Variability and heritability of photosynthetic traits in Saccharum complex

Sugarcane ( Saccharum spp.) is one of the main alternatives for the bioenergy sector due to its great potential for phytomass production, being the photosynthesis a key process related to conversion of the intercepted sunlight energy into phytomass. The aim of this study was to investigate the photosynthesis of nine sugarcane varieties originated from crosses between 1948 and 2006, as well as the species Saccharum officinarum , S. spontaneum and S. robustum . In plants grown inside a growth chamber, photosynthetic response curves to increasing air CO 2 concentration were performed and key photosynthetic traits and their heritabilities were estimated. Fourteen physiological traits explained ~ 95% of the variation observed. Significant differences were found in leaf CO 2 assimilation at air CO 2 concentration of 1500 ( A 1500 ) and 400 ( A 400 ) μmol mol −1 among sugarcane genotypes, with S. spontaneum , IAC87-3396 and RB83-5486 presenting the highest photosynthetic rates. Sugarcane photosynthesis was strongly correlated with effective quantum yield of photosystem II (r = 0.93), non-photochemical quenching (r = − 0.74), stomatal conductance (r = 0.87), in vivo maximum carboxylation rates of PEPC ( V pmax , r = 0.83) and Rubisco ( V cmax , r = 0.91) and leaf nitrogen content (r = 0.83). The heritability varied from 0.97 (leaf CO 2 assimilation) to 0.84 (leaf area). The A 1500 : A 400 ratio higher than one for all genotypes indicates that Rubisco carboxylation sites are not saturated by CO 2 and a non-efficient CO 2 concentration mechanism. This study revealed a significant natural genotypic variation in sugarcane photosynthesis with high heritability of important traits, suggesting the possibility of breeding for increased photosynthetic activity.