Gustavo Henrique Demari

Fontes e parcelamento do nitrogênio em híbridos de milho geneticamente modificados

This study sought to evaluate the effects of sources and splitting of nitrogen on the morphological parameters and yield of genetically modified maize hybrids. This study was conducted during 2012/2013 and 2013/2014 growing seasons in Tenente Portela, Rio Grande do Sul, Brazil. Randomized blocks design in factorial arrangement (2 x 2 x 11 x 3) were used for the growing seasons; seasons x maize hybrids x nitrogen management x nitrogen sources, with three replicates. Analysis of variance pointed to interaction between all factors through plant height and number of kernels per row. Significant interaction through season x maize hybrids x nitrogen management for ear insertion height and grain yield. The interaction seasons x nitrogen management x nitrogen sources, and maize hybrids x nitrogen management can be highlighted for the variable ear insertion height. The characteristic thousand grain weight showed interaction through seasons x maize hybrids. Maize hybrids respond similarly to nitrogen management, where different nitrogen sources show similar behavior for the studied variables, without response to grain yield. The different nitrogen management forms caused positive effects on the evaluated variables, especially when performed in the early stages of culture. The current recommendation of nitrogen splitting in maize is adequate, but for the hybrid DKB 250 VT PRO2 ® in water deficit, nitrogen can be applied until the V8 growth stage.

Ecology of Upland Rice Plants and Seeds Subjected to Growth Regulator

The objective of this work is to verify the influence of the plant regulator trinexapac-ethyl on plant growth and physiological quality of upland rice seeds. We used an upland rice genotype, and the growth regulator was the trinexapac-ethyl. The experiment was completely randomized in a 4 × 8 factorial design related to four concentrations of the plant regulator trinexapac-ethyl [0 (without growth regulator), 0.25, 0.50, and 0.75 L c.p. ha-1] and 7 plant collection times [14, 28, 42, 56, 70, 84, 98 days after emergence (DAE)], with four replicates. To determine growth attributes, we evaluated total dry matter, dry matter production rate, relative growth rate, leaf area ratio, leaf matter, leaf area index, solar energy conversion efficiency and partition of assimilates. The physiological quality of the seeds was evaluated based on germination, first germination count, field emergence, emergence speed index and seedling dry matter. Plant growth was affected by the growth regulator. Total dry matter, dry matter production rate and solar energy conversion efficiency decreased, while leaf area index, leaf area ratio and leaf matter increased due to the effects of the growth regulator. The dry matter partition of plants changed in plants subjected to the growth regulator, with a delay in the targeting of assimilates to reproductive organs and a greater allocation to roots at the end of the cycle in plants subjected to the doses 0.50 and 0.75 L·ha-1 of growth regulator. Seed vigor was adversely affected by the growth regulator.

Adaptability, Stability and Multivariate Selection by Mixed Models

The aim of this work was to estimate the adaptability and stability of grain yield per hectare and percentage of crude protein of maize grains combined in an index, and to establish a multicharacter selection through mixed models based on an objective character and 15 auxiliary traits. The trials were conducted in the 2013/2014 agricultural year in four growing environments of the Rio Grande do Sul, BR state. The experimental design was randomized blocks arranged in a factorial scheme, being four growing sites × 15 single cross maize hybrids, arranged in three repetitions. The genotypic index, composed by the grain yield and the crude protein percentage in the grains, is the best selection strategy to achieve maize superior genotypes. The multivariate genotypes selection, considering grain yield and crude protein, is efficient. The genotypes FORMULA TL®, AS1656PRO®, P30F53Hx®, LG6304YG® and 30F53 are more adapted and stable for grain yield and percentage of crude protein, in the conditions of this study. The mixed models were efficient to employ the multicharacter selection and to contribute for maize genetic breeding.

AMBIENTE DE CULTIVO E SEUS EFEITOS AOS CARACTERES MORFOLÓGICOS E BROMATOLÓGICOS DA SOJA

O objetivo deste trabalho foi avaliar o desempenho agronomico de dois genotipos de soja com habito de crescimento indeterminado em dois ambientes de cultivo e verificar as relacoes lineares dos caracteres morfologicos e bromatologicos, buscando ganhos via melhoramento genetico. Os experimentos foram conduzidos na safra agricola 2013/2014. O delineamento experimental utilizado foi de blocos casualizados em esquema fatorial 2 x 2 sendo, dois ambientes de cultivo (Tenente Portela e Independencia – RS) e dois genotipos de soja com habito de crescimento indeterminado (FPS Solimoes RR e FPS Paranapanema RR), alocados de tres repeticoes. A analise de variância revelou significância para a interacao ambiente de cultivo x genotipo para os caracteres insercao do primeiro legume, altura de planta, e comprimento de internodio. Ausencia de interacao foi revelada pelo numero de legumes na haste principal, numero de legumes na ramificacao, numero de ramificacoes, comprimento das ramificacoes, numero de legumes com um grao, numero de legumes com dois graos, numero de legume com tres graos, massa de mil graos, rendimento de graos, percentuais de fibra bruta, material mineral, proteina bruta, carboidratos totais, carboidratos nao fibrosos e lipidios. O ambiente de cultivo Tenente Portela influencia positivamente o rendimento de graos de ambos os genotipos, e apresenta inter-relacoes significativas entre os caracteres morfologicos que influenciam o mesmo, sendo FPS Paranapanema RR superior para rendimento de graos. Os caracteres bromatologicos nao revelam diferenca significativa entre ambientes de cultivo e genotipos de soja com habito de crescimento indeterminado.