Transmission by patch grafting of esfy phytoplasma to apricot (prunus armeniaca l) and japanese plum (prunus salicina lindl)

Apricot and Japanese plum plants belonging to diverse varieties obtained after grafting buds from mother plants survived to a natural severe phytoplasma outbreak were employed to test efficiency of phytoplasma transmission in experimental conditions. Three years old plants were patch-grafted with ESFY apricot infected tissue, maintained under insect-proof environment, and after one year and half from the grafting, tested to verify phytoplasma presence. Nested PCR with primers amplifying general and group specific ribosomal sequences followed by RFLP analyses to identify phytoplasmas was carried out. The presence of phytoplasma specific DNA bands was observed in positive samples examined after nested PCR using the R16(X)F1/R1 primers that gave specific products of 1.1 kb. No amplification was obtained from the reaction mixture devoid of nucleic acid template and when the PCR products were reamplified with the other group specific primer pairs. Patterns obtained from RFLP of sequences amplified were indistinguishable from one another and are identical to those of ACLR (16SrX-B) phytoplasma strain. The transmission by patch grafting was verified in five apricot varieties out of ten and in all the Japanese plum varieties used. The only symptoms on infected apricot trees were in some varieties show new, little leaves at the base of the grown-up ones and dead of young branches. In Japanese plum only one variety show witches' broom.