Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 21, 2006
Publication Date: June 20, 2006
Citation: Liu, Y., Mccreight, J.D. 2006. Responses of nasonovia ribisnigri (homoptera: aphididae) to susceptible and resistant lettuce. Journal of Economic Entomology. 99:972-978. Interpretive Summary: Lettuce aphid, Nasonovia ribisnigri, was tested on susceptible lettuce and resistant lettuce that contained resistance gene Nr in various bioassays. The objectives were to determine effective bioassay methods to screen for resistance to lettuce aphid in lettuce breeding and determine susceptibility of commercial lettuce cultivars to lettuce aphid infestation. Whole plant bioassays of 3 to 5 days were adequate to separate resistant and susceptible plants. Both nymphs and alates were suitable. Both choice and no-choice bioassays using alates can be used to separate resistant and susceptible lettuce plants because alates tended to leave resistant plants. Longer term bioassays reveal complete control of lettuce aphid on resistant plants. Leaf disc bioassays were not suitable. All commercial cultivars were susceptible to lettuce aphid infestation, indicating the importance of lettuce aphid to lettuce production and breeding for lettuce aphid resistance.
Technical Abstract: Nasonovia ribisnigri (Mosley) nymphs and alates were tested on 10 lettuce lines with N. ribisnigri resistance gene Nr and 18 cultivars without the resistance gene in various bioassays using whole plants, leaf discs, or leaf cages to determine susceptibility of commercial lettuce cultivars to N. ribisnigri infestation and screening methods for breeding lettuce resistance to N. ribisnigri. Resistant and susceptible plants were separated in 3 d using whole plant bioassays. Longer term tests yielded greater effects of resistant lettuce plants on aphid survival and reproduction. Long-term (7 days or more)no-choice tests using leaf cages or whole plants resulted in zero survival of N. ribisnigri on resistant plants, indicating great promise of the Nr gene for management of N. ribisnigri. Effective screening was achieved in both no-choice tests where resistant or susceptible plants were tested separately in groups or individually and choice tests where susceptible and resistant plants were intermixed. Leaf discs bioassays were not suitable for resistance screening. All lettuce cultivars without the resistance gene were highly susceptible to N. ribisnigri, indicating the great importance of this pest to lettuce production and the urgency in developing resistant lettuce cultivars to manage N. ribisnigri.