FIRST REPORT OF 'CANDIDATUS PHYTOPLASMA ASTERIS' AFFECTING SESAME CULTIVATION IN INDIA

Sesame (Sesamum indicum L.), family Pedaliaceae is one of the most ancient cultivated oilseed crops. India ranks first in area (46.5%) under sesame cultivation, producing about 27.9% of the total production of sesame in the world. A phyllody disease was noticed on sesame plants growing in various districts of Uttar Pradesh, India with a disease incidence of 12-20% in 2005. To detect the causal agent, the total nucleic acid isolated from infected and healthy leaf samples collected from Bahraich district were blotted on nylon membrane and hybridized with a probe prepared from a clone of Chilli little leaf phytoplasma 16S ribosomal RNA gene (GenBank Acc. DQ343288). All symptomatic plants showed strong hybridization but none was seen in symptomless samples, indicating an association of a phytoplasma with the phyllody disease. For molecular identification of this phytoplasma, PCR was performed using total DNA of infected samples and P1/P6 phytoplasma specific universal primers (Deng and Hiruki, 1991) which resulted in a ~1.5 kb amplicon. Further, nested-PCR was carried out with primers R16F2n/R16R2 (Gundersen and Lee, 1996) using diluted primary PCR product as template. The ~1.35 kb amplicon obtained was cloned and sequenced. Blast search analysis of sequence data (GenBank Acc. DQ431843) showed highest (99%) identity with the following phytoplasmas: Barley deformation (AY734453), Aster yellows (AY665676), Onion yellows (AP006628), Silene