The aim of this study was to evaluate popcorn genotypes for resistance to the fall armyworm, Spodoptera frugiperda. The experiment used a completely randomized design with 30 replicates. The popcorn genotypes Aelton, Arzm 05 083, Beija-Flor, Colombiana, Composto Chico, Composto Gaúcha, Márcia, Mateus, Ufvm Barão Viçosa, Vanin, and Viviane were evaluated,along with the common maize variety Zapalote Chico. Newly hatched fall armyworm larvae were individually assessed with regard to biological development and consumption of food. The data were subjected to multivariate analyses of variance and genetic divergence among genotypes was evaluated through the clustering methods of Tocher based on generalized Mahalanobis distances and canonical variable analyses. Seven popcorn genotypes, namely, Aelton, Arzm 05 083, Composto Chico, Composto Gaúcha, Márcia, Mateus, and Viviane,were shown to form a cluster (cluster I) that had antibiosis as the mechanism of resistance to the pest. Cluster I genotypes and the Zapalote Chico genotype could be used for stacking genes for antibiosis and non-preference resistance.

We conducted a five‐year survey (2011–2015) of barley and wheat fields in Paraná state, Brazil, obtaining 754 Fusarium isolates from spikes with fusarium head blight (FHB)‐symptoms. Multilocus genotyping and TEF‐1α gene sequence analyses confirmed the dominance of the F. graminearum species complex (FGSC, 75.7%), but F. poae (11.5%), as well as F. avenaceum and related members of the F. tricinctum species complex (FTSC, 8.1%) appeared as substantial contributors to FHB. Within the FGSC, F. graminearum of the 15‐ADON genotype was dominant (63%), followed by F. meridionale of the NIV genotype (23.1%), F. cortaderiae of the NIV (7%) or 3‐ADON (2.6%) genotypes, and F. austroamericanum (3.8%) of the 3‐ADON genotype. Substantial variation in pathogen composition was observed across years, with F. poae and F. meridionale frequencies significantly elevated in some years. Most F. poae strains produced DAS, diANIV, and butenolide, but not neosolaniol, T‐2, or HT‐2. All FTSC species produced moniliformin. Enniatin production was widespread among FTSC species, with the single F. acuminatum strain found to be the strongest producer of enniatins. Our findings confirm FGSC as a major contributor to FHB and expand considerably our knowledge of the presence, frequency, and conditions under which other pathogens may emerge, altering the spectrum of toxins that may accumulate in grain.

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Grapevine leaf rust, which is caused by the fungus Phakopsora euvitis, is an important late-season disease of 'Niagara Rosada' (Vitis labrusca) grapevine in Brazil. The early defoliation of plants caused by the disease impairs fruit ripening and reduces marketable yield. In a study carried out in northern Paraná State, the temporal progression of grapevine leaf rust was quantified in a production system of 'Niagara Rosada' grapevine with two growing seasons per year: mid-summerautumn and late winter-spring. The influence of weather-related variables on rust progression was examined through correlation analyses. It was observed that the rust was more severe in summer-autumn than in winter-spring. Significant positive linear correlations (P ≤ 0.05) were found between rust severity and rainfall (r ≥ 0.90) and average daily hours of leaf wetness (r ≥ 0.82). In addition, negative correlation was found between rust severity and temperature (r ≥ −0.84) in the mid-summer/autumn season. Mild temperatures in autumn were considered decisive for rust progression. In Brazilian tropical viticulture, management strategies for grapevine leaf rust must consider the risk of rust damage in autumn caused by temperature.

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Maize (Zea mays) fields from a tropical central (Goiás state) and a subtropical south region (Paraná state) of Brazil were surveyed for Cercospora species causing gray leaf spot (GLS), a foliar fungal disease of increasing concern to growers of the country. Single spore isolates were obtained from maize leaves showing GLS symptoms and species-specific primers were used for species identification. In addition, a phylogeny of isolates representative of each species was conducted based on partial DNA sequencing of the EF1-α, CAL, and HIS genes, and ITS-5.8S rDNA region. In the regional collections, Cercospora zeina was the dominant species in Goiás (68/75 isolates) and Paraná (73/75 isolates), followed by C. zeae-maydis and C. sorghi var. maydis, respectively. In three field collections of both states, C. zeina was the sole species found. The phylogenetic characterization of isolates representing C. zeina (n=18), C. zeae-maydis (n=6), and C. sorghi var. maydis (n=2) confirmed the identity of the species and grouped them in well-supported clades.

Corn has shown different degrees of positive response to inoculation with the nitrogen- fixing bacteria of the genera Azospirillum. Part of it has been attributed to the plant genotypic variation, including the root exudates, that are used by the bacteria as energy source. In this study, we grew two corn hybrids that differ for their response to Azospirillum, to investigate the effect of different exudates profiles on the bacteria growth and nitrogenase activity. Employing high performance liquid chromatography, we identified nine amino acids (asparagine, aspartic acid, serine, glutamic acid, valine, phenylalanine, threonine, tryptophan and alanine), six sugars (glucose, sucrose, xylose, arabinose, fructose and galactose) and four organic acids (citrate, malate, succinate and fumarate). The less responsive corn genotype showed reduced plant growth (root volume, shoot dry mass and shoot N content), a lower concentration of Azospirillum cells within the root tissues, a higher content of asparagine and glucose and a reduced amount of metabolites that serve as bacterial energy source (all organic acids + five sugars, excluding glucose). The genotypes did not interfere in the ability of Azospirillum to colonize the substrate, but the metabolites released by the less responsive one reduced the nitrogenase activity.

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