Mechanisms of woolly aphid [Eriosoma lanigerum (Hausm.)] resistance in apple

Abstract: The sourcing of new resistant accessions and understanding their resistance mechanisms are significantaspects of a breeding strategy for durable resistance. Resistance of a number of apple accessions to the woolly appleaphid (WAA) [Eriosoma lanigerum (Hausm.)] was assessed based on the biological parameters of the insect. Twoexperiments were conducted under glasshouse conditions in two consecutive years during January–February of 2002and 2003. In Expt 1 in 2002, settlement, development and survival of the aphids were assessed on five apple accessions[Roter Eiserapfel (RE), Freiherr von Berlepsch (FvB), Braeburn (B), Willie Sharp (WS) and Royal Gala (RG)]. RG wasthe most susceptible and WS the most resistant accession to WAA. RG and WS were included as references in Expt 2 in2003, with 11 further accessions (Malus floribunda 821 OP (open-pollinated) G01-078 (MF), Korichnoe Polosatoje OPG01-104 (KP), Geneva (G), Raritan (R), Malus 6 (M-6), Twenty Ounce (TO), Winter Majetin (WM), Aotea (A), IrishPeach (IP), Court Pendu Plat (CPP) and Colonel Vaughan (CV). Daily reproductive rate and colony establishmentwere added to the three paramaters assessed in Expt 1. The overall results showed resistance in G, MF, WS and KP tosettlement and development with low survival at the larval stage of the aphid, whereas R showed resistance in all theparameters tested. RG and CPP have proved to be susceptible while A, WM, TO, M-6, IP and CV were partiallyresistant.Key words: apple accessions, biological parameters, resistance, simulation, woolly apple aphid