Combining ability of twelve maize populations

Abstract

Genetic progress depends on germplasm quality and breeding methods. Twelve maize populations and their crosses were evaluated to estimate combining ability and potential to be included as source populations in breeding programs. Plant height, point of insertion of the first ear, number of ears per plant, number of grains per ear, root and stalk lodging and grain yield were studied in two locations in Brazil, during the 1997/98 season. Genotype sum of squares was divided into general (GCA) and specific (SCA) combining ability. Results indicated the existence of genetic divergence for all traits analyzed, where additive effects were predominant. The high heterosis levels observed, mainly in Xanxerê, suggested the environmental influence on the manifestation of this genetic phenomenon. Populations revealed potential to be used in breeding programs; however, those more intensively submitted to selection could provide larger genetic progress, showing the importance of population improvement for the increment of the heterosis in maize. Capacidade combinatória de doze populações de milho Resumo-O progresso genético depende da qualidade do germoplasma e dos métodos de melhora-mento empregados. Neste trabalho foram avaliadas doze populações de milho e seus cruzamentos para avaliar suas capacidades combinatórias e seu potencial de inclusão em programas de melhoramento de milho no sul do Brasil. A estatura de planta, ponto de inserção da primeira espiga, número de espigas por planta, número de grãos por espiga, acamamento, quebramento e rendimento de grãos foram ava-liados em dois locais, em 1997/98. A soma de quadrados de genótipos foi dividida em capacidade geral (CGC) e específica (CEC) de combinação. Os resultados indicaram a existência de variabilidade gené-tica em todas as características analisadas, em que os efeitos aditivos foram predominantes. Os altos níveis de heterose observados, principalmente em Xanxerê, sugerem forte influência ambiental na manifestação deste fenômeno genético. As populações revelaram potencial para serem utilizadas em programas de melhoramento; entretanto, aquelas que sofreram seleção prévia mais intensa poderiam proporcionar progresso genético maior, demonstrando, assim, a importância do melhoramento de po-pulações para o incremento da heterose em milho. Termos para indexação: Zea mays, germoplasma, heterose, variação genética.

Combining ability and heterosis for aluminium stress tolerance of soybean roots and shoots grown in acid sand culture

“…8º35'E). On the basis of the results obtained from screening experiments carried out in hydroponics, sand culture and on an acid soil between 2002and 2004(Ojo, 2010, six parents (TGX 1873-16E, TGX 1878-7E, TGX 1890-7F, TGX 1891-3F, TGX 1896-3F and TGX 1844-18E) were selected and crossed in all possible combinations to obtain 15 F1s and their 15 reciprocals. The TGX 1896-3F and TGX 1844-18E genotypes were selected because they were rated as aluminium tolerant in hydroponics and sand culture, and had grain yield of >1.8 t/ha; TGX 1873-16E and TGX 1878-7E (moderately tolerant genotypes) were selected because they were outstanding in only the hydroponics and sand culture; TGX 1890-7F was selected because it had an average performance in only one culture media (the field).…”

“…The diallel analytical technique has been very useful in the estimation of hybrid vigour and gene action, and hence the identification of appropriate heterotic combinations in hybrids (Kim, 1986). The diallel supplies important information on general and specific combining abilities, genetic variances, heritability, and maternal effects among others (Vacaro et al, 2002). Such information serves as a useful guide in the determination of the overall plant breeding objective (Ojo et al, 2007).…”

Combining ability of grain yield and agronomic traits in diverse maize lines with maize streak virus resistance for Eastern Africa region

“…Hallauer and Miranda Filho (1988) also found dominance effects to bemore important for grain yield than for other traits such as plant height and ear height. Several researchers have similarly indicated the importance of additive effects in the inheritance of different agronomic traits (Ligeyo, 2000;Vacaro et al, 2002). The importance of additive gene effects in controling MSV resistance has resistance also been observed for other major foliar diseases: gray leaf spot (Menkir and Ayodele, 2005;Vanegas-Angaritas et al, 2007;Derera et al, 2008;Vieira et al, 2009;Vivek et al, 2010), and northern leaf blight (Vieira et al, 2009).…”

“…For effective selection of grain yield and other desirable traits, information on the magnitude of useful genetic variances in the population, in terms of combining ability and heterosis is required (Vacaro et al, 2002). Significantly, however, the resistance to maize streak virus (MSV) of specific crosses cannot always be reliably predicted from pedigree information or by evaluating parental performance (Diallo, 1999).…”

Hybrid Vigor, Heterosis, and Genetic Parameters in Maize by Diallel Cross Analysis

“…This result confirms what found by Wuhaib [10] of that dry weight is under the control of non -additive gene action resulted to low proportion of heritability (40.5% and 31%) and the high value of the degree of dominance (1.7 and 2.1) to the inbred and testers used in Line x tester cross program. However, Vacaro [14] found that σ 2 GCA was the biggest of σ 2 SCA, suggesting that the trait was governed by the additive genes. Table 7 illustrates that yield of unit area was differed among parents.…”