Date of Award
12-2025
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Plant and Environmental Science
Committee Chair/Advisor
Dr. Hehe Wang
Committee Member
Dr. Vidya Suseela
Committee Member
Dr. Joseph Roberts
Committee Member
Dr. Jason Hong
Abstract
Xanthomonas arboricola pv. pruni (Xap), the causal agent of bacterial spot of peach, thrives in the warm, humid climate of the southeastern United States and poses a major threat to peach production. Although copper- and antibiotic-based sprays are commonly used, resistance and tolerance have reduced their effectiveness. Synthetic communities (SynComs) of beneficial microbes offer a promising, sustainable alternative. This study aimed to identify peach phyllosphere microbes with biocontrol potential and develop SynComs capable of suppressing bacterial spot under field conditions.
The peach phyllosphere microbiome was characterized using 16S and ITS amplicon sequencing in two orchard blocks with contrasting disease levels. Fruit and leaf harbored distinct microbial communities. Bacterial communities differed between symptomatic and asymptomatic samples. While overall community structure did not differ between blocks, Xanthomonas dominated both blocks, and its relative abundance strongly correlated with Xap populations quantified by qPCR.
Bacterial and fungal isolates from six peach farms were screened for antagonism against Xap. Thirty-three bacterial isolates, primarily Pseudomonas, Bacillus, Microbacterium, and Pantoea, showed inhibitory activity, and compatibility assays identified 15 candidate SynComs. The strongest performers, including one Pseudomonas, one Bacillus, and one Microbacterium strain, were evaluated in field trials.
On cultivars Coronet and Carored, SynComs containing the Pseudomonas strain significantly reduced disease, performing comparably to copper hydroxide and Bacillus subtilis AFS032321. Some combinations showed additive effects and were effective even at reduced cell concentrations.
Overall, this work demonstrates the potential of SynCom-based biocontrol as a sustainable component of integrated management strategies for bacterial spot of peach.
Recommended Citation
Farmer, Jordan, "Harnessing the Peach Phyllosphere Microbiome to Combat Xanthomonas Arboricola PV. Pruni" (2025). All Theses. 4619.
https://open.clemson.edu/all_theses/4619