Field-grown ictB tobacco transformants show no difference in photosynthetic efficiency for biomass relative to wildtype

In this study, four tobacco transformants with the overexpression of inorganic carbon transporter B (ictB) were screened for photosynthetic performance relative to wild-type (WT) in field-based conditions. The WT and transgenic tobacco plants were evaluated for photosynthetic performance to determine the maximum rate of carboxylation (Vc,max), maximum rate of electron transport (Jmax), the photosynthetic compensation point (Γ*), quantum yield of photosystem II (ΦPSII), and mesophyll conductance (gm). Additionally, all plants were harvested to compare differences in above-ground biomass. Overall, transformants did not perform better than WT on photosynthesis, biomass, and leaf composition related traits. This is in contrast to previous studies that have suggested significant increases in photosynthesis and yield with the overexpression of ictB, although not widely evaluated under field conditions.