Genetic Variability and Expected Gain in Three Maize Populations

Abstract

- The study of genetic variability in populations undergoing recurrent selection is important to quantify their real potential for breeding purposes. In the present work, three semiexotic maize populations were evaluated on their yield potential and variability for continuing the recurrent selection program. Half-sib families representing three semiexotic populations CRE-01, CRE-02, CRE-03 were evaluated for yield and agronomic traits male flowering (MF), plant height (PH), ear height (EH), ear placement (EP) - ratio = (EH/PH), tassel length (TL), tassel branches (TN), final stand (FS), ears per plot (NE), prolificacy (PR), ear length (EL), ear diameter (ED), ear yield (EY), grain yield (GY). The observed means for grain yield (GY), in percent of the hybrid check, were 93.8%, 89.4%, and 94.6%, showing a relatively good yield potential. Means (cm) for plant height (PH) and ear height (EH) were 221, 237, 241 and 117, 134, 137, respectively, with reductions in relation to the first cycle. Parameters estimates for GY were: additive genetic variance 582.28, 406.70 and 238.11 g2.plant-1; heritability 59.17%, 49.82% and 38.53%; progeny mean basis, and expected gain for progeny selection 8.16%, 6.86% and 3.88%; selection intensity of 20%.Keywords: Zea mays, recurrent selection, semiexotic population, genetic parameters.VARIABILIDADE GENÉTICA E GANHO ESPERADO EM TRÊS POPULAÇÕES DE MILHORESUMO - O estudo da variabilidade genética em uma população sob seleção é importante para quantificar seu potencial para fins de melhoramento. No presente trabalho foram avaliadas três populações semiexóticas de milho quanto ao seu potencial de produção e de variabilidade para continuar o programa de seleção recorrente em curso. Famílias de meios irmãos representando as três populações (CRE-01, CRE-02, CRE-03) foram avaliadas para caracteres agronômicos florescimento masculino (MF), altura da planta (PH), altura da espiga (EH), posição relativa da espiga (EP), comprimento do pendão (TL), ramificações do pendão (TN), estande final (FS), espigas por parcela (NE), prolificidade (PR), comprimento da espiga (EL), diâmetro da espiga (ED), peso de espiga (EY), peso de grãos (GY). As médias observadas para produção de grãos (GY) foram 93,8%, 89,4% e 94,6% da testemunha, mostrando um bom potencial de produção. As alturas médias da planta (PH) foram 221, 237 e 241 cm e da espiga (EH) foram 117, 134 e 137 cm, com reduções em relação ao primeiro ciclo. As estimativas de parâmetros para GY nas três populações foram, respectivamente: variância genética aditiva 582,28 g2 planta-1, 406,70 g2 planta-1 e 238,11 g2 planta-1; coeficiente de herdabilidade em média de progênies 59,17%, 49,82% e 38,53% e ganho com seleção para 20% de intensidade de 8,16%, 6,86% e 3,88%; ganho com seleção para 5% de intensidade de 10,81%, 10,47% e 5,32%, respectivamente para as populações CRE-01, CRE-02 e CRE-03.Palavras-chave: Zea mays L., seleção recorrente, população semiexótica, parâmetros genéticos.

Genetic variability and breeding potential of Flintisa Composite of maize in two levels of technology

“…when compared with data presented by Candido and Andrade (2008), Andrade and Miranda Filho (2008), Hallauer et al (2010) and Faluba et al (2010) and similar to estimates by Souza et al (2018). For GY, the estimate of 588.1 (g pl -1 ) 2 (hightech environment) was superior to the mean found by Hallauer et al (2010) and Reis et al (2014), similar to estimates by Souza et al (2018) for the populations CRE-1 and CRE-2, but lower than the estimate found by Faluba et al (2010) for UFV 7 population (622.7 (g pl -1 ) 2 ). For TB, the additive variances were 21.9 (high-tech) and 34.7 (branches pl -1 ) 2 (lowtech), close to that obtained by Souza Júnior et al (1985) (28.55), Souza et al (2018) (19.29 and 18.9) and higher than that obtained by Andrade and Miranda Filho (2008) (13.57 (branches pl -1 ) 2 ).…”

“…For GY, heritability at mean level (56% in high-tech and 41.7% in low-tech) was 3.8 and 4.9 times higher than at plant level. Heritability of these magnitudes was also found by Andrade and Miranda Filho (2008), Candido and Andrade (2008), Faluba et al (2010) and Souza et al (2018). Araújo et al (2005) also obtained similar estimate for the population CMS 39, evaluated at 0.9 m spacing (44.6%), and lower estimates at 0.5 m spacing (29.5%).…”

“…For GY, the expected gain with mass selection in high-tech environment was 7.7%, which is equivalent to the gain of 7.9% reported by Souza et al (2018) in three semi-exotic populations, and higher than that reported by Andrade and Miranda Filho (2008) (4.17%). In low-tech environment, it was calculated a 50% lower expected gain.…”

“…Over the selection cycles, this procedure helps in the checking, from time to time, of the evolution of genetic variability and the need for changes in the selection process (Freitas Júnior et al 2009). Large ranges of values in the genetic parameter estimates are reported for the traits studied in this work, as well as other traits that make part of yield components in Brazilian maize populations (Candido and Andrade 2008, Andrade and Miranda Filho 2008, Faluba et al 2010, Reis et al 2014 and semi-exotic populations (Oliveira et al 2015, Souza et al 2018).…”

“…The expected gain with mass selection for TB in low-tech environment (41.8%) was 1.4 times higher than in hightech, and also higher than expected for the varieties Centralmex (23.2%), Dentado composite (10.9%), Flint composite (13.4%) (Geraldi et al 1985), Esalq-PB1 (27.4%) (Andrade and Miranda Filho 2008) and three semi-exotic populations (1.4, 0.03 and 0.22%) (Souza et al 2018).…”