Molecular Identification of Co-infection with '<i>Candidatus</i> Phytoplasma' and Velarivirus 1 in Areca Palms on Hainan Island, China

Areca palm yellow leaf phytoplasma (AYLP) and Areca palm velarivirus 1 (APV1) are two critical pathogens associated with yellow leaf in areca palm, resulting in devastating damage to areca production. However, evidence of their co-infection remains unclear. Areca palms showing yellow leaf symptoms (suspected to be caused by phytoplasma and velarivirus 1) were surveyed and sampled around Hainan Island of China and the pathogens were identified and analyzed in the study. The results showed that infectious leaf yellowing symptoms of areca palms primarily occurred in eastern and southern cities and counties of Hainan Island. Molecular identification revealed co-infection of 'Candidatus Phytoplasma asteris' (16SrI-B subgroup) and APV1 in individual areca palm samples. Among 520 samples tested by qPCR, AYLP was detected in 23.46% (n=122), APV1 in 53.46% (n=278), and a co-infection with both AYLP and APV1 in 10.96% (n=57). A statistically significant difference in APV1 detection rate was observed between asymptomatic and symptomatic plantations (P < 0.0001), suggesting APV1 infection likely represents an important risk factor for yellowing development in cultivated areca palm populations. These results confirm the co-infection of AYLP and APV1 on Hainan Island, offering epidemiological evidence for targeted disease management.