ABSTRACT Sweet sorghum (Sorghum bicolor [L.] Moench) is a crop that is well known for its high production of biomass and sugars in the stem juice. The objective of this work was to evaluate the productivity of sweet sorghum ‘Roger’ based on the dynamics of sugar production and dry biomass by considering different production methods and plant phenological stages. The experimental design consisted of different tillage and fertilization methods established in a randomized complete block design with a split plot arrangement. Tillage treatments were assigned to the plot using the three levels of minimum tillage, traditional tillage, and traditional tillage that included a subsoil operation. Fertilization treatments were assigned to the subplot using the three levels of organic fertilizer, inorganic fertilizer, and without fertilizer. Data collection was performed at different plant phenological stages from anthesis to physiological maturity. Results showed that evaluated agronomic parameters depended on the phenological stage (P < 0.05) rather than the production methods (P > 0.05). Thus, the distribution and accumulation of sugar by stem internodes was associated with plant phenological components. The highest values of the concentration of total soluble solids (14.89%), juice sugar content (22.91 g), juice sugar concentration (527.46 mg g-1 DW), dry biomass (60.04%), and dry biomass yield (19.01 t ha-1) were observed at the physiological maturity stage of the plant.

Abstract Extreme weather, such as increased drought and high temperatures, has had a significant impact on crop yields. Therefore, it is important to identify characters in sorghum genotypes that help them lessen the impact of these factors and allow them to be productive. The objective of this work was to evaluate the heat tolerance of a group of granite sorghum B and R lines under two humidity conditions to select the best heat tolerant lines. 28 experimental lines B and R were planted on August 30, 2017 in Marin, NL, Mexico. The experiment was sown in a completely randomized design with an arrangement in divided plots and with two repetitions the moisture treatment under water stress was applied 43 days after sowing (DDS) for a period of four weeks without irrigation. Data were taken from days to flowering, damage to the cell membrane at 40 °C and relative leaf water content (CRA). The results showed that the CRA did not allow to establish differences between genotypes, while the heat treatment applied at 40 °C, allowed to establish differences and classify them according to the percentage of damage caused to the cell membrane, since this is one of the features widely used to select tolerant genotypes. Genotypes 20 and 22 were identified as heat tolerant and genotypes 5 and 8 were susceptible.

Resumen El clima extremo como el aumento de la sequía y altas temperaturas han tenido un impacto significativo en el rendimiento de los cultivos. Por lo tanto, es importante identificar caracteres en los genotipos de sorgo que les ayuden a disminuir el impacto de estos factores y les permita ser productivos. El objetivo de este trabajo fue evaluar la tolerancia a calor de un grupo de líneas B y R de sorgo granífero bajo dos condiciones de humedad para seleccionar las mejores líneas tolerantes a calor. Se sembraron 28 líneas experimentales B y R el 30 de agosto de 2017 en Marín, NL, México. El experimento se sembró en un diseño completamente al azar con un arreglo en parcelas divididas y con dos repeticiones El tratamiento de humedad bajo estrés hídrico se aplicó 43 días después de la siembra (DDS) por un periodo de cuatro semanas sin riego. Se tomaron datos de días a floración, daño a la membrana celular a 40 ºC y contenido relativo de agua en hoja (CRA). Los resultados mostraron que el CRA no permitió establecer diferencias entre genotipos, mientras que el tratamiento de calor aplicado a 40 ºC, permitió establecer diferencias y clasificarlos de acuerdo con el porciento de daño causado a la membrana celular, ya que este es uno de los rasgos ampliamente utilizado para seleccionar genotipos tolerantes. Se identificaron como tolerantes al calor los genotipos 20 y 22 y como susceptibles los genotipos 5 y 8.

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.