Abstract: The objective of this work was to evaluate the influences of the factors corn (Zea mays) genotypes, crop seasons, endosperm texture, genetic background, and genetic basis on putative haploid rates (PHRs) according to the expression of gene R1-navajo (R1-nj). Forty-one corn genotypes were evaluated as pollen receptors, in crosses with the Krasnodar haploid inducer, in two crops (summer and winter), in the municipality of Maringá, in the state of Paraná, Brazil. The experimental design was completely randomized with ten replicates (ears). The response variable analyzed was the PHR, determined by the proportion of putative haploids, obtained through the R1-nj marker, in relation to the number of diploid seeds in each ear. Subsequently, generalized linear models were used to choose the one best fit to explain the PHR in function of the tested factors. Crop seasons, genotypes, and the crop seasons x genotypes interaction affected significantly the PHR, showing the dependence of these factors on the expression of the phenotypic marker based on anthocyanin pigmentation and determined by gene R1-nj. The number of clusters formed by the genotypes was different in each crop season. Ten genotypes showed higher rates in summer than in winter. Endosperm texture, genetic basis, and genetic background did not affect the PHR.
RESUMO A mancha de Bipolaris, causada por Bipolaris maydis, é uma das principais doenças foliares de Zea mays, apresentando um considerável potencial de dano, notadamente, na cultura do milho-pipoca, embora trabalhos sobre este patossistema ainda sejam escassos. Neste trabalho, avaliaram-se as influências de diferentes meios de cultura sobre o crescimento micelial, esporulação e a infectividade de inóculo conidial de B. maydis em folhas da cultivar suscetível Beija-flor, de milho-pipoca. Para tal, instalaram-se experimentos em laboratório e em casa de vegetação em blocos casualizados com quatro repetições. Em laboratório, avaliaram-se o crescimento micelial e a esporulação de B. maydis em diferentes meios de culturas (Batata Dextrose Ágar, Feijão Ágar, Água de Coco Ágar, Arroz Polido Ágar, Folha de Milho Ágar e Lactose Caseína Ágar). Em casa de vegetação, avaliaram-se o número de lesões por folha e a incidência de doença na planta suscetível inoculada com uma suspensão de 104 conídios/mL. O meio de Arroz Polido Ágar foi o que mais promoveu o crescimento micelial do fungo, porém não favoreceu a esporulação. Para esporulação, destacaram-se os meios de cultura Batata Dextrose Ágar e Feijão Ágar. Maior número de folhas com sintoma da doença e maior número de lesões por folha foram obtidos com o inóculo produzido no meio Feijão Ágar. Palavras-Chave: Zea mays L., Crescimento micelial, Mancha de Bipolaris, Esporulação, Milho-pipoca.CULTURAL AND PATHOLOGICAL FEATURES OF Bipolaris maydis IN DIFFERENT CULTURE MEDIAABSTRACT. The Southern corn leaf blight, caused by Bipolaris maydis, is a major foliar disease of corn, presenting considerable potential of damage, especially in Zea mays, although studies with this pathosystem are still scarce. In this paper, the effect of different culture media was evaluated on mycelial sporulation and infectivity of conidial inoculum of B. maydis on leaves of the susceptible cultivar Beija-Flor, of corn-popcorn. Experiments in laboratory and greenhouse were installed in a randomized blocks design with four replications. The mycelial growth and sporulation of B. maydis on different culture media (Potato Dextrose Agar, Bean Agar, Coconut Water Agar, Rice Polished Agar, Corn Leaf Agar Lactose Casein Agar) were evaluated in the laboratory. In the greenhouse it was evaluated the number of lesions per leaf and the incidence of disease in susceptible plants inoculated with a suspension of 104 conidia/ml. The culture medium Polished Rice Agar promoted the highest mycelial growth, but did not promote sporulation. Sporulation was higher on culture media Potato dextrose Agar and Agar Bean. A greater number of leaves with symptoms of the disease and a higher number of lesions per leaf were obtained with the inoculum produced in the culture medium Bean Agar.Keywords: Zea mays L, Mycelial growth, Southern corn leaf bligh, Sporulation, Popcorn.
The use of more than one control technique can maximize the reduction of the damages caused by the fungus Asperisporium caricae causal agent of the black spot in the papaya crop. The objective of this work was to evaluate the sensitivity of the fungi Hansfordia pulvinata and Acremonium spp. to alternative products with potential for use in the control of the black-spotted ptarmigan. Three isolates of Acremonium spp. (A-598, A-602 and A-617) and an isolate of H. pulvinata (H-611) were grown in BDA medium containing Agro-Mos®, Bion®, Ecolife®, Hortifospk®, Matriz G®, Vitaphol® separately. The Amistar 500WG ® fungicide was used as a positive control and pure BDA as a negative control. The toxicity of the tested products was determined based on the values of the biological index, derived from the means of mycelial growth, sporulation and germination of conidia, in each experimental unit. In this way it was possible to select the products classified as compatible for all isolates, and to test them in vivo. In the greenhouse, only the isolates and isolates with selected products, were applied in papaya plants with foliar symptoms of black-spotted. The incidence of leaves with hyperparasites and the percentage of black-painted lesions colonized by the tested isolates were evaluated. Thus, the H-611 isolate proved to be compatible with most of the alternative products tested, except with Hortifos®. Bion® and Matrix® products were compatible with all tested isolates and could be used in conjunction with Acremonium spp. and H. pulvinata to control the papaya black spot, since these products did not present toxicity on the hyperparasitic fungi.
Abstract The use of more than one control technique can maximize the reduction of the damages caused by the fungus Asperisporium caricae causal agent of the black spot in the papaya crop. The objective of this work was to evaluate the sensitivity of the fungi Hansfordia pulvinata and Acremonium spp. to alternative products with potential for use in the control of the black-spotted ptarmigan. Three isolates of Acremonium spp. (A-598, A-602 and A-617) and an isolate of H. pulvinata (H-611) were grown in BDA medium containing Agro-Mos®, Bion®, Ecolife®, Hortifospk®, Matriz G®, Vitaphol® separately. The Amistar 500WG ® fungicide was used as a positive control and pure BDA as a negative control. The toxicity of the tested products was determined based on the values of the biological index, derived from the means of mycelial growth, sporulation and germination of conidia, in each experimental unit. In this way it was possible to select the products classified as compatible for all isolates, and to test them in vivo. In the greenhouse, only the isolates and isolates with selected products, were applied in papaya plants with foliar symptoms of black-spotted. The incidence of leaves with hyperparasites and the percentage of black-painted lesions colonized by the tested isolates were evaluated. Thus, the H-611 isolate proved to be compatible with most of the alternative products tested, except with Hortifos®. Bion® and Matrix® products were compatible with all tested isolates and could be used in conjunction with Acremonium spp. and H. pulvinata to control the papaya black spot, since these products did not present toxicity on the hyperparasitic fungi.
Variedades crioulas constituem alternativas para a ampliação da base genética e incorporação de genes de resistência a doenças em programas de melhoramento genético de plantas. Para tanto, há necessidade de utilização de métodos de seleção capazes de explorar eficientemente o material genético disponível. Com a finalidade de selecionar progênies de meios-irmãos derivadas de mamoeiros dióicos, para a efetiva concentração de alelos que condicionam resistência à pinta-preta, testaram-se os índices de seleção de Smith & Hazel, Pesek & Baker, Williams e Mulamba & Mock. A proposta de utilização de um índice visa buscar uma alternativa mais robusta na identificação de genótipos resistentes. Definiu-se a intensidade de seleção de 41,66%, correspondendo ao número de dez progênies. Os índices de Mulamba & Mock e Willians proporcionaram ganhos mais adequados para as características avaliadas quando utilizado o coeficiente de variação genético (CVg) como critério de peso econômico, sendo selecionadas as progênies 'STA-02', 'STA-04', 'STA-05', 'STA-08', 'STA-13', 'STA-15', 'STA-16', 'STA-17', 'STA-22' e 'STA-24', para compor um novo ciclo de seleção.
Because of its multi-purpose nature, popcorn has sparked the interest of the World Trade Organization as regards fungal contamination by mycotoxins. However, no investigations have been conducted on popcorn for resistance of genotypes to ear rot. The aim of this study was to evaluate the potential of popcorn genotypes as to resistance to ear rot and rotten kernels, as an initial step for the implementation of a breeding program with the popcorn crop in Northern Rio de Janeiro State, Brazil. Thirty-seven accessions from different ecogeographic regions of Latin America were evaluated in 2 cultivation periods, in a randomized block design with 4 replications. We evaluated the incidence of rotten ears, incidence of rotten ears caused by Fusarium spp., severity of ears with Fusarium spp. rot, and incidence of rotten kernels. The results were subjected to analysis of variance, and means were compared by the Scott-Knott clustering test (p < 0.05). A significant effect was observed for all evaluated variables, characterizing them as efficient in the discrimination of genotypic variability for reaction to fungal injuries in popcorn. The gene pool of the tropical and temperate Germplasm Collection evaluated here has the potential to generate superior segregants and provide hybrid combinations with alleles of resistance to diseases affecting ears and stored kernels. Based on the different variables and times, the experiment was conducted, and genotypes L65, L80, and IAC 125 showed the highest levels of resistance.
A resistência genética constitui-se em alternativa sustentável para o controle de doenças em culturas agrícolas, sendo esta, no entanto, dependente da avaliação de populações naturais ou tradicionais visando à ampliação da base genética. Este trabalho relata a avaliação fenotípica de 24 progênies de mamoeiro, oriundas de genótipos crioulos, cultivados por pequenos agricultores no sul do Estado do Espírito Santo. Avaliaram-se características associadas à resistência à pinta-preta, importante doença desta cultura, causada pelo fungo Asperisporium caricae. Para fins comparativos, foram incluídas uma variedade resistente ('Maradol') e uma suscetível ('Golden') à pinta-preta. Pelos parâmetros genéticos estimados, concluiu-se que na população estudada há variabilidade genética quanto à resistência à pinta-preta suficiente para indicar a seleção recorrente como método de melhoramento.
The extensive use of nitrogen (N) in agriculture has caused negative impacts on the environment and costs. In this context, two pot experiments were performed under different N levels and harvested at different vegetative stages to assess two popcorn inbred lines (P2 and L80) and their hybrid (F1 = P2 × L80) for the N use, uptake and utilization efficiency (with the inclusion and exclusion of root N content); to find the contrasting N levels and vegetative stages that effect nitrogen use efficiency (NUE) and to understand the relationship between the traits related to NUE. The hybrid and P2 were confirmed better than L80 for all the studied traits. NUE is mainly affected by the shoot dry weight, uptake and utilization efficiency. Extremely low and high N levels were found to be more discriminating for N use and dry weight, respectively. At the V6 (six fully expanded leaf) stage, root N content (RNC) should be considered; in contrast, at the VT (tasseling stage) stage, RNC should not be considered for the uptake and utilization efficiency. The genetic parameter performance for N use, uptake, shoot dry weight and N content could favor the achievement of the genetic gain in advanced segregating generations.
The global boom in agricultural production has been associated with the exponential increase of nitrogen (N) fertilizer application. This heavy use of nitrogen in agriculture has caused negative impacts on the environment. Therefore, new alternatives are needed to maintain or increase maize yield but reduce the environmental impact. For this purpose, one possibility is to plant N-use efficient (NUE) cultivars. In this context, the objective of this study was to identify popcorn hybrid cultivars that are highly NUE and N-responsive, bred from crosses between inbred lines with contrasting levels of N-use efficiency. For this purpose, 90 hybrids were evaluated in a 10 × 10 triple lattice design at two sites and two levels of N availability (low and ideal availability). The results indicated that for the environment with low nitrogen availability, the lack of nitrogen reduced the chlorophyll content, extended the interval between male and female flowering, and affected the performance of the tested hybrids. However, we observed the existence of hybrids with greater efficiency than the responsiveness to nitrogen and with high productivity. These can even be used on farms where the level of production inputs is low, thus contributing to ensure food security.
Grain yield and popcorn quality losses have become more common due to attacks by pathogens responsible for leaf diseases. Genetic resistance is the main control measure, as it is applicable in large areas and uses reduced costs and less environmental impact, compared to chemical control. In this context, the purpose was to select popcorn hybrids that meet resistance to Exserohilum turcicum, Bipolaris maydis, and Puccinia polysora and to have high levels of popping expansion and grain yield. We took into account two growing seasons (summer harvest - October 2014 to January 2015 - and winter harvest- April to July 2015). Twenty-eight hybrids from the complete diallel cross scheme were evaluated, among eight inbred lines (P8, P1, L55, L61, L70, L76, L77 and L88). For this purpose, we used a randomized block design with four replicates in two growing seasons. The traits investigated were the incidence of P. polysora (IPP), B. maydis (IBM), and E. turcicum (IET); severity of P. polysora (SPP), B. maydis (SBM), and E. turcicum (SET); grain yield (GY); and popping expansion (PE). Data from the experiments were submitted to the principal component analysis (PCA) through the R software. Results showed that the traits IET and IPP in the summer harvest, and IET and SET, in the winter harvest, were the most significant in the select of hybrids. The P8 x L76 and L70 x P8 hybrids were selected for summer harvest and the L77 x L61 hybrid, for winter harvest
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