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Phytoplasmas were detected and identified in some tomato cultivation areas in Mauritius. Symptoms most frequently observed were abnormal shoot proliferation, stunting, reduced leaf and fruit size and shortened internodes. In field-grown tomatoes the incidence of abnormalities rarely exceeded 10%, but under hydroponics up to 100% incidence has been recorded. Two different phytoplasmas were identified by PCR/RFLP analyses. Field-grown tomatoes were infected with a phytoplasma belonging to ribosomal subgroup 16SrI-C and the hydroponically-grown tomatoes were infected with a phytoplasma belonging to ribosomal group 16SrV. Further studies need to be done in order to determine their occurrence, incidence, characterization, host range and mode of transmission, so that eventually the most effective method to control phytoplasma diseases will be determined.

Leaf and root samples of carrot, and flower samples of broccoli with symptoms referable to phytoplasma presence were collected and tested for phytoplasma presence. Detection, identification and molecular characterization were performed on 16S rDNA, Tuf, rpS3, putative aminoacid kinase and putative DNA helicase phytoplasma genes. Analyses of all five DNA fragments showed that carrot was infected with aster yellows phytoplasmas belonging to ribosomal subgroups 16SrI-A and 16SrI-B and broccoli only with phytoplasmas belonging to ribosomal subgroup 16SrI-B.

During 2006 and 2007 eight batches of seed potatoes collected in different locations, and belonging to one cultivar were planted in spring under greenhouse conditions and tested after 2 months to verify phytoplasma presence. A total of 635 asymptomatic plantlets were examined. Nucleic acid was extracted from small shoots from either a single plant or from batches of 3 plants each. Nested PCR on both single and grouped samples with general ribosomal primers, without spacer region allowed specific phytoplasma detection. Phytoplasmas belonging to diverse ribosomal groups were identified after RFLP analyses according to the batch tested. Ribosomal subgroups 16SrI-B (related to ‘Candidatus phytoplasma asteris’), 16SrI-C (related to clover phyllody: CPh), 16SrII-D (related to tomato big bud from Australia: TBB), 16SrX-A (related to ‘Ca. P. mali’), and 16SrXII-A (related to stolbur) were identified in different percentages. After further validation tests, the system can be used to screen high quality seed potatos for phytoplasmas.

Severe apple proliferation (AP) epidemics are spread in the most important apple growing areas in Europe with a significant economic impact on the production of marketable fruits. A genotype screening was undertaken on 41 apple cultivars and selections showing no phytoplasma-related symptoms to identify natural resistance or tolerance to ‘Candidatus Phytoplasma mali’. Among the tested cultivars or selections most of asymptomatic trees of cultivars Brina and Enova resulted to be positive to phytoplasma presence, while in selection CO-OP12 only one out of 34 tested plants resulted positive to AP infection.