Universidade Federal de Viçosa

About: Universidade Federal de Viçosa is a education organization based out in Viçosa, Brazil. It is known for research contribution in the topics: Population & Dry matter. The organization has 16012 authors who have published 26711 publications receiving 353416 citations.

Produção de gramíneas do gênero Brachiaria sob níveis de sombreamento

Abstract: O trabalho foi realizado com o objetivo de avaliar a producao de B. decumbens cv. Basilisk e B. brizantha, cultivares Marandu e Xaraes, sob diferentes niveis de sombreamento. Utilizou-se delineamento em blocos casualizados com esquema de parcelas subdivididas, considerando os niveis de sombreamento (0, 50, 70%) como parcela e as especies ou cultivares como subparcelas. Sementes das gramineas foram postas a germinar em bandejas e transplantadas (tres plântulas por vaso). Foram realizados quatro cortes em cada subparcela. Antes de cada corte, mediram-se a altura de planta e a area foliar de quatro folhas em cada planta e quantificou-se o numero de perfilhos vivos por vaso. Apos a colheita, as plantas foram separadas em lâmina, colmo + bainha e material morto para determinacao da producao de materia seca. Para producao de materia seca total, calcularam-se a producao media em cada um os cortes e a producao total. No ultimo corte, avaliou-se a massa seca de raizes. As interacoes significativas foram desdobradas adequadamente. O fator qualitativo foi submetido a comparacao de medias pelo teste Tukey e o quantitativo a analise de regressao linear. A excecao da producao media em quatro cortes e da producao de colmos e de material morto, observou-se interacao significativa para todas as outras variaveis. Independentemente do nivel de sombreamento, o cultivar Xaraes destacou-se positivamente na maioria das caracteristicas analisadas, enquanto, no nivel de 50% de sombreamento, o capim-braquiaria apresentou maior produtividade, em porcentagem de producao a pleno sol. Na avaliacao da porcentagem de folhas, destacou-se o capim-xaraes, seguido do capim-marandu. Independentemente da forrageira, o nivel de sombreamento teve efeito direto sobre o numero de perfilhos/planta, a producao de MS do sistema radicular, a area foliar e o valor SPAD.

Gapless genome assembly of Colletotrichum higginsianum reveals chromosome structure and association of transposable elements with secondary metabolite gene clusters.

Abstract: The ascomycete fungus Colletotrichum higginsianum causes anthracnose disease of brassica crops and the model plant Arabidopsis thaliana. Previous versions of the genome sequence were highly fragmented, causing errors in the prediction of protein-coding genes and preventing the analysis of repetitive sequences and genome architecture. Here, we re-sequenced the genome using single-molecule real-time (SMRT) sequencing technology and, in combination with optical map data, this provided a gapless assembly of all twelve chromosomes except for the ribosomal DNA repeat cluster on chromosome 7. The more accurate gene annotation made possible by this new assembly revealed a large repertoire of secondary metabolism (SM) key genes (89) and putative biosynthetic pathways (77 SM gene clusters). The two mini-chromosomes differed from the ten core chromosomes in being repeat- and AT-rich and gene-poor but were significantly enriched with genes encoding putative secreted effector proteins. Transposable elements (TEs) were found to occupy 7% of the genome by length. Certain TE families showed a statistically significant association with effector genes and SM cluster genes and were transcriptionally active at particular stages of fungal development. All 24 subtelomeres were found to contain one of three highly-conserved repeat elements which, by providing sites for homologous recombination, were probably instrumental in four segmental duplications. The gapless genome of C. higginsianum provides access to repeat-rich regions that were previously poorly assembled, notably the mini-chromosomes and subtelomeres, and allowed prediction of the complete SM gene repertoire. It also provides insights into the potential role of TEs in gene and genome evolution and host adaptation in this asexual pathogen.

Assessing the expected response to genomic selection of individuals and families in Eucalyptus breeding with an additive-dominant model

Abstract: We report a genomic selection (GS) study of growth and wood quality traits in an outbred F2 hybrid Eucalyptus population (n=768) using high-density single-nucleotide polymorphism (SNP) genotyping. Going beyond previous reports in forest trees, models were developed for different selection targets, namely, families, individuals within families and individuals across the entire population using a genomic model including dominance. To provide a more breeder-intelligible assessment of the performance of GS we calculated the expected response as the percentage gain over the population average expected genetic value (EGV) for different proportions of genomically selected individuals, using a rigorous cross-validation (CV) scheme that removed relatedness between training and validation sets. Predictive abilities (PAs) were 0.40–0.57 for individual selection and 0.56–0.75 for family selection. PAs under an additive+dominance model improved predictions by 5 to 14% for growth depending on the selection target, but no improvement was seen for wood traits. The good performance of GS with no relatedness in CV suggested that our average SNP density (~25 kb) captured some short-range linkage disequilibrium. Truncation GS successfully selected individuals with an average EGV significantly higher than the population average. Response to GS on a per year basis was ~100% more efficient than by phenotypic selection and more so with higher selection intensities. These results contribute further experimental data supporting the positive prospects of GS in forest trees. Because generation times are long, traits are complex and costs of DNA genotyping are plummeting, genomic prediction has good perspectives of adoption in tree breeding practice.