Diversity of Serratia marcescens strains associated with cucurbit yellow vine disease in Georgia

Abstract

Cucurbit yellow vine disease (CYVD), caused by the squash bug (Anasa tristis)-transmitted bacterium Serratia marcescens, was first identified in Oklahoma and Texas in 1988 and in Georgia in 2012. S. marcescens is a highly diverse species found in many ecological niches. In previous studies, CYVD strains of S. marcescens formed a closely related group separate from non-CYVD strains based on biological and molecular characterization techniques. Multilocus sequence analysis (MLSA) of six housekeeping genes and repetitive elements-based polymerase chain reaction (rep-PCR) using the BOX and ERIC primers were used to assess the genetic diversity of CYVD strains of S. marcescens collected in Georgia together with a strain from Texas and seven non-CYVD strains of S. marcescens. rep-PCR results revealed genetic diversity among CYVD strains while MLSA results showed a 100% similarity across the six loci for all but one of the CYVD strains, which differed at the icd locus by five polymorphisms. For both methods, CYVD strains clustered separately from nonplant-pathogenic S. marcescens strains and were most similar to a rice endophyte strain. One CYVD strain isolated from a squash bug shared genetic similarities with non-CYVD strains, and may be the result of a recombination event between CYVD and non-CYVD strains.