Salicylic acid-induced defense responses against a newly identified cotton pathogen, Pantoea vagans

Abstract

Bacterial blight of cotton is a severe disease that significantly impacts cotton production worldwide. In 2022, cotton (Gossypium spp. plants exhibiting angular leaf spots, necrotic lesions, and blackened stems were observed in fields across Bahawalpur, Punjab, Pakistan. Pathogen isolation from symptomatic plants yielded Pantoea vagans (strains CPVB#1, CPVB#2, and CPVB#3), identified through morphological, biochemical, and molecular analyses. Molecular identification using 16S rRNA sequencing (GenBank Accession Nos. OQ925871, OQ925897, OQ925910) revealed high sequence similarity (99.8 %, 98.59 %, and 97.78 %) to Pantoea vagans reference strain MN661279. Further confirmation was achieved via multilocus sequence analysis (MLA) of fusA (OR184128–OR184130) and leuS (OR184131, OR188816, OR188817) genes, confirming the close genetic relationship. Our research revealed that, for the first time in Pakistan, Pantoea vagans is causing bacterial blight in cotton, according to our knowledge. To control bacterial blight in cotton, the efficacy of salicylic acid (SA) as a sustainable control method was also evaluated under greenhouse conditions. SA treatments at 0.5 mM, 1.0 mM, and 1.5 mM reduced disease severity significantly, with 1.5 mM SA achieving the greatest suppression (82.3 %). In addition to lowering disease severity, SA treatments increased total phenolic content and enhanced the activity of enzymes that are related to defense mechanisms, including CAT, POD, SOD, PAL and PPO with maximum enzyme activity observed four Days post-treatment. These results demonstrate the potential of SA as an eco-friendly and effective management strategy for bacterial blight in cotton. Further research is warranted to investigate the epidemiology of Pantoea vagans and develop integrated approaches to mitigate its impact on cotton production.