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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #156566
Title: SCREENING FOR NEW SOURCES OF RESISTANCE TO CORKY ROOT IN LETTUCE

Author
item Mou, Beiquan
item Bull, Carolee

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2004
Publication Date: 9/1/2004
Citation: Mou, B., Bull, C.T. 2004. Screening for new sources of resistance to corky root in lettuce. Journal of the American Society for Horticultural Science. 129(5):712-716.

Interpretive Summary: Corky root is a major disease of lettuce observed in most production areas of the world. The bacterium pathogen varies with regard to virulence, and several strains have been isolated that can cause certain disease symptom on cultivars with the only known resistance gene, cor. It is desirable to find new sources of resistance to diversify the genetic basis of the resistance and to confer resistance to isolates that are not adequately controlled by cor. We screened more than 1,000 plant introduction lines and cultivars in the greenhouse, growth chamber, and field. Four wild lettuce accessions were found to be highly resistant to corky root. The results from the field correlated with the results from greenhouse and growth chamber. None of the four resistant lines had the two molecular markers closely linked to the cor gene. The information on disease resistance for these germplasm will be useful in future breeding work.

Technical Abstract: Corky root is a major disease of lettuce (Lactuca sativa L.) observed in most production areas of the world. The pathogen Sphingomonas suberifaciens (formerly, Rhizomonas suberifaciens) varies with regard to virulence, and several strains have been isolated that can cause certain disease symptom on cultivars with the only known resistance gene, cor. It is desirable to find new sources of resistance to diversify the genetic basis of the resistance and to confer resistance to isolates that are not adequately controlled by cor. More than 1,000 plant introduction lines and cultivars were screened in the greenhouse, growth chamber, and field. Three L. serriola lines (PI 491239, PI 491096, and PI 491110) and a L. virosa line (PI 273597c) were highly resistant to corky root in all tests. Disease severity ratings in the field was correlated with the ratings in the greenhouse (r = 0.722) and in the growth chamber (r = 0.650). None of the four resistant lines had the two molecular markers closely linked to the cor allele. The information on disease resistance for these germplasm will be useful in future breeding work.