Comparative biochemical and physiological responses to the virus-induced mosaic disease in apple (Malus domestica)

The apple crop, integral to global agriculture, is facing a significant challenge in the form of mosaic disease, reducing productivity, particularly in temperate regions of the world. The intricate biochemical and physiological responses of apple genotypes to mosaic infection induced by apple mosaic virus (ApMV)/apple necrotic mosaic virus (ApNMV) were investigated in this study. Higher phenolic contents, DPPH, flavonoids and flavanols were recorded from mosaic-infected apple genotypes in comparison with their respective counterparts. The impact on carbohydrates/total starch and chlorophyll content revealed a substantial reduction in mosaic-infected as compared to healthy leaves, which emerges as a quantitative biomarker for measuring infection severity and offering insights into the compromised photosynthetic ability of infected leaves. In mosaic-infected genotypes, PAL activity, malondialdehyde and antioxidant enzymes were greater, strengthening the powerful antioxidative defense mechanism against mosaic infection. Principal component analysis provided a comprehensive overview, identifying key biomarkers and elucidating the underlying biochemical processes linked with apple mosaic disease. This research provides significant insights for future apple breeding programs by providing a more detailed knowledge of the biochemical intricacies underpinning plant defense systems against mosaic infection in apples.