Archivio Journal of Plant Pathology

Abstract:

Croton bonplandianum Baill., a member of the family Euphorbiaceae, is a problematic weed throughout India. During 2013, phytoplasma like symptoms of leaf yellows, little leaf and witches’ broom were observed in C. bonplandianum plants in the fields of the Sugarcane Research Station, Gorakhpur district of Uttar Pradesh (India). Leaves were collected from four symptomatic and three symptomless plants and DNA was extracted. Fragments of ca. 1.5 kbp of 16S rDNA were amplified from all four symptomatic samples in PCR assays using the phytoplasma specific primer pair P1/P6 (Deng and Hiruki, 1991) and the amplified product was sequenced (GenBank accession No. KJ410527). No amplification was achieved from any of the symptomless leaf samples. A pairwise 16S rDNA sequence comparison revealed the highest identity (99%) of C. bonplandianum phytoplasma strain with a member (JX104336) of the 16SrVI group (‘Candidatus Phytoplasma trifolii’). The phylogenetic analysis of the 16S rDNA sequence of the Croton phytoplasma strain also revealed its close relationship with strains of ‘Ca. Phytoplasma trifolii’. The ca. 1.5k bp product of 16S rRNA sequence of C. bonplandianum phytoplasma strain submitted to iPhyClassifier online tool assigned it to the 16SrVI-D subgroup. Earlier, Tiwari et al. (2014) had reported the natural occurrence of ‘Ca. P. asteris’ strain in ornamental croton (Codiaeum variegatum) in India, whereas Naik et al. (2015) reported a phytoplasma association with yellows and little leaf disease of C. bonplandianum in India on the basis of nested PCR amplifications but no group assignment was made. Hence, the present identification of 16SrVI-D subgroup phytoplasma associated with C. bonplandianum constitutes the first report worldwide.