Manoel Xavier dos Santos

Heterotic groups based on yield-specific combining ability data and phylogenetic relationship determined by RAPD markers for 28 tropical maize open pollinated varieties

Twenty eight maize open pollinated varieties (OPVs) were crossed in a diallel scheme and the 378 F1s were evaluated in 10 environments in Brazil. Based on yield-specific combining ability data (SCA), these varieties were classified in four heterotic groups. The consistence of the proposed heterotic groups was confirmed comparing intra- and inter-group F1 values and midparent heterosis. Superior OPVs combinations for use as a source of inbreds in hybrid breeding programs were determined. RAPD markers were used to genotype these varieties. A UPGMA dendogram, based on marker data from 50 primers and 178 polymorphic bands, was obtained. Phylogeny obtained with RAPD markers agreed with known pedigree data. Dent germplasm tended to group separately from flint germplasm. Multidimensional Scaling Analysis on marker data and morphological data showed a higher degree of genetic divergence among the dent germplasm than among the flint germplasm used in this study. Correlation between RAPD marker estimated genetic distance and SCA for yield was low and positive (r = 0.16**).

Adaptabilidade e estabilidade de cultivares de milho no nordeste brasileiro

Forty six maize cultivars were evaluated during two years in 11 different places of Brazilian Northeast Region. Trials were carried out during the biennium 2001/2002 using experimental randomized block design, three repetitions, in order to know the adaptability and stability for cultivars recommendation. It was verified that the cultivars showed differentiated behavior among themselves in the mean of environments. The magnitude of the variance for local x cultivars interaction was more expressive than cultivars x years interaction, which suggests that the evaluations have to be done in a larger number of environments. Evaluated cultivars differed in adaptability and stability, and are very important for Brazilian Northeast Region.

Inbreeding depression of 28 maize elite open pollinated varieties

The study of inbreeding depression is important for breeding strategies such as use of inbred progenies or extraction of inbreed lines. A diallel of 28 maize open-pollinated varieties was evaluated in 10 environments in the early 1990s. At the same time, S1 populations for each of the 28 varieties were evaluated in the same 10 experiments (environments). Yield reductions of the populations from S0 to S1 (mean of the 10 environments), varied from 34.6% (CMS-01) to 59.2% (CMS-30), with an average of 49.1%. Inbreeding depression was greater in populations with a wider genetic base, which had never been exposed to inbreeding (CMS-30, BR-107, PH4, Cunha, Saracura, Nitrodent, and Nitroflint). Inbred lines with greater yield means should be obtained from the BR-105, BR-111, CMS-01, CMS-03, BR-106, CMS-14c, and CMS-28 populations. The use of parameter estimates generated by analysis of inbreeding depression, allow to make inferences about frequencies of deleterious alleles in the population. The frequencies of favorable alleles in the parents can be obtained by diallel analysis. The association of these two types of information, can provide a better interpretation of the genetic parameters and also can improve the process of selection of parents for either an intra- or an inter-populational breeding program.

Heterotic responses of tropical elite maize accessions from Latin America with Brazilian testers

Little emphasis has been placed on identifying new sources of tropical maize germplasm that can be used in breeding programs. Additional information on the performance and heterotic classification of tropical germplasm is needed. This study was conducted to identify elite maize accessions from Latin America that could contribute to increase the level of heterosis with the best heterotic patterns of Brazil. Seventy-two elite accessions from the Latin American Maize Project (LAMP) were crossed with the testers BR 105 (flint kernel Suwan background) and BR 106 (dent kernel Tuxpeno background). The 72 crosses plus 9 checks were evaluated using a simple 9 ´ 9 lattice in four locations that represent one tropical region. The combined analysis showed highly significant differences among treatments for ear weight and the interaction treatment ´ location was also significant. With both testers better crosses for ear weight were identified in relation to the double cross BR 201 (commercial check). With the tester BR 105, the high parent heterosis ranged from ¾28% to 26%, the accessions SE 032 and PE 001 were selected for further work. With the tester BR 106, the high parent heterosis ranged from ¾35% to 17% and the accessions PE 011 and Pasco 14 were selected for further work. The selected accessions will be improved through recurrent selection schemes to increase yield and improve agronomic traits. Afterwards they can be exploited, within and between heterotic groups, to produce highly productive hybrid combinations, or used per se as improved maize varieties.

Adaptabilidade e estabilidade de produção de cultivares de milho no nordeste brasileiro

Twenty five cultivars of maize (Zea mays L.) were evaluated in 1994, in twelve different environments of the Northeast Region of Brazil. The trials were arranged in randomized block designs with three replications aiming to obtain knowledge concerning to the adaptability and yield stability of the cultivars in each environment. The significant effects related to environment, cultivars and cultivars x environments interaction gave the evidence of outstanding differences among that parameters. The hybrids showed better performance than the varieties, yielding in average 22.5% higher in relation to the environmental variations. Only the Cargill 505 and AG 510 hybrids showed poor adaptability in unfavorable environments. Taking in account the means presented by the varieties, CMS 39 was the most adjusted to the optimal genotype proposed in the model. None of the materials studied gave a determination coefficient (R2) lower than 80%, indicating a good production stability.

ASSOCIATION BETWEEN GRIFFING'S DIALLEL AND THE ADAPTABILITY AND STABILITY ANALYSES OF EBERHART AND RUSSELL*

The objective of the present work was to provide a methodology to study the inheritance of adaptability and stability through the breakdown of Eberhart and Russell regression coefficients and regression deviations in effects due to the mean and additive genetic effects (gis and gjs) as well as dominance effects (sijs) of Griffing´s methodology, when the diallel is conducted in several environments. It was concluded that the adaptability and stability parameters are determined in the same manner as are genetic effects. So an F1 cross inherits half the general combining ability (GCA) mean effect from each parent, while the effects due to specific combining ability (SCA) are subjected to the same considerations relative to sijs, i.e., they are dependent on specific combinations.

AVANÇOS NO PROCESSO SELETIVO DA VARIEDADE DE MILHO PIPOCA BRS ANGELA

A populacao e a distribuicao espacial de plantas na cultura do milho sao importantes para a interceptacao da radiacao, a qual e fundamental para o rendimento. A interceptacao da radiacao e funcao da latitude do local, do dia do ano, da hora do dia e do ângulo foliar. Nao se dispoe de metodologia para previsao da melhor populacao e distribuicao espacial de plantas em funcao da arquitetura da copa, sendo ambos, em geral, determinados por experimentacao em campo. Tambem nao se dispoe de metodologia para previsao do ângulo foliar que maximize a interceptacao da radiacao. Os objetivos do trabalho foram propor equacoes e metodologias para previsao da populacao e da distribuicao espacial de plantas em funcao da arquitetura da copa, bem como de ângulos foliares que maximizem a interceptacao da radiacao em funcao do local e do dia do ano. A metodologia proposta deve ser validada pela comparacao dos resultados de rendimento obtidos de genotipos com diferentes arquiteturas de copa e cultivados em diferentes latitudes e periodos do ano.O objetivo deste trabalho foi avaliar o efeito de genotipos de sorgo sobre a biologia do pulgao Rhopalosiphum maidis (Fitch). Os experimentos foram conduzidos na Embrapa Milho e Sorgo, em Sete Lagoas, MG. Foram testados oito genotipos de sorgo, sendo sete de reconhecida resistencia ao pulgao Schizaphis graminum (Rondani), e a cultivar comercial BRS 303. Para se obter folhas para a criacao dos pulgoes em laboratorio, foi plantada, semanalmente, no campo, uma fileira de cinco metros lineares de cada material. Os experimentos foram conduzidos durante duas geracoes do pulgao, utilizando-se, na primeira, insetos recem-nascidos, com aproximadamente uma hora de idade e oriundos da cultivar BR 304. As ninfas foram individualizadas e mantidas em secoes foliares provenientes de cada uma das oito cultivares estudadas. Como segunda geracao, utilizaram-se ninfas recem-nascidas, obtidas de progenitores criados em cada genotipo estudado na fase anterior, ou seja, individuos da segunda geracao. Em ambas as geracoes, os insetos foram mantidos em câmaras climatizadas reguladas a 25 ± 1oC, UR 70 ± 10% e fotofase de 12 horas, avaliando-se o numero de instares, periodos prereprodutivo, reprodutivo e pos-reprodutivo, ciclo total, numero de ninfas produzidas por femea e peso dos insetos aos quatro e oito dias de idade, com 15 repeticoes. O delineamento experimental foi o inteiramente casualizado, em esquema fatorial (genotipos x geracoes x repeticoes). Os genotipos TX 430 (IS x SC) e GR 1.1.1.1.1 apresentaram efeito adverso sobre a biologia do inseto, reduzindo a sobrevivencia, a capacidade reprodutiva, o periodo reprodutivo, pos-reprodutivo e o ciclo total. O genotipo BRS 303 foi o hospedeiro mais adequado, proporcionando uma elevada producao de ninfas, alta viabilidade e periodos reprodutivo, pos-reprodutivo e ciclo de vida mais longos.As doencas do milho causadas por molicutes (fitoplasma e espiroplasma) destacam-se em importância para a cultura, em consequencia da alta incidencia e dos prejuizos que causam a producao de graos. Os molicutes infectam o floema das plantas; sendo assim, podem alterar a sintese de acucares e proteinas. O objetivo deste trabalho foi verificar o efeito dos molicutes na sintese de acucares soluveis totais e de proteinas em duas cultivares de milho. O experimento foi conduzido em vasos de plastico contendo 30kg solo previamente analisado e adubado, com duas plantas por vaso. O delineamento experimental utilizado foi um fatorial 3 x 2 inteiramente casualizado, com seis repeticoes; sendo tres inoculacoes (fitoplasma, espiroplasma e sadia) e duas cultivares (Dina 766 e BR 201). Trinta dias apos a inoculacao, foram realizadas medidas de temperatura foliar, umidade relativa, resistencia estomatica e transpiracao. No estadio de grao leitoso, uma das plantas foi colhida e seccionada em tres partes, para analise de acucares soluveis totais, nutrientes e materia seca. Foi realizada uma amostragem do internodio abaixo da primeira espiga e da folha bandeira, para determinacao da atividade da peroxidase e do conteudo proteico. A planta restante foi conduzida ate o final do ciclo, quando foram avaliados: numero de espigas, peso de espigas e de graos e materia seca dos graos. A analise de variância de todas as caracteristicas avaliadas nao detectou significância na interacao cultivar x inoculacao. Alguns parâmetros mostraram significância para cultivares, para inoculacao ou para ambos. Acucares soluveis, materia seca, atividade da peroxidase e conteudo proteico foram semelhantes em ambas as cultivares e nas inoculacoes. A resistencia estomatica foi maior para Dina 766 e nas plantas inoculadas por fitoplasma. A proliferacao de espigas foi maior nas plantas inoculadas pelos molicutes que nas sadias. O peso de espigas e de graos foi maior nas plantas sadias e com fitoplasma que naquelas infectadas por espiroplasma. Concentracao de nutrientes e quantidade absorvida, em geral, foram semelhantes, excetuando P e Zn. Os molicutes nao interferiram na concentracao dos acucares soluveis e no conteudo proteico total; entretanto, os dados de produtividade sugerem uma maior susceptibilidade das cultivares ao espiroplasma.

Estimativas de parâmetros genéticos na população de milho CPATC-3 em dois locais de Sergipe

From 1999 to 2001, the maize population CPATC-3 was submitted to three selection cycles among and within half sib families in two sites of Sergipe State in order to obtain genetic parameters estimates and to verify the behavior of the genetic variability for ear weight. In each selection cycle, 196 half sib families were evaluated in a completely randomized block design with two replications per local and the recombination of the best families within the same agricultural year was made. The results showed highly significant differences among the families from the base population and for all selection cycles, evidencing the genetic variability presence for ear weight. The genetic parameters estimates showed that the maize population CPATC-3 presents genetic variability for increasing ear weight and offers good perspectives to continue the breeding program.

Potencial genético de um sintético de milho de grãos duros para formação de híbridos

The objective of this study was to determine the genetic potential of a semi-early maize synthetic with flint type kernel (Sin EEL Flint). The estimation of genetic parameters was obtained with S2 progenies, and the performance of the progenies in hybrid combinations were evaluated. One hundred fourty-two S2 progenies of Sin EEL Flint were used. They were obtained by top crossings with a contrasting heterotic synthetic of dent type kernel. These topcross progenies were tested in a lattice design 12 x 12 with two replications in two locations, Sete Lagoas and Londrina. The selected topcross no 101, with specific adaptation for Londrina. and no72, being adapted to both locations, were the best yieldings (PED) with 12069Kg ha-1 and 11068Kg ha-1, respectively. Values of the estimated parameters for , CVg and h2 were similar to those found in other studies conducted in tropical conditions. It was observed that this synthetic has enough genetic and potential variability to inbred line extraction for hybrid production and to be used as germoplasm source in breeding programs.

Adaptabilidade e estabilidade de comportamento de cultivares de milho em treze ambientes nos tabuleiros costeiros do nordeste brasileiro

The potential of the Brazilian Northeast coastal tablelands for corn production and the adaptability and stability of sixteen corn cultivars were evaluated at thirteen environments of this region in 1994/95 on a randomized block design experiment with three replications. The large potential of this coastal strip for corn production was evidenced by the obtained yield, highlighting the hybrids, on the coastal tablelands of Piaui, Sergipe and Bahia States, where corn would become a major crop option for the growers. Pooled variance analysis showed significant difference for environments and cultivars, and the interactions environment x cultivar, which were inconsistent. Hybrids had better adaptation than varieties and populations; they are recommended for higher input situations. The AG 510 hybrid showed good adaptation to low and high input conditions, and therefore is recommended for both situations. The BR 5011, BR 5028, BR 106 and BR 5033 varieties had reasonable yields and are suitable for small and medium corn growers.