Pathways to exploiting enhanced photosynthetic efficiency for higher sucrose and biomass yield

Abstract

Australia has one of the highest commercial cane sugar (CCS) levels in the world but unfortunately CCS appears to have plateaud at about 14% of fresh cane weight over the past 20 years. Up to now in breeding programs, increased fibre has been considered to have negative economic impacts because of adverse effects on sugar extraction and milling rate. It is possible that high fibre genotypes can produce higher biomass yields than high sucrose types because high sucrose content in the stalk may feedback negatively on photosynthesis either through end-product suppression or through sugar signalling compounds. This is now an assumption which is gaining acceptance through recent publications. Prior to this project this assumption had not been tested using high fibre and high sucrose clones. Feedback inhibition is also suspected to be the cause of the ‘reduced growth phenomenon’, a term applied to lower than expected biomass accumulation after a certain stage in crop development. This project aimed to establish the role of cane stalk sucrose in feedback inhibition of photosynthesis in order to reveal existing limitations to increasing sucrose content and biomass yield.