Com o intento de selecionar progênies superiores para a efetiva concentração de alelos favoráveis em uma população de terceiro ciclo de seleção recorrente intrapopulacional em famílias de meios-irmãos de milho-pipoca, avaliaram-se 192 progênies em delineamento em blocos casualizados com duas repetições em dois ambientes distintos: Colégio Estadual Agrícola Antônio Sarlo, em Campos dos Goytacazes, e Estação Experimental da PESAGRO-RIO, em Itaocara, Rio de Janeiro, em 2004/05. Definiu-se a intensidade de seleção de 15,6%, correspondendo ao número de trinta famílias de meios-irmãos para continuidade do programa. Foram empregados os índices de seleção de Smith e Hazel, Pesek e Baker, Williams, e Mulamba e Mock. O índice de Mulamba e Mock proporcionou as magnitudes mais elevadas de ganhos preditos para a maioria das características, incluindo-se capacidade de expansão e produção, com valores respectivos de 7,16% e 10,00%, na utilização de pesos arbitrários atribuídos por tentativas.

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-Reciprocal recurrent selection among full-sib families is one of the outstanding methodologies of maize improvement, since gains are possible in the per se and/or in cross populations. Here the selection index proposed by Smith and Hazel was used in the cited methodology; besides, an additional phase involving RAPD markers was introduced to preserve the genetic variability of the selected genotypes and identify contaminants before their recombination. Multivariate techniques of grouping and discriminant analyses were used for this purpose, to assure the continuance of the improvement program and amplify the genetic distance between the populations Cimmyt and Piranão, which were used for an intervarietal hybrid. The molecular technique proved useful to identify contaminants and helpful in the choice of the genotypes to be recombined to maximize heterosis among populations. The technique can be included in recurrent selection programs, mainly those that target the development of hybrids.

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Identifying forage species that are responsive in regions with marked water deficits is one of the greatest challenges for the sustainable development of agriculture. However, information is still lacking about the persistence response of those pastures and their abilities to produce new tissues at the times of water scarcity. We hypothesized that Brachiaria grass has a tillering capacity during water-stress periods. This study thus examined the tillering capacity and structural characteristics of four Brachiaria brizantha cultivars (Xaraés, Piatã, Marandu, and Paiaguás) and one Brachiaria decumbens cultivar (Basilisk) in the Brazilian semi-arid region during the dry season (September to March). The experiment was laid out in a randomized block design with repeated measures over time in which five treatments were tested in four replicates. Tillering parameters, pasture production, and structural variables were evaluated. There was no interaction effect of cultivar × evaluation period on the tiller appearance (p= 0.1774), mortality (p= 0.1952) or survival (p= 0.4469) rates. The highest tiller appearance and mortality rates were observed in Marandu, while the highest survival rates were found in Marandu and Paiaguás. The index of tiller population stability was higher than or equal to 1.0 in all cultivars. Cultivar Basilisk showed the highest herbage mass yield (4448.0 kg DM ha -1 ), whereas Basilisk exhibited the highest yields of leaf (1845.9 kg DM ha -1 ), stem (1676.9 kg DM ha -1 ), and dead material (925.2 kg DM ha -1 ). The highest leaf:stem ratio (1.8) was found in Marandu. Cultivar Xaraés had the highest canopy (70.8 cm). The B. brizantha and B. decumbens cultivars evaluated in this study have the potential for cultivation in areas with marked water deficits, as is the case of the Brazilian semi-arid region. Cultivars Marandu, Basilisk, and Paiaguás exhibited the greatest tillering dynamics as well as the highest herbage-mass yield.