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 <i>GhHemL</i>, <i>GhSGRL</i>, and <i>GhCAO</i> genes impairs chlorophyll biosynthesis, while the downregulation of <i>GhZEP</i> and <i>GhNCED</i> 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.