Exploiting pre- and post-harvest metabolism in sweet sorghum genotypes to promote sustainable bioenergy production

Sweet sorghum's high yielding ability, low-input demands and tolerance to stresses, render it highly suitable for syrup and bioenergy production. Exploiting its biomass, however is hampered by the seasonality of its production and the rapid post-harvest sugar catabolism degrading biomass quality. We aimed at elucidating aspects of sweet sorghum's metabolism at different developmental and post-harvest stages, to investigate possibilities of expanding the harvesting window. GC–MS-mediated metabolic profiling was employed to monitor changes across growth stages and targeted transcriptomic analysis was used to determine the expression of genes involved in sucrose metabolism. Changes were studied both in the leaves and stems before, during and after the stage considered as optimum for harvest, whereas harvested stems were analyzed to determine post-harvest changes. Significant alterations in the levels of sugars, amino acids and organic acids were found, sugar levels attaining a maximum at soft dough stage. Overall data suggest that sugar metabolic content is regulated at transcriptional level, while temporal regulation of development and sucrose metabolism is under strong genotypic dependency. Although total sucrose levels were relatively lower at stems harvested one month past the optimum stage or harvested on time and piled for one month, compared to the optimum stage, losses encountered are adequately compensated by the prolonged period of biomass supply to the processing plants. It becomes evident that fine tuning of crop's harvesting and delivery time could significantly contribute to relaxing seasonality-related bottlenecks, thus upgrading the economic operation of plants utilizing sweet sorghum as a bioenergy crop. © 2020 Elsevier B.V