The A3 cytoplasm mediated male sterility increased biomass, soluble solids, and total sugar in sweet sorghum hybrids

Sweet sorghum [Sorghum bicolor (L.) Moench] is listed as one of the viable high energy crops for use as feedstock in biofuel production and table sugar industry. Research has shown that eliminating the grain sink can remarkably increase stalk sugar buildup through reducing competition for assimilate. The objective of this study was to explore the opportunity for deploying the A3 cytoplasmic male sterility (CMS) system to achieve hybrid sterility and thereby increase sugar yield. Four seed parents in the A1 and A3 CMS systems were intercrossed with 10 diverse sweet sorghum lines to create 80 hybrids, 40 each in A1 (fertile) and A3 (sterile) backgrounds. All of the hybrids and their parents were evaluated in single row plot in three replicates across three environments using a randomized complete block design. Heads from all A3 hybrid rows were covered before anthesis to avoid seed set from random pollen. Data were collected on days to flowering and lodging on plot basis. At maturity, the entire above ground part in a one-meter section of each plot were harvested for measuring degrees Brix value, juice, biomass, and sugar yields. Significant differences were obtained among the hybrid entries, and between the A1 and A3 CMS systems for all biofuel traits. The A3 hybrids had 27, 29, 25 and 57 % higher degrees Brix value, biomass, juice yield and total sugar, respectively, than their corresponding A1 hybrids. They were also more resistant to stalk lodging. In conclusion, sterile sweet sorghum hybrids can be deployed using the A3 CMS system to allow accumulation of more biomass and sugar in the stalk.