Cross-protection test with ‘CandidatusPhytoplasma mali’ 1/93 strain against closely and distantly related phytoplasma strains

Abstract

Putative inhibitory effect of ‘Candidatus Phytoplasma mali’ 1/93 mild strain was tested under greenhouse conditions against the related ESFY and the distantly related STOL and AAY strains of ‘Candidatus Phytoplasma prunorum’, ‘Candidatus Phytoplasma solani’ and ‘Candidatus Phytoplasma asteris’, respectively, which are responsible for serious damages and yield losses in fruit orchards across Europe. A consequent decrease of the DNA amount of the virulent GSFY strain analysed by PCR and Real-Time PCR could be observed when the plants were preliminary immunised by 1/93 strain. The cross-protection phenomenon proved to be effective between closely related strains, but no inhibition occurred among distantly related strains due to preliminary infection. Our results support that immunization with a mild, antagonist strain can be of phytopathological relevance in phytoplasmal researches.