ON THE OCCURRENCE OF PEA APHIDS, ACYRTHOSIPHON PISUM, RESISTANT TO ISOLATES OF THE FUNGAL PATHOGEN ERYNIA NEOAPHIDIS

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Abstract
A laboratory colony of Acyrthosiphon pisum (Harris) has been found to consist of 2 biotypes distinct in their susceptibility to an isolate of the fungal pathogen Erynia neoaphidis Remaudière & Hennebert. Dosages which killed an average of 94% of the “susceptible” biotype did not kill a single “resistant” aphid. Clones were established and have bred true for over 25 generations on broad beans and over 16 generations on lucerne. Seven of 8 field populations tested contained the “resistant” biotype. Eleven isolates of E. neoaphidis were tested against the 2 clones and 2 were found to attack the “resistant” biotype as readily as they attacked the “susceptible”. This is the first time that field populations of aphids have been reported to contain a biotype resistant to a fungus disease and also the first time strains of a pathogen have been found capable of attacking an otherwise resistant biotype.ZUSAMMENFASSUNG: Qualitätskontrolle in einer Laboratoriumskolonie von Choristoneura occidentalis.Um das genetische Profil einer Kolonie von Choristoneura occidentalis in ihrer 88. Nondiapausegeneration zu vergleichen mit einer Wildpopulation aus derselben Gegend wie ein Teil des Ursprungsmaterials der Kolonie, wurde die Stärkegelelektrophorese verwendet. Der Index genetischer Ubereinstimmung beider Populationen nach Nei berechnet über 20 Genloci (12 polymorphe) betrug 0,995. Indessen war die Heterozygotie im Laboratoriumstamm durch den offensichtlichen Verlust von 15 Allelen reduziert. Der Verlust an Heterozygotie wirkte sich aber nicht in einem Qualitätsverlust der Insekten für Forschungszwecke aus.