Performance and feeding behaviour of two biotypes of the black currant-lettuce aphid,Nasonovia ribisnigri, on resistant and susceptibleLactuca sativanear-isogenic lines

Abstract

AbstractThe black currant-lettuce aphid,Nasonovia ribisnigri, is an important pest of cultivated lettuce,Lactuca sativa.Since 1982, the control of this aphid on lettuce is largely based on host plant resistance, conferred by theNrgene, introgressed fromLactuca virosa. The resistance mechanism remains to be identified.N. ribisnigripopulations virulent on theNr-based resistance in lettuce have emerged in several locations in Europe since 2007. The objective of this study was to investigate the resistance mechanism mediated by theNrgene in lettuce by detailed studies of aphid feeding behaviour and performance. Both avirulent (Nr:0) and virulent (Nr:1) biotypes ofN. ribisnigriwere studied on five resistant and two susceptible near isogenic lines (NILs). In addition, survival and colony development were quantified. Nr:0 aphids showed a strong decrease in sieve element ingestion and took longer to accept a sieve element on resistant NILs compared with susceptible NILs, and no aphids survived on the resistant NIL. Nr:1 aphids fed and performed equally well on the resistant and susceptible NILs. The resistance mechanism against Nr:0 aphids encoded by theNrgene seems to be located in the phloem, although we also observed differences in feeding behaviour during the pathway phase to the phloem. Nr:1 aphids were highly virulent to the resistance conferred by theNrgene. The consequences of the appearance of Nr:1 aphids for control ofN. ribisnigriare discussed.