First report of elm yellows subgroup 16SrV-B phytoplasma as the cause of rose balsam phyllody in China.
In August 2012, some rose balsams (Impatiens balsamina) were observed with typical phytoplasma symptoms in Handan City, Hebei Province, China, with an incidence of ∼70% in the fields. The flowers turned green and petals fascicled. The new leaves wrinkled and deformed and internodes shortened. Infected plants were stunted, matured prematurely, and failed to produce seeds. To confirm phytoplasma infection, 100 mg of plant tissue (leaves, petals) was collected from five symptomatic and four asymptomatic plants. Transmission electron microscopy showed phytoplasma-like cells in phloem sieve element of symptomatic plants, while no phytoplasma-like cells were observed in healthy phloem tissues. The phytoplasma cells ranged from 230 to 470 nm in diameter and were ellipsoidal or orbicular with visible membranes. Based on the restriction fragment length polymorphism pattern and sequence analysis by iPhyClassifier, the phytoplasma causing rose balsam phyllody was classified into subgroup 16SrV-B. This is thought to be the first report of 16SrV-B group phytoplasmas infecting rose balsam in China.