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

Abstract

The 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 the Nr gene, introgressed from Lactuca virosa. The resistance mechanism remains to be identified. N. ribisnigri populations virulent on the Nr-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 the Nr gene in lettuce by detailed studies of aphid feeding behaviour and performance. Both avirulent (Nr:0) and virulent (Nr:1)biotypes of N. ribisnigri were 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 the Nr gene 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 the Nr gene. The consequences of the appearance of Nr:1 aphids for control of N. ribisnigri are discussed.

Rearing history affects behaviour and performance of two virulent Nasonovia ribisnigri populations on two lettuce cultivars

“…For details on the EPG methods used, see ten Broeke et al. (). Winged adult aphids (alatae, the colonizing stage of aphids) were randomly collected from the rearing, to obtain a general view on the behaviour of alatae within a population.…”

“…Since 2007, a virulent biotype of N. ribisnigri (Nr:1 biotype) has been reported infesting resistant lettuce, making the Nr ‐resistance ineffective (Thabuis et al., ). An Nr:1 population from Germany performed equally well on resistant and susceptible lettuce and did not seem to be affected by the Nr ‐resistance (ten Broeke et al., ). In a previous study, it was shown that there is large variation in virulence among populations of N. ribisnigri ; however, it remains unclear what caused this variation (ten Broeke et al., ).…”

The effect of co-infestation by conspecific and heterospecific aphids on the feeding behaviour of Nasonovia ribisnigri on resistant and susceptible lettuce cultivars

“…In the EPG set-up, a plant and a piercing insect are made part of an electrical circuit, by attaching a thin gold wire to the insect's dorsum and inserting an electrode in the soil of the plant. For details on the EPG methods used see Ten Broeke et al (2013). Eight hour recordings were made from winged adult aphids (alatae) of unknown age of N. ribisnigri and M. euphorbiae aphids.…”

“…Nr:0 aphids are not able to ingest phloem and cannot survive on resistant lettuce. In contrast, Nr:1 aphids are able to survive and ingest phloem of resistant lettuce, performing equally well on resistant and susceptible lettuce cultivars (Ten Broeke et al 2013). The mechanism underlying the virulence of Nr:1 aphids is unknown.…”

“…However, resistance components were shown to operate during the pathway of the aphid stylets to the phloem and when in the phloem itself (Ten Broeke et al 2013), inhibiting and blocking sustained feeding of avirulent N. ribisnigri, biotype Nr:0. Nr:0 aphids are not able to ingest phloem and cannot survive on resistant lettuce.…”