Analysis of Glucose Contents in Sorghum (Sorghum bicolor (L) Moench)

Fossil energy as a fuel source in the world is decreasing. This research aims to provide bioenergy as an alternative renewable energy source, namely sweet sorghum (Sorghum bicolor (L.) Moench), which is cheaper, safer, and reduces air pollution. The specific objectives to be achieved were to identify sorghum varieties containing high stem glucose content (%brix) among several local, superior, and introduced varieties and to obtain the best panicle pruning percentage. The research was conducted by selecting several local, superior, and introduced sorghum varieties against panicle pruning. The design used was a group design with two treatment factors arranged factorially. The first factor was the type of variety consisting of 5 levels: Sorghum variety (V): Lokal Putih NTT (V1), Super 1 (V2), Kawali (V3), Numbu (V4), and Introduced Sweet-Sorghum (Kotobun sorgo/FS501) (V5) The second factor was panicle pruning time (P) which consisted of 4 levels: development stage (50% of a plot had swollen stems) (P1), flowering stage (100% of a plot had flowers (P2), seed filling stage (50% in a plot had seed filling phase) (P3) , and not pruned (Control) (P0). The results of this study showed that sorghum varieties on the variable production of stem juice (sap) in the Kawali variety, which was the highest at 6.28 ton/ha-1, gave a very significantly different effect (P<0.01) compared to the other four sorghum varieties, namely Numbu (4.94 ton/ha-1), Super 1 (4.88 ton/ha-1), FS501 (4.83 ton/ha-1), and Lokal Putih NTT (4,04 ton/ha-1). The highest stem glucose content of sorghum varieties fell to Kawali and Super 1, with 11.00% brix compared to the other three sorghum varieties, namely Lokal Putih NTT (10.00% brix), FS501 (9.53% brix), and Numbu (9.00% brix). The two variables of stem glucose content (%brix) and stem juice production (ml/kg) had a positive correlation (r = 43%). This will affect the result of bioethanol content. The glucose content in the stem juice of sweet sorghum varies by variety (Almodares et al., 1994). This is in line with the results of research by Sepahi (1996) and Almodares et al. (1997), which stated that the duration of sucrose accumulation in the stem varied among cultivars. In the treatment of panicle pruning on the production of stem juice (sap), there were various outcomes (P<0.01), with the highest results in (P2) 2.20 ml compared to (P1) 2.09 ml, (P3) 1.93 ml, and (P0) 1.85 ml. This is in accordance with the research of Almodares et al. (2008) that in sorghum stalks, the content of unstructured carbohydrates increases during the pre-boot (before the development stage) and reaches a maximum level near the post-anthesis. Keywords: sorghum varieties, panicle pruning, glucose contents, stem juice (sap) production.