Effects of Elevated Temperature and CO2 on Biomass and Sucrose Accumulation of Selected Sugarcane Genotypes

Global warming cause due by increasing atmospheric CO₂ concentration, and the resulting increase in air temperature is a considerable challenge in crop production. Hence, the objectives of this study were to determine the: (a) responses of biomass and sucrose accumulation of sugarcane to elevated CO₂ (ECO₂) and elevated temperature (ET_a), both individually and together, and (b) genotypic variation of these responses. A three-factor factorial experiment considering the combination of CO₂ concentrations and temperatures as the main-plot factor and eight sugarcane varieties as the sub-plot factor arranged in a split-plot design in open-top chambers. Plots in open field conditions were the negative control. The main plot factor had four levels, combinations of ambient/elevated CO₂ concentrations (344-351/777-779 ppm) and ambient/elevated temperatures (34.9-35.6/36.6-38.4°C). Significant treatment × variety interaction effects observed on the number of shoots per hill, sucrose% (Pol), and pure obtainable cane sugar (POCS) in cane juice. Genotypic variations were significant in all variables measured. Elevated T_a increased the number of shoots per hill in 4 out of 8 varieties. Biomass accumulation of sugarcane on the dry weight basis did not respond clearly to the simulated future climatic conditions. The response of Pol and POCS to ECO₂ and the combination of ECO₂ and ET_a varied depending on varieties with decreased, increased, or no response. Notably, Pol and POCS in the variety SL88116, which had higher respective values at ambient and simulated future climatic conditions, were not affected by either ECO₂ or ET_a individually or in combination. The responses and the significant genotypic variation observed in sucrose accumulation to ECO₂ and ET_a, both individually and together, demonstrate considerable scope in sugarcane to breed varieties to maintain the stability of sugar recovery in CO₂-rich warm climates.