Traits related to plant lodging and architecture are important determinants of plant productivity in intensive maize cultivation systems. Motivated by the identification of genomic associations with the leaf angle, plant height (PH), ear height (EH) and the EH/PH ratio, we characterized approximately 7,800 haplotypes from a set of high-quality single nucleotide polymorphisms (SNPs), in an association panel consisting of tropical maize inbred lines. The proportion of the phenotypic variations explained by the individual SNPs varied between 7%, for the SNP S1_285330124 (located on chromosome 9 and associated with the EH/PH ratio), and 22%, for the SNP S1_317085830 (located on chromosome 6 and associated with the leaf angle). A total of 40 haplotype blocks were significantly associated with the traits of interest, explaining up to 29% of the phenotypic variation for the leaf angle, corresponding to the haplotype hap LA4.04, which was stable over two growing seasons. Overall, the associations for PH, EH and the EH/PH ratio were environment-specific, which was confirmed by performing a model comparison analysis using the information criteria of Akaike and Schwarz. In addition, five stable haplotypes (83%) and 15 SNPs (75%) were identified for the leaf angle. Finally, approximately 62% of the associated haplotypes (25/40) did not contain SNPs detected in the association study using individual SNP markers. This result confirms the advantage of haplotype-based genome-wide association studies for examining genomic regions that control the determining traits for architecture and lodging in maize plants.

Fusarium ear rot [caused by Fusarium verticillioides (Sacc.) Nirenberg] is one of the most prevalent diseases of maize (Zea mays L.) worldwide, and has one of the greatest negative economic impacts on this cereal crop globally. Fusarium ear rot is a highly complex trait, under polygenic control with minor effects per gene and moderate heritability, and is strongly influenced by environmental conditions. The aim of this study was to identify genomic regions, including putative candidate genes, associated with resistance to Fusarium ear rot and the starburst pattern caused by F. verticillioides under artificial inoculation. We conducted a genome‐wide association study using phenotypic data from three environments on a panel of 183 inbred lines and a set of 267,525 single‐nucleotide polymorphism (SNPs) generated using genotyping by sequencing. Fourteen SNPs were significantly associated with Fusarium ear rot and two for starburst, some of which were colocalized to previously reported quantitative trait loci regions, and some of which were novel. Four genes linked to the associated SNPs encode defense‐related proteins, including gibberellin 2‐oxidase4, a glucosyltransferase, a Ras‐related protein RHN1, and phosphoribosylanthranilate transferase (PAT). Each of these SNPs explains a considerable proportion of the phenotypic variance, ranging from 15 to 25%. Once these SNPs are validated, they will be useful for marker‐assisted selection and for a better understanding of maize resistance to Fusarium ear rots.

ABSTRACT. The objective of the current study was to apply molecular markers (microsatellites) in the analysis of genetic diversity of 48 lines of the elite maize germplasm stored in the bank of the Cooperativa Central de Pesquisa Agrícola -Coodetec, PR, Brazil, and estimate the correlation between genetic distance and heterosis and hybrid performance from the crosses among these maize lines. Fortyfour random primers were used and amplification of 124 polymorphic fragments was obtained. The expected findings from the correlation of the yield and heterosis with the genetic distance were non-significant. However, the results suggested that data from the extreme distances could be used in breeding for more productive crosses and heterotic hybrids. Thereby, molecular markers are efficient tools for predicting hybrid performance.

ResumoO objetivo deste trabalho foi avaliar a capacidade geral de combinação dos genitores envolvidos nos cruzamentos e a capacidade específica de combinação dos híbridos, bem como o efeito recíproco em relação as características agronômicas em feijoeiro. Inicialmente foram realizados os cruzamentos dialélicos, intercruzando os seis genitores: Xan 159, Pérola, BAF 63, IPR Uirapuru, BRS Supremo, BRS Valente, gerando trinta e seis combinações. As sementes F 1 juntamente com os genitores foram levadas a campo em delineamento inteiramente casualizado com duas repetições, sendo que cada planta foi considerada uma unidade de observação, em que ocorre número desigual de plantas nas diferentes combinações híbridas. As plantas foram avaliadas quanto aos seis caracteres (ciclo, estatura de planta, inserção do primeiro legume, diâmetro do caule, número de legumes por planta e número de grãos por legume), sendo posteriormente realizadas as análises estatísticas utilizando o Método I de Griffing. Em relação à capacidade geral de combinação a cultivar Pérola é considerada promissora para o Planalto Catarinense. Com base na capacidade específica as melhores combinações foram Xan 159 x BRS Supremo, Xan 159 x BRS Valente, Pérola x BAF 63, BAF 63 x IPR Uirapuru e BAF 63 x BRS Valente. Os valores para o efeito recíproco também foram significativos indicando que existe a presença de efeito citoplasmático e de genes nucleares do genitor feminino nos caracteres avaliados. O genótipo indicado como um bom genitor feminino e masculino com base no efeito recíproco é o acesso BAF 63, quando se deseja aumentar EST e NLP. A linhagem Xan 159 foi promissora quando utilizada como genitor feminino para incrementar Ciclo, EST, IPL, DC, NLP e NGL. As cultivares BRS Valente e IPR Uirapuru são indicadas como genitores masculinos para proporcionar um aumento do Ciclo, EST, IPL, DC, NLP e NGL. Palavras-chave: Dialelo desbalanceado, dialell05SAS, Phaseolus vulgaris L AbstractThe objective of this study was to evaluate the general combining ability of parents involved in crosses, and specific combining ability of hybrids, as well as reciprocal effect on six agronomic traits in common

Southern corn rust (SCR) is a fungal disease found on corn in several countries worldwide. In Brazil, the disease can result in productivity losses of 65%, especially in areas with a history of the disease. In this study, the genetic architecture and identification of genomic regions associated with SCR resistance was investigated by performing a genome‐wide association study. Genotyping‐by‐sequencing was performed to carry out the association between single nucleotide polymorphism (SNP) markers and phenotypic data from two environments on a panel of 164 maize inbred lines. Eight SNPs were identified as significant for SCR resistance. These SNPs were colocalized with QTL regions, some of which underlie candidate resistance genes with functions that play an important role in the stress response during pathogen recognition. These candidate genes, involved in plant defense pathways, could be associated with partial resistance to SCR and provide a partial comprehensive insight into the genetic architecture of this trait. After validation of the SNPs, they will be useful for marker–assisted selection and for a better understanding of maize resistance to SCR.