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'.

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. Sorghum grain yield can be significantly affected by climatic changes, especially drought and high temperature. The purpose of this study was to evaluate hybrids of grain sorghum grown under normal irrigation conditions or water stress in order to select those likely to be more tolerant of drought. Forty-nine hybrids were grown in a randomized block design experiment, with three replications. The plots consisted of four rows of 5 m length. Grain yield, weight of 1000 grains, harvest index, days to flowering, and plant height were measured. All of these characteristics were affected by water stress; however, grain yield showed the largest relative reduction. Comparison of the various genotypes showed that some hybrids had an acceptable grain yield under water stress, and maintained a high average yield compared to growth without stress. Several hybrids gave better grain yield than commercial check

The objective of this study was to estimate the adaptability and stability of grain sorghum hybrids grown under post-flowering water stress and non-stress conditions. The trials were carried out in Nova Porteirinha-MG during the season of 2014 and 2015, and in Teresina-PI in the 2014 season. Twenty-nine-grain sorghum hybrids were evaluated, in a randomized complete block design, with three replications. Plots consisted of four lines with 3 m long. The grain yield data were submitted to the individual variance analysis, having considered the effects of the hybrids as fixed and the other effects as random. The joint analysis was carried out, and when the interaction genotypes x environments was significant, the grain yield data were submitted to the adaptability and stability analysis by the GGE biplot method. A substantial reduction in the grain yield in environments with water stress was found. The highest yielding hybrids under water stress conditions in Nova Porteirinha-MG were 50A50, AG1080, AG1090, DKB550, DKB590, Jade, and BM737, and the highest yielding hybrids under the water stress in Teresina-PI were 1G282, 1G244, and A9721R. Considering all environments, the highest yielding hybrids were 1G282, DKB540, A9721R, 1G100, and AG1090.

RESUMO -O objetivo do presente trabalho foi selecionar parentais e híbridos de sorgo granífero para características agronômicas. Foram avaliados 184 cruzamentos oriundos de um dialelo parcial envolvendo 16 linhagens machoestéreis e 12 restauradoras da fertilidade. Foram realizados 8 experimentos, com 23 híbridos cada e duas testemunhas adicionais (BRS 304 e BRS 330), em blocos casualizados, com duas repetições. Foram avaliadas as características rendimento de grãos, florescimento e altura de plantas. Os efeitos de CGC e CEC foram significativos para as três características, mostrando a importância dos efeitos aditivos e dominantes no controle destes caracteres. O quadrado médio para CGC foi superior ao da CEC. Todos os parentais que contribuíram para aumentar o rendimento de grãos também o fizeram para altura de plantas, exceto pelos parentais femininos CMSXS 1006 e CMSXS 1011, mostrando a dificuldade de dissociar estas duas características. Os híbridos mais produtivos apresentaram altura de plantas acima do recomendado para sorgo granífero, mesmo assim foi possível a seleção de cruzamentos que apresentaram rendimento de grãos acima da média, florescimento abaixo da média e altura dentro do padrão exigido. Dentre estes, pode-se destacar os híbridos CMSXS 1002 x CMSXS 1102, CMSXS 1006 x RTx2907, ATx ARG 1 x SC1155 e CMSXS 1008 x Tx2741. Palavras-chave: Sorghum bicolor, seleção de parentais, dialelo, hibridação, melhoramento de plantas. COMBINING ABILITY OF LINES AND SELECTION OF GRAIN SORGHUM HYBRIDSABSTRACT -The purpose of this work was to select grain sorghum lines and hybrids for growing as succession crop. Crosses, coming from a partial diallel involving 16 male sterile lines and 12 restorer lines, were evaluated. Eight experiments were carried out with 23 hybrids each and two additional checks (BRS 304 and BRS 330) in randomize complete blocks design, with two replications and plot of two lines of five meters long. Grain yield, days to flowering and plant height were evaluated. The effects of GCA and SCA were significant, showing the importance of both additive and dominant effects in the control of these traits. The mean square for GCA was well above the SCA, suggesting the importance of parental selection in sorghum. Only the lines CMSXS 1006 and CMSXS 1011 contributed to rise grain yield without increasing the plant height in the hybrids they compose. The most productive hybrids showed plants above 150 cm, however it was still possible to get crossings that had yield above average, cycle below average and plant height within the standard required for grain sorghum. Among these are the hybrids CMSXS 1002 x CMSXS 1102, CMSXS 1006 x RTx2907, ATX ARG 1 x SC1155 and CMSXS 1008 x Tx2741, with high yields and CEC.