Maria Elisa Ayres Guidetti Zagatto Paterniani

Tropical maize germplasm: what can we say about its genetic diversity in the light of molecular markers?

Knowledge about genetic variability of a crop allows for more efficient and effective use of resources in plant improvement programs. The genetic variation within temperate maize has been studied extensively, but the levels and patterns of diversity in tropical maize are still not well understood. Brazilian maize germplasm represents a very important pool of genetic diversity due to many past introductions of exotic material. To improve our knowledge of the genetic diversity in tropical maize inbred lines, we fingerprinted 85 lines with 569 AFLP bands and 50 microsatellite loci. These markers revealed substantial variability among lines, with high rates of polymorphism. Cluster analysis was used to identify groups of related lines. Well-defined groups were not observed, indicating that the tropical maize studied is not as well organized as temperate maize. Three types of genetic distance measurements were applied (Jaccard’s coefficient, Modified Rogers’ distance and molecular coefficient of coancestry), and the values obtained with all of them indicated that the genetic similarities were small among the lines. The different coefficients did not substantially affect the results of cluster analysis, but marker types had a large effect on genetic similarity estimates. Regardless of genetic similarity coefficient used, estimates based on AFLPs were poorly correlated with those based on SSRs. Analyses using AFLP and SSR data together do not seem to be the most efficient manner of assessing variability in highly diverse materials because the result was similar to using AFLPs alone. It was seen that molecular markers can help to organize the genetic variability and expose useful diversity for breeding purposes.

Correlação da heterose de híbridos de milho com divergência genética entre linhagens

The objective of this work was to evaluate grain yield of maize single cross hybrids obtained from diallel crosses among contrasting lines, to estimate the combining ability of the lines, and finally to confirm if the genetic diversity among those lines assessed by molecular markers is correlated with single cross hybrids heterosis. The 36 single cross hybrids resulting from partial diallel and 12 parental lines were evaluated in Campinas in randomized block design, with three replicates and two control lines checks. General combining ability of the lines was estimated according to Griffing model 4. Correlations among matrices were estimated through Mantel statistics, considering heterosis, yield and specific combining ability with genetic divergence assessed by AFLP and SSR. The hybrids PM518 x L111 exhibited an outstanding yield and the lines PM518, IP4035 and L111 showed positive general combining ability. The estimate heterosis ranged from 927 to 6,698 kg ha -1 . A positive and significant correlation was observed in parental lines between heterosis and genetic diversity assessed by AFLP and SSR. The genetic divergence, however, was not enough to determine the specific combining ability and the hybrids yield.The objective of this work was to evaluate grain yield of maize single cross hybrids obtained from diallel crosses among contrasting lines, to estimate the combining ability of the lines, and finally to confirm if the genetic diversity among those lines assessed by molecular markers is correlated with single cross hybrids heterosis. The 36 single cross hybrids resulting from partial diallel and 12 parental lines were evaluated in Campinas in randomized block design, with three replicates and two control lines checks. General combining ability of the lines was estimated according to Griffing model 4. Correlations among matrices were estimated through Mantel statistics, considering heterosis, yield and specific combining ability with genetic divergence assessed by AFLP and SSR. The hybrids PM518 x L111 exhibited an outstanding yield and the lines PM518, IP4035 and L111 showed positive general combining ability. The estimate heterosis ranged from 927 to 6,698 kg ha. A positive and significant correlation was observed in parental lines between heterosis and genetic diversity assessed by AFLP and SSR. The genetic divergence, however, was not enough to determine the specific combining ability and the hybrids yield.

Desempenho de híbridos top crosses de linhagens S3 de milho em três locais do Estado de São Paulo

The present work aimed to evaluate the performance end high parent heterosis of 27 hybrids of partially endogamic lines (S3) obtained from commercial hybrids, using top cross squemes with testers (IA 33). Also, the general combining ability (GCA) of the lines was evaluated. The 27 top cross hybrids, two commercial checks and the tester were evaluated by complete block design with three replications, in two years (2005/2006 e 2006/2007), and three locations (Campinas, Mococa and Palmital) of Sao Paulo State. The evaluated traits were: plant height (AP), ear height (AE), percentage of broken and loged plant (AC+Q), ear yield (PE) and grain yield corrected of 14% moisture (PG). Top cross hybrids of high yield performance that outperformed or did not differ from the commercial check were observed. Therefore top cross hybrids with high yield performance and with advantage of small production cost were identified. Also line S3 with high value of GCA were observed.

Capacidade combinatória, divergência genética entre linhagens de milho e correlação com heterose

The objectives of this research were to evaluate single cross hybrids of maize (Zea mays L.) obtained from partial diallel crosses among contrasting inbred lines, to estimate the combining ability of the lines and to verify whether the genetic diversity among those lines assessed by moleculars markers is correlated with single cross hybrid heterosis Thirty-six single-crosses resulting from partial diallel and the 12 parental lines were evaluated in Campinas, State of Sao Paulo, in randomized block design, with tree replicates and two commercial checks. The following traits were evaluated: plant and ear height, ear weight and grain weight. Individual variance analysis of hybrids were performed, and the averages were compared by Tukey test (P<0.05). General combining ability of the lines was obtained according to Geraldi e Miranda Filho. Correlations among matrices were estimated through Mantel statistics, considering heterosis, yield and specific combining ability with genetic divergence assessed by AFLP and SSR. The hybrid PM624 x IP398 exhibited outstanding yield capacity and the lines VER266 and L105 showed positive GCA for grain yield. Estimate heterosis ranged from -559 to 6.320 kg ha-1. No significant correlation was observed between heterosis, specific combination ability or grain yield with genetic distance assessed by AFLP and SSR. Therefore, no prediction of hybrids performance could be made on the basis of the genetic divergence of the parent lines.

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

Ten inbred lines and the resulting forty-five hybrids from the maize IAC breeding program were evaluated for Al tolerance by the nutrient solution technique. Net radicle lengths (CLR) of plants grown with 4.5 mg.L-1 were used to estimate Al tolerance. The experimental design was randomized complete block with four replications, and it was used two divergent inbred lines IAC Taiuba as control for Al tolerance and sensitivity, respectively. In addition to these data, it is shown also the grain yield of the same materials from field plots. It was identified two inbred lines (L 06 and L 09) as Al tolerance sources and hybrids potentially adapted to acid soil conditions (tolerant to Al toxicity). From the diallel analysis, the treatment effects were separated into general (CGC) and specific (CEC) combining ability and indicated the predominance of additive effects on the Al tolerance manifestation. High values of hybrid vigor were obtained, indicating the existence of interactions non-allelic in the manifestation of CLR. The hybrid HS 10X11 (named IAC 21) showed higher productivity and Al tolerance, and also a higher CEC estimate for CLR.

Desempenho de híbridos triplos de milho obtidos de top crosses em três locais do Estado de São Paulo

ABSTRACT PERFORMANCE OF MAIZE TRIPLE CROSS-WAY HYBRIDS IN THREE ENVIRONMENTSIN SAO PAULO STATE, BRAZIL The objectives of this investigation were to study the combining ability of 30 lines of the maizebreeding program of the Instituto Agronomico, Sao Paulo State, Brazil, in top crosses squemes, aimingat to identify lines for developing high yield triple cross hybrids with two testers (single cross hybrids).The 60 top crosses along with two checks were evaluated in 2001/2002, in two experiments, named TC1and TC2, following a randomized complete block design with three replicates, over three locations: ( 1 ) Recebido para publicacao em 27 de outubro de 2005 e aceito em 14 de agosto de 2006.( 2 ) Centro de Analise e Pesquisa Tecnologica do Agronegocio de Graos e Fibras, Instituto Agronomico (IAC), Av. Baraode Itapura, n.1481, 13020-902 Campinas (SP). E-mail: elisa@iac.sp.gov.br, * Autora correspondente; sawazaki@iac.sp.gov.br,rrluders@iac.sp.gov.br.( 3 ) Bolsista da FAPESP.( 4 ) Polo Regional de Desenvolvimento do Medio Paranapanema (APTA), Caixa Postal 263, 19800-000, Assis (SP). E-mail:aildson@femanet.com.br.(

Estimativas de parâmetros de heterose em híbridos de populações F2 de milho

Hybrids developed with the efficient use of heterosis contribute significantly for increasing maize yield. This study aimed to evaluate F 2 hybrid populations, concernings agronomic traits, and estimate genetic parameters of F 2 populations, as well as heterosis, by using the Gardner & Eberhart method. Higher estimates of F 2 populations effect, for grain mass, were noticed in the Pop.9, Pop.11, Pop.14, and Pop.15, being considered suitable for intrapopulational recurrent selection programs and for obtaining superior lines. The Pop.10 and Pop.16 distinguished themselves by presenting the higher effects of parental heterosis, for grain mass. The Pop.12 x Pop.10 and Pop.13 x Pop.10 hybrids showed high yield and specific heterosis effects, revealing the existence of dominant locus in the genetic control of grain mass.

POTENCIAL DE HÍBRIDOS TEMPERADOS DE MILHO PIPOCA EM CRUZAMENTOS COM O TESTADOR SEMITROPICAL IAC 12

Com o objetivo de verificar se a posicao da semente na espiga afeta diferentemente a produtividade e outros caracteres da planta e se essa diferenca pode ser ampliada por meio de ciclos seletivos, foi conduzido o presente trabalho. Para isto, na safra 1995/1996, foram semeadas, em lote isolado, cerca de 3.000 plantas da populacao CMS-39 e, por ocasiao da colheita, tomadas 300 espigas ao acaso. De cada espiga, foram coletadas sementes das extremidades e, posteriormente, as sementes da ponta de cada espiga foram misturadas e o mesmo foi realizado com as sementes da base. Esse procedimento foi repetido de modo analogo por cinco ciclos seletivos. As dez subpopulacoes, cinco da ponta e cinco da base, foram avaliadas em experimentos conduzidos nas safras 2000/2001 e 2001/2002. O delineamento utilizado foi o de blocos casualizados, com seis repeticoes, segundo esquema de parcelas subdivididas. Os tratamentos nas parcelas foram os cinco ciclos seletivos e, nas subparcelas, a origem das sementes, ponta ou base. Foram considerados os caracteres numero de dias para o florescimento masculino e feminino, altura de espiga e produtividade de graos. Constatou-se que a origem da semente da ponta ou da base nao alterou a expressao de varios caracteres avaliados e nao foi possivel, com a precisao experimental obtida, detectar efeito da selecao indireta para o vigor de polen pela posicao dos graos na espiga, em todos os caracteres considerados.

Avaliação da resistencia a ferrugem tropical em linhagens de milho

Avaliaram-se 440 linhagens endogâmicas de milho do Instituto Agronomico de Campinas, obtidas a partir de diversas populacoes, quanto a severidade da ferrugem tropical, causada por Physopella zeae, em condicoes naturais de infeccao. Foram instalados 22 experimentos em blocos ao acaso com duas repeticoes, em 1993/94, em Ribeirao Preto (SP) e utilizados como testemunhas resistente e suscetivel os hibridos Z 8568 e P 3069 respectivamente, incluidos de forma intercalar. A avaliacao foi realizada aos 30 dias apos o florescimento, mediante uma escala de notas de 1 a 9, correspondendo a 0%; 1%; 2,5%; 5%; 10%; 25%; 50%; 75% e >75% de area foliar afetada. Todas as populacoes estudadas apresentaram variabilidade quanto a resistencia a P. zeae, indicando que a utilizacao de metodos de selecao recorrente pode ser eficaz no melhoramento de populacoes visando a resistencia ao patogeno.

Resistance of conventional and isogenic transgenic maize hybrids to Spodoptera frugiperda (Lepidoptera: Noctuidae)

Avaliou-se o efeito dos danos ocasionados por S. frugiperda na produtividade de hibridos de milho convencionais e suas versoes isogenicas transgenicas com diferentes toxinas Bt, em condicoes de campo. Experimentos foram instalados nas localidades de Campinas e Mococa, nas safras 2010/2011 e 2011/2012, em delineamento experimental de blocos ao acaso, com 12 tratamentos e quatro repeticoes. As variaveis avaliadas foram: produtividade de graos, massa de cem graos e rendimento de graos. Para a avaliacao dos danos ocasionados por S. frugiperda, verificou-se a intensidade das injurias foliares por meio de escala visual de notas, com variacao de 0 a 9, dos 15 dias ate os 60 dias apos a semeadura. Menores notas de danos causados por S. frugiperda sao verificadas em hibridos transgenicos. A maioria dos hibridos convencionais nao difere em produtividade de graos de pelo menos uma de suas versoes isogenicas transgenicas. Os mesmos hibridos de milho com toxinas Bt diferentes podem apresentar comportamentos produtivos diferentes em condicoes de campo. Toxinas Bt diferentes respondem de forma distinta em relacao aos danos ocasionados por S. frugiperda.