A. C. C. Cordeiro

Adaptabilidade e estabilidade de acessos de uma coleção nuclear de arroz

The objective of this work was to determine the productive potential and the genotype by environment interaction of 550 accessions of the Embrapas Rice Core Collection. The performance, and yield adaptability and stability of each genotype was evaluated using the additive main effects and multiplicative interactions (AMMI) approach, in nine field experiments, carried out in six Brazilian states, under dry and irrigated conditions, during three years. The linear mixed model analysis was performed, and the estimates of the variance components were obtained by the residual maximum likelihood (REML), using the best linear unbiased prediction (BLUP) procedure for the prediction of the genotypic values of random effects (EBLUP) associated with each accession. The group of accessions with better performance was the one of lines and cultivars from Brazil (LCB), as expected. However, traditional varieties (VT) were identified among the best yielding genotypes, which shows the potential of this germplasm group to contribute as a new source of genetic variability to breeding programs. Superior accessions were identified for their stability, adaptability and grain yield, among which CA880078, CA840182 and CNA00091 stand out.

Effect of the number of intercrosses on grain yield in basic rice synthetic populations

The effect of 0, 1, 2, 3 and 4 intercross cycles using genetic male sterility on the mean yield and genetic variability of the CNA 5 irrigated rice synthetic population was assessed studying 300 S0:2 (1998/99) and S0:3 (1999/00) families grown in two locations (Lambari, MG and Goianira, GO). Each intercross was investigated using a 8 × 8 triple lattice design experiment containing 60 families and four control cultivars. Five experiments were carried out per location and generation, totaling 20 experiments. Individual, combined over locations, combined over generations and combined over locations and generations analyses of variance were performed. Linear regression equations were fitted to data of each location and generation as well as, genetic and phenotypic parameters were estimated. An average increase of 3.91% in grain yield was obtained with the increase in the number of intercrosses. However, when genetic gains obtained from selection of the five and ten highest yielding families were considered, negative b estimates were always obtained, suggesting a tendency of gain increase reduction with the increase in the number of intercrosses. This was confirmed by the analysis of the means of the best families, since increases in the number of intercrosses did not result in selection of families with greater mean grain yield. The estimates of the genetic variances and heritabilities did not suggest an increase in genetic variability with the increase in intercross cycles. Therefore, carrying out intercrosses on the base population did not improve the results of the irrigated rice recurrent selection program.The effect of 0, 1, 2, 3 and 4 intercross cycles using genetic male sterility on the mean yield and genetic variability of the CNA 5 irrigated rice synthetic population was assessed studying 300 S0:2 (1998/99) and S0:3 (1999/00) families grown in two locations (Lambari, MG and Goianira, GO). Each intercross was investigated using a 8 × 8 triple lattice design experiment containing 60 families and four control cultivars. Five experiments were carried out per location and generation, totaling 20 experiments. Individual, combined over locations, combined over generations and combined over locations and generations analyses of variance were performed. Linear regression equations were fitted to data of each location and generation as well as, genetic and phenotypic parameters were estimated. An average increase of 3.91% in grain yield was obtained with the increase in the number of intercrosses. However, when genetic gains obtained from selection of the five and ten highest yielding families were considered, negative b estimates were always obtained, suggesting a tendency of gain increase reduction with the increase in the number of intercrosses. This was confirmed by the analysis of the means of the best families, since increases in the number of intercrosses did not result in selection of families with greater mean grain yield. The estimates of the genetic variances and heritabilities did not suggest an increase in genetic variability with the increase in intercross cycles. Therefore, carrying out intercrosses on the base population did not improve the results of the irrigated rice recurrent selection program.

Desenvolvimento vegetativo da palma de óleo em ecossistemas de savana e floresta de Roraima.

Objetivou-se com este trabalho avaliar o desenvolvimento vegetativo de hibridos comerciais de palma de oleo aos 18 meses de idade em condicoes de campo, em dois ecossistemas de Roraima. Estao sendo conduzidos dois experimentos, sendo um em area de savana e outro em area de floresta alterada com a avaliacao dos hibridos comerciais BRS 2528, BRS 3701 e BRS 2301, em delineamento experimental de blocos ao acaso com seis repeticoes. Em ambos os ambientes foram realizadas avaliacoes mensais, iniciadas aos 14 meses de plantio, quanto ao numero de folhas emitidas, comprimento da folha no 4 (cm), altura de planta (cm) e diâmetro do coleto (cm). Foram realizadas analises de variância individuais e conjuntas, considerando o efeito de hibridos e epocas como fixos e os demais como aleatorios. Para a comparacao das estimativas das medias das caracteristicas avaliadas foi utilizado o teste de Tukey a 5% de probabilidade. Para detectar as alteracoes referentes as caracteristicas no decorrer do periodo avaliado, com relacao a cada local, foram estimadas equacoes de regressao, tendo como variavel dependente a caracteristica avaliada e como variavel independente as epocas de mensuracao. Conclui-se que, em area de floresta, os hibridos apresentam desenvolvimento vegetativo superior ao obtido na savana; os hibridos BRS 2528, BRS 3701 e BRS 2301 apresentam desenvolvimento vegetativo semelhante na savana e o hibrido BRS 2301 foi que apresentou o maior desenvolvimento vegetativo em relacao aos hibridos 2528 e 3701 no ambiente de floresta.

Avaliação de linhagens de arroz irrigado com tipo de grão para a culinária japonesa para o Estado de Roraima.

The cultivation of rice represents one of the few productive chains effectively stabilized in the State of Roraima, with enough production to supply the domestic market and allow export to other states. However the local agribusiness commercializes basically the long-thin class white rice. The diversification of grain types, as the demanded for Japanese cuisine, creates an opportunity for vertical integration of production and provides increased income, since the price of the product reaches an average of two to three times higher than the local type. Thus, the purpose of this study was to evaluate the performance and quality of irrigated rice strains with grain types for Japanese cuisine, under the cropping conditions of Roraima. From December 2003 to March 2004, ten strains of irrigated rice were evaluated in a randomized block experimental design, with four replications. In addition to the agronomic traits it was also evaluated the quality of the grains. The strain CNAi 9903 was the most suitable relative to the characteristic of low amylose content, presenting good productivity and adaptation to the growing conditions in lowland of Roraima, and therefore the greatest potential for use in Japanese cuisine.