Caracterização morfogênica de oito cultivares do gênero Brachiaria e dois do gênero Panicum

• Ano de defesa: 2006
• Autor(a) principal: Silveira, Márcia Cristina Teixeira da
• Orientador(a): Nascimento Júnior, Domicio do
• Banca de defesa: Valle, Cacilda Borges do , Fonseca, Dilermando Miranda da
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Zootecnia
• Departamento: Genética e Melhoramento de Animais Domésticos; Nutrição e Alimentação Animal; Pastagens e Forragicul
• País: BR
• Palavras-chave em Português: Morfogênese; Perfilhamento; Brachiaria brizantha; Brachiaria humidicola; Brachiaria decumbens; Panicum maximum
• Palavras-chave em Inglês: Morfogenesis; Tiller; Brachiaria brizantha; Brachiaria humidicola; Brachiaria decumbens; Panicum maximum
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PASTAGEM E FORRAGICULTURA
• Link de acesso: http://locus.ufv.br/handle/123456789/5749

The present experiment was carried out at Departamento de Zootecnia, Federal University of Viçosa (UFV), MG, from 31/12/2004 until 30/06/2005. The objective was to use the comparative morphogenesis of different forage grass plant cultivars in order to identify some characteristics that could enhance the current protocols used to evaluate and select forage plants. Treatments corresponded to 10 grass cultivars, eight belonging to the Brachiaria genus and two to the Panicum genus, all evaluated under continuous growth condition. The experimental design used was a complete randomised block with three replications and response-variables studied were: tiller height; tiller morphogenetic and structural characteristics; number of leaves per tiller (emerged, live and dead); tiller appearance, death and survival rates; and tiller demography. Tiller height of the two Panicum cultivars was higher than all the Brachiaria cultivars, except the Xaraés cultivar of B. brizantha. The lowest value of tiller height was recorded for the Tupi cultivar of B. humidicola, with the other Brachiaria cultivars ranking in intermediate positions. Cultivars differed in relation to number of days to flowering and could be separated into two groups: (1) Late flowering cultivars: Mombaça, Tanzânia, Capiporã and Xaraés; (2) Early flowering cultivars: Marandu, Piatã, Arapoty, Basilisk, Tupi and Humidicola Comum. The Tupi cultivar of B. humidicola showed the highest rate of leaf appearance (LAR) and the lowest rate of leaf elongation (LER) and phyllochron. Large phyllochron values were recorded for cultivars Capiporã, Xaraés and Piatã. Highest values of leaf elongation rate were recorded for the two Panicum cultivars and the lowest for cultivars Humidicola Comum, Basilisk and Tupi. The cultivar Tupi of B. humidicola and Capiporã of B. brizantha showed high and low stem elongation rates (SER), respectively. Leaf lifespan was lowest for the Tupi cultivar, followed by cultivars Humidicola Comum and Arapoty in relation to cultivars Piatã, Xaraés, Capiporã, Mombaça and Tanzânia, indicating higher tissue turnover on the former three cultivars. There was no difference among cultivars in rates of leaf senescence. The number of live leaves per tiller (NLL) varied with grass cultivar, with Tupi being the cultivar with the highest recorded value. In general, considering the pattern of variation in NLL, the B. brizantha cultivars showed a similar behaviour to the Panicum cultivars, and B. decumbens similar to the B. humidicola cultivars. Rates of tiller appearance, death and survival varied with grass cultivars, with higher tillering potential being associated with cultivars with high leaf appearance rates. Tiller death was higher for the B. humidicola cultivars and B. decumbens cv. Basilisk, and tiller survival higher for cultivars Xaraés, Capiporã and Mombaça, which were not different from cultivars Marandu, Arapoty and Tanzânia. There was also difference among cultivars in relation to tiller demography. In general, tiller appearance was initially high, and the second and/or third generation of tillers contributed significantly for tiller population at the end of the experiment. A principal component analysis (PCA) carried out initially on the 17 response-variables studied, showed the potential for grouping cultivars according to functional characteristics. A second PCA was carried out with a lesser number of variables, obtained by suppressing those that were calculated as derived variables. This new PCA sorted all the grass cultivars into three functional groups: (1) Mombaça, Tanzânia and Xaraés; (2) Piatã, Capiporã, Marandu and Arapoty; and (3) Basilisk, Humidicola Comum and Tupi. Among the eight response-variables used in the analysis, the most efficient in discriminating groups and cultivars were leaf appearance and elongation rate, final leaf length and tiller mortality rate. This four variables explained around 85% of the total variation in the data set, suggesting the potential for using morphogenesis as part of the protocols used for evaluating and selecting new forage plant cultivars.