enraizamento de diversas espécies silvestres de Arachis, usando a técnica de folhas destacadas para a obtenção de raízes a partir de pecíolos. Foram avaliados 130 acessos e 27 híbridos interespecíficos aos 15, 31 e 49 dias após o plantio. A formação de raízes a partir de folhas observada em espécies silvestres confirmou a ampla variabilidade genética típica do gênero Arachis, indicando que o número de dias também interfere na porcentagem de enraizamento. A Secção Arachis apresentou a maior taxa de enraizamento de folhas e a Secção Caulorrhizae apresentou o mesmo padrão da Secção Erectoides. Acessos pertencentes às Secções Heteranthae, Trierectoides, Extranervosae e Rhizomatosae não diferiram com relação à porcentagem de enraizamento. A Secção Erectoides apresentou comportamento similar ao das Secções Rhizomatosae e Extranervosae. A quantidade e morfologia de raízes obtidas por meio dessa técnica mostraram-se promissoras para uso em preparações citológicas.The genus Arachis has 69 species, the majority native to Brazil. Arachis spp. seedling root tips have been used to obtain dividing cells for cytological preparations. Several wild species produce small amounts of seeds and consequently few root meristems, making the cytogenetic characterization very difficult. The purpose of this study was to evaluate the rooting capacity of several wild species of Arachis using the detached leaves technique for obtaining roots from petioles. One hundred and thirty accessions and 27 interspecific hybrids were studied. Three evaluations were performed at 15, 31, and 49 days after planting. Leaf rooting observed in the wild species confirmed the great genetic variability typical of the Arachis genus, indicating that the number of days interferes with the rooting percentage. The Arachis Section presented the highest rate of rooting leaves. The Caulorrhizae Section showed the same pattern observed in the Erectoides Section. Accessions from Heteranthae, Trierectoides, Extranervosae, and Rhizomatosae Sections did not differ among each other. Differences were not observed in Erectoides Section when compared to Rhizomatosae and Extranervosae Sections. The number and morphology of roots obtained through this technique were promising to be used on cytological preparations

Rooting performance from leaf petioles of accessions and hybrids of wild Arachis species

The genus Arachis has 69 species, the majority native to Brazil. Arachis spp. seedling root tips have been used to obtain dividing cells for cytological preparations. Several wild species produce small amounts of seeds and consequently few root meristems, making the cytogenetic characterization very difficult. The purpose of this study was to evaluate the rooting capacity of several wild species of Arachis using the detached leaves technique for obtaining roots from petioles. One hundred and thirty accessions and 27 interspecific hybrids were studied. Three evaluations were performed at 15, 31, and 49 days after planting. Leaf rooting observed in the wild species confirmed the great genetic variability typical of the Arachis genus, indicating that the number of days interferes with the rooting percentage. The Arachis Section presented the highest rate of rooting leaves. The Caulorrhizae Section showed the same pattern observed in the Erectoides Section. Accessions from Heteranthae, Trierectoides, Extranervosae, and Rhizomatosae Sections did not differ among each other. Differences were not observed in Erectoides Section when compared to Rhizomatosae and Extranervosae Sections. The number and morphology of roots obtained through this technique were promising to be used on cytological preparations

Diversity of soil fungal communities of Cerrado and its closely surrounding agriculture Welds

Cerrado is a savanna-like region that covers a large area of Brazil. Despite its biological importance, the Cerrado has been the focus of few microbial diversity studies. A molecular approach was chosen to characterize the soil fungal communities in four areas of the Cerrado biome: a native Cerrado, a riverbank forest, an area converted to a soybean plantation, and an area converted to pasture. Global diversity of fungal communities in each area was assessed through Ribosomal intergenic spacer analysis which revealed remarkable diVerences among the areas studied. Sequencing of approximately 200 clones containing 18S rDNA sequences from each library was performed and, according to the genetic distance between sequences, these were assigned to operational taxonomic units (OTUs). A total of 75, 85, 85, and 70 OTUs were identiWed for the native Cerrado, riverbank forest, pasture, and soybean plantation, respectively. Analysis of sequences using a similarity cutoV value of 1% showed that the number of OTUs for the native Cerrado area was reduced by 35%; for the soybean plantation, a reduction by more than 50% was observed, indicating a reduction in fungal biodiversity associated with anthropogenic activity. This is the Wrst studydemonstrating the anthropogenic impact on Cerrado soil fungal diversity