Submitted to: HortScience
Publication Type: Abstract Only
Publication Acceptance Date: March 31, 2005
Publication Date: July 4, 2005
Citation: Mccreight, J.D. 2005. New sources of lettuce aphid resistance in lettuce. Hortscience 40(4) p. 1109. Technical Abstract: Lettuce aphid (Nasonovia ribisnigri Mosley) is a recent insect pest to lettuce (Lactuca sativa L.) production in the U.S. The single dominant gene, Nr, conditions resistance to the lettuce aphid in Lactuca virosa accession IVT280 from The Netherlands and is available in a limited number of commercial lettuce cultivars. New and genetically unique sources of resistance are sought to broaden the genetic base for resistance to the lettuce aphid. Approx. 1200 lettuce PI lines were evaluated for resistance to lettuce aphid in greenhouse tests using a strain of lettuce aphid obtained from commercial lettuce in Salinas Valley, Calif. In 2002, plants were individually infested with five 24-hr nymphs per plant (controlled protocol), and the numbers of aphids per plant were counted 10 to 14 days post-infestation (dpi). Beginning in 2003, plants were mass-infested (mass protocol) with nymphs and alates of various ages and numbers. Using the mass protocol, the number of aphids per plant 10 to 14 dpi were estimated and categorized using a 1 to 5 scale where 1 = 0 aphids per plant, 2 = 1'10 aphids per plant, 3 = 11' 20 aphids per plant, 4 = 21'30 aphids per plant, and 5 >30 aphids per plant. 'Salinas' and 'Barcelona' were included as susceptible and resistant controls, respectively. Most of accessions were susceptible. A few accessions had a few plants with very low numbers of aphids after repeated infestation, but their progeny were susceptible. Two accessions were highly resistant: PI 491093, aLactuca serriola accession from Turkey, and PI 274378, a L. virosa accession from France. Inheritance of resistance in these two accessions and their allelism to Nr remain to be determined.