Resumo O objetivo deste trabalho foi selecionar, simultaneamente, híbridos pré-comerciais de sorgo granífero com alta adaptabilidade e estabilidade da produção de grãos, por meio de modelagem mista, em 20 ambientes, por seis anos. O material vegetal avaliado consistia de 57 híbridos comerciais de sorgo granífero. Em todos os experimentos, os híbridos foram arranjados em delineamento fatorial triplo; alguns experimentos utilizaram um fatorial 6x6, e outros, um fatorial 5x5. Os parâmetros de adaptabilidade e estabilidade foram obtidos com base na predição por média harmônica da performance relativa dos valores genéticos (MHPRVG). Os modelos mistos mostraram-se adequados para analisar a interação genótipo x ambiente (GxE) e os estudos de adaptabilidade e estabilidade genotípica do sorgo granífero. Os híbridos que se destacam, considerando-se todos os ambientes, são 1G282, A9904, 50A50, A9902 e XB6022. O híbrido A9904 destaca-se em ambientes favoráveis, com rendimento de grãos acima da média. Apenas 1G282 está entre os cinco melhores híbridos para cada grupo de ambientes e é o melhor híbrido de sorgo granífero quanto ao rendimento, à adaptabilidade e à estabilidade. Os valores genotípicos preditos com base em médias genotípicas podem ser usados em relação aos ambientes com o mesmo padrão de interação GxE por estarem livres da interação GxE.

Abstract The objective of this work was to simultaneously select pre-commercial grain sorghum hybrids with high adaptability and yield stability, through mixed modeling, in 20 environments, during six years. The evaluated plant material consisted of 57 commercial grain sorghum hybrids. In all experiments, hybrids were arranged in a triple lattice design; some experiments used a 6x6 lattice, and others, a 5x5 lattice. Adaptability and stability parameters were obtained based on the prediction by harmonic mean of the relative performance of genotypic values (HMRPGV). The mixed models proved to be adequate to analyze the genotype x environment (GxE) interaction and the genotypic adaptability and stability studies on grain sorghum. The hybrids that stand out, considering all environments are 1G282, A9904, 50A50, A9902, and XB6022. The A9904 hybrid stands out in favorable environments, with a grain yield above average. Only 1G282 is among the five best hybrids for each group of environments, and it is the best grain sorghum hybrid for yield performance, adaptability, and stability. The predicted genotypic values based on genotypic means can be used in the environments with the same GxE interaction pattern because they are free of the GxE interaction.

ABSTRACT: Sorghum breeding programs are based predominantly on developing homozygous lines to produce single cross hybrids, frequently with relatively narrow genetic bases. The adoption of complementary strategies, such as genetic diversity study, enables a broader vision of the genetic structure of the breeding germplasm. The purpose of this study was to evaluate the genetic diversity of sorghum breeding lines using structure analysis, principal components (PC) and clustering analyses. A total of 160 sorghum lines were genotyped with 29,649 SNP markers generated by genotyping-by-sequencing (GBS). The PC and clustering analyses consistently divided the R (restorer) and B (maintainer) lines based on their pedigree, generating four groups. Thirty-two B and 21 R lines were used to generate 121 single-cross hybrids, whose performances were compared based on the diversity clustering of each parental line. The genetic divergence of B and R lines indicated a potential for increasing heterotic response in the development of hybrids. The genetic distance was correlated to heterosis, allowing for the use of markers to create heterotic groups in sorghum.

RESUMO. Os solos do cerrado são caracterizados por apresentarem elevada acidez e alumínio solúvel em níveis tóxicos para as plantas, o que assume um papel de fator limitante ao aumento da produtividade destas culturas. A toxidez causada pelo alumínio afeta o desenvolvimento das plantas e em particular, inibe o crescimento das raízes e a absorção de água e nutrientes pela planta. Com o presente trabalho objetivou-se fenotipar híbridos de sorgo granífero quanto à tolerância ou susceptibilidade ao alumínio tóxico. O estudo foi realizado em câmara de crescimento na Embrapa Milho e Sorgo, entre os dias 04/04 a 30/05/2014. Foi realizado um experimento em solução nutritiva testando-se dois níveis de Al (0 e 27 µM), em 18 híbridos de sorgo, utilizando delineamento de blocos ao acaso, com duas repetições. Como testemunhas foram utilizadas as linhagens ATF 13B (suscetível) e ATF 14B (Tolerante). Com base nos caracteres avaliados: crescimento líquido de raiz após 120 horas, crescimento líquido de raiz após 168 horas e o crescimento relativo de raiz seminal após 168 horas foi possível distinguir os híbridos tolerantes dos suscetíveis. Os híbridos BRS 310 e BRS 373 apresentaram tolerância significativa, com redução no crescimento abaixo de 30% quando submetidos ao estresse de alumínio. O híbrido BRS 330 foi classificado em grupo intermediário com redução de tamanho de raiz em torno de 50%. Todos os outros híbridos foram suscetíveis com reduções de crescimento de raiz muito afetado pelo alumínio.

ABSTRACT. Sorghum (Sorghum bicolor L. Moench) is one of the most important cereal crops in the world. In Brazil, the acreage of grain sorghum during off-season is quite expansive. Most of this area is the Cerrado, a Brazilian biome that is similar to a Savannah and is characterized by high acidity and soluble aluminum at toxic levels for plants. The aluminum acts as a limiting factor in achieving high yields. The purpose of this work was to phenotype sorghum hybrids for aluminum tolerance. Eighteen hybrids were evaluated in a nutrient solution containing {0} or {27} µM Al3+. The work was carried out in a growth chamber at the Embrapa Maize and Sorghum, from April 4 to May 30, 2014. The lines ATF 13B (susceptible) and ATF 14B (tolerant) were used as check cultivars. Based on the Net Root Growth after 120 hours (NRG120), Net Root Growth (NRG168) after 168 hours and Relative Net Root Growth after 168 hours (RNRG168), it was possible to distinguish tolerant hybrids from susceptible ones. The high aluminum saturation reduced root growth by 70%. The hybrids BRS 310 and BRS 373 were tolerant to aluminum stress under nutrient solution. The hybrid BRS 330 was clustered in an intermediate group, with an approximately 50% root growth reduction. The other hybrids were susceptible with significant root reduction.

A magnitude do erro experimental tem efeito direto no sucesso de experimentos, no melhoramento de plantas. Este trabalho objetivou verificar a interferência de métodos de correção de estande na produtividade de 25 híbridos de sorgo granífero, em sete ambientes. Os métodos avaliados foram: sem correção, regra de três, covariância de estande médio e de estande ideal, Zuber, Cruz, Vencovsky & Cruz e correção estratificada, com base no agrupamento de genótipos. O coeficiente de correlação de Pearson foi utilizado para verificar a magnitude da influência de cada método, em relação aos dados sem correção. Os métodos de correção de estande baseados em covariância e de Vencovsky & Cruz reduziram o coeficiente de variação e apresentaram alta correlação com parâmetros de adaptabilidade e estabilidade dos híbridos, no entanto, estas diferenças não foram expressivas a ponto de justificarem a correção.

The magnitute of the experimental error has a direct effect on the success of plant breeding experiments. This study aimed at evaluating the interference of stand correction methods on the yield of 25 grain sorghum hybrids, in seven environments. The methods tested were: without correction, rule of three, covariance of medium and ideal stand, Zuber, Cruz, Vencovsky & Cruz and stratified correction, based on genotype groups. The Pearson correlation coefficient was used to assess the magnitude of the influence exerted by each method, concerning the data without correction. The stand correction methods based on covariance and Vencovsky & Cruz reduced the coefficient of variation and showed a high correlation with the adaptability and stability parameters of hybrids, however, these differences were not so significant to justify such adjustment.

When it comes to recommending sorghum (Sorghum bicolor) cultivars, it is essential to carry out a genetic evaluation of the agronomic traits of promising genotypes from several common environments where the crop is cultivated. This study consisted of a genetic evaluation of 52 experimental grain sorghum hybrids and eight commercial cultivars. Hybrids were evaluated in 19 experiments representing the most varied cultivation conditions in Brazil. Traits of agronomic interest such as grain yield, flowering and plant height were analysed. Genotypic evaluation was performed following the REML/BLUP (Restricted Maximum Likelihood/Best Linear Unbiased Predictor) procedure; the MHPRVG (Harmonic Mean of Relative Performance of Genotypic Values) method was also employed to study stability and adaptability. Hybrids which stood out in terms of highest grain yield based on genotypic values, stability and adaptability were 0306037, 1G150, DKB 599, 0306039, 1G282 and 0307671. Of these, only 1G282 showed restrictions as to plant height. For flowering, experimental hybrids showed shorter cycles than commercial cultivars, confirming the efficiency of genetic improvement for this trait. With the analysis of grain yield considering days to flowering and plant height as covariates, it was observed that most of the hybrids of greater performance, showed grain yield to be positively influenced by plant height and days to flowering.