RESUMO
Sweet sorghum (Sorghum bicolor (L.) Moench) is an important crop in Chad that plays an economic role in the countryside were stalks are produced mainly for human consumption without any processing. Unfortunately, very little information exists on its genetic diversity and brix content. Studies performed in 2014 and 2015 showed that there were significant variations (p < 0.001) for all assessed quantitative traits. Potential grain yield (0.12-1.67 t ha-1), days to 50% flowering (68.3-126.3 days), and plant height (128.9-298.3 cm) were among traits that exhibited broader variability. Brix content range from 5.5 to 16.7% across accessions, was positively correlated to stalk diameter and plant height, but negatively correlated to moisture content in fresh stalk and potential grain yield. Fresh stalk yield range from 16.8 to 115.7 Mg ha-1, with a mean value of 58.3 Mg ha-1 across accession. Moisture content in fresh stalk range from 33.7 to 74.4% but was negatively correlated to fresh stalk yield. Potential sugar yield range from 0.5 to 5.3 Mg ha-1 across accession with an average of 2.2 Mg ha-1. Theoretical ethanol yield range from 279.5 to 3,101.2 L ha-1 across accession with an average of 1,266.3 L ha-1 which is significantly higher than values reported under similar semiarid conditions. Overall, grain yields were comparatively low. However, two accessions had grain yield of more than 1.5 t ha-1; which is greater than the average 1.0 t ha-1 for local grain sorghum varieties in Chad. These could have multi-purpose uses; grains, sugar and bioenergy production.
RESUMO
Dry-season sorghum is a type of sorghum whose establishment ends at the end of the rainy season and its development takes place during the dry and cold harmattan period. Its root system is particularly well developed with deep penetration for water withdrawal. This study was conducted to assess the level of genetic diversity present among dry-season sorghum in Chad's Sudanese zone using phenotypic traits, and to identify new sources of drought tolerance that could be used in sorghum breeding programs. A high variability in qualitative traits was observed except for the botanical race which showed that all cultivars were of durra race. It was also observed that most cultivars had compact panicles (66.67%), mostly black glumes (66.67%), glume hairiness (58.33%) and did not have aristation (91.67%). Most qualitative traits showed a coefficient of variation of less than 30%, and the analysis of the variance showed that at 0.1% probability, there were significant differences between cultivars for all traits except botanical race. It was observed that the potential productivity of dry-season sorghum of this collection was strongly related to their staygreen characteristic; a trait of enormous importance in breeding for postflowering drought tolerance in sorghum. Plant height was highly heritable (91.9%), followed by the peduncle length (90.2%), panicle length (87.5%) and the internodes number (86.5%). Structuring of diversity separated the cultivars into four statistically distinct groups; with group 2 clustering cultivars with panicle productivity, early maturity and high staygreen, and other traits that contribute to the performance of cultivars. The findings will help to enhance the selection and production of dry-season sorghum in Chad and also provide alternative sources for staygreen introgression into the larger sorghum breeding community.
