CHARACTERIZATION OF A NEW SPANISH POTATO VIRUS X STRAIN INDUCING SYMPTOMS IN TOMATO

Abstract

Potato virus X (PVX), one of the most common plant viruses causing disease to solanaceous crops around the world, is usually asymptomatic in tomato. After mechanical inoculation, a PVX isolate from Northeastern Spain (Sp2013) induced leaf yellowing and light curling in tomato plants, while no symptoms were observed with strain CP4 (GenBank accession No. AF172259.1). Both PVX strains were detected by ELISA with the same antiserum. In order to determine PVX population variability and structure, the full-length coat protein (CP) gene of this Spanish isolate (accession No. KJ631111 corresponding to SPCP1 strain in GenBank) was cloned, sequenced and compared with 90 PVX CP gene sequences available in the database. The global PVX population is divided in three clusters comprising: (i) mainly of South American isolates, including strain CP4; (ii) a mix of isolates from different continents, including isolate Sp2013; (iii) European isolates only. The low variability and lack of recombination events in the CP gene, except for isolate Sp2013, which has 77% nucleotide sequence identity with strain CP4, point to a homogeneous structure. Marked genetic differences between the CP gene sequence of PVX strains Sp2013 and CP4 could explain the differential symptomatology on tomato.