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    Effects of plot size on the estimation of genetic parameters in sugarcane families
    (Crop Breeding and Applied Biotechnology, 2006) Leite, Mauro Sérgio de Oliveira; Peternelli, Luiz Alexandre; Barbosa, Márcio Henrique Pereira
    An optimization of the use of resources in sugarcane breeding programs that would not interfere with the genetic evaluations is desirable and of great importance. The costs could be reduced and the chances of success would be higher through the possibility of investing rationally in a larger number of available genetic resources. Our study evaluated the smallest number of rows per plots of sugarcane families for yield traits; the variations in the parameter estimates for different plot sizes were discussed; and the ideal plot size was estimated by the maximum curvature method. Plot reduction leads to gradual CV increases and interferes with the ratio CVg/CVe, which in some cases dropped to values below one unit, indicating experimental inaccuracy. Heritability estimates decrease with plot size. The maximum curvature method showed that 2-row plots are enough to evaluate all characteristics.
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    Genetic diversity among Capsicum accessions using RAPD markers
    (Crop Breeding and Applied Biotechnology, 2006) Costa, Fabiane Rabelo da; Pereira, Telma Nair Santana; Vitória, Angela Pierre; Campos, Karina Pereira de; Rodrigues, Rosana; Silva, Derly Henriques da; Pereira, Messias Gonzaga
    Genus Capsicum has 27 species, being five domesticated and 22 semi-domesticated and wild ones. For an enhanced use of the germplasm in breeding programs it is necessary to know the accessions in the collections, to identify them and evaluate the genetic diversity. Objectives of this research were to quantify the genetic diversity among 70 Capsicum accessions, confirm their identification and verified possible duplicated accessions, using RAPD markers. Results showed that there is genetic diversity within and among species and were in agreement with botanical and morpho-agronomic classifications. The identification of 53 accessions was confirmed (16 C. annuum, 7 C. frutescens, 14 C. baccatum and 16 C. chinense) and among botanically non-identified accessions results suggested that six belong to C. baccatum and five to C. chinense. The most distinct accession was UENF 1620, probably a wild species that is not represented in the collection yet.
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    Analysis of cotton genetic diversity by microsatellites and pedigree
    (Crop Breeding and Applied Biotechnology, 2005) Bertini, Cândida Hermínia Campos de Magalhães; Schuster, Ivan; Sediyama, Tocio; Barros, Everaldo Gonçalves de; Moreira, Maurílio Alves
    The main objective of this study was to verify the association between the coefficient of parentage estimates and multivariate techniques which were used as measures of genetic diversity in cultivars. Thirty cotton cultivars were used for this purpose among which genetic diversity was estimated by means of the parentage coefficient (CP) and also through multivariate techniques employing microsatellite markers (SSR). The correlation between genetic distances obtained by CPs and SSRs for cultivars was positive and significant, with a value of 0.25. The 18 ancestors evaluated in the current study contributed with 69% to the genetic constitution of the 30 cotton cultivars. The evidence that few ancestors actually contribute to the genetic constitution of the cotton cultivars used in Brazil indicates that new alleles should be introduced into the gene pool of these cultivars in order to broaden the genetic base of cotton.
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    Selection of sugarcane families and parents by Reml/Blup
    (Crop Breeding and Applied Biotechnology, 2005) Barbosa, Márcio Henrique Pereira; Resende, Marcos Deon Vilela de; Bressiani, José Antônio; Silveira, Luís Cláudio Inácio da; Peternelli, Luiz Alexandre
    Were evaluated 113 full-sib families obtained by unbalanced diallel matings in three experiments in an augmented block design (ABD) planted side by side in the same area. The individual and joint analyses of the experiments were performed by the Reml/Blup method. The use of the ABD without replication did not prove adequate in experiments of family selection owing to the low heritability estimate at the level of family means in comparison to the joint analysis of the three experiments. The results presented predominance of the additive effects for all evaluated traits: number of stalks, tons of stalks per hectare and mean stalk weight. The Components of estimated means via BLUP allowed the selection of families and superior parents.
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    Selection of discrepant maize genotypes for nitrogen use efficiency by a chlorophyll meter
    (Crop Breeding and Applied Biotechnology, 2005) Miranda, Glauco Vieira; Godoy, Cleiton Lacerda; Galvão, João Carlos Cardoso; Santos, Izabel Cristina dos; Eckert, Fernando Roberto; Souza, Leandro Vagno de
    The objective of the present study was to verify if it is possible to discriminate maize genotypes for their efficiency of nitrogen use by readings obtained with a portable chlorophyll meter. 76 topcross hybrids and 5 previously tested controls were evaluated without sidedress nitrogen fertilization and 81 S1 families that only differed in relation to nitrogen sidedress fertilization (with and without). Readings were obtained by the chlorophyll meter in the phenological stages of four and eight fully unfolded leaves. Different negative selection pressure was simulated by the chlorophyll meter readings at each phenological stage and the genotypes were screened for grain yield and efficiency of N use. It was verified that the portable chlorophyll meter can be used to eliminate the least productive genotypes before flowering in quick tests, especially in environments without nitrogen sidedress, although the most effective genotypes regarding nitrogen use could not be discriminated this way.