Lauro José Moreira Guimarães

Multivariate analyses of genotype x environment interaction of popcorn

The objectives of this work were to evaluate the genotype x environment (GxE) interaction for popcorn and to compare two multivariate analyses methods. Nine popcorn cultivars were sown on four dates one month apart during each of the agricultural years 1998/1999 and 1999/2000. The experiments were carried out using randomized block designs, with four replicates. The cv. Zelia contributed the least to the GxE interaction. The cv. Vicosa performed similarly to cv. Rosa-claro. Optimization of GxE was obtained for cv. CMS 42 for a favorable mega-environment, and for cv. CMS 43 for an unfavorable environment. Multivariate analysis supported the results from the method of Eberhart & Russell. The graphic analysis of the Additive Main effects and Multiplicative Interaction (AMMI) model was simple, allowing conclusions to be made about stability, genotypic performance, genetic divergence between cultivars, and the environments that optimize cultivar performance. The graphic analysis of the Genotype main effects and Genotype x Environment interaction (GGE) method added to AMMI information on environmental stratification, defining mega-environments and the cultivars that optimized performance in those mega-environments. Both methods are adequate to explain the genotype x environment interactions.

DISCRIMINAÇÃO DE LINHAGENS DE MILHO QUANTO À UTILIZAÇÃO DE NITROGÊNIO, POR MEIO DA AVALIAÇÃO DE CARACTERISTICAS DO SISTEMA RADICULAR

Estrategias que busquem aumentar a produtividade de palha pelas culturas devem ser implementadas na regiao dos Cerrados, no sentido de consolidar o plantio direto. Objetivou-se avaliar a influencia das epocas de aplicacao e do parcelamento da fertilizacao nitrogenada suplementar a adubacao de semeadura no milho sobre a produtividade de palha de aveia preta, especies espontâneas e a influencia desse parcelamento nos diversos componentes da cultura. Os tratamentos constaram da aplicacao de 70kg/ha de nitrogenio, como dose suplementar a adubacao de semeadura do milho, em epocas distintas: na semeadura da aveia-preta; oito dias antes da semeadura do milho; em cobertura, quando as plantas tinham quatro a cinco folhas; em cobertura, quando as plantas tinham sete a oito folhas. Na semeadura, aplicaram-se 42kg/ha de N em todas as parcelas. A adubacao nitrogenada aplicada na semeadura da aveia nao resultou em aumento da produtividade de palha, na entressafra. Houve aumento da produtividade de palha pelo milho quando se aplicou o nitrogenio suplementar a semeadura, assim como a aplicacao mais proxima da semeadura proporcionou aumento da produtividade em relacao a aplicacao do fertilizante na semeadura da aveia.

Selection of sorghum hybrids grown under aluminum saturation

The purpose of this study was to evaluate 165 hybrids derived from lines previously selected for aluminum (Al) tolerance. Nine check cultivars were used, eight commercial hybrids and one experimental hybrid. Hybrids were evaluated at three levels of Al saturation (0, 20 and 40% on average). The differences between the environments were significant. Environment with 0% Al saturation yielded 29.5% more than that with 40% Al saturation, showing the importance of genotype selection for acid soils. The best check cultivar was the hybrid DKB550. The hybrids AG1020 and AG1040 also performed well, where the latter was more tolerant but the former more responsive to environment improvement. The hybrid BRS304 was susceptible to high levels of Al saturation. The three commercial BRS hybrids (BRS310, BRS330 and BRS332) performed better than BRS304 at high Al saturation. The hybrid BRS330 was the best BRS hybrid to grow on a field with high Al saturation. The hybrid DKB559 performed well at high Al saturation but did not respond to environment improvement. The hybrids 727029, 727039, 729041, 729095, 729109, AG1040, and DKB550 were tolerant to higher levels of Al saturation and responsive to environment improvement, and showed good stability and adaptability at both low and high Al saturation.