Polymerase Chain Reaction -based Diagnosis of Citrus Huanglongbing Disease in Nepal

Huanglongbing disease (HLB) or citrus greening disease (CGD) is the number one threat to the citrus production of Nepal. The greening organism produces leaf mottle symptoms, but they are not specific for confirmative diagnosis. The pathogen cannot be cultured in artificial medium that makes its diagnosis more complicated. In this context quick and reliable polymerase chain reaction (PCR)-based molecular diagnosis of this disease is crucial. In the present investigation, two PCR-based assays viz. one based on 16S ribosomal DNA (rDNA) and another based on ribosomal protein gene from the  b operon (rpl KAJL-rpoBC) of HLB oganism were used to diagnose HLB disease in suspected citrus samples collected from 10 districts of Nepal. Out of 198 samples tested, 38 were detected positive for HLB. Of the 10 districts studied, eight were found infested with HLB disease. Result of the present preliminary study on distribution of HLB disease in Nepal highlights the alarming potential threat to citrus industry of Nepal. In order to save Nepalese citrus industry this disease has to be properly understood not only by the scientific community but by all those who are directly or indirectly involved (planners, business people, nurserymen and farmers) in citrus cultivation in Nepal. This paper highlights the importance of PCR-based diagnosis of HLB for the integrated management of this disease in Nepal