Identification and expression analysis of candidate genes imparting resistance to pomegranate bacterial blight.

• The bacterial blight disease caused by Xanthomonas citri pv. punicae (Xcp) poses a severe menace to pomegranate orchards. • Newly identified 126 expressed sequence tags from differential gene studies of resistant and highly susceptible genotypes associated with bacterial blight disease in pomegranate were deposited in the NCBI gen bank. • ROS changes were assessed during the course of pathogen infection and defence mechanisms were ascertained in comparison with gene expression studies. • The extent of damage due to disease was also assessed through histo-pathological studies. • Candidate genes associated with bacterial blight resistance in pomegranate were identified and qPCR validation of defence-related genes also confirmed the resistant reaction. The bacterial blight disease caused by Xanthomonas citri pv. punicae (Xcp) poses a severe menace to pomegranate orchards. The control of disease incurs huge expenditures, increasing the cost of cultivation. Hence, developing resistant varieties is an alternative measure for ecological sustainability and is the need of the hour. In this study, Suppression Subtractive Hybridization (SSH) was employed to identify candidate genes associated with bacterial blight resistance in pomegranate. A comparison was made between two genotypes, IC318734 (resistant-R) and Ruby (highly susceptible-HS), for differential gene elucidation and expression against Xcp. Through SSH, a panel of bacterial blight-resistant candidate genes was identified, including MLP-like protein 423, transcription factor MYB114-like, E3 ubiquitin-protein ligase ARI1, protein trichome birefringence-like 34, and serine/threonine-protein kinase. These genes play vital roles in energy and metabolism, transcription, signal transduction, intracellular traffic signaling, protein synthesis, defence, and stress responses. Validation through qRT-PCR revealed higher expression levels of these candidate genes in the R genotype compared to the HS one. Additionally, the levels of Reactive Oxygen Species (ROS) and Malondialdehyde (MDA) in both genotypes aligned with the differential gene expression data. Notably, the study also highlighted the augmented production of 12-oxophytodienoate reductase, associated with ROS generation, in the resistant genotypes. A sustained release of ROS triggered defence responses in the R genotype. Thus, these findings unravel defence mechanisms underlying bacterial blight resistance in pomegranate and provide potential targets for future crop improvement programmes. [ABSTRACT FROM AUTHOR]