Evaluation of combining ability in white corn for special use as corn grits

Abstract To assess the genetic potential of white corn for corn grits, 28 hybrids resulting from diallel crosses of eight parents, including parents and S1 generations, were evaluated. The combining abilities and levels of heterosis and inbreeding depression were estimated. The parents used were the main white maize hybrids of the Brazilian germplasm. The combinations HT 9332 x HT 392, IAC Nelore x HT 9332, IAC Nelore x HT 932, and IPR 119 x IAC Nelore are promising for reciprocal recurrent selection programs targeting higher grain yield. Hybrid IPR 127 was indicated as a source of industrial lines with favorable traits for dry-rolled corn production. Hybrid IAC Nelore had the lowest estimate of inbreeding depression and was recommended for the breeding of lines and participation in higher-yielding hybrids and composites

Desempenho esempenho agronômico de novos híbridos de milho-pipoca no Noroeste do Estado do Paraná, Brasil = Agronomic performance of new popcorn hybrids in Northwestern Paraná state, Brazil

Em milho, variações de desempenho agronômico são comuns em ambientesdistintos, havendo resposta ainda mais diferenciada em híbridos simples. Este trabalho teve como objetivo avaliar o desempenho de novos híbridos simples de milho-pipoca, desenvolvidos pelo Programa de Melhoramento da Universidade Estadual de Maringá, no noroeste do Paraná. Para isso, avaliaram-se as características agronômicas de rendimento de grãos, capacidade de expansão, altura de planta, altura de espiga, resistência à ferrugem polissora (Puccinia polysora), à helmintosporiose (Exserohilum turcicum) e à mancha branca(Phaeosphaeria maydis/Pantoea ananas). O experimento foi conduzido em blocos completos, com tratamentos ao acaso com três repetições, em Maringá-PR, na safra 2006/2007. Os tratamentos foram 27 híbridos de linhagens S5 e as cultivares BRS Angela, IAC 112 e Jade. Constataram-se diferenças significativas (p ≤ 0,05) entre os híbridos para todas as características avaliadas. O híbrido proveniente da combinação das linhagens C e K expressou os melhores índices de rendimento de grãos e capacidade de expansão e foi susceptível à ferrugem polissora. Os híbridos provenientes das linhagens L, H e Kdestacaram-se com relação à resistência à ferrugem polissora, enquanto os híbridos da linhagem G foram mais resistentes à helmintosporiose, e os das linhagens M e G, à mancha branca.In maize, variations on agronomic performance in distinctenvironments are common and more evident for one-way hybrids. The objective of this work was to evaluate the performance of new one-way popcorn hybrids developed by the Breeding Program of the State University of Maringá, in northwestern Paraná. The characteristics evaluated were: grain yield, popping expansion, plant height, ear height and the intensity of Southern rust (Puccinia polysora), Northern leaf blight (Exserohilum turcicum), and phaeosphaeria leaf spot (Phaeosphaeria maydis/Pantoea ananas). The assay was carried outinto randomized block design with three replications in Maringá, state of Paraná, Brazil, during the 2006/2007 cropping season. The treatments were 27 simple popcorn hybrids obtained from S5 endogamic inbreds and commercial cultivars BRS Angela, IAC 112 andJade. Significant differences (p ≤ 0.05) were verified among hybrids for all characteristics. The hybrid from C and K inbreds presented better indexes for grain yield and popping expansion; and was susceptible to Southern rust. About diseases, the hybrids from the L, H and K inbreds showed greater resistance levels to Southern rust, and hybrids from G inbred had better Northern leaf blight resistance. Hybrids from L and M inbreds showed better phaeosphaeria leaf spot resistance

Heterotic parametrization for economically important traits in popcorn

Six popcorn varieties were crossed in a diallel mating scheme to obtain 15 F1 hybrids, with the purpose of analyzing the estimates of heterotic parametrization for agronomically important traits. The genitors and hybrids were evaluated in randomized block design with three replications in Viçosa and Visconde do Rio Branco, in Minas Gerais State, Brazil, in three growing seasons. Six traits were evaluated, including grain yield and popping expansion. There were highly significant effects for treatments, varieties and mean heterosis for plant and ear heights, and for the others traits the significance extended to all sources of variation. Amarela and Viçosa revealed superiority for grain yield in relation to performance per se, while Rosa Claro expressed the highest effect of varietal heterosis. The best combinations for grain yield were Roxa x Viçosa, Amarela x Rosa Claro, Rosa Claro x Beija-Flor and Branca x Beija-Flor. For popping expansion, there were positive and negative values for specific heterosis in all growing seasons evaluated, ratifying the influence of bidirectional dominance on this trait. Simultaneous genetic gains for grain yield and popping expansion may be obtained by using Viçosa in intrapopulational programs, while Amarela and Rosa Claro are recommended for using in interpopulational breeding