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    Genetic dissimilarity in cassava clones determined by multivariate techniques
    (Crop Breeding and Applied Biotechnology, 2008) Nick, Carlos; Carvalho, Mychelle; Assis, Luiz Henrique Bambini de; Carvalho, Samuel Pereira de
    The genetic dissimilarity in 15 cassava clones was evaluated based on seven morpho-agronomic traits and multivariate procedures, aiming to select the most divergent and best in an approach to future hybridizations. The experiment was carried out in 2003/2005, in random blocks, with three replications. Based on the matrix of Mahalanobis’ generalized distance, the clones were grouped as related to similarity, using the algorithms of Tocher and Nearest neighbor. The relative importance of the traits was also evaluated. The multivariate techniques were concordant in the study of genetic dissimilarity and efficient in grouping clones with short genetic distance. The following traits contributed most to the genetic diversity: total weight of the aerial part, root diameter, root weight, length of tuber roots and harvest index.
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    Field and greenhouse inoculation methods for assessment of sheath blight resistance in rice
    (Crop Breeding and Applied Biotechnology, 2007) Araújo, Leila Garcês de; Prabhu, Anne Sitarama; Silva, Gisele Barata da
    Field and greenhouse inoculation methods were compared to determine the genetic variation for resistance to Rhizoctonia solani in 38 somaclones of rice cultivar Metica-1. Rice plants in pots were inoculated with isolate 4F1 at the age of sixty four days, with 2.0 g of the fungal culture, multiplied on rice grain and hull medium and placed on the soil surface around the plant. The differences among somaclones in relation to lesion height were significant and varied from 6.5 to 15.5 cm. In the field trial of artificial inoculation with fungal culture, 52 days after planting, the lesion height varied from 6.2 to 17.7 cm. The correlation between disease severity in the greenhouse and the field was positive and highly significant (r=0.44; P< 0.01), indicating the greenhouse inoculation as a safe method for screening germplasm for sheath blight resistance.
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    A new species of Brachycephalus fitzinger, 1826 (Anura: brachycephalidae) from the cloud dwarf forest in southern mantiqueira mountain range
    (Universidade Federal de Viçosa, 2026-07-13) Contim, Marília Rocha; Feio, Renato Neves
    Brachycephalus é um gênero de anuros miniaturizados que habitam o folhiço, conhecidos como sapinhos-pingo-de-ouro ou sapos-pulga, endêmicos da Mata Atlântica brasileira. Nas últimas décadas, inúmeras espécies foram descritas, expandindo significativamente nosso entendimento sobre a riqueza e diversificação do gênero. Descrevemos aqui uma nova espécie do grupo de Brachycephalus ephippium da porção sudeste da Mata Atlântica, localizada no município de Lima Duarte, estado de Minas Gerais, Brasil. A descrição é sustentada por análises morfológicas, morfométricas e bioacústicas. Brachycephalus sp. nov. é distinguido de todos os congêneres pela combinação de corpo bufoniforme, coloração aposemática laranja e uma placa óssea dorsal hiperossificada, ornamentada e fortemente desenvolvida, além de placas cranianas cobertas por tecido cutâneo pigmentado acinzentado e tecido conjuntivo melanizado cobrindo a fáscia muscular do dorso, ventre e membros. Adicionalmente, a nova espécie é caracterizada pelo menor tamanho rostro-cloacal dos machos adultos (CRC = 12,98–15,68 mm) e por um canto de anúncio composto por uma única nota (7–10 pulsos) emitida a uma taxa de 3,74 notas/s, com frequência dominante de 3,3–4,1 kHz. Por fim, fornecemos comparações morfológicas com espécies congêneres, juntamente com uma breve descrição de aspectos de sua história natural, habitat e comportamento. Palavras-chave: Amphibia, Mata Atlântica, diversidade Neotropical, taxonomia.
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    Inbreeding depression simulation in popcorn cultivars to estimate the effective population size for germplasm conservation
    (Crop Breeding and Applied Biotechnology, 2007) Arnhold, Emmanuel; Silva, Derly José Henriques da; Mello Filho, Odilon Lemos de; Viana, José Marcelo Soriano
    Nowadays the corn variability is preserved mainly in germplasm banks. A population maintained in a germplasm bank can lose genetic variability when regenerations are performed with an inadequate effective population size. We therefore aimed at an estimation of the effective population size that minimizes alterations in the plant means of ear height, prolificity index, weight of 100 grains, grain yield and expansion capacity after ten regenerations in six popcorn populations. Six populations and their respective selfed generations were appraised in complete blocks with two replications. Yield was the trait with the most pronounced inbreeding depression. Population Rosa-Claro presented the strongest depression for yield (94.3%) and was used to simulate different effective sample sizes. It was concluded that an effective sample size of 200 unrelated non-inbred plants is enough to minimize inbreeding depression after ten regenerations, in all analyzed traits in the six populations.
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    Relative importance of per se and topcross performance in the selection of popcorn S3 families
    (Crop Breeding and Applied Biotechnology, 2007) Viana, José Marcelo Soriano; Condé, Aurinelza Batista Teixeira; Almeida, Ramon Vinicius de; Scapim, Carlos Alberto; Valentini, Lúcia
    The objective of this paper was to discuss the relative importance of per se and topcross performance in the selection of inbred families. The analyses, considering expansion volume and yield, were based on two trials of S3 progenies from the popcorn population Beija-Flor, and six experiments with the corresponding topcross hybrids, derived from crosses with the tester Viçosa, another popcorn population. With respect to the estimates of heritabilities (assessment of the selection efficiency), predicted genetic gains, genotypic correlations and the percentages of coincidence between selected and non selected families, the equivalence with the selection procedures based on per se and topcross performance was good. The correspondence would certainly be greater if the genotypic correlations were of higher magnitude. The selection based simultaneously on the phenotypic values of progenies and hybrids tends to be satisfactory when the weights of the per se and topcross merits are proportional to the heritabilities.