In Burkina Faso, sweet grain sorghum [Sorghum bicolor (L.

Sweet sorghum is mainly cultivated for the sweetness of its stems and the quality of its fodder. Unfortunately, its cultivation is gradually being abandoned in Burkina Faso due to climatic hazards. In a general context of strong variations in the rainfall regime, it is, therefore, important to determine the effect of the sowing period on the expression of agromorphological traits and Brix content. Thus, 29 sweet sorghum accessions were evaluated using 15 quantitative variables in a three-replicate Fisher block design with two sowing dates spaced 25 days apart. The results of the study showed that only stalk length (pr. = 0.519) and internode length (pr. = 0.367) were not significantly influenced by sowing date. Indeed, delayed sowing resulted in an increase in the number of vegetative (+2.44) and useful (+1.3) tillers, as well as Brix (+1.16%). However, a reduction in leaf area (−4.35 cm × 1.43 cm), plant height (−85.69 cm), panicle length (−2.63 cm), and panicle weight (−6.19 g), as well as a reduction in the sowing-to-flowering cycle from 3 to 21 days, was obtained at the second sowing date. Thus, all accessions are sensitive to photoperiod with photoperiodic coefficients varying from 0.19 (GB02) to 0.93 (BSA5). These results could be exploited in the sweet sorghum improvement program.

In Burkina Faso, tree types of sorghum are mainly grown. Despite their genetic proximity revealed by molecular markers, the identification of distinctive agro-morphological traits between sweet grain sorghum, sweet sorghum and grain sorghum could contribute to better management of their genetic resources. Thus, 42 genotypes consisting of the three sorghum types were evaluated in a three replicate Fisher incomplete block design using 20 quantitative traits. The results showed a high variability of traits within each sorghum type and a greater closeness between sweet grain sorghum and sweet stalk sorghum. In addition, nine traits clearly discriminated sweet grain sorghum from the other sorghum types. Sweet grain sorghum expressed the highest values of the sowing-heading cycle, leaf sheath length, stem diameter, productive tillers, and panicle width and the lowest values of mean heading-flowering difference, 100-grain weight, and Brix. Moreover, the ‘sorghum type’ factor is less preponderant than the ‘genotype factor’ in expressing the variability of all traits. Therefore, the 42 genotypes are organized into three genetic groups independently of the sorghum- type factor, where the group I contains all sweet grain sorghum genotypes and three sweet stalk sorghum genotypes. These results could be exploited in sorghum breeding programs.

Sweet grain sorghum is an under-exploited crop mainly grown around dwelling houses. Its production faces harsh environmental conditions. This study aims to assess sowing date effect on morpho-agronomical traits of sweet grain sorghum. Thus, 30 genotypes of sweet grain sorghum were assessed under 2 planting dates (June 26 and July 20) 24 days apart in a Randomized Complete Block Designs with 3 replications using 10 traits. The results showed a significant effect of sowing date on most of the traits, except internode length. All genotypes were sensitive to photoperiod variation by reducing their sowing-flowering cycle from 08 to 20 days, size and yield at the second planting date. Delayed sowing also resulted in a decrease in plant height (66.4 cm), 100 grain weight (8.3%), panicle weight (16.84%) and grain yield per plant (18.93%). The genotypes expressed a differential sensitivity to photoperiod variation with a mean coefficient of 0.59. Finally, a clustered flowering of all genotypes between September 11 and 27 was observed for both sowing dates. These results could be exploited by sweet sorghum breeding programme in the definition of the cropping calendar.