Wednesday, November 7, 2007
261-10

Effect of Recurrent Selection for Sucrose on Growth and Sugar Accumulation in Sugarcane internodes.

Sarah Lingle, Thomas Tew, Ryan Viator, and Richard Johnson. USDA-ARS, USDA-ARS, 1100 Robert E Lee Blvd, New Orleans, LA 70124

Commercial sugarcane cultivars are complex, polyploid, interspecific hybrids, primarily of S. officinarum and S. spontaneum. Most breeding programs need about twelve years to develop a new cultivar. Since the 1920's, Louisiana sugarcane breeding programs have used recurrent selection to improve sucrose yield, a product of cane yield and juice sucrose content. We were interested in how this recurrent selection program had changed growth and sugar accumulation of sugarcane internodes. In this study, we sampled internodes 2, 5, 8 and 11 from the top of five cultivars each from the first (old) and seventh (new) cycle of recurrent selection for sucrose. The cultivars were planted in November 2004, and sampled 3-4 November 2005. The internodes were measured, weighed, freeze-dried, weighed again, and then ground to a 1 mm screen using a Wiley mill. Simple sugars (glucose, fructose and sucrose) were extracted in 80% ethanol and quantified by high performance anion chromatography with pulsed amperometric detection. On average, internodes of the old cultivars were longer than internodes of the new, but the new cultivars accumulated more sugar, suggesting that recurrent selection for sucrose has altered the partitioning of assimilate between growth and storage. Internodes of new cultivars also had a higher sucrose:total sugar ratio than internodes of old cultivars. Since this ratio is an indication of maturity in sugarcane, the new cultivars appear to mature faster than the old cultivars. We conclude that recurrent selection to improve sucrose yield has had fundamental effects on growth and sugar accumulation in sugarcane internodes.