Occurrence of ‘Candidatus Phytoplasma omanense’-related strains and other phytoplasmas in Sophora alopecuroides plants showing dwarfing and yellowing

Abstract

Sophora alopecuroides dwarfing and yellowing symptoms were observed at the edge of several Damaneh and Fereydun Shahr (Isfahan province, Iran) fields. Polymerase chain reaction using primers P1/P7 and nested PCR using the same primers followed by R16mF2/R16mR2 and R16F2n/R16R2 primer pairs amplified the 16S ribosomal RNA-encoding gene in all the symptomatic plants tested, but not in the asymptomatic ones. RFLP analysis of R16F2n/R16R2 amplicons with AluI, HaeIII, HhaI, HpaI, HpaII, RsaI, MseI and TaqI restriction enzymes showed profiles referable to 16SrII, 16SrVI, 16SrIX, 16SrXII and 16SrXXIX phytoplasma ribosomal groups indicating also the presence of mixed infection in several samples. The identity percentage and the phylogeny obtained after direct sequencing of selected 16S rRNA-encoding gene sequences (R16F2n/R2 amplicons) from symptomatic S. alopecuroides confirmed the presence of phytoplasma strains related to ‘Candidatus Phytoplasma omanense’ (group 16SrXXIX), ‘Ca. P. australasia’ (group 16SrII), and ‘Ca. P. trifolii’ (16SrVI). Moreover, in a few samples/amplicons, 16SrXII-A, 16SrIX-H, 16SrVI-F and 16SrXXIX-A phytoplasma subgroups were identified by real and virtual RFLP analyses. The other phytoplasmas detected were classified in subgroups 16SrII-D and 16SrVI-A. This is the first report of the presence of 16SrII and 16SrXXIX phytoplasma groups and of mixed infection of phytoplasma strains belonging to groups 16SrII, 16SrVI, 16SrIX, 16SrXII and 16SrXXIX in S. alopecuroides worldwide.