Depressão endogâmica e heterose de híbridos de populações F2 de milho no estado de São Paulo

Abstract

A heterose e a depressão por endogamia são fenômenos complementares importantes nas estratégias de melhoramento, como para a obtenção de híbridos convencionais e melhoramento de populações. Este trabalho teve por objetivos avaliar híbridos de populações F 2 de milho quanto aos caracteres agronômicos, estimar a heterose em relação à média dos pais e determinar a depressão endogâmica na obtenção das populações de genitores F 2 . Foram avaliados 10 híbridos de populações F 2 , cinco populações de genitores F 2 e os respectivos híbridos comerciais (HC) quanto aos seguintes caracteres agronômicos: florescimento masculino (FM), altura de planta (AP), altura de espiga (AE) e massa de grãos (MG), em dois locais do estado de São Paulo, Mococa e Palmital, sob delineamento de blocos ao acaso. A estimativa de depressão por endogamia ao passar da geração F 1 para F 2 variou de 18,0% no HC12 a 48,1% no HC10, para MG. A heterose média em relação à média dos pais obtida para massa de grãos foi de 37,2%, representada pela elevada produtividade alcançada pelos híbridos de F 2 . Baseando-se nesses resultados foi possível evidenciar dois híbridos de populações F 2 que apresentaram potencial produtivo, alta heterose média e populações F 2 com potencial para extração de linhagens.Palavras-chave: Zea mays, vigor híbrido, endogamia, melhoramento populacional, produtividade.Inbreeding depression and heterosis of hybrids in F 2 populations of maize in the Sao Paulo State, Brazil Abstract Heterosis and inbreeding depression are complementary phenomena, both important to the establishment of breeding strategies, such as conventional hybrids and population breeding. This study aimed to evaluate the agronomic traits of hybrids in F 2 populations, estimate of heterosis in relation to the average of the parents and determine the inbreeding depression in F 2 parents populations. Ten hybrids of F 2 populations, five F 2 parents populations and the respective commercial hybrids (HC) were evaluated for male flowering, plant height, ear height and grain mass. Plants were evaluated in Mococa and Palmital counties at the Sao Paulo State and the experiment was arranged in a completely randomized block design. The estimated inbreeding depression from F 1 to next F 2 generation ranged from 18.0% in HC12 to 48.1% in HC10 for grain mass. The heterosis in relation to the parents' mean was 37.2%, represented by high yield in F 2 hybrids. Based on these results, it was possible to highlight two hybrids of F 2 populations with high yield potential, high average heterosis and F 2 populations with potential for extraction of inbred lines.

Análise dialélica e depressão endogâmica de híbridos forrageiros de milho para características agronômicas e de qualidade bromatológica

“…Still, such hybrids showed high estimates of û + â, qualifying them to compose populations source of superior lines for GY (Table 4). The results coincide with studies that show a wide variation in the levels of inbreeding depression for grain yield in corn (Bernini & Paterniani, 2012;Bernini et al, 2013;Pacheco et al, 2002). This variation stems from differences in the levels of dominance between the traits, different allele frequencies and degree of relatedness between individuals in the population (Hallauer et al, 2010).…”

Combining abilities and inbreeding depression in commercial maize hybrids

“…The authors observed that specific hybrid combinations overcame the means of the witnesses and the means of the populations in question, demonstrating the potential of the genotypes in the production of intermediate hybrids. Similar results were obtained by Carvalho et al (2004), Garbuglio and Araújo (2006), Santos (2009), Bernini and Paterniani (2012) and Bernini et al (2013).…”

Productive potential and castor bean selection of the FCA-PB cultivar progenies

“…also explained by the good combining ability between its parents, in which each parent had favorable complementary genes with the other parent (Bernini et al, 2013). With regard to progeny 81, because it is a progeny originated by self-pollination, which provides the highest level of homozygousness, their grain yield is somewhat surprising, since its productivity was about six times the national average of the 2005/2006 crop (714 kg ha -1 , CONAB, 2017), however as castor bean is a kind of reproduction type taken as mixed, may have decreased the deleterious effects deriving from the increase of homozygosity.…”

“…Rev. Ceres, Viçosa, v. 67, n.1, p. 042-051, jan/feb, It can be observed that of the more stable preselected progenies, are from free pollination and the other 9 from cross-pollination, can these 9 progenies of crosspollination resulting in highly productive hybrids (Bernini et al, 2013).…”