Potential of maize (Zea mays L.) populations derived from commercial single-cross hybrids for extraction of partially inbred lines under different nitrogen availability

Extraction of inbred lines is a very important step in maize breeding since these lines will be used to obtain hybrids intended for the market. However, this expensive process, hinders genotype evaluation in contrasting environments, especially regarding nitrogen (N) content. This study aimed to evaluate the potential of maize populations for line extraction and select partially inbred lines under different soil nitrogen (N) availability. Five populations were evaluated regarding their potential for line extraction. Fifty-five S1 partially inbred lines were extracted from these populations. The top-cross method was used to evaluate lines by crossing them with two testers. Hybrids evaluation used 110 top-cross hybrids, five base populations, and six checks. Two trials were carried out in Dourados and Caarapó. One trial had adequate fertilization (high N) while the other was under stress condition (low N). Hybrid DKB 789 showed potential for extraction of partially inbred lines, aiming at selecting N use efficiency. Base population BP (07) was the most suitable for the extraction of partially inbred lines aiming at N use efficiency. Partially inbred lines BP (07) 13, BP (07) 14, and BP (07) 17 are the most suitable for the extraction of top-cross hybrids with high grain yield, efficiency, and responsiveness to N. Highlights Extraction of inbred lines is a very important step in maize breeding. Hybrid DKB 789 showed potential for extraction of partially inbred lines. BP (07) 13, BP (07) 14, and BP (07) 17 are the most suitable for the extraction of top-cross hybrids.Extraction of inbred lines is a very important step in maize breeding since these lines will be used to obtain hybrids intended for the market. However, this expensive process, hinders genotype evaluation in contrasting environments, especially regarding nitrogen (N) content. This study aimed to evaluate the potential of maize populations for line extraction and select partially inbred lines under different soil nitrogen (N) availability. Five populations were evaluated regarding their potential for line extraction. Fifty-five S1 partially inbred lines were extracted from these populations. The top-cross method was used to evaluate lines by crossing them with two testers. Hybrids evaluation used 110 top-cross hybrids, five base populations, and six checks. Two trials were carried out in Dourados and Caarapó. One trial had adequate fertilization (high N) while the other was under stress condition (low N). Hybrid DKB 789 showed potential for extraction of partially inbred lines, aiming at selecting N use efficiency. Base population BP (07) was the most suitable for the extraction of partially inbred lines aiming at N use efficiency. Partially inbred lines BP (07) 13, BP (07) 14, and BP (07) 17 are the most suitable for the extraction of top-cross hybrids with high grain yield, efficiency, and responsiveness to N. Highlights Extraction of inbred lines is a very important step in maize breeding. Hybrid DKB 789 showed potential for extraction of partially inbred lines. BP (07) 13, BP (07) 14, and BP (07) 17 are the most suitable for the extraction of top-cross hybrids

Incidência de fungos de armazenamento em função de nitrogênio em cobertura e variedades de milho

Maize is the main cereal grown in Brazil and is used mainly for animal feed and food consumption of its derivates. Under favorable environmental conditions, toxigenic fungi such as Fusarium, Aspergillus, and Penicillium spp. could produce mycotoxins in maize grain during plant growth or storage. This study aimed to evaluate the incidence of toxigenic fungi and its relationship with the grain weight of maize varieties grown under high and low topdressing nitrogen. The first factor consisted of 11 open-pollinated varieties, and the second factor of two topdressing nitrogen rates (60 and 180 kg ha-1). After harvesting the experimental units, the following variables were evaluated: 100-grain weight (HGW) and incidence of A. flavus, Penicillium spp., and Fusarium spp. There were differences (p<0.05) among maize varieties for all evaluated variables. There was a significant interaction between varieties and nitrogen for the percentage of seeds infected by A. flavus, Fusarium spp., and HGW. The incidence of fungi and HGW of maize depends on the variety and the topdressing nitrogen used.O milho é o principal cereal cultivado no Brasil e é utilizado principalmente para alimentação animal e consumo alimentar de seus derivados. Em condições ambientais favoráveis, fungos toxigênicos como Fusarium, Aspergillus e Penicillium spp. poderiam produzir micotoxinas nos grãos de milho durante o crescimento da planta ou no armazenamento. O objetivo deste trabalho foi avaliar a incidência de fungos toxigênicos e sua relação com o peso de grãos de variedades de milho cultivadas sob alta e baixa adubação de nitrogênio. O primeiro fator consistiu de 11 variedades de polinização aberta e o segundo fator de duas doses de nitrogênio em cobertura (60 e 180 kg ha-1). Após a colheita das unidades experimentais, foram avaliadas as seguintes variáveis: massa de cem grãos (MCG) e incidência de A. flavus, Penicillium spp. e Fusarium spp. Houve diferenças (p<0,05) entre as variedades de milho para todas as variáveis avaliadas. Houve interação significativa entre variedades x nitrogênio para a porcentagem de sementes infectadas por A. flavus, Fusarium spp. e MCG. A incidência de fungos e o MCG do milho dependem da variedade e do nitrogênio de cobertura usado

Correlations between soil attributes and the occurrence of nematodes and grain yield in an off-season maize crop in Mato Grosso do Sul

Systems of soil cultivation and use directly influence crop yield by interfering with the soil chemical, physical, and biological attributes. This study aimed to evaluate the correlation between maize grain yield, soil chemical and biological attributes, and the occurrence of nematodes in maize crops grown in the off-season, in the state of Mato Grosso do Sul. Soil samples from 21 off-season maize crops were collected in 2015. The samples were used to identify and quantify nematodes, determine biomass carbon and microbial activity, and for chemical analysis. The attributes were clustered based on the variables evaluated using the mean Euclidean distance and Ward's clustering method.  The interrelationship between the variables was analyzed by correlations, and its unfolding in the cause and effect investigations was evaluated by the path analysis. Organic matter and microbial biomass carbon positively influence grain yield. Magnesium negatively influences the population of Pratylenchulus spp. in maize crops. The potential acidity and organic matter are related to the presence of Rotylenchulus spp

Environmental stratification in the brazilian cerrado on the yield and fiber quality of cotton genotypes

Environmental stratification studies are important for the plant breeding, since they allow to adequately plan the experimental network. The objective of this work was to identify similar environments for cotton cultivation in the Brazilian Cerrado regarding yield and fiber quality. Nineteen field studies were carried out in a randomized complete block design with twelve genotypes and four replicates. Agronomic (cotton seed yield and fiber percentage) and technological traits (length, micronaire, fiber strength) were evaluated. These results indicate that there are six environments (PVA3, MON, SHE1, SIN, PPA e TRIN) in which the cotton trials should be installed as a matter of priority owing to the phenotypic response pattern obtained for the evaluated traits. The remaining 13 environments are similar to each other for all traits and can be summarized in strategic locations depending on the ease of installation of the trials

Número mínimo de medições para a avaliação acurada de características agronômicas de pinhão‑manso

The objective of this work was to identify the most effective method to estimate the coefficient of repeatability in progenies of half‑sib families of physic nut (Jatropha curcas), and to predict the minimum number of measurements required for some agronomic traits of this oilseed crop. Eighteen half‑sib families, in a randomized complete block design with three replicates, were evaluated from 2009 to 2013. In this period, the following traits were evaluated: plant height, stem diameter, number of branches per plant, crown projection on the line, crown projection on the space between rows, and grain yield. The repeatability coefficient (r) was estimated considering different strategies: analysis of variance; principal component analysis (PCA) based onthe correlation matrix (PCCOR); PCA based on the matrix of phenotypic variance and covariance (PCCOV);and structural analysis based on the correlation matrix. The PCCOV strategy provides the most accurate estimates of the repeatability coefficient and of the number of measurements (minimum of four), which are required for an accurate evaluation (minimum 80% accuracy) of the traits, due to the cyclical behavior of the progenies.O objetivo deste trabalho foi identificar o método mais eficaz para estimar coeficientes de repetibilidade em progênies de meios‑irmãos de pinhão‑manso (Jatropha curcas) e predizer o número mínimo de medições necessárias para algumas características agronômicas da oleaginosa. Avaliaram-se 18 famílias de meios‑irmãos, em delineamento de blocos ao acaso, com três repetições, de 2009 a 2013. Nesse período, as seguintes características foram avaliadas: altura de plantas, diâmetro do caule, número de ramos por planta, projeção da copa na linha, projeção da copa na entrelinha e produtividade de grãos. O coeficiente de repetibilidade (r) foi estimado a partir de diferentes estratégias: análise de variância; análise dos componentes principais (ACP), com base na matriz de correlações (CPCOR); ACP, com base na matriz de variâncias e covariâncias fenotípicas (CPCOV); e análise estrutural, com base na matriz de correlações. A estratégia CPCOV proporciona estimativas mais acuradas do coeficiente de repetibilidade e do número de medições necessárias (no mínimo quatro) para avaliação acurada (mínimo 80%) das características, devido ao comportamento cíclico das progênies

Phenotypic adaptability of cotton genotypes to the brazilian cerrado for yield and fiber quality

Studies on the adaptability and stability are fundamental for plant breeding as they are an alternative to reduce the effects of genotypes x environments interaction (GxE). Moreover, they help identify cultivars with predictable behavior, which are responsive to environmental improvements, subsidizing cultivar recommendation. This study aimed to investigate the genotypes x environments interaction in cotton genotypes grown in the Brazilian Cerrado and identify genotypes for favorable and unfavorable environments. During the 2013/2014 and 2014/2015 seasons, 19 competition trials were carried out with cotton in a randomized block design, with 12 treatments, and four replications. The traits cotton seed yield, fiber percentage, fiber length, and fiber strength were evaluated. Results revealed significant GxE interaction for all the fiber traits evaluated. Genotype BRS 369 RF revealed general adaptability and high predictability for the fiber traits evaluated

Avaliação multiambiental de híbridos de sorgo durante a entressafra no Brasil

The objective of this work was to simultaneously select pre-commercial grain sorghum hybrids with high adaptability and yield stability, through mixed modeling, in 20 environments, during six years. The evaluated plant material consisted of 57 commercial grain sorghum hybrids. In all experiments, hybrids were arranged in a triple lattice design; some experiments used a 6x6 lattice, and others, a 5x5 lattice. Adaptability and stability parameters were obtained based on the prediction by harmonic mean of the relative performance of genotypic values (HMRPGV). The mixed models proved to be adequate to analyze the genotype x environment (GxE) interaction and the genotypic adaptability and stability studies on grain sorghum. The hybrids that stand out, considering all environments are 1G282, A9904, 50A50, A9902, and XB6022. The A9904 hybrid stands out in favorable environments, with a grain yield above average. Only 1G282 is among the five best hybrids for each group of environments, and it is the best grain sorghum hybrid for yield performance, adaptability, and stability. The predicted genotypic values based on genotypic means can be used in the environments with the same GxE interaction pattern because they are free of the GxE interaction.O objetivo deste trabalho foi selecionar, simultaneamente, híbridos pré-comerciais de sorgo granífero com alta adaptabilidade e estabilidade da produção de grãos, por meio de modelagem mista, em 20 ambientes, por seis anos. O material vegetal avaliado consistia de 57 híbridos comerciais de sorgo granífero. Em todos os experimentos, os híbridos foram arranjados em delineamento fatorial triplo; alguns experimentos utilizaram um fatorial 6x6, e outros, um fatorial 5x5. Os parâmetros de adaptabilidade e estabilidade foram obtidos com base na predição por média harmônica da performance relativa dos valores genéticos (MHPRVG). Os modelos mistos mostraram-se adequados para analisar a interação genótipo x ambiente (GxE) e os estudos de adaptabilidade e estabilidade genotípica do sorgo granífero. Os híbridos que se destacam, considerando-se todos os ambientes, são 1G282, A9904, 50A50, A9902 e XB6022. O híbrido A9904 destaca-se em ambientes favoráveis, com rendimento de grãos acima da média. Apenas 1G282 está entre os cinco melhores híbridos para cada grupo de ambientes e é o melhor híbrido de sorgo granífero quanto ao rendimento, à adaptabilidade e à estabilidade. Os valores genotípicos preditos com base em médias genotípicas podem ser usados em relação aos ambientes com o mesmo padrão de interação GxE por estarem livres da interação GxE

Droplets size in the phytosanitary control of potato / Tamanho da gota no controle fitossanitário de batata

The use of different spray nozzles with droplet size ranging from fine to coarse may compromise the application efficiency in potato crops. This study aimed to evaluate the production of potato in the northeast region of Mato Grosso do Sul by using different cultivars and droplet sizes in phytosanitary treatments. Potato is one of the crops that mostly depends on the application of phytosanitary products.  Potato cultivars were planted in the experimental area of the Universidade Federal de Mato Grosso do Sul, in the municipality of Chapadão do Sul. Plots consisted of three seedbeds (0.8 m x 1.4 m), and the plants were spaced at 0.35 m. The area of each experimental unit was 3.36 m2, to9taling 12 plants per unit. The experiment was carried out in subplots, in a randomized block design (2x3); the spray system had two droplets sizes (tips TT 110015 and TXA 8001VK, fine and coarse, respectively) in the plots and three potato cultivars (Yacon, Sminia, and Marcy) in the subplots, with four replications. The different droplets sizes interfere with the yield and morphology of potato tubers. The highest yield values are associated with fine droplets. Cultivar Sminia had longer tubers; however, Marcy showed thicker and wider tubers

Application technology of boron via foliar and its effects on cotton crop phenology / Tecnologia de aplicação de boron através de foliar e seus efeitos na fenologia da cultura de algodão

Boron can be applied to cotton crops together with pesticides. Producers have allied medium and fine droplets to low application rates, which can lead to low boron deposition on the leaves. This work aimed to evaluate the spray deposition and absorption of boron leaf application on a cotton crop, by varying the surfactant and the application rate, comparing the effects on the crops’ phenology and yield. Boron was applied using a backpack sprayer pressurized with CO2. Spray deposition was estimated based on the mass balance methodology. Plant leaves were collected for analysis at 17 days after application. The use and variation of the application technology affect micronutrient B absorption by leaf spray application. The application rate of 120 L ha-1 with siliconized surfactant adjuvant provides higher spray deposition on cotton plants and consequently higher boron absorption. The application rate of 70 L ha-1 without siliconized surfactant adjuvant provides lower boron absorption

Soil macrofauna in green manures preceding cotton growing

The objective of this work was to evaluate the abundance of the soil macrofauna in four green manure species, before the cotton crop. The experimental design was a randomized block design with four treatments: Mucuna pruriens (gray mucuna), Canavalia ensiformes (pork bean), Cajanus cajan (pigeon pea) and Crotalaria juncea (crotalaria). The macrofauna was captured by means of collections with collections using pitfall traps. The data were processed through the cluster analysis to verify the similarity among green manure species as to the occurrence of soil macrofauna. The orders Orthoptera, Coleoptera L (Larval), Hymenoptera and Coleoptera (adult), respectively, had the highest local relative abundance. There was a significant effect of the cover plants on the taxonomic groups and relative density of the soil macrofauna. Green manures were more determinant in the abundance and relative density of the soil macrofauna than the region climate. Up to 60 days after sowing the cotton crop, there was a beneficial influence of the green manures on the soil macrofauna