Diallel crosses among maize lines with emphasis on resistance to foliar diseases

Abstract

Ten elite maize (Zea mays L.) lines were crossed in a complete diallel scheme and the single-cross hybrids obtained were assessed at four experimental stations of the Agronomic Institute of Campinas, in São Paulo State, Brazil. The experiments were set up in a randomized complete block design with three replications, including four commercial checks. The experimental plots consisted of two 5-m rows spaced at 0.9 m, with a total of 50 plants. The traits assessed included: days to mid-tassel pollen shed (DPS), plant height (PH), ear height (EH), grain yield, corrected for a 50-plant stand and 14% moisture (GY corr.), and resistance to Phaeosphaeria maydis and Puccinia polysora. General and specific combining ability effects (GCA and SCA) were determined. There was extensive genetic variability among hybrids with the best hybrids (HS 04 x 10 and HS 10 x 11) not differing from the commercial checks. The lines with the greatest potential for hybrid synthesis included: L 10, L 11 and L 13, because they had higher GCA for yield, moderate resistance to P. maydis and reduced EH. The greatest contribution to reduction of the Phaeosphaeria stain was obtained with L 5. The magnitude of the GCA relative to the total variation indicated that additive effects predominated for resistance to P. maydis and P. polysora. Significant SCA (P < 0.01) was also found, indicating dominance effects as well.<br>Cruzaram-se dez linhagens-elite de milho em esquema dialélico completo e os híbridos simples obtidos foram avaliados em quatro Núcleos Experimentais do Instituto Agronômico de Campinas, SP, Brasil. Os ensaios foram instalados sob delineamento de blocos casualizados com três repetições, incluindo quatro testemunhas comerciais. As parcelas consistiram em duas linhas de 5 m espaçadas por 0,90 m, contendo 50 plantas. Avaliaram-se os caracteres: dias para o florescimento masculino (DPS), altura da planta (PH) e da espiga (EH), produtividade de grãos corrigida para estande ideal de 50 plantas e 14% de umidade (GY corr.) e resistência a Phaeosphaeria maydis (Pm) e a Puccinia polysora (Pp). Estimaram-se os efeitos da capacidade geral e específica de combinação das linhagens. Houve grande variabilidade genética entre os híbridos, sendo que os melhores (HS 04 x 10 e HS 10 x 11) não diferiram das testemunhas comerciais. As linhagens de maior potencial para síntese de híbridos no conjunto em questão foram: L 10, L 11 e L 13, por aliarem alta GCA para produtividade, resistência moderada a P. maydis e redução da altura da espiga. A maior contribuição para redução da mancha de Phaeosphaeria foi proveniente de L 5. A magnitude da GCA em relação à variação total corroborou a natureza preponderantemente aditiva da resistência às doenças estudadas. A presença da SCA significativa (P < 0,01) foi também confirmada, indicando a existência de efeitos de dominância

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

“…The association of both GCA and SCA with grain yield concurs with other findings (Nass et al, 2000;Machado et al, 2009;Qi et al, 2010). The observation that GCA x location interaction was highly significant and greater than SCA x location interaction also agreed with other authors (Nass et al, 2000;Paterniani et al, 2000;Bello and Olaoye, 2009). However, since SCA x environment interaction was generally non-significant, stability of SCA effects across environments was indicated as similarly observed by Machado et al (2009).…”

Inheritance of resistance to anthracnose stalk rot (Colletotrichum graminicola) in tropical maize inbred lines

“…Significant differences between and within populations for mean of internal lesion length of C. graminicola were found in both trials (Table 1) likewise Pereira et al (1989) and Rezende et al (2004). The coefficients of variation of two trials were small magnitude and suitable for trials involving interaction pathogen-host in agreement with Zuber et al (1981), Paterniani et al (2000) and Rezende et al (2004).…”

Tolerância à toxicidade de alumínio de linhagens e híbridos de milho em solução nutritiva

“…Os valores de produtividade de grãos dos híbridos simples foram obtidos em quatro localidades paulistas (Campinas, Mococa, Ribeirão Preto e Assis), em 1997, em experimentos com solos corrigidos e apresentados por PATERNIANI et al (2000).…”