Pods Of Rape Research Articles

The feeding and mating behaviour of pollen beetles (Meligethes aeneus Fab.) and seed weevils (Ceutorhynchus assimilis Payk.) on oil-seed rape (Brassica napus L.)

SUMMARYDuring the early period of infestation of winter rape, pollen beetles and seed weevils were mainly feeding and attaining sexual maturity. Before a crop flowered pollen beetles fed on buds but only some of those which they had perforated to obtain pollen dropped off. When flowering started adults obtained pollen from flowers rather than from buds. They laid their eggs in the buds but not in the flowers. Larvae moved from flower to flower up the raceme and caused no damage. Probably many podless stalks have been wrongly attributed to pollen beetle damage.Overwintered seed weevils caused no damage by feeding on rape pods. New generation seed weevils caused some loss of seed weight and viability when feeding on pods of spring rape; this is probably unimportant on a field scale.Pollen beetles and seed weevils mated from mid-May until the emergence of new generation adults; these did not mate before hibernating.

A survey of the damage caused to crops of oil-seed rape (Brassica napus L.) by insect pests in south-central England and their effect on seed yield

SummaryNo correlation was found between the seed yield per plant of oil-seed rape, the percentage of podless stalks and the percentage of pods infested with seed weevil larvae. The weight per seed and the percentage of podless stalks of winter and spring rape plants were similar.In winter crops the mean number of seeds per plant, weight of seeds per plant, and number of pods per plant were greater near the crop centre than near the crop edge. Plants with relatively few seeds tend to compensate by having heavier ones.Pods infested with seed weevil had fewer and lighter seeds than pods not infested, but the overall decrease in weight of seed per pod was small. The proportion of pods infested with seed weevil in winter rape was twice that in spring rape plants, but was not great. In lightly infested fields the weevils were concentrated at the edges, but the opposite occurred as infestation increased.Infestation of pods of winter rape by seed weevil increased with the number of years rape had been grown on the farm. There was no correlation between insecticide application and yield, but the number of insecticide applications to spring rape crops was positively correlated with the number of years for which the farmer had grown rape.

Comparison of the ultraviolet absorption spectrum curves of phytoalexins produced by different host and parasite combinations

Experiments were carried out to know if there were any differences among their properties of phytoalexins (PA) produced by different host and parasite combinations.1) Seed-rooms of opened pea pods were mounted with conidia suspension of each of Ascochyta pisi, Glomerella cingulata and Gibberella zeae, and incubated at 20°C for 24 hours. These three kinds of suspensions were then collected and centrifuged to obtain the supernatants (PA-solution). Five ml of each PA-solution was extracted three times with equal volume of petroleum ether, and then the solvent was evaporated at 80°C. Ethanol was added to each of the residues and ultraviolet absorption of the ethanol solution was measured by spectrophotometer (Shimazu QB-50). Three curves thus obtained showed the same tendency, and was concluded that these three PA substances were chemically the same.2) Seed-rooms of opened pods of rape (Brassica napus L.) and of the pods of common vetch (Vicia sativa L.), and leaves of broad bean (Vicia faba L.) from which the epidermis had been peeled off were mounted respectively with conidia suspension of G. cingulata. Thus three PA-solutions of different origins were obtained with the same method as described above. Ten ml of each PA-solution was extracted with equal volume of petroleum ether. Petroleum ether was evaporated under nitrogen gas at 20°C and 1ml of 3per cent ethanol was added to the residue. 0.2ml of each of three kinds of the liquids was mounted on a hole-slide-glass and its biological activity was assayed on conidia of G. cingulata. Parallel to the above experiment, 0.8ml of each of the liquids was diluted with 5ml of ethanol and ultraviolet absorption was measured. Three curves thus obtained and that of the PA liquids from pea were compared and found that these four PAs were distinctly different from each other.It was concluded from these results that chemical nature of PA was specific to the host plant species and was not specific to the fungi that was introduced to the hosts.

Relationship between the host specificity of pathogen and phytoalexin

In order to know whether the inhibitory action of a phytoalexin (PA) obtained from a certain host-parasite combination is specific to the parasite species used or not, three kinds of PAs were assayed on several phytopathogenic fungi including congenial and non-congenial to the host plants. The following three PAs were used: (1) garden pea pods versus Ascochyta pisi (pea-PA), (2) rape pods versus Glomerella cingulata (rape-PA), and (3) broad bean leaves versus Glomerella cingulata (broad bean-PA). These pods were inoculated, on the inner epidermis, with spore suspensions, incubated for 24 hours at 20°C, then the spore suspensions were collected, and the resulting PAs were extracted with petroleum ether, the latter being evaporated under reduced pressure at 20°C, then dissolved in ethanol. Broad bean leaves were inoculated, after the epidermis of lower surface were peeled off, on this surface with spore suspension of Glomerella cingulata. The PA was prepared by the same procedure as above.Series of PA agar media were made by adding varying amounts of PA ethanol solution to malt extract agar so as to prepare the media containing the PA at the concentrations of 8, 4, 2, 1, 1/2, 1/4, and 1/8 times of that of original PA-solution in the case of pea-PA, and 4, 2, 1, 1/2 and 1/4 times in the cases of rape- and broad bean-PAs, assuming that PAs were extracted throughly from the original PA-solutions with petroleum ether.Each of these media, 0.7ml was poured into a watch glass, 30-32mm in diameter, and was inoculated with a disc of agar, 0.3mm in diameter, on which the fungus to be tested had been grown. After being incubated for 2-7 days at 20°C the diameter of the colony was measured. The results were presented in Figures 1, 2, and 3.These results show that the pea-PA strongly inhibits the growth of Piricularia oryzae which can not infect the pea plant, inhibits to a medium extent the growth of Glomerella cingulata, which is a facultative parasite to the same plant, while inhibits very weakly that of Ascochyta pisi which is really a parasite to the plant.The detoxication of pea-PA by A. pisi and also by Fusarium oxysporum, both being pathogenic to the plant, was certified by in-vitro tests. The disappearance of the opaqueness around the colonies of the fungi on the PA agar media indicated the existance of PA-decomposing ability of both fungi. Ethanol extraction of the transparent zone thus appeared on the agar media around the colony showed a very low inhibitory action on the conidia germination of Glomerella cingulata, and also a remarkable decrease in its optical density at 309mμ by spectrophotometer (Table 5).