FIRST REPORT OF IRIS MILD MOSAIC VIRUS FROM IRIS XIPHIUM IN IRAN

Abstract

Iris mild mosaic virus (IMMV, genus Potyvirus, family Potyviridae) has been previously reported in Iris species worldwide (Brunt, 1986). Since November 2015, a total of 85 symptomatic leaf samples of bulbous Iris xiphium plants showing mild mosaic and chlorosis were collected from greenhouses of four different provinces of Iran. 94% of collected samples reacted positively with genus-specific monoclonal antibodies for potyviruses (AS- 0573/1 DSMZ, Germany) in antigen coated-plate ELISA (Jordan and Hammond, 1991). Crude leaf extracts of 15 symptomatic potyvirus infected Iris plants were individually mechanically inoculated on nine seedlings (three replications of three plants each) of 16 different indicator plant species belonging to Chenopodiaceae, Cucurbitaceae, Fabaceae and Solanaceae families. No symptoms developed on inoculated test plants except for Chenopodium quinoa in which numerous chlorotic local lesions were induced by all inoculated isolates. Total RNA was extracted from several local lesions of five C. quinoa leaves and used in RT-PCR assay with a new specific primer pair, IMMV-F/IMMV-R (5'- CGAGATACGGAAGTTCTACGCA-3'/5'-GGGTTGTGCGTAATCAAGTAGTGG-3'), which was designed based on nucleotide sequence of IMMV-WA-1 isolate (GenBank accession No. JF320812) to amplify a ca. 700 bp region encompassing the partial nuclear inclusion protein b and coat protein (3'-NIb, 211 bp /5'-CP, 492 bp) genes of IMMV genome. Following cloning and sequencing, BLAST analysis of an isolate (IMMV-Ar, KX870019) sequence showed the highest range of identity (82-99%) with existing IMMV sequences, including isolates DC4b (99%, DQ436919; New Zealand) and Bate2 (98%, JN127338; Australia). Phylogenetic analysis based on partial NIb-CP sequences of all five available IMMV isolates showed that IMMV-Ar clustered with isolates Bate2 and DC4b. To our knowledge, this is the first report of IMMV occurrence on Iris xiphium from Iran.