P-689 - Bacterial spot severity and pathogen diversity on pepper varieties across four farms in North Carolina

Monday, August 4, 2025

4:30 PM - 5:15 PM HST

Location: Exhibit Hall 3

Presenting Author(s)

IM

Inga M. Meadows

Extension Plant Pathologist
NC State University
Waynesville, NC, USA

Author(s)

NT

Noah G. Totsline

Graduate student
NC State University
Raleigh, North Carolina, United States
AH

Alejandra I. Huerta

Assistant Professor
North Carolina State University
Raleigh, North Carolina, United States

Abstract Text: Outbreaks of bacterial spot (BS) on pepper in North Carolina (NC) are primarily caused by four species of Xanthomonas and can be severe—up to 40% yield loss. Varieties with resistance to 11 races of this pathogen are commercially available, but growers often select varieties with only resistance to some races. Our objectives were to: 1) evaluate bacterial spot severity on 19 pepper varieties with no resistance (n=5), resistance to some (n=9), or all (n=5) races of BS Xanthomonas based on infections arising solely from naturally occurring inoculum on four farms in North Carolina; and 2) identify species of Xanthomonas causing outbreaks. At each farm, four replicate eight-plant plots were rated every two weeks for percent leaf area affected. Symptomatic leaves were collected for pathogen isolation and identification using newly developed species-specific end-point PCR primers. Disease occurred on three of four farms and severity varied among farms and host resistance. At trial termination, disease severity on varieties with no resistance, resistance to races 0 to 3 or 0 to 5, and resistance to all races was 0 to 28%, 0 to 17%, 0 to 2% leaf area affected, respectively. Of 43 Xanthomonad-like colonies from 18 cultivars, 13 were X. perforans from 10 cultivars (Rowan County, 10; Henderson County, 2; Haywood County, 1), and one X. euvesicatoria (Henderson County,). Results suggest that growers should select varieties with resistance to at least some races and confirm a previously reported population shift toward X. perforans in pepper production systems in the southeast.