వైరాలజీ: ప్రస్తుత పరిశోధన

Multigene analysis for differentiation of Candidatus Phytoplasma australasiae-related strain associated with witches-broom of Daucus carota in India.

Abstract

V.Venkataravanappa, P. Swarnalatha, C.N. Lakshminarayana Reddy, K.V. Ashwathappa and M. Krishna Reddy

Leaf samples (seven) from carrot plants exhibiting witches’ broom symptoms were collected from the farmers’ fields of Bangalore Rural and Chikkamaglore Districts of Karnataka, India. The presence of the causal agent was identified through PCR using the 16SrRNA, Ribosomal protein (rp) and SecY gene-specific primers. The seven carrot samples gave positive amplification for the phytoplasma specific primers. The amplified products were cloned and sequenced. The sequence analysis showed that the 16SrRNA, rep gene and SecY gene of seven CarWB phytoplasma isolates shared highest not identity of 94.5 to 97.0%, 94.2 to 98.8% and 99.1 to 99.5% with 16SrRNA, rep and SecY gene of Ca. P. australasiae (16SrII) group isolates reported so far. This result is well supported by close clustering of CarWB phytoplasma isolates in the current study with Ca. P. australasiae (16SrII) group isolates in the phylogenetic analysis. The virtual RFLP pattern generated for the CarWB phytoplasma revealed seven out of six isolates infecting carrot were different (similarity coefficient is ranged from 0.87 to 0.93) with respect to the nine enzymes from the reference pattern of the Ca. P. australasiae (16SrII) subgroups reported so far. Based on the threshold similarity coefficient for the new subgroup, delineation is set at 0.97. Therefore, the six CarWB phytoplasmas may be considered as a new subgroup under Ca. P. australasiae 16SrII group. This is the first the report of a phytoplasma associated with the little leaf disease of carrot from India