ALBERT

Beschreibung / Inhaltsverzeichnis: Summary Reciprocal grafts of aphid-resistant (Rastatter) and susceptible (Schlanstedter) field beans (Vicia faba) should demonstrate whether the resistance of the scions is influenced by the stock or not. To ensure a solid and inflexible connection between the partners to be grafted a glass capillary was fitted in the stem hollows of both the scion and the stock. In “pertelar” cages (Müller 1954) one young aptera of Aphis fabae could choose to infest a leaf of a grafted scion or a leaf of a normal plant. The percentage of initial colonies established by 740 such tested virginoparae decreased from 90,6 (S/R+S) to 78,5 (S/R+R), 76,7 (R/S+S) and 48,8% (R/S+R). In all cases, where a decision was possible at all, S-leafs were preferred to R-leafs, independently of whether they grew on a scion or on a normal plant (Table I): With reproduction rate experiments the percent of apterous virginoparae settling on grafts and controls dropped in a similar manner from 51,0 on S and 43,9 on S/R to 21,8 on R and 17,7 on R/S respectively (Table II). Also the reproductive rate (number of larvae born by an apterous virginopara in the time between the birth and maturity of its first born daughter decreased from S (33,6+-9,0) and S/R (31,8+-8,3) to R (27,2+-8,2) and R/S (26,7+-7,9)). There is no statistically significant difference between S and S/R on the one side and R and R/S on the other (Fig. 4). The diminution of numbers from S to S/R and from R to R/S respectively in all experiments is suggested to be an effect of grafting in itself rather than a mutual influence of the partners. The present results prove that both the preference-nonpreference-und the antibiosismechanism of the relative aphid resistance of R-and S-field beans are not altered by the stock after reciprocal grafting. In view of this and the findings of Harvey & Hackerott (1958) on alfalfa resistance against Therioapbis maculata substances produced by the roots cannot be the cause of aphid resistance.

Beschreibung / Inhaltsverzeichnis: Summary In a further study of host selection behaviour of the black bean aphid (Aphis fabae Scop.) and of Myzus persicae (Sulz.) alate alienicolae were caught immediately after landing on young plants of equal size and growth of beet (Beta vulgaris var. rapa Dum.), field beans (Vicia faba L.), poppies (Papaver somniforum L.), potatoes (Solanum tuberosum L.) and white mustard (Sinapsis alba L.). A total of 1495 A. fabae and 1054 M. persicae were collected during 59 observation periods totalling 107 hours, with two or more persons operating. The aphid numbers showed no statistically significant differences between the five plants, so it is concluded that host selection cannot take place during the initial approach, but only after alighting. The subsequent behaviour of the aphids after landing on the five plant species was studied by continuous observations by several observers. 1556 bean aphids landed over a total period of 44 hours. The behaviour included slow or fast walking, frequent or less frequent changes in walking and in probing, and, in almost all cases, the aphids took off again in a few minutes. On an average the insects took off sooner from the non-hosts, mustard and potato, than they did from the potential hosts, poppy, beans and beet. Thus 75 per cent left the mustard and potatoes within one and a half minutes, but the same proportion remained for nearly four minutes on poppy and field beans and more than five and a half minutes on beet. The number of probes on the non-hosts was about 1, but was greater (2–4) on the hosts, the number increasing from poppy to bean to beet. The walking and probing behaviour on each plant was characteristic. On beet most aphids showed short probing times and rapid continuous walking, on potatoes walking and probing times were short, and long sequences of intermediate behaviour took place on beans. Only 1.7 per cent of the aphids which alighted settled down, but lack of observations during darkness makes it impossible to state whether this is the whole measure of the selection process. However a study of these potential “settlers” showed that the numbers of probes increased from non-host to host plants, in parallel with previous results. These results from systematic field studies confirm those of Bruce Johnson and of Ibbotson & Kennedy based on laboratory experiments regarding the change-over from the motor phase of the migrating aphids to the vegetative phase of the parasitic period, and support also the unpublished results of Hennig regarding the gradual development of host selection and of plant puncturing reactions. The processes are promoted by specific qualities of the host plants, particularly those of the leaf surface. Thus on host plants only do the motor impulses die away. These quantitative measurements of field reactions show how aphid behaviour may be important in transmitting nonpersistant viruses.

Beschreibung / Inhaltsverzeichnis: Summary The developmental cycle of the aleyrodid Aleurochiton complanatus was studied at fortnightly intervals during 1961 in a wild population on Norway leaves (Acer platanoides) from a park in Quedlinburg. The seasonal dimorphism of the puparia, previously described by Haupt in 1934, from a few observations, was confirmed. The species is almost completely bivoltine and forms two different puparial types: teneral, almost colourless summer puparia which develop immediately, and more sclerotised, dark-coloured winter puparia with white wax patterns and strongly marked dormancy. Summer puparia are found during July, predominating in the first generation produced by the spring adults hatching from the over-wintering puparia. A small proportion of summer puparia are also found in the next generation. The winter puparia develop mainly during late summer and are produced in the second generation. However, up to 10% of the first generation pupae are of the over-wintering type. The winter puparia were examined for development and hatching at 20° C after exposure to 0°, 5°, 8°, 15°, and 20° for different periods. The results demonstrated the typical features of a diapause; i.e. almost complete check of development at 20° C, strong retardation and reduced hatching rate at 15° C, rapid and complete hatching after chilling for at least one to two months at the lower temperatures. Chilling to 0° C for this period was most effective. Only when the chilling period lasted more than five months was there a significantly increased mortality. Seasonal dimorphism is thus connected with a facultative diapause. Nevertheless some individuals in each generation behave abnormally and there is some tendency to a monovoltine and a trivoltine cycle in addition to the normal bivoltinism. Breeding Aleurochiton acerina Hpt. in nylon bags on Field Maple (Acer campestre) showed similar results. However, under the same conditions Nealeurochiton pseudoplatani (Visnya) formed only one generation on its host, sycamore (Acer pseudoplatanus), due to the slow speed of development in the climate of Central Germany. It is probable that offspring of the few summer puparia, formed in the first (summer) generation, are seldom able to finish their development before the leaves wither in autumn. The normal latent seasonal dimorphism may be developed fully where favourable conditions are provided, including long day illumination and a healthy host plant, with an adequate environmental temperature.

Beschreibung / Inhaltsverzeichnis: Summary The biggest and smallest seeds of Schlanstedt (S or s) and Rastatt (R or r) field beans were selected in order to produce under otherwise identical conditions young plants of differing growth. When the third primary leaf pair unfolded the plants were decapitated so as to leave only one leaflet of the first pair. On such seedlings were determined the numbers and lengths of young Aphis fabae specimens borne by each young virginoparous aptera during the time from birth to maturity of her first-born daughter. The young plants formed the series S〉s≧R〉r according to the size of the first leaf, and another series S〉R〉s〉r according to the cross sectional area of the stem. Quite similarly, the mean numbers and lengths of the first-born daughters were found to decrease as the leaf area of their host plants diminished, though the difference between R and s was not so great as between other members of the series. The mean length of the adult daughters was shown to be proportional to the mean leaf area available to each larva during postembryonic development. When R- and s-plants of identical growth activity were used, the antibiotic effects of their differing resistance against the bean aphids were no longer demonstrable between Schlanstedt and Rastatt field beans. Therefore one wonders whether the differing antibiotic resistance of these varieties should not be interpreted in terms of their differing growth intensities rather than as the result of some other quantitative or qualitative difference between them.

Beschreibung / Inhaltsverzeichnis: Summary Different coloured summer lettuces of the Quedlinburg Assortment (Saatzuchtleiter Fabig) allowed tests of the landing reaction of aphids, especially Aphis fabae Scop. and Myzus persicae Sulz., on plants of different colours to be compared with Moericke's findings using artificial coloured carriers. Direct captures of landing aphids, as described by H. J. Müllér (1962), showed twice as many aphids, and from three to five times as many Myzus persicae, on green varieties Ramses and Rhenania and on yellow-green Rudolfs Liebling than on the almost completely dark reddish brown Indianerperle. However the brown-red but yellow-green striped variety Pirat was landed upon by almost as many aphids as the green varieties. When the yellowish and yellow-green varieties Rudolfs Liebling and Ramses were planted within a plot of whitish-green young winter wheat, many more aphids alighted than would have been expected if chance only had operated. Fewer alighted on the whitish-green Rhenania in the same situation. The dark brown Indianerperle received few aphids when grown among wheat. The landing impulse on yellow and green lettuces is thus increased when their colour contrasts with that of the surroundings, but this does not apply to the brown varieties. Colourless glass dishes, filled with water, were used as traps and set in the middle of plots of different coloured lettuces (using many replicates during the whole growing period) caught only twice as many aphids among yellow as among green or brown varieties; this was due to an edge effect. The stronger the impulse to land on a lettuce variety, the more aphids are caused to land at the edge of the plot. Thus only a few reach the trap in the middle. When yellow dishes replace the colourless traps, a much higher number of aphids is caught among reddish-brown lettuces. Brown lettuce varieties are known to show a lower incidence of lettuce mosaic than yellow or green varieties. This is presumably due to the smaller number of aphids alighting, thus diminishing the chance of infection.

Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird über eine Methode zur Identifizierung von Y-Körperchen in Haarwurzelzellen mittels Fluorescenzfärbung berichtet. In den Zellen von 52 normalen Männern konnte das Y-Körperchen in einem Prozentsatz zwischen 15 und 64 nachgewiesen werden. 2 Y-Körperchen fanden sich unter 5200 Zellen nur 60mal. Bei normalen Frauen findet sich ein Fluorescenzkörperchen nur äußerst selten. Die Methode eignet sich für Screening-Untersuchungen zum Auffinden Y-chromosomaler Aberrationen.