Elucidate the Impact of Rust Infection on Primary Metabolic Processes in Phyllanthus emblica

This study investigated the effect of rust infection on primary metabolic processes in Phyllanthus emblica (Aonla), a nutritionally important fruit crop known for its exceptionally high vitamin C content and medicinal value. Rust disease, mainly caused by Ravenelia emblicae, is one of the most destructive foliar diseases affecting Aonla cultivation and often leads to severe reductions in plant vigor, photosynthetic efficiency, and fruit quality. The experiment was evaluating rust-induced changes in photosynthetic pigments, carbohydrate metabolism, protein and lipid composition, and important fruit quality parameters across different genotypes. Principal Component Analysis (PCA) under healthy conditions revealed that the first two principal components explained 91.80% of the total variation (PC1: 81.75%, PC2: 10.05%), indicating strong genetic differentiation and coordinated metabolic activity among the genotypes. Genotypes G13 (NA-25) and G12 (NA-26) exhibited superior biochemical performance, recording the highest values for vitamin C, total sugars, chlorophyll, carotenoids, and total soluble solids. Strong positive associations among sugars, proteins, fats, fiber, pectin, acidity, and antioxidant pigments indicated efficient photosynthetic activity and stable metabolic balance, contributing to improved fruit quality and nutritional value. Under infection, PC1 and PC2 explained 91.39% of the total variation (PC1: 82.14%, PC2: 9.25%), suggesting that disease stress strongly influenced biochemical variability. Rust infection caused substantial reductions in biochemical traits, including nearly 50% decline in vitamin C, up to 70% reduction in chlorophyll, and about 60% loss of carotenoids, along with decreases in sugars, proteins, fats, fiber, and pectin. These changes indicate metabolic imbalance and deterioration of fruit quality under rust stress.