# Host-resistance in Allium genotypes against pantaphos producing Pantoea ananatis

## TL;DR

This study identifies a single onion genotype resistant to a bacterial pathogen that causes onion center rot and explores the molecular responses involved in resistance.

## Contribution

The first identification of an onion genotype resistant to pantaphos-producing Pantoea ananatis and its associated transcriptomic responses.

## Key findings

- Only one Allium genotype, DPLD 19-39, showed consistent resistance to P. ananatis.
- Resistant genotypes showed differential regulation in defense pathways like cell wall reinforcement and oxidative stress.
- The findings suggest potential molecular targets for breeding resistant onion cultivars.

## Abstract

Onion (Allium cepa L.) is a globally important crop severely affected by Pantoea ananatis, the causal agent of onion center rot (OCR). The pathogen’s virulence is driven by the chromosomally located HiVir cluster, which produces the phytotoxin pantaphos. Despite its economic significance, resistant Allium genotypes against P. ananatis have not been identified.

We screened 982 Allium genotypes under field conditions to evaluate resistance against pantaphos-producing P. ananatis and conducted in vivo transcriptome sequencing of resistant vs. susceptible genotypes under controlled growth-chamber conditions.

Only one genotype, DPLD 19-39, exhibited consistent resistant phenotype, displaying reduced foliar necrosis and bulb rot. Transcriptomic analyses revealed differential regulation of key defense-associated pathways, including cell wall reinforcement, oxidative stress regulation, and programmed cell death.

These findings provide the first evidence of a resistant A. cepa genotype against pantaphos-producing P. ananatis. The identified molecular responses highlight potential targets for developing onion cultivars with durable resistance to onion center rot.