Photosynthetic characteristics of upland cotton (Gossypium hirsutum) recessive genic male sterile line YA-1 with virescent trait.

The upland cotton strain YA-1 can be used for hybrid seed production and recurrent selection. However, the effect of YA-1 virescent phenotype on photosynthetic traits remains unclear. This study demonstrated that the chlorophyll and carotenoid contents, light-saturation point, light-compensation point, and PSII reaction center activities are lower than those of green leaves of wide type. In contrast, light-energy utilization efficiencies, net photosynthetic rate, transpiration rate, stomatal conductance, concentrations of Rubisco and phosphoenolpyruvate carboxylase, photosynthetic performance indices, and energy distribution parameters of the yellowish leaves of YA-1 are higher than those of wild type green leaves. The lower expression of GhHemL, GhSGRL, and GhCAO genes impairs chlorophyll biosynthesis, while the downregulation of GhZEP and GhNCED disrupts carotenoid biosynthesis, altering the pigment composition in yellowish leaves. The yellowish phenotype of YA-1 had significant positive effects on photosynthetic efficiency. This finding provides a valuable basis for optimizing the use of YA-1 in cotton breeding programs.