Location: Crop Diseases, Pests and Genetics Research
Title: Detection of bacteria in Asian citrus psyllid and citrus trees in addition to HLB pathogenAuthor
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 10/6/2021 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Citrus Huanglongbing (HLB) is associated with an unculturable bacterial pathogen,‘Candidatus Liberibacter asiaticus’ (CLas). HLB was found in southern California in 2012 and the current management strategy is based on suppression of the Asian citrus psyllid (ACP) that transmits CLas and removal of confirmed CLas-positive trees. CLas in ACP and citrus is detected using PCR technology based on the characteristic sequence of DNA, typically 16S rDNA, in the CLas genome. Recent research has shown that in ACP and citrus, there can be bacteria other than CLas present. Most of these non-CLas bacteria are poorly known or unknown. Some of the non-CLas bacteria are close relatives to CLas and may interfere with CLas PCR detection. We recently developed a procedure using a technology called metagenomic analysis to detect and identify non-CLas bacteria in samples being tested for CLas. With assistance from CDFA and CRB, five ACP and two citrus samples were obtained from HLB quarantine zones for these experiments. From these samples, nine bacteria along with CLas were identified with high confidence by full or partial bacterial genome sequences. Two of these bacteria, from the genus of Bradyrhizobium and Mesorhizobium, are known to be phylogenetically related to CLas. These bacteria, if present in high concentration, could cross-react with a key PCR component, particularly when CLas concentration is low or absent, and result in a false positive result for CLas. |
