Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

First record of a Hop stunt viroid variant on Nagpur mandarin and Mosambi sweet orange trees on rough lemon and Rangpur lime rootstocks.

Abstract

In a survey of Citrus orchards in certain parts of central India, bark scaling and splitting and leaf yellowing symptoms were observed on Nagpur mandarins (Citrus reticulata) and Mosambi oranges (C. sinensis) grafted on rough lemon and Rangpur lime rootstocks. After grafting of C. reticulata and C. sinensis on Etrog citron (C. medica), an indicator host for Citrus exocortis viroid (CEVd), unusual symptoms of reduced size and yellowing of newly emerged leaves developed. Electrophoresis of nucleic acids extracted from grafted infected Etrog citrons indicated the presence of viroid-like, low molecular weight (LMW) RNA in all samples. RT-PCR was conducted on these LMW RNAs using a set of CEVd-specific primers. Amplicons (300 bp) were obtained in all samples with primers specific to Hop stunt viroid (HSVd). No amplification occurred when the CEVd-specific primers were used. Cloning and sequencing of these amplicons identified a viroid RNA (Accession No. AY237168) with 100% sequence similarity to HSVd-Ca905 (Accession No. AF131250) and HSVd-ycv (Accession No. AJ490824). This is thought to be the first isolation of an HSVd viroid (HSVd-RL) from Citrus rootstocks showing bark scaling and splitting symptoms in central India.