Morpho-chemical characterization of Huanglongbing in mandarin (Citrus reticulata) and orange (Citrus sinensis) varieties from Pakistan

Huanglongbing (HLB) is one of the world's worst diseases of citrus trees. The research was conducted to characterize positive citrus samples of two local varieties, 'Kinnow' mandarin (Citrus reticulata Blanco) and 'Mosambi' orange (C. sinensis (L.) Osbeck), based on morphological, physical and biochemical characters. Physical and biochemical parameters of greening infected and healthy samples of both the cultivars were significantly different. Citrus fruits were lopsided and half to full green in the HLB infected trees compared to healthy. The HLB infected leaves samples were small and narrow. Fruit diameter, leaf area, and juice weight of HLB infected samples were significantly less than healthy samples. The rind thickness of infected fruits (70% and 80%) was significantly higher than healthy ones (20% and 30%). Starch content of leaves from mandarin (5.54 mu g mL(-1)) and orange (6.12 mu g mL(-1)) were significantly higher in HLB infected plants, while juice percentage of HLB infected fruit samples was lesser in mandarin and orange (22.73%, and 14.70%, respectively) than healthy fruits (38.22% and 31.30%, respectively). Acidity was significantly increased in juice of HLB infected mandarin and orange fruits (0.57%, and 0.53%, respectively). Similarly, there was significant reduction in biochemical parameters; total sugars in mandarin and orange (5.16% and 4.79%), total soluble solids (8.54% and 8.28%), total chlorophyll (13.50 and 14.92 mg mL(-1)) and ascorbic acid (34.28% and 34.12%) in HLB infected samples of both cultivars. This study determined differences of physical and biochemical parameters of two local citrus varieties, commonly cultivated in the Asian region.