Application of chemicals and nutrients differs in bacterial titre of Candidatus Liberibacter asiaticus on infected Citrus sinensis (L.) Osbeck

Abstract

Huanglongbing (HLB), or citrus greening disease, is significant havoc to the citrus cultivation that influences citrus industry decline in India and elsewhere. HLB is a systemic, fastidious, phloem inhabited alpha-proteobacterial disease caused by ‘Candidatus Liberibacter asiaticus’ (CLas). Currently, there is no established cure for this emerging but century-old disease. The present study discussed change in cycle threshold (Ct) values of CLas bacterium using qPCR diagnostic method upon applying antibiotics and micronutrients to HLB infected sweet orange cv. Sathgudi plants. Five antibiotics and three micronutrients were selected and applied as a foliar spray in 3 different spraying periods. Results demonstrated that ampicillin sodium (Ct=25.41) and rifampicin (Ct=23.62) showed a significant effect on the suppression of bacterial titre compared to other selected antibiotics at 90 days after the first spray. However, there was no significant effect on the bacterial population regarding its titre and symptom expression when any of the selected micronutrients were applied in any of the spraying periods. Hence, the reported antibiotics could help in the management of an infected HLB citrus orchard at the expense of minimizing total yield loss when they are judiciously used.