Replication of the cauliflower mosaic virus: role and stability of the cloned delta 3 discontinuity sequence

A fragment of cauliflower mosaic virus (CaMV) DNA, containing delta 3, one of the three discontinuity sequences, was cloned in various ways into CaMV DNA deleted for the delta 3 sequence. The series of constructions was monitored for the appearance of the typical single-strand (ss) discontinuity after hybrid CaMV replication in plants. The delta 3 discontinuity was observed only if the orientation of inserted DNA sequence was the same as in the wild-type virus. Long polylinker sequences used for insertion of the fragment into cloned viral DNA, affected the stability of the insert in progeny viral DNA in plants by acting as recombination targets.     

Epithiospecifier protein in turnip and changes in products of autolysis during ontogeny

An epithiospecifier protein present in turnip tissue gives rise to 1-cyano-epithioalkanes during autolysis. Volatile hydrolysis products are produced from glucosinolates during autolysis of seeds, seedlings and plant tissue more than 6 weeks after sowing.     

Effects of the angle of inclination of traps on the numbers of large Diptera caught on sticky boards in certain vegetable crops

The angle of inclination of the surface on which flies prefer to land in vegetable crops was studied in field plots and in field-cages using one-sided sticky traps aligned in one plane but orientated in eight directions. The four Delia species studied, D. antiqua, D. floralis, D. platura and D. radicum, preferred to land on horizontal surfaces, indicating that they are likely to be trapped in largest numbers on traps with a horizontal trapping surface, such as water traps. This trend was even more pronounced with the Syrphidae. In contrast, greatest numbers of the carrot fly, Psila rosae, were caught on the lower surface of traps inclined at 45° to the vertical. The advantages of using traps inclined in this way for trapping P. rosae are that more flies are caught on such surfaces, the sticky trapping compound is protected from the adverse effects of rain, and the traps are highly selective.

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Résu,é L'angle d'inclinaison de la surface sur laquelle les mouches préfèrent atterrir dans les cultures de légumes a été examiné dans la nature, dans des parcelles et dans des cages, en utilisant des pièges englués sur un côté, alignés dans le même plan, mais orientés dans 8 directions. Les 4 espèces de Delia étudiées: D. antiqua, D. floralis, D. platura, D. radicum, ont préféré atterrir sur des surfaces horizontales, ce qui implique qu'elles sont probablement prises en plus grand nombre sur des pièges avec une surface de capture horizontale, comme des pièges liquides. Cette tendance est encore plus prononcée chez les Syrphidae. A l'opposé, de nombreuses mouches de la carotte, Psila rosae, ont été capturées sur la face inférieure de pièges inclinés de 45°. Il est avantageux d'utiliser des pièges inclinés de cette façon contre P. rosae parce que, d'une part ils sont très efficaces, d'autre part le produit actif est protégé de la pluie et enfin, le piège est très sélectif.

     

The making of a pest: recruitment of Meligethes aeneus onto oilseed Brassicas

Populations of the rapeseed pollen beetle Meligethes aeneus F. (Col., Nitidulidae) from areas with 0–16 years of history of intensive rapeseed growing were compared for key ecological characters. During the first 16 years of rapeseed cultivation the reproductive success of M. aeneus increased 200–300% over that of the beetles living on the natural host plants, cruciferous weeds. The increase was linear over time and statistically highly significant, and it did not appear to be related to food quality or to the size of the beetles. During the same period the tolerance to intraspecific competition decreased, possibly due to the relative absence of such competition on the new crop. Furthermore, the optimum population density for M. aeneus to maximize the size of its next generation on summer turnip rape was determined to be 0.5–1.0 beetles/plant, which is slightly below the economic threshold for chemical control (1 beetle/plant). Therefore the practical protection of the rapeseed yield also ensures the highest possible pest population size for the next year. These mechanisms may in part explain the particular noxiousness of the species as a pest all over Europe. In general these data show that after the introduction of a new crop plant into a region, significant changes during the recruitment process in a pestiferous insect may take place, contributing to the future pest status of the insect. It is suggested that such genetic and ecological changes in insects may be a more common mechanism than previously thought in initiating and sustaining pest outbreaks, and that conventional pest management methods may enhance that effect.     

Volatile constituents from cauliflower and other crucifers

Vapour emanating from intact turnip and radish plants contained small amounts of only one component, probably hexenyl acetate, distinguishable from background vapours. From disrupted leaf tissues of cauliflower, turnip, radish and wallflower at 30°, the predominant vapour component was cis-hex-3-enyl acetate, whereas allyl isothiocyanate was the chief component from Brassica juncea. Other minor components were also identified. Apart from isothiocyanates, the only sulphur-containing component identified from these crucifers was dimethyl disulphide which was detected only from cauliflower, particularly in vapour from disrupted curd tissue.     

Effect of age on the responsiveness of peripheral chemosensory sensilla of the turnip root fly (Delia floralis)

The effect of insect age on the neural responsiveness of gustatory sensilla was investigated. Electrophysiological recordings were obtained from type A and type D sensilla on the pro- and meso-thoracic tarsi, and from sensilla on the labellum of the turnip root fly,Delia floralis (Fallen) in response to potassium chloride, sucrose and sinigrin. The age of the fly did have an effect on the numbers of sensilla responding to the test stimuli and on the magnitude of the response, but there was no consistent pattern in these effects among sensilla. The labellar sensilla were more responsive to sucrose than the tarsal sensilla and the proportion of flies whose labellar sensilla responded to sucrose was initially low, but increased after day 2 of adult life. In contrast, the number of flies whose tarsal sensilla responded to stimulation with sucrose was initially high and decreased as the flies aged. There was a similar decline in the proportion of tarsal sensilla responding to potassium chloride. Neither the proportion of flies whose tarsal sensilla responded to sinigrin nor the magnitude of the response was influenced by the age of the fly. These finding are discussed in relation to the feeding and host selection behaviour of the fly.