Celery leaf curl disease: Unraveling the causal agent, population genetics, symptomology and fungicide performance for improved diagnostics and management
Open Access
- Author:
- May, Sara
- Graduate Program:
- Plant Pathology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 10, 2019
- Committee Members:
- Beth Krueger Gugino, Dissertation Advisor/Co-Advisor
Beth Krueger Gugino, Committee Chair/Co-Chair
Maria Del Mar Jimenez Gasco, Committee Chair/Co-Chair
David Michael Geiser, Committee Member
Richard P Marini, Outside Member
Kari Anne Peter, Committee Member - Keywords:
- celery
Colletotrichum
leaf curl
fioriniae
population genetics
management - Abstract:
- Celery leaf curl disease was first reported in Australia in 1981 and first observed in the United States (U.S.) in 2010. The pathogen was initially identified as Colletotrichum acutatum J. H. Simmonds, which is now recognized as a species complex with over 30 identified species. Limited research has been conducted on this disease over the past 38 years. To expand our narrow understanding, research was conducted to identify the causal species and determine if they cause the same or different symptoms, explore population genetics and improve disease management strategies. Multilocus phylogenetic analyses were used to determine that C. fioriniae is the primary causal agent of leaf curl in North America and an Australian isolate was identified as C. godetiae. This is the first reported association of C. godetiae with leaf curl disease. To gain a better understanding of pathogen population structure and diversity and regional population differentiation, microsatellite markers were used to evaluate genetic diversity and population relationships. Analyses were conducted using C. fioriniae isolates collected from celery in the U.S. and Canada from 2010 to 2017. Populations from celery showed high genetic diversity with evidence of clonality, while isolates from apple showed evidence of sexual reproduction indicating different inoculum sources for these pathosystems. The sudden appearance of leaf curl disease, especially in locations where celery has been cultivated for many years, indicates a potentially seedborne pathogen. Preliminary experiments have demonstrated the potential seedborne nature of C. fioriniae through vertical transmission. Distinctions in disease symptoms on celery have been reported in association with different species of Colletotrichum and have resulted in different names for the same or very similar diseases. Comparative analyses showed the same symptomology is caused by three Colletotrichum species on two cultivars of celery indicating these different species cause the same disease. Observations of 40 to 100% disease incidence in natural epidemics make this a potentially devastating disease for celery growers. Field trials evaluating conventional and biorational materials showed that only conventional materials were effective on the highly susceptible cultivar ‘Tango’. However, one trial comparing ‘Tango’ to the moderately resistant cultivar ‘Merengo’ revealed significant disease reduction in this cultivar indicating its potential for use in both conventional and organic production systems.