Genetic diversity among phytoplasma strains infecting Citrus and coconut in Cuba

Lethal yellowing diseases are among the most important diseases affecting palms worldwide. The lethal yellowing phytoplasmas affecting coconut in Cuba were enclosed in the 16SrIV group and the presence of phytoplasmas in this ribosomal group was detected also in coinfection with phytoplasmas belonging to other ribosomal groups. Recently a mixed infection of ‘Candidatus Liberibacter asiaticus’ with several phytoplasmas (including the 16SrIV phytoplasmas) was reported also in citrus in Cuba. The objective of this study was to determine the genetic diversity of the strains of ‘Ca. Phytoplasma palmae’ detected in citrus and in coconuts. HLB-symptomatic leaf samples of citrus were collected from Jaguey Grande, Matanzas province. The 58 samples were tested to detect ‘Ca. L. asiaticus’ and phytoplasmas using the 16S ribosomal and the groEl genes. The characterization of citrus infecting phytoplasma strains confirmed the relationship with some of the strains detected previously in coconut. This finding is suggesting the lack of specificity in ‘Ca. P. palmae’ strains indicating that their presence in the agroecosystems could represent a threat also to citriculture. Additionally, the presence of phytoplasma strains in group 16SrIX was detected for the first time in Cuba in some of the sampled citrus. All these elements makes it necessary to perform deeper and accurate surveys on phytoplasma presence in Cuba as basis to understand epidemiology of these bacteria associated diseases in the different agroecosystems and to devise the best management practices.