Citrus Huanglongbing correlated with incidence of Diaphorina citri carrying Candidatus Liberibacter asiaticus and citrus phyllosphere microbiome.

In China, citrus Huanglongbing (HLB) disease is caused by the Liberibacter asiaticus bacterium, which is carried by the Asian citrus psyllid Kuwayama. It was hypothesized that the epidemic of the HLB may related with the rate of bacterium presence in the insect vector and bacterium content in plant tissues, as well as the phyllosphere microbe communities changes. This study systematically analyzed the presence or absence of L. asiaticus in citrus tree leaves and in the insect vector over a 6-year period using real-time PCR. In addition, changes in the number of bacteria carried by over 12 months were quantified, as well as the relationship between the proportion of carrying L. asiaticus and the proportion of plants infected with L. asiaticus were analyzed. Results showed that the proportion of carrying bacteria was stable and relatively low from January to September. The bacteria in citrus leaves relatively low in spring and summer, then peaked in December. The proportion of carrying bacteria gradually declined from 2014 to 2019. The proportion of carrying L. asiaticus showed a significant positive correlation with the proportion of diseased citrus. The phyllosphere bacterial and fungal communities on the healthy citrus leaf were significantly different with the disease leaf in April and December. Pathogenic invasions change the citrus phyllosphere microbial community structure. It could be summarized that citrus Huanglongbing correlated with incidence of carrying Liberibacter asiaticus and citrus phyllosphere microbiome.