Increased Photosynthetic Activity and Hypoxic Stress Causes Variation in Biomass Accumulation in Allopolyploid Sugarcane Hybrids

Concerns for climate change and quest for sustainable energy source has accelerated search eforts for high biomass yielding plant species/varieties. Plant based fuels recycle atmospheric carbon, have reduced carbon footprint and are sustainable. Majority of ethanol is fermented from plant sugars which comes from starch or grain-based feedstock e.g. corn and sugarcane. Sugarcane is a fast growing C4 plant adapted to suboptimal environment and has high potential to serve as bioenergy crop. Saccharum spontaneum is a highly adaptive wild sugarcane and the major source of germplasm for vigor, hardiness, tillering, ratooning ability, drought tolerance, disease and pest resistance. Saccharum officinarum, also known as noble cane, is major source of germplasm for high sugar trait. We used a segregating F2 population developed from selfing of 3 F1s derived from a cross from LA-Purple (S. officinarum) x US56-14-4 (S. spontaneum), for the identification of genes affecting biomass production. The developed population segregated for dry weight and stalk volume and several progenies outperformed the parents for biomass yield. The high biomass yielding individuals had photosynthesis and major carbohydrate biosynthesis related processes enhanced. In contrast low yielding sugarcane individuals suffered from hypoxia which led to the upregulation of genes for fermentation and carbohydrate degradation related bioprocess. The hypoxic stress in low yielding sugarcane most probably originated from aggregation of deleterious alleles and not due to environmental factors causing low oxygen availability to the plants. These results will accelerate breeding process to select for high biomass yielding varieties using expressed QTLs in sugarcane.