MOVED TO ONLINE: From Identification to Epidemiology: Studies on an Emerging Pathogen Occurring on Cucurbit Fruit in Washington

This event can be watched live on Zoom at:

Dr. Lydia Tymon will discuss recent research in plant pathology. In 2015 and 2016, ‘Cinnamon Girl’ pumpkin was used as a test crop for evaluating biodegradable plastic mulch films at Washington State University’s Northwestern Washington Research & Extension Center. In both years, marginal leaf chlorosis, often bordered by necrotic tissues, and circular lesions on the fruit were observed. The fruit lesions had a discolored spot, sunken dimple or necrotic spot located in the center, giving a bull’s-eye appearance, and raised warts often developed later on causing the rind to crack near wart edges. Bacteria were isolated from symptomatic leaves and fruit. Koch’s postulates were fulfilled, and a multilocus sequence analysis and phylogenetic analysis were performed. Bacterial isolates were distinct from Pseudomonas syringae pv. lachrymans, the strain historically associated with cucurbits. The isolates clustered within the P. syringae genomospecies 1 phylogroup 2b clade, which also includes P. syringae pv. syringae. Although plant disease epidemics caused by bacteria can be initiated from a variety of inoculum sources (e.g. irrigation water, weeds and plant debris, soil), contaminated seeds represent a major source for disease outbreaks and facilitate movement of pathogens into new geographical locations. For strains occurring in Washington, seed infection via systemic infection of the host is unlikely. However, further studies are warranted before systemic seed infection can be conclusively ruled out. 

Faculty and practitioners discuss their current research and field projects in the Science and Mathematics Colloquium Series, held throughout the academic year at ASU’s Polytechnic campus. All seminars are free and open to the public.

Science and Mathematics
Steven Saul
Join via Zoom, March 18, 3-4 p.m.
Polytechnic campus