Sugarcane Genotype Variation in Juice Sugar Composition As Affected By Sampling Date.

Harvest of sugarcane in Florida lasts more than 180 days from late October through mid April. Sugarcane juice sucrose content and extractable sugar composition are closely related to sucrose yield and quality. The objectives of this study were to determine dynamics of sugar components (glucose, fructose, and sucrose) in juice during maturity and to identify their variation among genotypes. Eighteen sugarcane genotypes were planted on a sand soil in December 2010 using a random complete block design with three replications. Juice samples were collected monthly in all plots using a handheld punch from September through February in the plant-cane and first-ratoon crops. Brix was determined using a digital refractometer. Juice sucrose, glucose, and fructose were quantified using the microplate enzymatic method. As sugarcane ripened from September through December, juice Brix and sucrose content rapidly increased while glucose and fructose contents sharply declined. Thereafter, no substantial changes in any of these variables were detected. Overall, the first-ratoon crop had 15% lower juice sucrose and 44% lower hexose (glucose + fructose) contents than the plant-cane crop. Juice hexose contents differed significantly among the cultivars and interactions of genotype × sampling date on sugar components were significant. These results provide useful information for growers to make decision of best harvest time for each cultivar for maximizing profits of production.