Genetic structure of Phoma betae populations on Beta vulgaris in New York and Washington States, USA

Phoma betae is an economically important seedborne pathogen of table beet worldwide that is responsible for damping off, foliar disease, and root decay. The majority of seed used in New York is sourced from the Pacific Northwest region of the USA. During the growing season, P. betae spreads through polycyclic epidemics resulting from the dispersal of conidia by water splash. P. betae may then survive on colonized plant debris in the soil for up to 2 years. P. betae is capable of sexual reproduction, producing pseudothecia that release ascospores that can be dispersed long distances via wind. However, the teleomorph has not been observed in New York or Washington. Understanding the population biology of P. betae can provide insights into pathogen etiology. No information on population genetics of P. betae is available currently. In this study, 10 microsatellite markers were used to genotype P. betae isolates from table beet fields in New York (n=70) and table beet seed crops in Washington (n=105). Isolates were divided into five populations based on collection location in each state. The genetic diversity, differentiation, and linkage equilibrium of each population were assessed. This information can inform management strategies of P. betae in the future.