Comparison of Stem Damage and Carbohydrate Composition in the Stem Juice between Sugarcane and Sweet Sorghum Harvested before and after Late Fall Frost

A late fall frost may significantly affect sugar crops’ stem sugar composition, yield and juice quality for biofuel and bioproduct manufacture. Research on the effects of late fall frost in sugarcane is well documented, but information is lacking for sweet sorghum. Three and six commercial cultivars of sugarcane and sweet sorghum, respectively, were selected and evaluated for exposure to a late fall frost (-2.8&degC) in Griffin, Georgia, USA. Under the same controlled environmental conditions in a screen house, the late fall frost induced more damage to sugarcane than sweet sorghum stems. The frost caused damage to sugarcane tissue and for juice to exude from stems, whereas similar behavior was not observed for sweet sorghum. In both sugarcane and sweet sorghum, the glucose/fructose ratio was significantly reduced, but this change may not be totally directly related to the frost effect. Overall, these initial results suggest that sweet sorghum may have a better tolerance to fall frost than sugarcane. Two sweet sorghum cultivars, Grassl and M81E, responded well to the late fall frost, and they can possibly be used as feedstocks for biofuel/bioproduct manufacture in areas susceptible to frosts including northern regions of the Southeastern US.