Cauliflower is a New Host of a Subgroup 16SrVII-B Phytoplasma Associated with Stunting Disease in Brazil

Cauliflower stunt has occurred with high levels of incidence and caused significant yield reduction in Brazil (Canale and Bedendo 2013). A phytoplasma belonging to subgroups 16SrIII-J and 16SrXV-A (Canale and Bedendo 2013) were previously reported to be associated with the disease in Brazil. In 2014, plants with typical symptoms cauliflower stunt, characterized by stunting, reddening of leaves, malformation of inflorescences, and vessel necrosis were sampled in the state of Sao Paulo. Total DNA was extracted from stems obtained from six symptomatic and two asymptomatic plants and used as template in a PCR assay using primer pair fU5/rU3 (Lorenz et al. 1995). The result was consistent with phytoplasmal infection, as the expected 0.9-kbp amplicon was produced (GenBank Accession No. KT444690). To identify the putative phytoplasma, primers P1/16S-SR followed by P1A/16S-SR were used in seminested PCR assays (Lee et al. 2004). DNA fragments of 1.6 kpb were generated from DNA template from affected plants, confirming the association of phytoplasmas with symptomatic plants. Amplified products were purified and sequenced, using 10 primers to achieve 4x to 5x coverage per base position. A BLASTn search yielded a representative of the ash yellows group with 100% sequence identity, Artemisia witches'-broom phytoplasma (DQ989178) affiliated with 16SrVII-B subgroup. Virtual restriction patterns obtained by employing the i PhyClassifier online tool (Zhao et al. 2009) revealed complete identity between the electrophoretic profiles produced by the phytoplasma found in cauliflower and the representative of the 16SrVII-B subgroup. The DNA sequences from cauliflower phytoplasma demonstrated 100% similarity with those of Artemisia phytoplasma when aligned with MegAlign program (Lasergene software; DNASTAR). The phytoplasma isolated from diseased cauliflower and molecularly characterized in this study was designated CfS-Br10, and the respective 16S rDNA sequence was deposited in GenBank (KR270802). Thus, our findings revealed a distinct phytoplasma associated with cauliflower stunt, in addition to the two different phytoplasmas previously described for this pathosystem. Moreover, it was evidenced that similar symptoms may be induced in the same cauliflower host by distinct phytoplasmas, as previously found by others in different plant-phytoplasma interactions. In Brazil, representatives of the 16SrVII-B subgroup were first identified in erigeron and periwinkle plants (Barros et