The aim of this work was to identify genomic regions associated with northern leaf blight resistance (Exserohilum turcicum) in common maize lines and to study the control involved in the resistance. For association mapping, 72 maize lines were previously genotyped for SNP markers on the 650K platform (Affymetrix®), and their respective genotypic values were predicted by mixed models for northern leaf blight. In order to avoid spurious associations between SNP markers and the studied character, the analysis of population structure was initially performed. The analysis of association between the SNP and northern leaf blight markers was carried out using a linear mixed model. For the study of genetic control, the experiment was conducted in 2016 and it was composed of randomized blocks with three repetitions. Through the notes attributed to the lines and their respective generations, the genotypic data related to the inheritance of the studied disease were extracted. Analyzing the results, QTLs were found on chromosomes 1, 2, 3, 4, 6, 8, 9 and 10 for northern leaf blight in maize, which may increase, reduce or even override the effect of this attribute. Among the QTLs found, five genomic regions were detected for increased resistance to northern leaf blight with the use of SNP markers, found in chromosomes 3 (SNP210703), 8 (SNP507268 and SNP507269), 9 (SNP544616) and 10 (SNP610500). The genetic control of resistance to northern leaf blight is quantitative, with the additive effects being more important in the character determination. In addition, it presents high restricted heritability (88%), which allows good selection efficiency and selection gains.

Among the maize leaf diseases, white leaf spot, northern leaf blight, gray leaf spot, and southern rust are recognized not only by the potential for grain yield reduction but also by the widespread occurrence in the producing regions of Brazil and the world. The aim of this study was to characterize common maize lines for resistance to white leaf spot, northern leaf blight, gray leaf spot, and southern rust and suggest crosses based on the genetic diversity detected in SNP markers. The experiment was conducted in a randomized block design with three replications in order to characterize 72 maize lines. Genotypic values were predicted using the REML/BLUP procedure. These 72 lines were genotyped with SNP markers using the 650K platform (Affymetrix®) for the assessment of the genetic diversity. Genetic diversity was quantified using the Tocher and UPGMA methods. The existence of genetic variability for disease resistance was detected among maize lines, which made possible to classify them into three large groups (I, II, and III). The maize lines CD 49 and CD50 showed a good performance and can be considered sources of resistance to diseases. Therefore, their use as gene donors in maize breeding programs is recommended. Considering the information of genetic distance together with high heritability for leaf diseases, backcrossing of parent genotypes with different resistance levels, such as those of the lines CD49 x CD69 and CD50 x CD16, may result in new gene combinations, as they are divergent and meet good performances.

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Maize is the main crop of Paraná State second season, however the heterogeneity of the environmental conditions creates a challenge for the selection of adapted superior genotypes. The objective of this study was to stratify the environments of the Western and Mid-western mesoregions, to identify the environments that are essential for the selection of genotypes to ensure yield and crop moisture. Data sets regarding the yield and crop moisture of 16 commercial hybrids were used, sourced from Cooperativa Central de Pesquisa Agrícola (COODETEC) Value for Cultivation and Use ("VCU"), testing in a randomized complete block design with two replicates, of crops grown in the interim-harvests of 2014 and 2015 in the west of Paraná, in the Cascavel, Toledo and Foz do Iguaçu microregions, the Mid-western Campo Mourão microregion and Mariluz, constituting the Caiuá sandstone formation. The evaluation of the representativeness of the environments was carried out over one year of study, through environmental stratification analysis, using the factor analysis methodology. The results of the environmental stratification demonstrated that trials in the same environment provide redundant results, both for yield and for crop moisture. There were no gains for the selection of superior genotypes and the positioning in the different microregions yielded complementary data, aiding the selection.

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RESUMO - As plantas daninhas constituem um dos fatores que reduzem a produtividade do milho e, portanto, é importante conhecer o mecanismo de tolerância da cultura aos herbicidas, de forma a fornecer informações que minimizem os riscos de danos aos cultivos. Dessa forma, o objetivo do trabalho foi avaliar a resposta de linhagens de milho e o controle genético envolvido na tolerância aos herbicidas nicosulfuron e tembotrione. Duzentas e cinco linhagens de milho foram avaliadas quanto à reação aos herbicidas. Para a avaliação do controle genético de tolerância aos herbicidas foram empregadas duas linhagens tolerantes e duas sensíveis, as quais foram intercruzadas empregando um dialelo de meia tabela. As linhagens e as populações oriundas desses cruzamentos foram avaliadas quanto à reação aos herbicidas em delineamento de blocos casualizados com quatro repetições. As dosagens foram de 60 g ha-1 de nicosulfuron (Sanson®) e 100 g ha-1 de tembotrione (Soberan®). A avaliação fenotípica constituiu-se de número de plantas sensíveis e/ou tolerantes e o teste do Qui-quadrado (χ2) foi utilizado nas análises. Quanto à resposta à aplicação dos agroquímicos verificaram-se linhagens tolerantes ou sensíveis a ambos os herbicidas ou apenas a um deles. Nas avaliações do controle genético, as análises evidenciaram um gene com dominância completa que, pela análise de segregação das famílias F3, permitiu levantar a hipótese de genes fortemente ligados ou pleiotrópicos. Os resultados obtidos, associados ao retrocruzamento assistido por marcadores moleculares (RCAM), auxiliaram o processo de introgressão da tolerância nas linhagens sensíveis aos herbicidas nicosulfuron e tembotrione.Palavras-chave: Zea mays L., herança, melhoramento genético, marcadores moleculares.GENETIC TOLERANCE OF MAIZE LINES TO TEMBOTRIONE AND NICOSULFURON ABSTRACT - As weeds are one of the factors that reduce maize productivity it is important to know the mechanism of crop tolerance to herbicide in order to minimize the risk of damage to the plants. Thus, the objective of this work was to evaluate the response of maize inbred lines and the genetic control of the tolerance to the herbicides nicosulfuron and tembotrione. Two hundred and five maize inbred lines were evaluated for herbicides reaction. For the evaluation of the genetic control of tolerance to herbicides, two tolerant and two sensitive inbred lines were used, which were intercrossed using a half diallel table. The inbred lines and the populations obtained from these crosses were evaluated for reaction to the herbicides in a randomized complete block design with 4 replicates. The dosages were 60 g ha-1 of nicosulfuron (Sanson™) and 100 g ha-1 of tembotrione (Soberan™). The phenotypic evaluation was based on the number of sensitive and / or tolerant plants and the chi-square test (χ2) was used in the analysis. Regarding the response to the application of the agrochemicals, inbred lines were tolerant or sensitive to one or both herbicides. The analysis of genetic control showed a gene with complete dominance, and the segregation analysis of the F3 families hypothesized the occurrence of strongly linked or pleiotropic genes. The data obtained associated to marker-assisted backcrossing allowed the tolerance introgression in sensitive inbred lines to nicosulfuron and tembotrione.Keywords: Zea mays L., inheritance, plant breeding, molecular markers.

Grain yield and maturity class are among the commercial traits that most often direct maize breeding that aims to meet the requirements of the seed market. Thus, the aim of this study was to evaluate genetic diversity in maize inbred lines for grain maturity and yield components. The phenotypic attributes of 81 maize inbred lines were assessed in a field experiment in a square lattice design with three replications. Analysis of variance and multivariate analysis were performed considering complete randomized blocks due to the equivalence to the estimation for lattice efficiency. The results of analysis of variance indicated genetic diversity in the germplasm for all the traits, showing high variability for number of days to male flowering (DMF) and female flowering (DFF). Genetic diversity was also detected for grain water loss, which was determined by the area under the water loss curve (AUWLC), an index representing the dynamic progress of field water loss, based on area under the disease progress curve (AUDPC). The high magnitude of genetic correlation between the AUWLC and the moisture content of grain (0.98) collected at different moments in the R6 stage suggests the possibility of its substitution by the moisture content evaluation in only one collection. Weak genetic correlations (0.07 to 0.45) between yield and maturity components indicated the possibility of selection for earliness without compromising yield. In addition, the results of the Tocher method and the UPGMA were compatible, enabling classification of the germplasm and suggestion of hybrid combinations among inbreds that might have a higher heterotic effect on yield associated with earliness.

The aim of this study is to identify homogeneous rainfall zones in the winter and summer 1 st and 2 nd crops, in the state of Paraná, Brazil. The zones were defined by clustering using the expectation-maximization (EM) algorithm to transform seasonal rainfall series. Monthly average rainfall data collected from 157 weather stations for 20 years (1996 to 2015) were employed. The results show that the number of homogeneous zones varied among growing seasons. The summer crop presented two clusters, with rainfall averages of 1489 and 1925 mm; the second crop presented four clusters, with averages of 1849, 1004, 1454, and 1182 mm; and the winter crop had three clusters, with averages of 969, 1498, and 1171 mm. Clustering was a useful instrument to identify geographical regions with similar rainfall regimes during different growing seasons in the state of Paraná. Rainfall distribution was more homogeneous in the summer crop. In all crops analyzed, the clusters with the lowest rainfall rate were present in the northwestern, northern center, and northern pioneer of the state of Paraná, whereas the clusters with the highest rainfall rate were found in the coastal regions.