Some observations on susceptibility and resistance of winter wheat to the aphid Sitobion avenae (F.) in Britain

Resistance to Sitobion avenae (F.) (Hemiptera: Aphididae) was assessed in glasshouse tests of 20 winter wheat varieties that were of major importance or are currently recommended for British agriculture. The varieties Kador, Bounty, Rapier, Virtue, Bouquet and Maris Ranger were relatively resistant and the varieties Maris Huntsman, Armada, Joss Cambier, Bersée and Hybrid 46 were the most susceptible. The significance of these findings for growers, for integrated control of cereal aphids and for plant breeding is considered.     

Contamination of pathogen-free seed potato stocks byErwinia carotovora during multiplication: Results of a six-year monitoring study

Summary Recontamination byErwinia carotovora of seed potato stocks (VT) derived from stem cuttings in the process of multiplication was monitored on four farms in the east of Scotland from 1973 to 1978. Randomly selected VT stocks of different ages from a wider range of farms were also examined. The results showed that although contamination can occur early during stock multiplication there was, in general, no stepwise increase in contamination level from one generation to the next. However, contamination tended to be greater after the third multiplication year when stocks are grown by conventional methods used for lower-grade seed stocks. It is notable that contamination was consistently high on some farms and low on others. Contamination byE. carotovora var.carotovora tended to be greater than byE. carotovora var.atroseptica. These results may be explained by the farm practices of individual growers, soil moisture status and aerial transmission of the bacteria. The results also indicate that contamination of some potato stocks derived from stem cutting could be maintained at a low level over several generations more readily on some farms than on others.

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Zusammenfassung Von 1977 bis 1978 wurde auf vier Betrieben im Osten Schottlands im Laufe der Vermehrung von Pflanzkartoffelposten (SC), die von Stengelschnitten stammten, eine erneute Verseuchung durchErwinia carotovora beobachtet. Zudem wurden Stichproben von SC-Posten unterschiedlichen Alters aus einer gr?sseren Zahl von Betrieben untersucht. Die Zusammenfassung aller Ergebnisse der vier Betriebe zeigte, dass die ersten drie Generationen der Best?nde (Vermehrungsjahre 1 bis 3) zu weniger Ansteckung neigten als jene in den Jahren 4 und 5, wenn die Posten zur Erzielung von Saatgut tieferer Anbaustufen (Tabelle 1) mit konventionellen Handelsmethoden behandelt wurden. H?here Verseuchungsgrade wurden auch in den Jahren 4 und 5 in den Stichprobenposten erreicht (Tabelle 5). Wenn die Daten Betrieb für Betrieb analysiert wurden, fand man auf einigen Betrieben durchwegs hohe und auf anderen niedrige Verseuchungsgrade (Tabelle 2). Obwohl die Gesamtzusammenfassung der Daten (Tabelle 1) darauf hinwies, dass sowohlE. carotovora var.carotovora als auchE. carotovora var.atroseptica in ungef?hr gleichem Ausmass vorhanden waren, war der erste Organismus auf drei von vier Betrieben und der letztere auf dem vierten Betrieb vorherrschend (Tabelle 3). Obwohl die Ansteckung früh w?hrend der Bestandesvermehrung auftreten kann, gab es im allgemeinen keinen Entwicklung im Verseuchungsgrad. Statt dessen fiel der Verseuchungsgrad manchmal von einer Generation zur n?chsten (Tabelle 4). Diese Ergebnisse wurden versuchsweise mit dem Aufwand an Sorgfalt durch den einzelnen Pflanzen, durch den Zustand der Bodenfeuchtigkeit und durch den Lufttransport der Bakterien erkl?rt. Auf einigen Betrieben konnten die Kartoffelbest?nde nicht nur über einige Generationen relativ frei von Ansteckung durchE. carotovora erhalten werden, sondern weisen auch darauf hin, dass seit 1973 eine deutliche Verbesserung eintrat, selbst wenn einige Jahre n?sser und damit für die Bestandesverseuchung günstiger waren als andere (Tabelle 6). Parallel mit dieser Abnahme der Verseuchung verl?uft ein schw?cheres Auftreten der Schwarzbeinigkeit in Pflanzbest?nden, die seit 1973 zur Feldbesichtigung angemeldet wurden, als ein stets h?herer Anteil von Best?nden von Stengelschnitten stammte (Tabelle 7).

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Résumé La recontamination parErwinia carotovora de lignées de pommes de terre de semences (SC)_ provenant de bouturage dans le procédé de multiplication a été contr?lée dans quatre exploitations agricoles dans l'est de l'Ecosse de 1977 à 1978. Des lignées de bouture, sélectionnées au hasard, de différents ages, provenant d'une plus grande gamme d'exploitations, furent aussi examinées. Le résumé des résultats obtenus dans les quatre exploitations montraient que les trois premières générations de récolte (années de multiplication 1 à 3) avaient tendance à être moins contaminées que celles des années 4 et 5 quand les lignées avaient été traitées par des méthodes commerciales conventionnelles utilisées pour des clones de qualité inférieure (tableau 1). De hauts niveaux de contamination furent aussi obtenus dans les années 4 et 5 des lignées sélectionnées au hasard (tableau 5). Quand les données furent analysées ferme par ferme, les niveaux de contamination montrèrent qu'ils étaient significativement hauts dans certaines exploitations et bas dans d'autres (tableau 2). De la même manière, quoique le résumé des résultats (tableau 1) suggère queErwinia carotovora var.carotovora etErwinia carotovora var.atroseptica étaient présents en même quantité, le premier pathogène prédominait dans 3 exploitations sur quatre, et le dernier dans la quatrième exploitation (tableau 3). Bien que la contamination puisse avoir lieu au début de la multiplication de la lignée, il n'y a pas eu, en général, de niveau de contamination avancée. Le niveau de contamination tombait même quelquefois d'une génération à l'autre (tableau 4). Les résultats s'expliquaient par l'importance des précautions prises par les agriculteurs, le niveau d'humidité dans le sol et la transmission aérienne des bactéries. Non seulement on a pu maintenir dans quelques exploitations des lignées de pommes de terre relativement indemnes de contamination parErwinia carotovora pendant plusieurs générations, mais encore les résultats suggèrent qu'une amélioration notable a eu lieu depuis 1973 pendant certaines années plus humides, et par conséquent plus favorables à la contamination de la récolte que d'autres (tableau 6). Parallèlement à cette réduction de contamination, la jambe noire a eu moins d'importance dans les cultures de semence soumises au contr?le depuis 1973, tandis qu'une proportion de plus en plus élevée provenait de bouture (tableau 7).

     

Oxytocin receptors in dioestrous and anoestrous canine uteri

The aim of the study was to localize oxytocin receptors (OTR) and measure mRNA expression of OTR in the canine uterus with and without the influence of progesterone. Uterine samples were taken from nine anoestrous and eight dioestrous bitches during ovariohysterectomy. Histological changes were evaluated in haematoxylin and eosin (HE)‐stained samples. Purified polyclonal antibody for OTR was used in immunohistochemistry to localize receptors in uterine layers. Relative mRNA concentration of OTR was evaluated with real‐time PCR from full‐thickness uterine samples taken from the middle horn and the body. Myometrial smooth muscle cells, endometrial luminal epithelium (LE) and deep and superficial glandular epithelium were positively stained for oxytocin receptors in non‐pregnant animals. No significant difference in staining intensity was detected between uterine middle horn and body. However, the staining intensity of LE was significantly higher in dioestrous than in anoestrous uteri (p < .05). Leucocytes and endothelium of blood vessels were also positively stained for OTR. Real‐time PCR showed no significant differences in OTR mRNA expression between the middle horn and the body of the uterus, or between anoestrous and dioestrous uterus. No correlation was noted between OTR mRNA expression and blood progesterone concentration. In conclusion, despite the apparent inactivity, the uterus of the non‐pregnant bitch expresses OTR. The distribution or relative expression of OTR does not differ between uterine horn and body in dioestrus or anoestrus except in LE. LE may have more oxytocin‐dependent activity during dioestrus than anoestrus.     

A free-fall determination of the newtonian constant of gravity

Recent determinations of the Newtonian constant of gravity have produced values that differ by nearly 40 times their individual error estimates (more than 0.5%). In an attempt to help resolve this situation, an experiment that uses the gravity field of a one-half metric ton source mass to perturb the trajectory of a free-falling mass and laser interferometry to track the falling object was performed. This experiment does not suspend the test mass from a support system. It is therefore free of many systematic errors associated with supports. The measured value was G = (6.6873 +/- 0. 0094) x 10(-11) m3 kg-1 sec-2.     

Killer whale predation on sea otters linking oceanic and nearshore ecosystems

After nearly a century of recovery from overhunting, sea otter populations are in abrupt decline over large areas of western Alaska. Increased killer whale predation is the likely cause of these declines. Elevated sea urchin density and the consequent deforestation of kelp beds in the nearshore community demonstrate that the otter's keystone role has been reduced or eliminated. This chain of interactions was probably initiated by anthropogenic changes in the offshore oceanic ecosystem.     

Circular polarization in star- formation regions: implications for biomolecular homochirality

Strong infrared circular polarization resulting from dust scattering in reflection nebulae in the Orion OMC-1 star-formation region has been observed. Circular polarization at shorter wavelengths might have been important in inducing chiral asymmetry in interstellar organic molecules that could be subsequently delivered to the early Earth by comets, interplanetary dust particles, or meteors. This could account for the excess of L-amino acids found in the Murchison meteorite and could explain the origin of the homochirality of biological molecules.     

Reconstitution of muscle F‐actin from Atlantic salmon (Salmo salar L.) with carotenoids—binding characteristics of astaxanthin and canthaxanthin

The binding of carotenoids to the myofibrillar protein F‐actin purified from the white muscle of Atlantic salmon (Salmo salar L.) was studied using in vitro reconstitution. The binding of astaxanthin and canthaxanthin was saturable, and analysis revealed the presence of a single carotenoid‐binding site. The dissociation constants (K_d) for actin prepared from 2.5 kg FW (Fresh Weight) fish were 1.04 ± 0.13 μg carotenoid per milligram of actin and 0.54 ± 0.11 μg/mg for astaxanthin and canthaxanthin, respectively. The saturation binding level (B_max) for astaxanthin was 1.39 ± 0.07 μg/mg and 1.04 ± 0.08 μg/mg for canthaxanthin. These values were higher for F‐actin prepared from organic and small (~0.5 kg FW) salmon than for non‐organic and larger, mature fish. The structural specificity of carotenoid binding revealed a preference for carotenoids that possess a keto group at C‐4 on the β end group of the molecule, but the presence of hydroxyl groups at C‐3 or C‐4 reduced overall binding efficiency. The study suggests that the ability of myofibrillar proteins to bind carotenoids is not a limiting factor governing the deposition of carotenoids in the muscle of salmonids.     

Ecological studies on cocco1d bacteria in a pine forest soil—III. competitive interactions between bacterial strains in soil

Strains of bacteria with differing degrees of overall (phenetic) similarity have been paired and grown together and separately in both acid and alkaline soils from a pine forest. A decrease in yield of an organism when grown in the presence of a second organism was taken as evidence of competition. It was shown that, contrary to expectations, pairs of organisms with different degrees of similarity might have similar competitive interactions. It is postulated that this is because one key property could result in a marked change in competitive ability while not markedly altering the taxonomic relationships of the organisms. The possibility that spatial separation of organisms can result in two or more organisms with identical functions becoming established in soil is discussed.