Chromosome behavior and sterility of hybrids between the common onion,Allium cepa,and the related wild A. oschaninii

Summary Four hybrid plants were obtained when cytoplasmic male-sterile onion inbreds, Allium cepa L., were pollinated with a wild cepa-like allium introduced from northeastern Iran and identified as A. oschaninii O. Fedtsch. It has been proposed on morphological grounds that A. oschaninii is wild A. cepa or the ancestor of A. cepa. Nevertheless, chromosome irregularities and complete sterility in the hybrids suggest that there may be a greater sterility barrier between A. cepa and A. oschaninii than between A. cepa and 3 other species reported to cross with A. cepa, namely A. fistulosum L., A. galanthum Kar. et Kir., and A. pskemense B. Fedtsch.Cooperative investigation of the U.S. Department of Agriculture and the Idaho Agricultura Experiment Station, Parma Branch Station.     

Continuous Plant Regeneration from Established Embryogenic Cell Suspension Cultures of Italian Ryegrass and Tall Fescue

The suitability of different protocols was compared for entire plant regeneration by somatic embryogenesis, of the forage plants Lolium multiflorum Lam. (Italian ryegrass) and Festuca arundinacea Schreb. (tall fescue). In the first protocol, miniature embryos were used as starting material, while mature seeds were retained in the other two. Whichever the considered protocol, undifferentiated calli were produced on Murashige and Skoog MS medium supplemented with 2,4-D. The calli were subcultured in the dark on solid MS agar medium, containing 5 mg/1 2,4-D (protocol 2) or on solid MS medium followed by transfer to a rotated liquid MS medium with 2 mg/1 2,4-D (protocol 1). In these conditions, induction of somatic embryogenesis occurred, and whole plants were regenerated during a limited lapse of time, upon transfer in the light, to MS medium supplemented with BAP but devoid of 2,4-D. The simultaneous elimination of 2,4-D and transfer to light appeared essential for full regeneration of the plants. Using this characteristic, an additional step was added to a new protocol (protocol 3) in which microcalli, cultured on liquid MS medium containing 5 mg/1 2,4-D, were transferred to the same medium with 2 mg/1 2,4-D, in the dark. In these conditions, the suspensions kept their embryogenic potential for months. In all cases, plantlets were successfully transferred into the soil. An evaluation of the somaclonal variation potential of the plants issued from each protocol is now underway.     

Determination of aflatoxin concentrations in peanut butter by enzyme-linked immunosorbent assay (ELISA): study of three commercial ELISA kits

Sixteen United Kingdom analytical laboratories participated in an evaluation of 3 commercially available enzyme-linked immunosorbent assay (ELISA) kits for analysis of aflatoxin in peanut butter. Each laboratory was sent 3 sets of 10 randomly numbered samples of peanut butter. Each set consisted of 5 pairs of undisclosed duplicates. Four of the sets of duplicates were naturally contaminated butters with "target" aflatoxin values (estimated by liquid chromatography) between 8 and 81 micrograms/kg. The fifth pair was a blank peanut butter containing approximately 3 micrograms/kg of total aflatoxins. A statistical treatment of the results of the study is presented, together with discussion of the relative merits of the different kits.     

Perceived risk, displacement and refuging in brown bears: positive impacts of ecotourism?

Ecotourism is a rapidly growing industry with unknown impacts on viewed wildlife that may require novel management action. We examined the impact of viewing activities on the behaviour of brown bears (Ursus arctos) in coastal British Columbia.Domination of the best feeding sites and human avoidance by large male bears has consistently been reported. We, however, saw displacement in time rather than space - during the viewing day large males were less active than at other times, while females with cubs tended to be more active.In each year, females with cubs spent similarly high proportions of their time fishing when people were present. In years with large male activity, less time was spent fishing when people were absent. When freed from the potential threat of large male bears, females with cubs showed no measurable impact of controlled human activity.Human presence at a feeding site impacts the behaviour of brown bears, but not as expected. Temporal avoidance of human activity by large males was observed; indications that they departed upon satiation, before the arrival of morning tours, however, suggests that there was little energetic impact. By displacing large males, viewing activities created a temporal refuge, enhancing feeding opportunities for subordinate age/sex classes. With the strong positive relationships between mean female mass and litter size, this may in turn increase population productivity.     

Butterfly-Plant Coevolution: Has Passiflora adenopoda Won the Selectional Race with Heliconiine Butterflies?

Hooklike trichomes of Passiflora adenopoda provide a specific, effectively absolute defense against heliconiine butterfly larvae, a major class of Passiflora herbivores. It is suggested that since mechanical defenses are usually more selective in their action against herbivores, they usually are evolved by a plant only after it has accumulated a series of chemical defenses.     

Ovarian Dynamics in Heliconiine Butterflies: Programmed Senescence versus Eternal Youth

New oocytes are generated throughout long lives in butterflies of the genus Heliconius, which as adults feed on amino acids from pollen. In Dryas julia, a related heliconiine that feeds only on nectar and is relatively short-lived, the original oocyte supply is eventually depleted. Such divergent ovarian dynamics in closely related organisms are significant in terms of both their evolutionary basis and their physiological controls.