Variation for aphid resistance and insecticidal acyl sugar expression among and within Lycopersicon pennellii-derived inbred backcross lines of tomato and their F-1 progeny

Five inbred backcross lines (IBL) were selected for higher relative express ion of insecticidal acyl sugars (rank average) from an inbred backcross pop ulation derived from the cross Lycopersicon esculentum cultivar 'Peto 95' x Lycopersicon pennellii accession LA 716. These five BC2S5 IBLs were crosse d in a partial diallel design (Method II), and their self and F-1 progeny a nd three control cultivars were tested at two California field locations in 1996. Counts of potato aphids, Macrosiphum euphorbiae Thomas, on leaves, a s a measure of plant infestation, revealed significant general combining ab ility (GCA) for lower aphid numbers with IBL44 and IBL59; the F-1 hybrid IB L44 x IBL59 had significantly fewer aphids per leaflet than the susceptible cultivar 'Alta'. GCA for acyl sugars was associated with IBL59 only. Of al l the IBL and IBL x IBL F-1 hybrids, only IBL59 produced significant levels of acyl sugars. Significant within IBL59 variation for acyl sugars was obs erved, but not for aphid resistance. Our results suggest that factors other than acyl sugars contributed to L. pennellii-derived aphid resistance in I BL x IBL F-1 hybrids and IBL that do not produce significant amounts of acy l sugars. IBL59 and IBL44 may be useful for breeding for aphid resistance i n cultivated tomato.