Molecular Identification of a Candidatus Phytoplasma asteris Associated with Cabbage Witches’-Broom in China

Abstract

In 2010, cabbages (Brassica oleracea L.) showing symptoms of proliferated axillary buds, crinkled leaves and plant stunting with shortened internodes typical to phytoplasma infection were found in a breeding facility in Beijing, China. Three symptomatic plants and one symptomless plant were collected, and total DNA was extracted from the midrib tissue and the flowers. With phytoplasma universal primers R16F2n/R16R2, a special fragment of 1247 bp (16S rDNA) was obtained from all three symptomatic cabbage plants, but not from the one symptomless cabbage plant. The 16S rDNA sequence showed 99% similarity with the homologous genes of the aster yellows group phytoplasma (16SrI group), and the phytoplasma was designed as CWBp-BJ. Phylogenetic and computer-simulated restriction fragment length polymorphism (RFLP) analysis of the 16S rDNA gene revealed that CWBp-BJ belongs to subgroup 16SrI-B. This is the first report of a phytoplasma associated with cabbage witches’-broom in China.