| Popis: |
“Huanglongbing” (HLB) is one of the most devastating diseases of citrus orchards worldwide. Samples from about 200 citrus plants of different cultivars and rootstock/cultivar combinations, showing HLB symptoms in Cuba, Jamaica and Guadeloupe-France, were tested to verify the possible presence of 'Candidatus Phytoplasma' in 'Candidatus Liberibacter asiaticus' infected species. About the 14% of the samples infected with 'Ca. Liberibacter' were also found positive to phytoplasmas, indicating the presence of mixed infection especially in the orchards located in Cuba. Moreover, in one of the samples from Jamaica mixed phytoplasma infection was detected. Further, the detection of only phytoplasmas in several symptomatic citrus samples collected from Cuba and Guadeloupe, confirmed that the symptomatology cannot be the sole criterium to discriminate between the presence of the two pathogens, and molecular identification of the bacteria is necessary to verify the sanitary status of symptomatic plants. Diaphorina citri insects collected in Cuba and Guadeloupe resulted positive to the 'Ca. L. asiaticus' presence confirming its active role in the dissemination of the pathogen in the Caribbean areas. Only one insect of the Cicadidae family, collected in Guadeloupe, was found positive for phytoplasma presence. Phytoplasmas enclosed in groups 16SrI and 16SrXII were identified in all the three islands; the 16SrII, 16SrIV, 16SrVII, 16SrX and 16SrXI groups were present in both Guadeloupe and Cuba. This could indicate that the surrounding cultivated species are influencing the phytoplasma population composition in citrus orchards as indicated by the relevant presence of the lethal yellowing phytoplasmas that was severely affecting the Cuban palm plantations in the past. Moreover the identification of phytoplasmas enclosed in groups 16SrIII, 16SrVI and 16SrIX only in Guadeloupe and of 16SrXV group only in Cuba is corroborating this hypothesis (Bertaccini et al., 2019; Luis-Pantoja et al., 2021). Considering that diverse 'Candidatus Phytoplasma'-related species were detected in the three countries in different citrus varieties, a relevant role as phytoplasma reservoir can be attributed to citrus orchards for the natural and agricultural ecosystems. |
