Seleção simultânea em progênies de sorgo-sacarino por meio de índices de seleção

Abstract

Resumo -O objetivo deste trabalho foi comparar ganhos genéticos obtidos por diferentes índices de seleção aplicados a múltiplos caracteres agronômicos de sorgo-sacarino (Sorghum bicolor). Foram feitas avaliações de 189 progênies F5 e sete testemunhas, em delineamento de blocos incompletos, com três repetições. Mensuraram-se os caracteres produtividade de matéria verde, teor de sólidos solúveis totais, extração de caldo, teor de sacarose no caldo e sólidos solúveis totais por hectare. Analisaram-se os índices de soma de postos de Mulamba e Mock (ou índice de ranks), da soma dos valores padronizados (ou índice Z), índice padronizado pela média e índice padronizado pela média modificado. As correlações e as percentagens de coincidência na seleção das progênies foram elevadas entre o índice Z, o índice padronizado pela média e o índice padronizado pela média modificado. Entre os índices de seleção testados, o de soma de postos de Mulamba e Mock foi o menos eficiente. A seleção simultânea de progênies de sorgo-sacarino permite ganhos genéticos expressivos para todos os caracteres mensurados.Termos para indexação: Sorghum bicolor, ganho genético, melhoramento genético de plantas. Simultaneous selection in sweet sorghum progenies by selection indicesAbstract -The objective of this work was to compare the genetic gains obtained by different selection indices applied to various agronomic traits of sweet sorghum (Sorghum bicolor). Evaluations were carried out for 189 F5 progenies and seven controls, in an incomplete block design, with three replicates. The measured traits were green matter yield, content of total soluble solids, juice extraction, sucrose content in juice, and total soluble solids per hectare. The rank summation index of Mulamba and Mock (or index of ranks), standardized value summation index (or Z index), standardized by the mean index, and the modified standardized by the mean index were analyzed. The correlations and coincidence percentages in the progeny selections were high between the Z index, the standardized by the mean index, and the modified standardized by the mean index. Among the tested selection indices, the rank summation index of Mulamba and Mock was the less efficient. The simultaneous selection of sweet sorghum progenies allows expressive genetic gains for all measured traits.

Strategies for Multi-trait Selection of Sweet Sorghum Progenies

“…The absence of genetic variance for TSS might have occurred due to environmental fluctuations, especially rainfall during the harvest season (Figure 1), which may have led to the dilution of soluble solids of the stem juice. Unlike what was observed in this study, França et al (2016) observed high heritability estimates for TSS.…”

“…The sum of rank index was not promising because it showed the lowest estimated gain from selection for the trait GMP in the single-trait approach and PH, GMP, and TBH in the multi-trait analysis (Figure 2). Inefficiency in obtaining satisfactory gains in the sweet sorghum crop by the Mulamba and Mock index was also observed by França et al (2016) through the univariate mixed-model approach, since this index provided the lowest estimates of gains from selection for all traits measured by the authors, some of which were the same as those evaluated here (GMP and TBH).…”

“…High-magnitude and positive genetic correlation was observed between TBH and almost all traits (Table 2). Working with sweet sorghum progenies, França et al (2016) also observed a high genetic correlation between the traits GMP and TBH (0.80). In a study of phenotypic correlations using path analysis, Lombardi et al (2015) demonstrated that TBH showed a high positive correlation and a direct effect on ethanol yield.…”

Path analysis in the evaluation of ethanol and culm yield components in sweet sorghum

“…Characteristics that have a high heritability and high correlation with a quantitative characteristic are likely to be used in the indirect selection. Oliveira (2015) and França et al (2016) estimated H 2 values > 0.7 for soluble solids content in studies of genetic parameters in sorghum. Therefore, the measurement of soluble solids content may be considered of great importance for studies on biofuel yield, which can The total and direct effects exerted by culm yield presented values similar to those by soluble solids content, but of lesser magnitude, presenting 0.8516 for total effect and 0.5254 for direct effect on yield of theoretical ethanol.…”

Multi-trait genomic selection indexes applied to identification of superior genotypes

“…This strategy consists in establishing a new trait from a linear combination of all the target traits, considering that the weight coefficients are estimated to maximize the correlation between the index and the true genetic values of the genotypes to be selected. Several studies have addressed the application of selection indexes to plant breeding, leading to gains in a set of traits simultaneously (França et al 2016;Junqueira et al 2016;Kumar et al 2016;Silva et al 2016). Thus, the interest for studying the methodology efficiency in genomic selection has increased (Ceron-Rojas et al 2015;Covarrubias-Pazaran et al 2018;Fernandes et al 2018).…”