RESUMO. O objetivo desta pesquisa foi comparar parâmetros genéticos para características relacionadas com germinação das sementes e vigor de plântulas de cruzamentos simples (SCH) vs. três vias (TWH) híbridos de sorgo. O estudo foi realizado em substrato a base de areia em estufa; 67 genótipos (4 pares de linhas A- e B-, 4 linhas R-, 13 SCH e 42 TWH) foram alocados em blocos completos com delineamento experimental inteiramente casualizado, com três repetições. A análise estatística incluiu testes de ANOVA e "t" Student; o teste de Tukey (p ≤ 0,05) foi aplicado para comparação de média. As linhas - R apresentaram melhores atributos fisiológico de sementes de qualidade do que as linhas A- e B. Os valores de qualidade e de heterose de sementes de SCH vs. que TWH não apresentaram diferenças significativas (p > 0,05) para qualquer variável. No entanto, heterobeltiose de SCH foi maior do que a de TWH de plântulas normais, peso seco de plúmula e velocidade de emergência de plântulas. A Linha A2 e linha restauradora R14 apresentou os maiores valores da CGC nos dois tipos de híbridos. Não foram encontradas diferenças (p ≤ 0,05) entre os efeitos maternos e paternos das linhas A- e B- envolvidas em cruzamentos entre plantas esteriles do sexo masculino (progenitor feminino) do TWH, exceto para o comprimento plúmula na Linha 5.

ABSTRACT. The aim of this research was to compare genetic parameters for traits related with seed germination and seedling vigour of single cross (SCH) vs. three-way (TWH) sorghum hybrids. The study was conducted in a sand bed under a greenhouse; 67 genotypes (four pairs of A- and B- lines, four R- lines, 13 SCH and 42 TWH) were allocated in a randomized complete blocks experimental design with three replications. Statistical analysis included ANOVA’s and Student “t” tests, while Tukey test (p ( 0.05) was applied for mean comparisons. The R-lines showed better physiological seed quality attributes than the A- and B- lines. The seed quality and heterosis values of SCH vs. that of TWH did not show significant differences (p > 0.05) for any variable; however, heterobeltiosis of SCH was higher than that of TWY for normal seedlings, dry weight of plumule and seedling emergence rate. The A2- line and R14 restorer line showed the highest GCA values in both types of hybrids. No differences (p ≤ 0.05) were found between maternal and paternal effects of the A- and B- lines involved in the male sterile cross (female parent) of the TWH, except for plumule length in Line 5.

ABSTRACT Ustilago maydis is a basidiomycete known as the causative agent of 'common smut', worldwide disease of maize that is recognized by the galls it forms, which have considerable potential as a gourmet food. Results of infection are quite variable, even under optimal greenhouse conditions. In order to find pathogenic strains able to be used as a highly infective and stable inoculum for the successful production of galls either in greenhouses or in the field, ears with gall symptoms containing teliospores were recovered from maize plants. The teliospores were suspended in water and plated on nutrient-rich medium. Twenty-six colonies developed, containing three types of yeast-like colonies: saprotrophic, pathogenic, and solopathogenic. DAPI staining confirmed the presence of solopathogenic strains with diploid sporidia. Groups of different mating types were found when pairs of the 26 strains were arranged resembling partial-diallel combinations. Amplification of the partial b locus revealed that the strains found harbor the alleles b3 and b4, allowing the formation in dikaryotic strains of heterodimeric regulatory proteins associated with fungal development and pathogenicity. In this study, we isolated compatible haploid and solopathogenic diploid strains for their high capacity for inducing smut.