Comportamento do milho Piranão [Braquítico-2] e de milhos de porte normal em diferentes níveis de nitrogênio e populações de plantas

• Autor(a) principal: Galvao, Jose Domingos
• Data de Publicação: 1974
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/11/11137/tde-20240301-143900/
• topic: MILHO; NITROGÊNIO; POPULAÇÕES VEGETAIS; VARIEDADES VEGETAIS

Piranão', a dwarf maize variety having the brachytic-2 gene, together with two normal commercial types, hybrid Ag-257 and variety 'Centralmex', were grown at two levels of nitrogen (1.6 and 2.4 g/plant) and four plant populations (50,000; 75,000; 100,000 and 125,000 plants/ha). The yield trials were carried out during the 1972/73 season, at Piracicaba, SP, Capinópolis and Viçosa, MG, using a randomized block design with split-split-plots and four replications. Varieties, nitrogen levels and plant populations represented main plots, split and split-split-plots respectively. Data were recorded for plant height, ear height, stem diameter, plant survival, barren plants, lodged and broken plants, ears per plant, ear weight, shelling percentage, grain size and grain yield. The following conclusions were obtained: 1 - Varieties adapted to higher plant densities thon those presently employed can be developed in properly conducted breeding programs; 2 - 'Piranão' showed considerably shorter plant height, which was associated with a larger stem diameter, and this resulted in less lodging and fewer broken plants. It had a much more desirable plant type than the normal Brazilian varieties and hybrids; 3 - Although 'Piranão' is still in the process of selection, it yielded as well as hybrid Ag-257 and bettor than 'Centralmex' in two locations. In spite of the abnormal rainy season, 'Piranão' showed good tolerance to high plant density; 4 - The lack of uniformity of 'Piranão' was responsible for o somewhat poorer performance. Uniformity of plant type is on important character for outstanding performance in high populations; 5 - The use of the brachytic-2 gene may play an important role in future breeding for improved plant type. Even for obtaining inbred lines it might be better to introduce the br2 gene in populations rather than in normal inbred lines; 6 - Further studies are necessary to determine the best plant types for higher planting densities in different ecological regions.