The resistance of lettuce (<i>Lactuca sativa</i> L.) to <i>Nasonovia ribisnigri</i>: bionomics of <i>N. ribisnigri</i> on near isogenic lettuce lines

Abstract

Abstract The intrinsic rate of increase (r m ‐values), mean relative growth rates and mortality of Nasonovia ribisnigri (Mosley) (Homoptera, Aphididae) on different lines of lettuce ( Lactuca sativa L.) were determined. Near isogenic resistant and susceptible lines, plus their ancestors, were used. Bionomics of N. ribisnigri on the resistant lines (NrNr) with the dominant Nasonovia resistance gene (Nr‐gene) differed clearly from the susceptible lines (nrnr). Mortality was high, no larvae reached adulthood, and no reproduction nor honeydew production was seen on the resistant lines. Transfer of aphids to susceptible plants after a period of 2 days on the resistant lines showed no signs of intoxication of aphids. Apparently there is no feeding on the resistant lines. It is not clear whether the aphids can not reach the phloem or do not accept it on the resistant line.