Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/25/2008
Publication Date: 8/1/2008
Citation: McCreight, J.D. 2008. Potential sources of genetic resistance in lettuce to the lettuce aphid, Nasanovia ribisnigri (Mosely) (Homoptera: Aphididae). HortScience. 43:1355-1358. Interpretive Summary: Lettuce aphid has been an economically important pest of lettuce in Europe since the 1970s. It is a relatively new insect pest of lettuce in the U.S., and first caused economic damage to lettuce in Salinas Valley, California in 1998. Lettuce aphid has since become problematic in all the western lettuce areas of California and Arizona. Lettuce infested with this aphid cannot often times be sold in U.S. markets, and is unacceptable in export markets such as Japan and Taiwan. Lettuce aphid infests the heart leaves of lettuce which shield it from chemical protectants. Host plant resistance is, therefore, desirable to prevent infestation of lettuce. Genetic resistance to lettuce aphid is available in European cultivars and is being commercially transferred to U.S. cultivars. Widespread use of this one source of resistance could result in resistance-breaking strains of the insect that would be able to infest lettuce cultivars with this genetic source of resistance. This research evaluated the U.S. collection of germplasm of lettuce and four of its most closely related relatives as the first step in identifying unique genes for resistance to the lettuce aphid. Two accessions of two wild relatives, Lactuca serriola and Lactuca virosa, expressed resistance to the lettuce aphid in greenhouse tests. Additional research is needed to characterize their inheritance and relationship to the currently available source of resistance.
Technical Abstract: Lettuce aphid, Nasanovia ribisnigri (Mosely) (Homoptera:Aphididae), is an economically important pest of lettuce (Lactuca sativa L.). High-level resistance was found in a wild relative, Lactuca virosa L. accession PIVT-280, and transferred to European cultivars. This resistance is conditioned by the Nr gene and is being commercially transferred to U.S.A.-adapted cultivars. New sources of resistance to guard against resistance-breaking strains of lettuce aphid were sought in a greenhouse screening of 1213 accessions (PI) of lettuce (1055 accessions) and its wild relatives, L. perrenis L. (7 accessions), L. saligna L. (19 accessions), L. serriola L. (125 accessions), and L. virosa (7 accessions). Two new sources of resistance to lettuce aphid were found in L. serriola accession Plant Introduction (PI) 491093 and L. virosa accession PI 371798. Resistance in PI 491093 appears to be genetically distinct from that found in PIVT-280 and other reported sources of lettuce aphid resistance. The genetic basis of resistance in PI 274378 is being investigated in crosses with lettuce aphid-susceptible accessions of Lactuca virosa and the first reported source of resistance, PIVT-280.