Chamomile Floricolous Downy Mildew Caused by Peronospora radii

Area of Science:

• Plant pathology
• Oomycete biology
• Medicinal herb pathology

Background:

• Floricolous downy mildews (Peronospora) are poorly understood pathogens affecting only flowers.
• Chamomile (Matricaria chamomilla) in Serbia suffers significant losses due to flower malformation caused by a Peronospora species.

Purpose of the Study:

• To identify and characterize the causal agent of chamomile flower malformation.
• To investigate the biology, infection routes, and life cycle of the pathogen.

Main Methods:

• Morphological and molecular characterization of the pathogen.
• Phylogenetic analysis using ITS and cox2 sequences.
• Histological and molecular analyses to confirm systemic infection.
• Experiments to validate soilborne and blossom infection impacts.

Main Results:

• Peronoscia radii was identified as the causal agent of chamomile flower malformation.
• Diseased flowers exhibited severe malformations, including phyllody and secondary inflorescence formation.
• Phylogenetic analysis confirmed the pathogen's identity, with Serbian isolates forming a distinct subcluster.
• Evidence of systemic infection and validation of soilborne/blossom infection routes were established.

Conclusions:

• This study provides novel insights into the biology of Peronospora radii on chamomile.
• The findings enable a comprehensive reconstruction of the floricolous Peronospora species' life cycle.
• Understanding the pathogen's biology is crucial for managing disease and reducing crop losses in medicinal herbs.