ÜBER DIE URSACHEN DER UNTERSCHIEDLICHEN RESISTENZ VON VICIA FABA L. GEGENÜBER DER BOHNENBLATTLAUS, APHIS (DORALIS) FABAE SCOP. V. ANTIBIOTISCHE WIRKUNGEN AUF DIE VERMEHRUNGSKRAFT1

Abstract

An Primärblättern junger Keimpflanzen von Rastatter und Schlanstedter Ackerbohnen (Vicia faba) zeigt sich ein antibiotischer Resistenzunterschied in der parthenogenetischen Vermehrungsrate und ‐geschwindigkeit der Schwarzen Bohnenlaus, Aphis fabae, der auf abgeschnittenen Blättern nahezu völlig verschwindet. Dies steht vermutlich mit dem wechselnden Nährstoffgehalt in ihren Phloemen in Beziehung.SummaryThe rate of reproduction and the velocity of development of Black Aphids, Aphis (Do‐ralis) fabae Scop., are proofed on first‐formed leaves (see Abb. 1 above) of Rastatter (R) and Schlanstedter (S) fieldbeans 1) by numbering the daughters, which are born by one young virginogen mother in the time between birth and maturity of her first born daughter and 2) by measuring this time (of a such a “firstborn generation”) in days for many generations, which are continued by placing the young ripe first born daughter as mother of the next generation on a new leaf each time. The breedings are made during half a year in two parallel series of five lines each on R and S a) on cut and watered first‐formed leaves and b) on equivalent leaves of rooted plants.On the cut leaves in water the velocity of development, the total number of progeny, and the rate of reproduction (calculated by dividing the number of daughters in the firstborn generation by the period from birth to maturity of the first‐born daughter) were on the average much greater than on rooted seedlings of the same varieties. The duration of each generation and the mortality of the mothers was significantly lower on the cut leaves.The differences between the two varieties were only slight on cut leaves in water, but they were more conspicuous on the rooted leaves. With reference to Kennedy's idea of the nutritional value of differently aged leaves, it is suggested that the different concentrations of soluble protein components in the phloem may be the cause of these antibiotic effects. As this concentration is probably the same in cut leaves as in ageing ones, the aphids find more food there and therefore produce more progeny more rapidly than on the mature leaves of rooted plants.As the optimum conditions for reproduction are found on cut leaves of R, and as these seem similar to those found on S, the increase in food available apparently compensates for the differences in antibiotic resistance between the two varieties.Some possible mechanisms for this antibiotic resistance are discussed, especially as it has formerly been stated that R beans appear to be resistant to alate aphids when these choose their host plants.