Effect of different combinations of antibiotics on fruit quality and antioxidant defense system in Huanglongbing infected Kinnow orchards.

Huanglongbing (HLB), also known as citrus greening disease, is the most devastating disease of citrus across the world, caused by the phloem limited fastidious bacterium 'Candidatus Liberibacter spp.'. This research was conducted on HLB infected 10-year-old Kinnow orchard located at Multan, Pakistan. Different classes of antibiotics in various combinations were applied on HLB-infected trees. The antibiotic treatments were applied before flowering in February, during fruit setting in April and at fruit growth stage in June. The different antibiotics combinations used were Ampicillin sodium + Rifampicin, Cefalexin + Rifampicin, Ampicillin sodium + Cefalexin, Ampicillin sodium + Cefalexin + Rifampicin and Control (distilled water). Different fruit qualitative and quantitative attributes were examined. The application of antibiotics significantly decreased 2-11% in flower, June and pre-harvest drops as compared to control. Further, antibiotics increased fruit weight and yield by five times while the juice content, total soluble solids, ripening index, total sugars, phenolic and vitamin C content were also increased in fruits. In addition, total soluble proteins, peroxidase and catalase activities were increased in fruits harvested from antibiotic treated plants compared to control, however the superoxidase dismutase activity was decreased in fruits of antibiotic treated plants. Finally, it is concluded that application of different antibiotics combinations helps in improving the fruit yield and different quality attributes of HLB infected Kinnow trees.