Sugar metabolism of plant and ratoon crops in sugarcane

Investigation on the sugar metabolism through various enzymatic assay viz. sucrose phosphate synthase (SPS), sucrose synthase (SS), acid and neutral invertase (AI & NI) activities, carbon allocation in the form of reducing, non reducing and total sugar content in relation to juice quality of plant and ratoon crop was made in 11 sugarcane varieties during maturity phase. Results of the study revealed that, except acid invertase (AI), all these enzyme activity was significantly higher in ratoon crop as compared to plant crop. Though the AI activity negatively correlated with sucrose % juice both in plant (r = -0.562*) and ratoon crop (r = -0.235), the association found to be significant only in plant crop. Among the varieties studied, Co 94012, CoC 671, Co 86032 and Co 99004 showed higher brix %, sucrose % and purity % than rest. Differences between plant and ratoon and among the varieties in juice quality might be related to differences in activities of sucrose metabolic enzymes viz., SPS, SS, and AI & NI between plant and ratoon crops. Apart from these enzymes, higher carbon allocation particularly non reducing sugars towards economic sink might also contribute for high sugar in ratoon crop.