Synthesis of a kinetin and graphene oxide nanoensemble and its effects on defense responses of cotton against Verticillium dahliae

In this study, a kinetin-graphene oxide nanoensemble (KN+GO) was synthesized via non-covalent interactions. Its structure and morphology were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and powder X-ray diffraction (XRD), confirming the successful immobilization of kinetin on graphene oxide. The loading efficiency of kinetin on GO was determined by UV–Vis spectroscopy. The effects of the KN+GO nanoensemble on the physiological and biochemical responses of two cotton genotypes (Gossypium hirsutum L. TM-1 and G. barbadense L. Pima 3-79) were investigated during infection with Verticillium dahliae. Morphometric traits, seedling survival, antioxidant enzyme activities (catalase, peroxidase, and polyphenol oxidase), nitric oxide and proline levels, and photosynthetic pigment composition were analyzed. Pathogen infection induced oxidative stress and significantly altered the growth and biochemical parameters in both genotypes. Free kinetin exhibited genotype-dependent effects, whereas the KN+GO nanoensemble consistently enhanced stress tolerance, particularly under pathogen pressure. In the TM-1 plants, KN+GO markedly improved seedling survival, increased antioxidant enzyme activity, promoted proline accumulation, and stabilized photosynthetic pigment levels. In the Pima 3-79 plants, the nanoensemble mainly supported survival and redox balance, although the responses were less pronounced. These findings demonstrate that graphene oxide–based kinetin nanoensembles modulate cotton defense responses in a genotype- and stress-dependent manner, highlighting their potential as nano-enabled phytohormone delivery systems for improving resistance to fungal pathogens.