Identification of a novel Burkholderia species causing onion bulb rot disease
Research Poster Health & Life Sciences 2025 Graduate ExhibitionPresentation by Ram Neupane
Exhibition Number 192
Abstract
This study reports two bacterial strains (22PA0099 and 22PA0106) of a previously undescribed Burkholderia species causing bulb rot in onion. These strains were recovered from symptomatic onion plants collected from Pennsylvania (PA) during the routine scouting of onion fields in 2022. The strains were identified as Burkholderia sp. through 16S rRNA sequencing with the highest percentage of identity, coverage, and E-value of 98.7%, 98 to 100%, and zero respectively. In addition, primers targeting the recA gene (BUR3 and BUR5) were used to characterize species. Both strains had the closest hits with B. perseverans and B. gladioli, with 94 to 100% coverage and 92 to 95% identity in the recA gene. The whole genomes of both strains were sequenced using long-read sequencing. Comparisons with available genomes indicated that these strains had the closest identity with Burkholderia gladioli, with 92% average nucleotide identity. Furthermore, the two strains shared 97% sequence identity, suggesting they belong to the same species. These percentages indicate that the strains likely represent a novel Burkholderia species not reported previously on onion. A whole onion bulb assay confirmed the two strains pathogenicity. The proper identification and monitoring of this pathogen is important to help growers make informed decisions regarding disease diagnosis and management.
Importance
Onion production in the northeastern United States is a multi-million-dollar industry, yet bacterial diseases pose a serious threat. Bacterial bulb rot can lead to annual losses of up to 40% in Pennsylvania. The disease is especially problematic because it affects the internal scales of the onion, making infected bulbs hard to detect. Even a small number of affected bulbs can cause entire shipments to be rejected. This study identifies and characterizes the bacteria responsible for onion bulb rot, including a previously undescribed Burkholderia species. The findings are crucial for developing better diagnostic tools and management strategies that can help safeguard the onion industry.
DEI Statement
This research was done in collaboration with growers and is deeply rooted in extension. It directly supports the land grant mission of Penn State. In Pennsylvania, onions are mainly grown by Plain Sect farmers, such as Amish and Mennonites, in fields ranging from 0.5 to 2 acres. This study helps these smallholder farmers reduce losses from bacterial diseases, improving crop health and boosting profitability. By offering targeted disease management strategies and practical diagnostic tools, the research directly supports Plain Sect farmers, ensuring they receive tailored solutions that safeguard their crops and secure their economic stability.