DIVERGENCIA GENÉTICA DE GENOTIPOS DE MAÍZ CULTIVADOS BAJO FERTILIZACIÓN NITROGENADA E INOCULACIÓN CON Azospirillum brasilense

Objetivou-se avaliar e caracterizar o desempenho agronômico de genótipos de milho submetidos a dois fornecimentos de nitrogênio (químico e biológico). O experimento foi conduzido na em segunda safra 2017 e primeira safra 2017/2018, utilizando-se 48 genótipos de milho. Foram adotados dois manejos de fornecimento de nitrogênio em cobertura, sendo eles (1) aplicação de 140 kg ha-1 de nitrogênio mineral em cobertura e (2) inoculação com Azospirillum brasilense (600 mL ha-1 via solo). Os dados foram submetidos a análises exploratórias multivariadas de agrupamento, por método hierárquico, e de componentes principais. Foram identificados quatro grupos, associando as maiores produtividades de grãos com plantas com maior altura e as menores produtividades com período de florescimento curto, plantas com menor altura a com maiores taxas de quebramento e acamamento. Os dois primeiros componentes principais explicaram 70,67% e 66,54% da variabilidade total dos dados para a inoculação com A. brasilense e adubação nitrogenada em cobertura, respectivamente. As análises exploratórias de dados são ferramentas eficientes na caracterização, seleção e agrupamento de genótipos superiores e contrastantes de milho aos manejos de fornecimento de nitrogênio.The aim was to characterize and evaluate the agronomic performance of corn genotypes submitted to two nitrogen supply managements (chemical and biological). The experiment was conducted in the first season (summer season) of the 2017/2018 agricultural year, using 48 corn genotypes. Two managements of nitrogen supply in topdressing were adopted, namely (1) application of 140 kg ha-1 of mineral nitrogen in coverage (urea) and (2) inoculation with Azospirillum brasilense (600 mL ha-1 via soil). The data were submitted to exploratory multivariate analysis of grouping, by hierarchical method, and of main components. Four groups were identified, associating the highest grain yields with plants with higher height and the lowest yields with short flowering period, plants with shorter height and with higher rates of breakage and lodging. The first two main components explained 70.67% and 66.54% of the total variability of the data for inoculation with A. brasilense and nitrogen fertilization in topdressing, respectively. Exploratory data analysis is an efficient tool in the characterization, selection and grouping of superior and contrasting maize genotypes for nitrogen supply management.El objetivo fue caracterizar y evaluar el rendimiento agronómico de los genotipos de maíz sometidos a dos gestiones de suministro de nitrógeno (químico y biológico). El experimento se realizó en la primera cosecha (cosecha de verano) del año agrícola 2017/2018, utilizando 48 genotipos de maíz. Se adoptaron dos gestiones de suministro de nitrógeno en cobertura, a saber (1) la aplicación de 140 kg ha-1 de nitrógeno mineral en cobertura (urea) y (2) la inoculación con Azospirillum brasilense (600 ml ha-1 a través del suelo). Los datos se sometieron a análisis exploratorios multivariados de agrupación, por método jerárquico y de componentes principales. Se identificaron cuatro grupos, que asociaron los rendimientos de grano más altos con plantas con mayor altura y los rendimientos más bajos con un período de floración corto, plantas con altura más corta y con mayores tasas de rotura y alojamiento. Los primeros dos componentes principales explicaron el 70.67% y el 66.54% de la variabilidad total de los datos para la inoculación con A. brasilense y la fertilización nitrogenada en cobertura, respectivamente. El análisis exploratorio de datos es una herramienta eficiente en la caracterización, selección y agrupamiento de genotipos de maíz superiores y contrastantes para el manejo de la oferta de nitrógeno

Effect of Sugarcane Cultivars Infected with Sugarcane Yellow Leaf Virus (ScYLV) on Feeding Behavior and Biological Performance of Melanaphis sacchari (Hemiptera: Aphididae)

Sugarcane yellow leaf virus (ScYLV), Polerovirus, Luteoviridae, is one of the main viruses that infect sugarcane worldwide. The virus is transmitted by the aphid Melanaphis sacchari in a persistent, circulative manner. To better understand the interactions between ScYLV, sugarcane genotypes and M. sacchari, we explored the effect of sugarcane cultivars on the feeding behavior and biological performance of the vector. The number of nymphs, adults, winged, total number of aphids and dead aphids was assayed, and an electrical penetration graph (EPG) was used to monitor the stylet activities. Multivariate analysis showed changes in the vector’s behavior and biology on cultivars, identifying specific groups of resistance. In the cultivar 7569, only 5.5% of the insects were able to stay longer on sustained phloem ingestion, while in the other seven cultivars these values varied from 20% to 60%. M. sacchari showed low phloem activities in cultivars 7569 and Bio266. Overall, cultivar 7569 showed the worst biological performance of aphids, with the insects presenting mechanical difficulties for feeding and a shorter duration of the phloem period, and thus being considered the most resistant. We conclude that ScYLV virus infection in different sugarcane cultivars induced specific changes in the host plant, modifying the behavior of its main vector, which may favor or impair virus transmission

Agronomic performance of maize (Zea mays L.) genotypes under Azospirillum brasilense application and mineral fertilization: Agronomic performance of maize genotypes

Maize has a high nitrogen demand; as a result, more sustainable alternatives are needed to reduce demand for mineral fertilizers. This study aimed to evaluate and characterize the agronomic performance of maize genotypes submitted to topdressing nitrogen fertilization and inoculation with Azospirillum brasilense. An experiment was conducted in the second season of 2017, in Jaboticabal-SP (Brazil), using 48 maize genotypes in a randomized block design. Treatments consisted of: 1) application of 140 kg ha-1 nitrogen, using urea as mineral fertilizer; 2) A. brasilense inoculation via soil, at a rate of 600 mL ha-1, as biological fertilization. Grain yield and agronomic traits were evaluated. The data were subjected to analysis of variance (F-Test), means were compared by Scott-Knott test at 5% probability, and multivariate statistical analysis was performed by principal component analysis. A. brasilense inoculation via soil has a significant effect on female flowering, on the interaction between genotype versus N supply for Fusarium spp., and increases the maize grain yield; however, the responses of agronomic attributes vary with genotype. Highlights The inoculation with Azospirillum brasilense via soil increases maize grain yield, becoming viable and more sustainable alternative in the supply of nitrogen. The choice of the genotypes is an essential fator for the sucessful use of Azospirillum brasilense application or mineral fertilization, because the responses of agronomic attributes vary with the genotype. The most contrasting genotypes can be recombined in new stages of crossbreeding and selection, aiming at obtaining genotypes with greater yield potential in the use of Azospirillum brasilense inoculation. Further studies are needed to better understand this technology under conditions with different genotypes, soils and production systems.Maize has a high nitrogen demand; as a result, more sustainable alternatives are needed to reduce demand for mineral fertilizers. This study aimed to evaluate and characterize the agronomic performance of maize genotypes submitted to topdressing nitrogen fertilization and inoculation with Azospirillum brasilense. An experiment was conducted in the second season of 2017, in Jaboticabal-SP (Brazil), using 48 maize genotypes in a randomized block design. Treatments consisted of: 1) application of 140 kg ha-1 nitrogen, using urea as mineral fertilizer; 2) A. brasilense inoculation via soil, at a rate of 600 mL ha-1, as biological fertilization. Grain yield and agronomic traits were evaluated. The data were subjected to analysis of variance (F-Test), means were compared by Scott-Knott test at 5% probability, and multivariate statistical analysis was performed by principal component analysis. A. brasilense inoculation via soil has a significant effect on female flowering, on the interaction between genotype versus N supply for Fusarium spp., and increases the maize grain yield; however, the responses of agronomic attributes vary with genotype. Highlights The inoculation with Azospirillum brasilense via soil increases maize grain yield, becoming viable and more sustainable alternative in the supply of nitrogen. The choice of the genotypes is an essential fator for the sucessful use of Azospirillum brasilense application or mineral fertilization, because the responses of agronomic attributes vary with the genotype. The most contrasting genotypes can be recombined in new stages of crossbreeding and selection, aiming at obtaining genotypes with greater yield potential in the use of Azospirillum brasilense inoculation. Further studies are needed to better understand this technology under conditions with different genotypes, soils and production systems