Water deficit is one of the most common causes of severe crop‐production losses worldwide in maize (Zea mays L.). The main goal of this study was to infer about genotype × environment interaction (G × E) and to estimate genetic correlations between drought tolerance traits in maize using factor analytic (FA) multiplicative mixed models in the context of multi‐environment trial (MET) and multi‐trait multi‐environment trial (MTMET) analyses. The traits measured were: grain yield (GY), ears per plot (EPP), anthesis‐silking interval (ASI), female flowering time (FFT), and male flowering time (MFT). Three‐hundred and eight hybrids were evaluated in a total of eight trials conducted under water‐stressed (WS) and well‐watered (WW) conditions across 2 yr and two locations in Brazil. For most of the traits (GY, ASI, and FFT), the magnitude of the genetic variances differed across WS and WW conditions. Genetic correlations between water conditions for FFT and MFT were 0.81 and 0.82, respectively, indicating that it might be unnecessary to measure these traits in both water conditions. Grain yield and EPP showed moderate to high G × E, with genetic correlations of 0.57 and 0.39 between WS and WW conditions, respectively, which suggested that gene expression was not consistent across different water regimes. Therefore, it is necessary to evaluate these traits under both water conditions. Genetic correlations between pairs of traits, in general, were higher under WS conditions compared with WW conditions. Grain yield exhibited moderate correlations with EPP (r = 0.62) and FFT (r = −0.42) under WS conditions. The FA models can be a useful tool for MET and MTMET analyses in maize breeding programs for drought tolerance.

Foram avaliadas quarenta e seis cultivares de milho em dois anos, em 11 locais do Nordeste brasileiro, no biênio 2001-2002, em blocos ao acaso, com três repetições, com o objetivo de avaliar a adaptabilidade e a estabilidade desses materiais, para fins de recomendação na região. As cultivares mostraram comportamento diferenciado entre si, na média dos ambientes. A magnitude da variância da interação cultivares x locais foi mais expressiva que a magnitude da variância da interação cultivares x anos, o que sugere que as avaliações devam ser realizadas em um maior número de locais. As cultivares avaliadas diferiram quanto à adaptabilidade e à estabilidade; são de grande importância para o Nordeste brasileiro os híbridos e variedades de melhor adaptação (b0> média geral) e com estimativas de b1 semelhantes à unidade (adaptabilidade geral).

ABSTRACT. Twenty-five cultivars of grain sorghum [Sorghum bicolor (L.) Moench] were examined under both drought stress and normal conditions in 4 experiments. In each condition, genotypes were evaluated in a factorial experiment using a randomized complete block design with 3 replications. Eight drought tolerance indices including stability tolerance index, mean productivity (MP), geometric MP, harmonic mean, stress susceptibility index, tolerance index, yield index, and yield stability index were estimated for each genotype based on grain yield under drought (Ys) and irrigated conditions (Yp). The results indicated that there were positive and significant correlations among Yp and Ys with geometric MP, MP, harmonic mean, and stability tolerance index, indicating that these factors are better predictors of Yp and Ys than tolerance index, stress susceptibility index, yield stability index, and yield index. Based on adjusted means at Yp and Ys, indices geometric MP, MP, harmonic mean, and stability tolerance index, unweighted pair group method with arithmetic mean cluster and biplot analysis, the most tolerant cultivars were '9929020', '9929034', and 'N 95B'.

, in a randomized block design with 36 treatments (genotypes) and four replications. The sum of irrigation depth and rainfall totaled 691.6 mm and 490.8 mm for the experiments under full irrigation (FI) and water deficit, (WD), respectively. The fraction of soil water depletion reached maximum values of 26 and 75 % for FI and WD, respectively. The traits evaluated in both experiments were: number of grains (NG m-2), number of ears per square meter (NE m-2), grain yield (GY) with 13% humidity, and the water use efficiency (WUE). Cultivation under water deficit caused reduction of 59.23% in NG m-2 ; 33.27% in NE m-2 , 59.

Resumo-N a cultura do milho (Zea mays L.), o suprimento inadequado de nitrogênio e a densidade de plantio são considerados fatores limitantes ao rendimento de grãos. Objetivou-se, neste trabalho, avaliar a influência de doses de nitrogênio e diferentes densidades de plantas nos componentes de produção e no rendimento da cultura de milho. O experimento foi instalado na Região de cerrado do sul do Maranhão, MA, em um Latossolo Vermelho-Amarelo distrófico, textura argilosa, cultivado há seis anos em sistema de plantio direto (SPD). O delineamento experimental utilizado foi o de blocos casualizados, com quatro repetições, e os tratamentos segundo o arranjo em um esquema fatorial 5 x 4. Os tratamentos foram constituídos pela combinação de cinco doses de nitrogênio, na forma de uréia (0; 50; 100; 150 e 200 kg ha-1), e quatro densidades de plantas (25.000; 50.000; 75.000 e 100.000 plantas ha-1). O número e massa de grãos por espiga e massa de grãos por planta aumentaram com o acréscimo da dose de N e com o decréscimo da densidade de plantas. Maiores rendimentos de grãos foram obtidos com acréscimos, concomitantemente, nas doses de N e nas densidades de plantas. A máxima produtividade de grãos de milho (11,9 Mg ha-1) foi obtida com 120 kg ha-1 de N e 83.000 plantas ha-1. Palavras-chave-Milho. Planta-efeito do Nitrogênio. Plantio direto.

The objective of this work was to identify sorghum lines tolerant to water stress at post-flowering. The treatments were set as a factorial arrangement, comprised of two water regimes and 25 genotypes, during the years of 2006, 2007 and 2008. The experimental design was a randomized block, with three replications. Since the combined analysis of variance revealed significant differences among the lines, among the environments and the presence of significant genotypes x environments interaction, two univariate stability estimates (Lin & Binns and Annicchiarico) and one multivariate (AMMI) were utilized for ranking the yield stability of the genotypes. Water stress decreases significantly the yield of the genotypes. The two univariate methods presented similar results, and were complementary to AMMI, allowing the selection of tolerant and responsive lines. Lines 9929020, CMSXS 230B and N 95B were drought tolerant and stable, followed by the lines BR 008B, Tx 2737 e Tx 2908 with high yield, but intermediate stability.

ABSTRACT. The aim of this study was to identify sorghum hybrids that have both high yield and phenotypic stability in Brazilian environments. Seven trials were conducted between February and March 2011. The experimental design was a randomized complete block with 25 treatments and three replicates. The treatments consisted of 20 simple pre-commercial hybrids and five witnesses of grain sorghum. Sorghum genotypes were analyzed by the genotype main effects + genotype environment interaction (GGE) biplot method if significant genotype x environment interaction, adaptability, and phenotypic stability were detected. GGE biplot methodology identified two groups of environments, the first composed of Água Comprida-MG, Montividiu-GO, and Vilhena-RO and the second of Guaíra-SP and Sete Lagoas-MG. The BRS 308 and 1G282 genotypes were found to have high grain yield, adaptability, and phenotypic stability and are thus indicated for cultivation in the first and second groups of environments, respectively.

-The maize genebank (GBmaize) preserves nearly 4,000 accessions for conservation and use. The use is however restricted because the accessions do not perform as well as the elite genotypes. This problem can be reduced by prebreeding, i.e., by extending the information on germplasm and introgressing useful alleles. Since irregular rainfall distribution and drought induce maize yield losses, drought tolerance is a main breeding target. In this study, the GBmaize accessions were evaluated for drought tolerance. Environmental factors, genotypes and the respective interactions influence the phenotypic expression. There was however no interaction genotype -irrigation level, so no accessions with different performance under the two water regimes could be identified. The performance of the following accessions was promising for a number