Phylogenetic analysis and disease severity assessment of Burkholderia strains isolated from symptomatic onion leaves and bulbs in Pennsylvania and New York

Burkholderia spp. are found in diverse ecological niches, including soil, water, and the rhizosphere of plants, the latter with which they exhibit pathogenic, non-pathogenic, and symbiotic interactions. Some Burkholderia species are known to cause slippery skin and sour skin diseases in onion. This study aimed to characterize the species of Burkholderia strains recovered from symptomatic onion bulbs and leaves in Pennsylvania (PA) and New York (NY) and assess their disease severity on pearl onion bulbs. A total of 89 Burkholderia strains were included, and their phylogenetic relationships were determined using recA gene sequences. Phylogenetic analysis identified five Burkholderia species and two Paraburkholderia species. Burkholderia cepacia and B. orbicola were predominant in NY, while B. gladioli was identified only in PA. Non-parametric statistical analyses comparing disease severity among Burkholderia strains by state (PA vs. NY) showed significant differences between PA and NY strains. Furthermore, ordinal logistic regression was conducted to evaluate how predictor variables (species, state, and isolation source) influence the probability of strains having higher or lower disease severity. This analysis indicated that state (PA vs. NY) was the only significant predictor of increased disease severity among PA strains may partly reflect differences in species composition between states. Local environmental conditions, region-specific cropping systems, and cultural practices could also influence disease severity, but their potential role require further investigation.