Abstract
Symptoms of stunting (shortening of internodes), twisting and flat stem (the fasciation of a stem), discoloration of petals, deformed flowers, and witches' broom were recorded on an ornamental plant, plumed cockscomb (Celosia argentea L., fam: Amaranthaceae). The survey conducted at Indian Agricultural Research Institute (IARI) campus, New Delhi and Karnal region, Haryana, India, during September 2014 to March 2015 revealed disease incidence of 40 and 10%, respectively. The 16S rRNA gene sequence comparison and phylogenetic relationships of Celosia phytoplasma strains under study confirmed that they were associated with two different phytoplasma groups ('Candidatus Phytoplasma australasia' and 'Ca. P. asteris'). Virtual RFLP analysis of 16S rRNA gene sequences allowed further classification of the Celosia phytoplasma strains into the 16SrI-B and 16SrII-D subgroups. Notably, the detection of 'Ca. P. asteris' phytoplasma was reported in seeds of C. argentea by nested PCR assays; however, no evidence of phytoplasma presence was detected in seedlings raised from these seeds. This observation is the first record of the association of 16SrI-B and 16SrII-D subgroups of phytoplasmas with flat stem and witches' broom disease of C. argentea anywhere from the world.