P-016 - Genetic diversity of Serratia ureilytica causing Cucurbit Yellow Vine Disease

Cucurbit yellow vine disease (CYVD) affects most commercially important cucurbits and is vectored by the squash bug (Anasa tristis), a significant pest. Symptoms include leaf yellowing, scorching, and internal stem discoloration. Previously, the causal agent was identified as Serratia marcescens based on 16S rDNA and groE gene analysis, with subsequent DNA-DNA hybridization studies comparing it to other S. marcescens isolates. This study investigated the genetic diversity of CYVD-causing bacteria from three geographic regions and times of collection. Using Illumina sequencing, we analyzed 23 isolates from New York, Georgia, and Oklahoma, including 20 from CYVD-symptomatic plants, two red-pigmented isolates from CYVD symptomatic cucurbits, and one rice endophyte. Average Nucleotide Identity (ANI, cutoff >95%) and in-silico DNA-DNA hybridization (cutoff >70%) analyses revealed that all CYVD-associated isolates and the rice endophyte were, in fact, S. ureilytica, not S. marcescens, while the red-pigmented isolates were confirmed as S. marcescens. CYVD-causing S. ureilytica isolates showed minimal genetic diversity across years and regions of collection, and they all formed a distinct clade within the species. Using bioinformatic tools to find unique regions of the CYVD-causing S. ureilytica genomes, we developed CYVD-specific PCR primers. Ongoing research with 75 additional isolates from other states will further elucidate the genetic diversity of this pathogen.