Pseudocercospora oenotherae causing leaf spot on ornamental Lantana strigocamara: characterization and host resistance.

Abstract

Lantana (Lantana strigocamara R.W. Sanders, syn. L. camara L.) is an important ornamental shrub that is widely grown in containers and in landscapes. Recent breeding efforts have focused on reducing its invasiveness and developing infertile cultivars for the ornamental industry while maintaining its desirable characteristics such as resilience to abiotic stresses and low maintenance requirements. During fall and winter 2020, a novel fungal pathogen was isolated and found to be associated with leaf spots on infertile ornamental lantana cultivars in field trials in Florida, USA. The pathogen was found causing leaf spot symptoms, leading to severe defoliation and diminishing ornamental value, worthy of pathogen characterization and evaluation of host resistance. Genetic and morphological analyses coupled with pathogenicity assays identified Pseudocercospora oenotherae as the causal agent of observed symptoms. Cultivar screenings revealed high susceptibility of commercial cultivars Lucky™ Red, Lucky™ Rose, and Landmark™ Gold to this disease and partial resistance (lower disease incidence, severity, and defoliation) in breeding line UF-T48. Further research is required to elucidate the epidemiology of P. oenotherae and its potential reservoirs in surrounding flora. This is the first record worldwide of P. oenotherae on ornamental lantana, which is currently considered a minor problem, but continued surveys will be needed to determine its spread. Integrated disease management strategies, including the development of resistant cultivars and appropriate cultural and chemical controls, will be essential for management if this pathogen becomes a major concern in the future.