Indagini epidemiologiche su ‘Candidatus Phytoplasma asteris’ in colza

The presence of ‘Candidatus Phytoplasma asteris’ in oilseed rape already reported in Italy was studied to verify its epidemiological aspects using three cultivars: PR45D01, Excalibur and Catalina. In particular results of analyses carried out to verify germination ability for this phytoplasmas/plant species show that seeds from infected plants have 77.3%, while seeds from asymptomatic plants 89.8% and commercial seeds 93.9%. Seedlings from infected mother plants show malformation, stem thickening, leaf yellowing, however no significant differenced were reported between these plants and seedlings from healthy mother plants in both weight and amount of vegetation. Molecular analyses carried out during the vegetation period show that 40% of seedling from infected mother plants was positive to ‘Ca. P. asteris’. Seedlings from asymptomatic mother plants was positive in 22% of the cases to phytoplasmas allowing to speculate an field-insect transmission or a latent infection in mother plants. Among the insect species collected in infected fields Macrosteles quadripunctulatus, Psammottetix alienus, P. confinis, P. striatus and Toya propinqua, resulted to carry 16SrI phytoplasmas. Phytoplasma infected plants are able to produce seed, seedlings produced were highly infected with same phytoplasma. This can explain the geographic spreading of the disease in non infected areas and the presence of numerous potential insect vector can be the way to further disseminate the disease producing eventually serious epidemic. Research are in progress to verify the roles of both transmission ways in the epidemiology of winter oil seed rape phytoplasmas disease epidemiology.