Reciprocal recurrent selection (RRS) has been successfully applied to maize breeding for more than 60 years. Our objective was to assess the relative efficiency of the genotypic value and the effects of general and specific combining abilities (GCA and SCA) on selection. The GCA effect reflects the number of favorable genes in the parent. The SCA effect primarily reflects the differences in the gene frequencies between the parents. We simulated three traits, three classes of populations, and 10 cycles of half- and full-sib RRS. The RRS is a highly efficient process for intra- and interpopulation breeding, regardless of the trait or the level of divergence among the populations. The RRS increases the heterosis of the interpopulation cross when there is dominance, and it decreases the inbreeding depression in the populations and the genetic variability in the populations and in the hybrid. When there is not dominance and the populations are not divergent, the RRS also determines population differentiation. The half-sib RRS, which is equivalent to selection based on the GCA effect, is more efficient than the full-sib RRS based on the genotypic value, regardless of the trait or the level of improvement of the populations. The full-sib RRS based on the SCA effect is not efficient for intra- and interpopulation breeding.

Devido a fatores culturais e bioclimáticos, durante muitos anos, o cultivo de trigo se restringiu à região Sul do Brasil. No entanto, a região central do país constitui-se em uma ótima alternativa para a expansão da produção tritícola, tanto em condições de sequeiro como sob irrigação. Isto, desde que atendidas certas premissas, principalmente em termos de limites mínimos de altitude, época de semeadura e cultivares a serem utilizadas, pois existem duas estações climáticas bem definidas. Nesta região, existe a possibilidade de colheita em épocas de baixa probabilidade de ocorrência de pluviosidade, o que proporciona a obtenção de um produto de alta ABSTRACT RESUMOqualidade, com peso hectolítrico médio superior a 80 kg hL -1 . A diversidade de áreas para cultivo de trigo constitui-se em alternativa para diminuir a variação na produção total deste cereal, decorrente das adversidades climáticas comuns na região Sul do Brasil, principal produtora. A triticultura também é ótima opção para rotação de culturas, em substituição às culturas de verão, muito comuns na região central do Brasil (Cargnin et al. 2006). Com relação ao melhoramento genético, o processo de seleção depende, também, da magnitude da interação genótipos x ambientes, para que não ocorra queda inesperada de desempenho de um material testado (Yamamoto 2006).

ABSTRACT

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RESUMOO cultivo de trigo de sequeiro constitui ótima opção para o Estado de Minas Gerais em regiões com altitude superior a 800 m. Neste estudo objetivou-se estimar a divergência genética entre genótipos de trigo com o auxílio de métodos de análise multivariada, objetivando identificar potenciais genótipos para obtenção de combinações híbridas promissoras. Foi utilizado o delineamento experimental em blocos ao acaso, com quatro repetições. Avaliaram-se seis caracteres morfoagronômicos em 11 genótipos de trigo cultivados em condições de sequeiro no município de Patos de Minas-MG, nos anos de 2007 e 2008. Houve grande variabilidade fenotípica entre os genótipos de trigo avaliados em cultivo de sequeiro. Os genótipos IAC 289-L22 e IAC 289-L4 foram os mais similares, enquanto os CD 113 e EP 011106, os maisdivergentes, promissores nos cruzamentos para obtenção de materiais adaptados e com bons atributos fenotípicos emcultivo de sequeiro. Palavras-chave:Triticum aestivum L., análise multivariada, dissimilaridade. ABSTRACT Genetic divergence in rainfed wheat based on morphoagronomic traitsWheat cultivation in rainfed conditions is a good option for regions in Minas Gerais with altitudes above 800 m. The objective of this study was to estimate the genetic diversity of eleven wheat genotypes grown in rainfed conditions, using multivariate analysis based on six morpho-agronomic traits to identify which genotypes have potential for hybrid combinations. The treatments were arranged in a randomized complete block design with four replicates. The experiments were carried out during the wheat cropping season 2007/2008. Great variability was found among the wheat genotypes evaluated in rainfed conditions. The genotypes IAC 289-L22 and IAC 289-L4 were the most similar. The genotypes CD 113 and EP 011106 were the most diverging and the most promising for breeding towards generating material adapted and with good characteristics for rainfed cultivation.

Abstract

The lowland rice breeding program, developed in Minas Gerais state, has as basic objective to release new commercial cultivars. In this way, this program is making available a new cultivar named BRSMG Alterosa, which has as main characteristics: high grain yield, high tillering, medium cicle, diseases tolerance and high grain quality. It was recommended in 2017.

Rice is one of the most consumed cereals in the world and of extreme social and economic importance in Brazil. Minas Gerais is the leading State in irrigated rice production in the Southeast Region. This study aimed to estimate the genetic progress of 26 years of the irrigated rice breeding programme of Epamig in Southeast Brazil by time meta‐analysis. Genetic progress was estimated for grain yield, plant height and days to flowering. The dataset understood 162 genotypes in 91 trials of value for cultivation and use of 26 seasons. The rate of annual genetic gain for grain yield was estimated .99% (49.85 kg year−1). It was also verified that was a reduction in plant height and an increase in days to flowering, even if very low. Due to distinct historical phases of the rice breeding programme, there were changes in research focus and, consequently, affected the genetic gains. With this study, it was possible to evaluate the selection strategies carried out in the past and identify important points to maintain.