Detection of Potato spindle tuber viroid sequence variants derived from PSTVd-infected Phelipanche ramosa in flower organs of tomato plants

Potato spindle tuber viroid (PSTVd) is an infectious small, circular, non-coding single-stranded RNA that induces disease on many crop species, ornamental plants, weeds and parasitic plants. PSTVd propagate in their host as a population of closely related but non-identical RNA variants referred to as quasispecies. Recently, we have described three de novo arising PSTVd variants in the parasitic plant Phelipanche ramosa after mechanical inoculation with the PSTVd KF440-2 isolate. These P. ramosa derived mutants were designated as G241-C, C208-U and C227-U PSTVd variants. Each of these variants carries a single-nucleotide substitution compared to the PSTVd KF440-2 sequence from which they are considered to have evolved. Here we complement our previous studies on these mutants by exploring their potential to infect the floral organs of tomato plants. We found that the PSTVd G241-C and C208-U variants were able to replicate in systemic leaves and floral organs of tomato plants, while the PSTVd C227-U variant did not develop systemic infection. Furthermore, we analysed the progeny of these PSTVd variants in sepals and petals of tomato plants for retention of the specific mutations.