FIRST REPORT OF APPLE STEM GROOVING VIRUS FROM POME AND STONE FRUITS IN INDIA

Apple stem grooving virus (ASGV), the type member of the genus Capillovirus, induces severe pitting and grooving of the xylem, brown line and graft union abnormalities, reduced vigour of the canopy and an overall decline in susceptible Malus species (Yoshikawa, 2000). It also infects apricot, cherry, and pear. Infection rate in apple can be as high as 80-100% and yield losses my reach 40%. During a survey in the temperate fruit-growing Indian districts of Himachal Pradesh (Shimla, Solan and Palampur) and Jammu & Kashmir (Srinagar), preliminary evidence for the presence of ASGV was obtained by DAS-ELISA, using a commercial kit (Adgen Phytodiagnostics, UK). To confirm the record, total RNA was extracted using RNeasy Plant Mini kit (Qiagen, Germany) from one of the positive apple samples (cv. Starkrimson) which had reacted strongly in ELISA. PCR primer pair ASGV6396 (reverse), 5’-CTG CAA GAC CGC GAC CAA GTT T-3’ and ASGV5641 (forward), 5’-ATG AGT TTG GAA GAC GTG CTT C- 3’, yielding an amplicon of 755 base pairs (bp) was used to amplify the complete ASGV coat protein (CP) gene, as described by Nickel et al. (2001). ASGV was detected in eleven different cultivars of apple, nectarine, plum, cherry, quince and apricots by DAS-ELISA and dot blot hybridization using the cloned CP of the present isolate as a probe. Multiple alignment of CP sequences of the Indian ASGV isolate showed 100% identity at the amino acid level with a Brazilian isolate from apple (accession No. AF438409) whereas identities of 95-98% and 95-100% were found with a citrus strain (Citrus tatter leaf virus) and other isolates, respectively. To our knowledge, this is the first report of ASGV infection to pome and stone fruit trees in India