Resistance to a new biotype of the lettuce aphid Nasonovia ribisnigri in Lactuca virosa accession IVT280

Host plant resistance is an effective protection strategy to control aphids in many crops. However, the evolution of insensitive aphid biotypes necessitates the search for new resistance sources. Wild relatives of crop plants can be important sources for resistance genes to be introgressed into new cultivars. Nasonovia ribisnigri (Mosely) (Homoptera: Aphididae) is an important pest of cultivated lettuce, Lactuca sativa. Since 1982, resistance introduced into lettuce cultivars has relied on the Nr-gene, originating from a wild relative, Lactuca virosa. In 2007 first reports appeared that Nr-based resistance had become ineffective against certain populations of N. ribisnigri. The objective of this study was to establish if the original donor of the Nr-gene L. virosa accession, IVT 280, is resistant against recently emerged virulent (Nr:1) N. ribisnigri biotypes. To this end we investigated feeding and penetration behaviour of virulent and avirulent (Nr:0) aphids on the resistant L. virosa, IVT 280, and two susceptible L. virosa accessions, using the electrical penetration graph method. Additionally, aphid performance was analysed in terms of survival, development time and reproduction on these accessions. L. virosa accession IVT 280 was resistant against all populations of N. ribisnigri tested. The ingestion of phloem was strongly reduced on the resistant accession compared to the susceptible L. virosa accessions. Additionally, none of the aphids survived on the resistant accession that, therefore, constitutes a good source of resistance in lettuce against both biotypes of N. ribisnigri.