Medlar (Mespilus germanica), a novel natural host for Hop stunt viroid (HSVd)

Abstract

Hop stunt viroid (HSVd) infects various plants such as citrus, hop, almond, grapevine, pear, plum, peach, mulberry, fig, and pistachio. Medlar trees in an orchard in Malatya province of Türkiye were surveyed for the presence of HSVd in 2021. Twenty leaf and flower samples were collected and tested by RT-PCR methods using pathogen-specific primers. HSVd was found in five of the twenty medlar samples showing novel sequence variations. Two of the five HSVd variations were chosen at random and registered in GenBank. Both Turkish HSVd isolates had genomes that were 300 nucleotides long. The complete genome sequence of these variations was compared to isolates in GenBank. The nucleotide sequences of HSVd isolates exhibited 89.7-100% similarity with HSVd isolates found in various crops worldwide. Analysing the alignment of multiple sequences and conducting phylogenetic analyses revealed that identified HSVd variants clustered with citrus Türkiye (MZ995256), citrus Italy (KC584022), citrus Iran (GQ260203) and citrus Japan (X06719) isolates with 100% similarity rate and citrus China (FJ716172) and citrus Spain (AF213503) isolates with 99.5% and 98.0% similarity rates, respectively. To our knowledge, this is the first report of medlar serving as a natural host for HSVd. HSVd infection in medlar could be a problem in the future, and additional study is needed. The infection appears to be latent, but it might be a source of infection for susceptible plants.

Keywords

• medlar
• hop stunt viroid
• phylogenetic analysis
• polymerase chain reaction
• türkiye