First Report of Clover Yellow Edge and STRAWB2 Phytoplasmas in Strawberry in Maryland

Commercial strawberry (Fragaria × ananassa Duchesne) plants that were either chlorotic and severely stunted or exhibiting fruit phyllody were collected in Maryland. The plants were assessed for phytoplasma infection by nested polymerase chain reactions primed by phytoplasma universal primer pairs R16mF2/R1 and F2n/R2 (2) or P1/P7 (3) and F2n/R2 for amplification of phytoplasma 16S ribosomal (r) DNA (16S rRNA gene) sequences. Phytoplasma-characteristic 1.2-kbp DNA sequences were amplified from all diseased plants. No phytoplasma-characteristic DNAs were amplified from healthy plants. Restriction fragment length polymorphism patterns of rDNA digested with AluI, KpnI, HhaI, HaeIII, HpaII, MseI, RsaI, and Sau3A1 endonucleases indicated that chlorotic and stunted plants were infected by a phytoplasma that belonged to subgroup 16SrIII-B (clover yellow edge [CYE] subgroup) and that the plant exhibiting fruit phyllody was infected by a phytoplasma that belonged to subgroup 16SrI-K (STRAWB2 subgroup). The STRAWB2 phytoplasma was first reported from strawberry plants grown in Florida and characterized as representative of a new subgroup of the aster yellows group, 16SrI (3); this is the first report of this phytoplasma occurring in strawberry outside of Florida. A STRAWB2-infected plant produced phylloid fruits in two consecutive years of observation in the greenhouse; the plant previously had been field-grown in a breeder's evaluation plots in Beltsville, MD. The CYE phytoplasma was first experimentally transmitted by leafhopper to commercial strawberry and F. virginiana Duchesne in Ontario Canada (1); this is the first report of natural CYE phytoplasma infection of strawberry in Maryland. CYE phytoplasma-infected plants, representing ≈5% of the total number of plants of one advanced sselection, were located in a breeder's evaluation plots in Beltsville. References: (1) L. N. Chiykowski. Can. J. Bot. 54:1171, 1976. (2) D. E. Gunderson and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996. (3) R. Jomantiene et al. Int. J. Syst. Bacteriol. 48:269, 1998.