Differential biochemical and physiological responses to cotton leaf curl virus infection in contrasting cotton genotypes

Cotton production is tremendously impacted by the cotton leaf curl virus (CLCuV) in the Indian subcontinent. Viral infection modifies physiological and biochemical processes in plants, which leads to the appearance of symptoms. Hence, the current study was to discern the quantifiable changes in physiological and biochemical parameters in leaves of cotton plants graft inoculated with CLCuV on different days after infestation (DAI). The results revealed that in the CLCuV-infected plants, the relative water content (RWC) and total soluble protein were decreased. Some enzymes involved in the activities like anti-oxidative and defence mechanisms such as polyphenol oxidase (PPO), catalase (CAT), phenylalanine ammonia-lyase (PAL), and peroxidase (POX) were increased as the infestation period progressed with a concomitant increase in gossypol and total phenolic level. Contents of total soluble sugar, chlorophyll (Chl) along with hydrogen peroxide (H₂O₂) were increased initially and decreased afterwards in all genotypes. Correlation analysis elucidates that RWC is negatively associated with electrolyte leakage (EL) and malondialdehyde (MDA) content. In contrast, Chl content showed a positive correlation with total soluble proteins, secondary metabolites like phenol and gossypol, anti-oxidative and defence enzymes. Three principal components (PCs) were produced by the principal component analysis (PCA) contributing 87.33% of the total variability in various physiological and biochemical traits of different genotypes. Phenolics profiling reveals that concentrations of rutin hydrate in the infected sample increased by 49.6% compared to the control one. Overall, the findings imply that CLCuV infection causes substantial changes in enzyme levels that result in the development of unrectifiable symptoms in susceptible genotypes.