Phytopathogenic Mollicutes

Peach, a highly remunerative fruit crop of Himachal Pradesh has been hampered by a phytoplasma disease for last three decades in Rajgarh valley, India. The disease spreads in nature through insect vectors and propagation plant materials but, reservoir/alternate hosts also play an important role in its epidemiology and management. In order to find out the reservoir/alternate weed hosts of this peach phytoplasma, an extensive survey was conducted in district Sirmour where a disease incidence ranging between 0.06 to 100% was recorded in different orchards. Two diseased orchards were identified as hot spots and an inventory of plant species present in and around these orchards was prepared. Symptomatic samples of plant species and insects were collected and subjected to DNA ext raction and nested PCR assays employing ribosomal DNA phytoplasma primers. Amplified products were obtained from Prunus persica, Erigeron annuus, Dryopteris sp. Acacia catechu, and Toona ciliata plant species and Atkinsoniella opponens and Evacanthes repexus insects, showing that they were phytoplasma positive. These positive samples were further subjected to nested PCR employing primers PD1/PD2 designed on the basis of nucleotide sequences of a 16SrV strain from peach and amplifying a DNA fragment of ∼ 200 bp. Positive results were obtained from Erigeron annuus, Dryopteris sp. and Toona ciliata. However, none of the insect tested resulted positive.