|GEBBEN, SAMANTHA - HARTNELL COMMUNITY COLLEGE|
|TRENT, MARK - FORMER ARS EMPLOYEE|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2014
Publication Date: 3/1/2015
Citation: Bull, C.T., Gebben, S.J., Goldman, P.H., Trent, M., Hayes, R.J. 2015. Host genotype and hypersensitive reaction influence population levels of Xanthomonas campestris pv. vitians in lettuce. Phytopathology. 105:316-324.
Interpretive Summary: Over 80% of the 890 million lbs of lettuce consumed annually by Americans is produced in the United States. Lettuce production in California accounts for 70-75% of the US total. Bacterial leaf spot of lettuce is an important disease world-wide and in some seasons reduces marketable yield significantly. This research describes the effect of resistant and susceptible lettuce cultivars on the population dynamics of the pathogens. Population levels were depressed on cultivars of lettuce that have complete resistance against the pathogen as compared to population levels on susceptible cultivars. Pathogen populations on other resistant cultivars were not influenced to the same extent. This information has implications on the epidemiology of the disease and is being used by private and public breeding programs to strategize the breeding commercial cultivars with resistance to the bacterial leaf spot pathogen.
Technical Abstract: Population dynamics of Xanthomonas campestris pv. vitians spray inoculated on or infiltrated into lettuce leaves were monitored on cultivars that were well characterized for resistance or susceptibility to the pathogen. In general, population growth was greater for susceptible (Clemente, Salinas 88, and Vista Verde) than resistant (Batavia Reine des Glaces, Iceberg, and Little Gem) cultivars. Specifically, when spray inoculated or infiltrated, population levels of X. campestris pv. vitians increased significantly less on Little Gem than on susceptible cultivars. Populations increased at an intermediate rate on cultivars Iceberg and Batavia Reine des Glaces. There were significant positive correlations between bacterial concentration applied and disease severity for all cultivars but bacterial titer had a significantly greater influence on disease severity in the susceptible cultivars than in Little Gem and an intermediate influence in Iceberg and Batavia Reine des Glaces. Infiltration of X. campestris pv. vitians strains into leaves of Little Gem resulted in an incompatible reaction, whereas compatible reactions were observed in all other cultivars. It appears that the differences in the relationship between population dynamics for Little Gem and the other cultivars tested were due to the hypersensitive response (HR) in cultivar Little Gem. These findings have implications for disease management and lettuce breeding because X. campestris pv. vitians interacts differently with cultivars that differ for resistance mechanisms.