Role of Infested Seed as Primary Inoculum for Cercospora Leaf Spot in Table Beet

Area of Science:

• Plant Pathology
• Mycology
• Agricultural Science

Background:

• Cercospora leaf spot (CLS), caused by the fungus Cercospora beticola, significantly impacts table beet (Beta vulgaris) foliar health.
• Primary inoculum sources for CLS include infested crop residues and alternative hosts, with seed-to-seedling transmission also being a concern.

Purpose of the Study:

• To investigate the localization of Cercospora beticola within table beet seeds.
• To determine the contribution of infested seeds to Cercospora leaf spot outbreaks in field conditions.

Main Methods:

• Seed dissection experiments to isolate C. beticola from different seed parts.
• Field trials comparing CLS development in plots from infested versus non-infested seed lots.
• Microsatellite genotyping of C. beticola populations from seeds and field-grown plants.

Main Results:

• Cercospora beticola was predominantly isolated from the pericarp and operculum of table beet seeds.
• Significantly higher CLS incidence, severity, and disease progress were observed in plots from infested seed lots.
• Genotyping revealed two distinct clonal lineages of C. beticola, with populations from infested seeds and resulting field outbreaks clustering together.

Conclusions:

• Infested table beet seeds serve as a crucial primary inoculum source for Cercospora leaf spot.
• Seed-to-seedling transmission of C. beticola is a viable pathway for initiating CLS epidemics.
• Understanding seed transmission dynamics is vital for effective CLS management strategies in table beet production.