Host-resistance in Allium genotypes against pantaphos producing Pantoea ananatis

Bhabesh Dutta^1*Brendon Myers¹Navjot Kaur¹Angelo Manzatto²Michelle Pena¹Adriano Ferrasa²Elkin Fernando Mendoz³Jhon Jairo Gonzale³Roberto H. Hirochi Herai⁴

• ¹University of Georgia, Athens, United States
• ²Universidade Estadual de Ponta Grossa, Paraná, Brazil
• ³Francisco de Paula Santander University, Cúcuta, Colombia
• ⁴Pontifícia Universidade Católica do Paraná, Paraná, Brazil

Onion (Allium cepa L.) is a widely cultivated crop that suffers from substantial losses due to Pantoea ananatis (PA) infection, a bacterial pathogen responsible for onion center rot disease (OCR). Severe outbreaks of OCR have been reported globally, leading to significant economic impacts, particularly in onion-producing regions worldwide. The virulence of the pathogen is driven by the chromosomally located HiVir gene cluster, which produces the phytotoxin 'pantaphos', causing extensive necrosis in infected tissues. Despite its economic importance, Allium genotypes with resistance against PA are unknown. In this study, we conducted a comprehensive screening across 982 Allium genotypes to evaluate resistance against PA. Only one A. cepa genotype, DPLD 19-39, demonstrated a consistent resistant phenotype by exhibiting lower foliar necrosis and bulb rot. Moreover, we also performed in vivo transcriptome sequencing and analysis of onion plants infected by PA under distinct conditions, and identified several mis-regulated pathways involved with plant resistance, including cell wall reinforcement, oxidative stress regulation, and programmed cell death. Our findings indicate a potential mechanism for resistance against PA in A. cepa and suggest that future efforts should focus on these defense pathways to develop PA-resistant onion genotypes.