Submitted to: Northeast Potato Technology Forum
Publication Type: Abstract Only
Publication Acceptance Date: March 2, 2010
Publication Date: March 11, 2010
Citation: Olanya, O.M., Honeycutt, C.W., Larkin, R.P., He, Z. 2010. Occurrence of Phytophthora infestans on potato and tomato hosts [abstract]. Northeast Potato Technology Forum. p. 40. Technical Abstract: Assessment of Phytophthora infestans on diverse hosts and its distribution in the potato agro-ecosystem is crucial for effective disease management. The occurrence of P. infestans on potato and tomato hosts was recorded in Maine potato fields from 2006-2009. Over 90% of disease occurrences were on potato plants located in northern Maine fields from 2006-2008. In 2009, the frequency of late blight on tomato and potato hosts was 43% and 57%, respectively. The distribution of pathogen occurrence on both hosts was random, implying widespread presence of pathogen inoculum in the state in 2009. Differences in the frequency of late blight among locations and years suggest variation in inoculum presence among locations and years, or different mechanisms of pathogen spread. From 2006 to 2008, over 95% of P. infestans isolates were of the 100/111/122 (US 8) genotype designation and 5% was 100/122. In 2009, both the 100/111/122 and 100/122 genotypes (based on allozymes) were recorded on potato and tomato, implying that pathogen genotypes are not host-specific. The dynamics of infection pressures and Phytophthora-efficiency (pew values) computed from meteorological data showed that conditions were conducive for pathogen infection and disease spread. P. infestans occurrence on tomato and potato across years and locations implies that host diversity, inoculum sources, tomato transplant distribution, and dispersal mechanisms should be considered as risk factors for effective management of late blight.