RESUMO A resistência genética a doenças em plantas representa um importante pilar de sustentação na agricultura moderna. Objetivou-se determinar a herança genética da resistência à antracnose do colmo em milho tropical. Nove famílias segregantes foram obtidas a partir de cruzamentos de linhagens endogâmicas contrastantes. As linhagens parentais e as gerações filiais (F1, F2, BC1 e BC2) foram avaliadas quanto à resistência à antracnose do colmo em um experimento em blocos casualizados, com três repetições. Os tratamentos foram arranjados em delineamento de parcelas subdivididas, com efeito de famílias nas parcelas e de gerações nas subparcelas. Os resultados mostraram herança semelhante entre as famílias, com predominância de efeitos genéticos aditivos. As linhagens endogâmicas (LR 04-2, LR 03-2 e LR 23-1) foram muito eficazes na transmissão de genes de resistência a seus descendentes, pois permitiram diminuições acentuadas no comprimento das lesões nos colmos. Também observou-se uma herança oligogênica envolvida na resistência à antracnose do colmo nas famílias avaliadas. Pode-se inferir que os ganhos genéticos com a seleção artificial poderiam ter sucesso no desenvolvimento de linhagens endogâmicas de milho mais resistentes à antracnose do colmo.

ABSTRACT The genetic resistance to diseases in plants represents an important support pillar in modern agriculture. This study aimed to determine the genetic inheritance to anthracnose stalk rot resistance in tropical maize. Nine segregating families were obtained from contrasting inbred lines crosses. The parental lines and the filial generations (F1, F2, BC1 and BC2) were evaluated for antrachnose stalk rot resistance in an experiment in randomized blocks, with three replications. The treatments were arranged in a split-plot design, with family effect in the plots and generation effect in the split-plots. The results showed a similar inheritance among the families, with predominance of additive genetic effects. The inbreed lines (LR 04-2, LR 03-2 and LR 23-1) were very effective in transmitting resistance genes to their descendants because they allowed sharp decreases in the lesions length in the stalks. It was also possible to notice an oligogenic inheritance involved in the anthracnose stalk rot resistance for the evaluated families. It may be inferred that genetic gains from artificial selection could be successful for developing maize inbred lines more resistant to anthracnose stalk rot.

Abstract The aims of this study were to evaluate the homology of the ZmMATE1 and ZmMATE2 gene sequences with those deposited in the international banks of sequences and quantify the differential expression of the genes ZmMATE1, ZmMATE2, and ZmNrat1 in germplasms of landrace and hybrid maize under aluminum (Al) stress in minimal solution. Fifty-two hybrids from different companies and 50 landrace varieties were genotyped for the genes ZmMATE1 and ZmMATE2. For studies of gene expression, the tolerant (H 44 and V 18) and the sensitive (H 22 and V 25) genotypes were exposed to minimal solution containing 4 mg L-1 of Al for different periods (0, 1, 3, 6, 9, 12, 24, and 48 h). The results showed greater differential expression in the tolerant V 18 landrace variety of the gene ZmMATE1, indicating that exudation of citrate may be the main mechanism of Al tolerance in this genotype.

ABSTRACT Aluminum (Al) toxicity is the most limiting factor to maize crop productivity in acid soils. Therefore, the understanding of inheritance of Al tolerance in maize is important for the developmentof more adequate procedures for Al tolerant genotypes selection. In this sense, the objectives of this study were to determine the inheritance, and the general (GCA) and specific combining ability (SCA) for Al tolerance in tropical maize. First, we evaluated diallel crosses of maize from landrace and hybrid germplasms for Al tolerance through the minimal solution methodology. The DIF data (root growth difference) were analyzed by Griffing diallel model. Later the additive-dominant genetic model proposed by Mather and Jinks (1971) was used to estimate the genetic effects. The results of the diallel analysis showed greater variability associated with the estimates of the SCA for both germplasm. The diallel crosses involving the V 06 (Dente de Ouro 2) landrace stood out by high SCA and GCA for Al tolerance. The generation mean analysis indicated quantitative inheritance of Al tolerance in this germplasm, with most of the variance explained by the additive effects. The heritability in the narrow sense varied from 47% to 71%, indicating the possibility of genetic gain with the selection of tolerant genotypes in F2 generation. Additive gene action associated with intermediate heritability and quantitative inheritance demonstrates the possibility of genetic gains with artificial selection for Al tolerance in this maize germplasm.

Abstract The objectives of this study were to map genomic regions associated with QTL for aluminum (Al) tolerance in maize and determine the phenotypic effects of tolerance loci. QTL analysis for Al tolerance was carried out in a population of F2:3 progenies resulting from a cross between the contrasting lines LT 99-4 and LS 04-2. SSR (Simple Sequence Repeat) loci and AFLP (Amplified Fragment Length Polymorphism) were used to construct the linkage map and to detect QTL mapped by composite interval mapping analysis. Nine tolerance QTL among eight linkage groups (chromosomes 2, 4, 5, 6, 7, 8, 9, and 10) were mapped, which explained 70.3% of the phenotypic variance. The results confirmed three major QTL (bins 6.00, 8.05, and 10.01) that are described in the literature for Al tolerance, which accounted for most of the phenotypic variance (40.3%).

Abstract The objectives were to map genomic regions associated with quantitative trait loci (QTL) to anthracnose leaf blight (ALB) in tropical maize, and to determine the effects of the loci on resistance to the pathogenic fungus Colletotrichum graminicola (Ces.). QTL analysis to ALB was carried out in a population of F2:3 progenies resulting from the cross between the contrasting lines LR 04-2 and LS 95-1. Seventeen QTL were located by mapping analysis by composite interval on eight chromosomes. Four QTL mapped on chromosomes 9 (1 QTL) and 10 (3 QTL) were the most stable, detected in at least two experiments, and represented the most part of the phenotypic variation (27.7 to 54.3%) of resistance. The majority of QTL mapped were associated to specific severity evaluations/development stage of maize growth, and may explain the quantitative inheritance of resistance of tropical maize to ALB.

RESUMO O presente trabalho objetivou estimar a divergência genética entre progênies de meios-irmãos de milho visando direcionar a recombinação entre progênies contrastantes e superiores para a produção de milho-verde. Noventa e seis progênies foram avaliadas no delineamento de blocos casualizados com 3 repetições, sendo mensuradas 18 características associadas à adaptação agronômica e ao rendimento de milho-verde. A divergência genética foi estimada a partir da distância quadrada generalizada de Mahalanobis e as progênies agrupadas pelos métodos UPGMA e de Tocher. A análise de variância conjunta evidenciou variabilidade genética entre as progênies para as características. O método UPGMA foi mais sensível que o de Tocher, pois levou à formação de 11 grupos geneticamente dissimilares em comparação com os 5 de Tocher. O agrupamento identificou progênies superiores e contrastantes para a produção de milho-verde. A recombinação dessas progênies possibilitará incrementar a variabilidade genética e a frequência de alelos favoráveis à produção de milho-verde.

ABSTRACT The present study aimed to estimate the genetic divergence among corn half-sib progenies seeking to direct recombination between contrasting and superior progenies for green corn production. Ninety-six progenies were evaluated in a randomized block design with 3 replications, and 18 characteristics associated with agronomic adaptation and green corn yield were measured. The genetic divergence was estimated using generalized square Mahalanobis distance and the progenies grouped by UPGMA and Tocher’s methods. The joint analysis of variance showed genetic variability among the progenies for the characteristics evaluated. The UPGMA method was more sensitive than Tocher’s, since it led to the formation of 11 groups genetically dissimilar compared to the 5 ones of Tocher’s method. The grouping allowed to identify superior and contrasting progenies for green corn production. The recombination of these progenies allows increasing genetic variability and the frequency of alleles favorable to the green corn production.

Abstract The objectives of this study were to evaluate the resistance of maize inbred lines to anthracnose leaf blight (Colletotrichum graminicola Ces.), and to estimate genetic parameters associated with resistance. Sixteen lines (S5) were evaluated for resistance to anthracnose leaf blight in three experiments, in a randomized block design with four replications. From three evaluations of severity, it was estimated the area under the disease progress curve (AUDPC), and the genetic parameters associated with resistance. Results showed the existence of genetic variability for resistance to anthracnose leaf blight in the set of studied lines. Five lines stood out for the high resistance pattern to anthracnose leaf blight, presenting the lowest AUDPC values in the three experiments, and thus were considered important sources of C. graminicola resistance genes. Estimates of genetic parameters indicated low participation of the environment and highlighted the possibility of genetic gains with artificial selection for resistance in this pathosystem.

Análise de médias foi usada para estudar o modo de herança da resistência a antracnose do colmo em milho tropical. Cada população foi composta de seis gerações que foram avaliadas para resistência em dois ensaios no delineamento de blocos ao acaso. As inoculações foram realizadas usando uma suspensão de 10(5) conídios mL-1 aplicados dentro do colmo. O comprimento interno de lesão foi medido diretamente após abertura do colmo 30 dias após a inoculação. Os resultados indicaram modos contrastantes de herança. Em uma população, os efeitos gênicos dominantes predominaram. Embora as interações, aditivo x dominante e aditivo x aditivo, também foram encontradas. Valores intermediários de herdabilidade indicaram herança da resistência complexa, provavelmente condicionada por vários genes de pequeno efeito. O modelo genético aditivo-dominante foi suficiente para explicar a variação na segunda população, onde os efeitos aditivos predominaram. Poucos genes de grande efeito controlam a resistência neste cruzamento. Heterose diferiu amplamente entre as populações o que pode ser explicado pelo background genético das linhagens genitoras resistentes.

Generation means was used to study the mode of inheritance of resistance to anthracnose stalk rot in tropical maize. Each population was comprised of six generations in two trials under a randomized block design. Inoculations were performed using a suspension of 10(5) conidia mL-1 applied into the stalk. Internal lesion length was directly measured by opening the stalk thirty days after inoculation. Results indicated contrasting modes of inheritance. In one population, dominant gene effects predominated. Besides, additive x dominant and additive x additive interactions were also found. Intermediate values of heritability indicated a complex resistance inheritance probably conditioned by several genes of small effects. An additive-dominant genetic model sufficed to explain the variation in the second population, where additive gene effects predominated. Few genes of major effects control disease resistance in this cross. Heterosis widely differed between populations, which can be attributed to the genetic background of the parental resistant lines.

O objetivo deste trabalho foi avaliar a diversidade genética, entre e dentro de progênies de dendezeiro tipo dura, de origem Deli. A caracterização genética foi feita com uso de marcadores microssatélites em 24 progênies usadas na produção comercial de sementes, sendo 22 provenientes de autofecundação e duas de cruzamentos entre irmãos completos. Foi realizada análise de variância molecular entre e dentro das progênies, com posterior construção de um dendrograma. Observou-se baixa variabilidade genética nas progênies, com média de 1,32 alelos por loco e variância genética total igual a 0,3241. A maior parte da variação ocorreu entre progênies. A menor variabilidade genética dentro das progênies pode ser explorada nos cruzamentos com progênies endogâmicas de outras origens, o que facilitaria o alcance de heterose para o desenvolvimento de novas variedades.

The objective of this work was to assess the genetic diversity between and within progenies of dura type oil palm from Deli. Genetic characterization was performed with microsatellite markers on 24 oil palm progenies used in commercial seed production, of which 22 originated from self-fertilization and two from cross-fertilization between full siblings. Molecular analysis of variance was carried out among and within progenies, and a dendrogram was constructed. Low genetic variability was observed within progenies, with an average of 1.32 alleles per locus and total variance of 0.3241. Most of the variation was found between progenies. The lower genetic variability within progenies can be explored in crossings with endogamic progenies from other origins, which would facilitate heterosis in order to develop new varieties.

O controle biológico consiste no uso de organismos que atacam outros que causam danos a culturas de plantas. Esta é uma estratégia muito utilizada no Controle Integrado de Pragas (CIP). O mofo branco, causado por Sclerotiniasclerotiorum (Lib.), causa danos em culturas de feijão. Este fungo é encontrado no solo e seus sintomas são caracterizados por lesões úmidas cobertas por micélios algodonosos, crescidos a partir do solo e/ou da planta hospedeira. Há relatos de pesquisas buscando agentes potenciais de controle biológico isolados de plantas para controlar fungos fitopatogênicos. Entre estes agentes encontram-se os microrganismos endofíticos, habitantes de espaços intercelulares de tecidos vegetais, muitas vezes responsáveis pela produção de substâncias antimicrobianas. Este trabalho teve por objetivo selecionar linhagens endofíticas isoladas de folhas de confrei (Symphytumofficinale L.), com potencial de antagonismo in vitro contra a linhagem fitopatogênica S. sclerotiorum. Doze linhagens de fungos endofíticos foram utilizadas na técnica de desafio em placa contra um isolado patogênico de S. sclerotiorum. Com o auxílio desta técnica, quatro linhagens com melhor atividade antagonística contra S. sclerotiorum foram selecionadas. Zonas de inibição no crescimento da linhagem patogênica foram consideradas como indicativo de antibiose. Foram efetuadas análises da porcentagem de elongação micelial com e sem antagonismo, mostrando resultados de 46,7% a 50,0% de redução no crescimento micelial do fitopatógeno. Estas análises consistiram de avaliações das medidas do crescimento em mm/dia das linhagens endofíticas/patogênica em testes de antagonismo.

Biological control consists of using one organism to attack another that may cause economic damage to crops. Integrated Pest Management (IPM) is a very common strategy. The white mold produced by Sclerotiniasclerotiorum (Lib.) causes considerable damage to bean crops. This fungus is a soil inhabitant, the symptoms of which are characterized by water-soaked lesions covered by a white cottony fungal growth on the soil surface and/or the host plant. Possible biological control agents taken from plants are being investigated as phytopathogen inhibitors. These are endophytic microorganisms that inhabit the intercellular spaces of vegetal tissues and are often responsible for antimicrobial production. The objective of the present study was to select endophytic fungi isolated from comfrey (Symphytumofficinale L.) leaves with in vitro antagonist potential against the phytopathogenic fungus S. sclerotiorum. Twelve isolates of endophytic fungi and a pathogenic strain of S. sclerotiorum were used in the challenge method. With the aid of this method, four endophytes with the best antagonistic activity against S. sclerotiorum were selected. Pathogen growth inhibition zones were considered indicative of antibiosis. The percentages of pathogenic mycelia growth were measured both with and without the antagonist, resulting in growth reductions of 46.7% to 50.0% for S. sclerotiorum. These analyses were performed by evaluating the endophytic/pathogenic mycelia growth in mm/day over an eight-day period of antagonistic tests.

O minimilho, uma espiga imatura ainda não fertilizada, vem ganhando importância no Brasil para o consumo como conserva, principalmente por ser agradável e apresentar baixo valor calórico. A pesquisa se propôs avaliar a qualidade das conservas de quatro híbridos; determinar a composição nutricional destes híbridos; e determinar o rendimento de minimilho para a produção de conserva. Os procedimentos de acidificação aplicados durante o processamento, essencial para a qualidade dessas conservas, resultaram em produtos seguros para o consumo. Os provadores preferiram a conserva de minimilho mais ácida, apresentando um valor de pH projetado para o equilíbrio de 3,9 ao invés de 4,2, bem como, a conserva contendo a salmoura de 4,0 %, p/v, de sal. As conservas dos híbridos DKB 214, P 3021, AG 6018 e DKB 215 não diferiram estatisticamente quanto ao paladar. As composições nutricionais desses híbridos foram similares e confirmaram se tratar de um produto de pouco valor calórico, apresentando concentrações porcentuais baixas de carboidratos digeríveis mais proteínas (6,87-7,21 %) e insignificante de lipídeo (< 0,30 %). Considerando o rendimento em massa média de minimilho sem palha em relação à matéria-prima com palha, o híbrido P 3021 foi o recomendado, pois, apresentou 25,90 % a mais em relação ao híbrido de menor rendimento AG 6018.

Baby corn, immature corn-cob yet fertilized, has become important for the canning in Brazil, because it is specially pleasant and low-calories. This research proposed to evaluate the quality of canned baby corn from four cultivars; determine the nutritional compositions of these cultivars; and determine the baby corn yield for canning. The acidification procedures used in processing resulted in a product safe for consumption. The tasters preferred the canned baby corn with highest acidity, which had an estimated pH 3.9 for stabilization, instead of 4.2 and canned with 4.0% brine. The canned of the cv. DKB 214, P 3021, AG 6018 and DKB 215 were considered equally palatable by the tasters. The nutritional compositions of the four cultivars were similar and these were low-calories because they had law-concentration in both the carbohydrate and the protein, and the lipid was insignificant (lower than 0.30%). Thus, considering the yield in baby corn for the canned, the cv. P 3021 was recommended, because it had a yield of 25.90% higher than the cv AG 6018, which had the lower.

A mancha-de-Phaeosphaeria, de ampla ocorrência no Brasil, tem causado expressiva redução na produtividade da cultura do milho no país. Por isso, o desenvolvimento de híbridos resistentes à doença é um dos principais objetivos dos programas de melhoramento genético da cultura. Informações sobre o controle genético da resistência à doença são necessárias para que os programas de melhoramento sejam eficientes. O objetivo deste estudo foi determinar o controle genético da resistência à mancha-de-Phaeosphaeria em milho a partir da avaliação das médias de gerações oriundas de dois cruzamentos entre linhagens resistentes (DAS95 ou DAS72) com uma suscetível (DAS21), sob condições de infecção natural da doença. Os ensaios foram conduzidos em Indianópolis (MG), em duas épocas de semeadura, outubro e novembro de 2000. Foi utilizado o delineamento experimental blocos ao acaso com três repetições. A avaliação para resistência foi realizada 30 dias após o florescimento com auxílio de uma escala diagramática de porcentagem de tecido foliar total da planta afetado pela doença. As médias da severidade da doença dos genitores e das gerações F1, F2, RCP1 e RCP2 foram analisadas segundo o modelo de MATHER & JINKS (1971). A variação genética devida a efeitos aditivos foi de 73 a 84%, enquanto, devido aos efeitos dominantes, foi de 13 a 23%. Foi evidenciada a predominância dos efeitos gênicos aditivos sobre dominantes em ambas as populações estudadas. Os valores da herdabilidade foram altos, variando de 61 a 88%. Os resultados indicaram condições favoráveis ao melhoramento genético visando àresistência à mancha-de-Phaeospheria nas populações estudadas.

The Phaeosphaeria leaf spot, of ample occurrence in Brazil, has been causing an expressive reduction in the corn yield in the country. Thus, the development of resistant hybrids to this disease is one of the main objectives of corn breeding programs. Information about the genetic control of resistance to the disease is necessary so that the programs can be efficient. The main goal of this study was to determine the genetic control of resistance to the Phaeosphaeria leaf spot in maize through the assessment of the generation means from two crossing between a resistant inbred line (DAS95 or DAS72) with a susceptible line (DAS21) under natural infection conditions of the disease. The experiment was carried out in Indianópolis (MG) in two sowen dates, October and November, 2000. The randomized blocks design with three repetitions was utilized. The evaluation to resistance was performed thirty days after the flowering using a diagrammatic scale of percentage of the total foliar tissue of the plant affected by the disease. Disease severity means of parental lines and generations F1, F2, RCP1 and RCP2 were analysed according to the model by MATHER & JINKS (1971). Genetic variation due to additive effects varied from 73% to 84% whilst dominant effects ranged from 13% to 23%. In both studied population, the predominance of gene additive over dominant effects was evidented. The inheritance values were high, varying from 61% to 88%. These results indicate favourable conditions to develop new resistance lines to Phaeosphaeria leaf spot with the studied populations.

In this work we describe the cytogenetic analyses performed in specimens of Astylus variegatus (Germar, 1824) collected in two localities: one area of natural vegetation and one of agricultural crops, where agrochemical products were used. Astylus variegatus had karyotypes with 2n(male) = 16+Xy p and 2n (female) = 16+XXp, with exclusively metacentric chromosomes. Pachytene spermatocytes showed synapsed autosomal bivalents and non-associated sex chromosomes. In diplotene, the autosomal bivalents exhibited one or two terminal chiasmata and the Xy p had a typical parachute configuration. In meiotic cells of some specimens, an extra chromosome, interpreted as a B chromosome, was observed. C-banding showed constitutive heterochromatin in the pericentromeric region of all chromosomes, with the exception of the y p. Silver nitrate staining revealed one nucleolus organizer region (NOR) on the terminal region of the short arm of the second autosome pair. Silver staining of meiotic cells confirmed the NOR pattern detected in mitotic cells and revealed an argentophilous material on the Xy p. A cytogenetic comparison between the two populations of A. variegatus showed a statistically significant divergence (chi2 = 117.10; df = 1) in the number of aneuploid cells and a higher frequency of B chromosome in the population exposed to agrochemicals.

A utilização de raças silvestres em hibridações com o grupo cultivado em aveia (Avena sativa L.) tem sido fonte de incremento da variabilidade genética. Desta forma, o presente trabalho foi desenvolvido com o objetivo de identificar e caracterizar a variabilidade genética dos caracteres morfo-fisiológicos estatura de planta e dias da emergência à floração em grupos de genótipos cultivados de aveia, introduções silvestres de A. fatua L., e em populações segregantes dos cruzamentos naturais de A. sativa x A. fatua. Ampla variabilidade genética foi revelada para os caracteres avaliados tanto dentro como entre os grupos. O grupo silvestre A. fatua demonstrou plantas de elevada estatura e precoces. Foi possível encontrar populações segregantes de A. sativa x A. fatua com reduzida estatura e precocidade. As introduções silvestres de A. fatua avaliadas neste trabalho podem ser utilizadas em programas de melhoramento para incrementar a variabilidade genética, pela transferência de caracteres específicos para o germoplasma cultivado.

The use of wild oat races in artificial hybridization with cultivated oat (Avena sativa L.) has been used as a way of increasing the variability. This work aimed to identify the variability for plant height and flowering date of groups of cultivated oat genotypes, wild introductions of A. fatua L. and segregating populations of natural crosses between A. sativa and A. fatua. Wide genetic variability was observed for both traits in the groups and between them. The wild group of A. fatua L. showed high plants with early maturity, but in the segregating group there was reduced plant height and early maturity. The wild introductions of A. fatua L. studied in this work can be used in oat breeding programs to increase genetic variability by transferring specific characters into the cultivated germ plasm.

O incremento no rendimento de grãos tem sido uma das principais metas dos programas de melhoramento da aveia. A busca de variabilidade genética para componentes do rendimento é considerada uma estratégia de melhoria no potencial de rendimento de grãos. O presente trabalho foi realizado com o objetivo de identificar variabilidade genética para os caracteres morfofisiológicos peso de grão e número de espiguetas por panícula em genótipos de aveia cultivada (Avena sativa L.), introduções silvestres de Avena fatua L. e populações híbridas naturais de A. sativa L. x A. fatua L. Ampla variabilidade genética foi detectada entre e dentro dos grupos, para os caracteres avaliados. Os genótipos do grupo cultivado (Avena sativa L.) revelaram peso de grão superior e pequeno número de espiguetas por panícula. As introduções silvestres de A. fatua L. apresentaram reduzido peso de grão e baixo número de espiguetas por panícula. Entretanto, algumas populações híbridas da geração F2 revelaram alto peso de grão e baixo número de espiguetas por panícula, passíveis de serem utilizadas no programa de melhoramento.

Raising oat grain yield has been one of the main goals of breeding programs. The search for genetic variability in yield components is considered a strategy to increase yield potential. The present study was done aiming to identify genetic variability for morpho-physiological traits (grain weight and number of spikelet /panicle) in cultivated oat genotypes (Avena sativa L.), wild introductions of A. fatua L. and natural hybrid populations of A. sativa L. x A. fatua L. Wide genetic variability was detected among groups and within them for the evaluated traits. Genotypes in the cultivated group (Avena sativa L.) revealed a higher grain weight and low number of spikelet/panicle. A. fatua L. wild introductions showed low grain weight and low number spikelet/panicle. However, some hybrid F2 populations revealed high grain weight and low spikelet number/panicle, being able to be used in the breeding program.