A glasshouse method for testing chemicals for control of potato common scab

Summary Plants of scab-susceptible varieties (Majestic orMaris Piper) were grown in pots in the glasshouse in field soil infested withS. scabies, with or without added chemicals; the stolons were confined to the top 4 cm of soil by a buried layer of ‘Terylene’ net and the plants, when well rooted, were watered from saucers only. Tubers became heavily scabbed in untreated soil. Results from comparative glasshouse tests and field trials of seven chemicals agreed well on both control and yield. The glasshouse method was quick (8 weeks or possibly less) and could be throughout most of the year.

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Zusammenfassung Für die Infektion von Knollen durch Flachschorf (Streptomyces scabies) sind nachstehende bedingungen notwendig: die Stolonen einer anf?lligen Sorte sollten, um kleine Knollen zu bilden, in warmen, trockenem, schorfbefallenem Boden mit pH>5,5 anschwellen. Die Anforderungen an eine Glashausmethode zur Prüfung von chemischen Pr?paraten für die Schorfbek?mpfung unter den obenerw?hnten Bedingungen bestehen in folgendem: Tont?pfe wurden mit drei gleich hohen Schichten Erde gefüllt. Die unterste Schicht bestand, aus gew?hnlichem Kompost für Topfversuche. Als mittlere und obere Schicht, die durch die Einlage eines ‘Terylene-Netzes’ voneinander getrennt wurden verwendete man einheitliche, nicht sterilisierte, mit Schorf infizierte Ackererde, der die zu prüfenden Chemikalien in der notwendigen Menge beigefügt wurden (in der Regel 50 ppm). Ein einzelner, gut bewurzelter Trieb (SorteMajestic oderMaris Piper) wurde in die oberste Schicht eines jeden Topfes eingepflanzt (Abb. 1). Die T?pfe (20 pro Verfahren) wurden wahllos in einem Glashaus bei 20°C (Tag) und 15°C (Nacht) aufgestellt. Sie wurden die ersten 10 Tage reichlich begossen, aber nachher bekamen sie nur noch 50 ml pro Topf und Tag in den Unterteller. Nach weiteren 10 Tagen wurde dreimal pro Woche das Wasser durch 50 ml Hoagland-L?sung ersetzt. Die Wurzeln durchdrangen das Netz rasch, um die feuchte Nahrungsmischung am Boden zu erreichen, aber die Stolonen taten dies nicht; die Knollen wurden im trockenen Boden nahe der Oberfl?che gebildet, und in unbehandeltem Boden waren sie fast immer stark mit Schorf befallen. Bei der Ernte (8–10, Wochen nach dem Eintopfen) wurden die Knollen gewogen und auf Schorfbefall beurteilt. Ergebnisse mit sieben chemischen Pr?paraten wurden mit solchen aus Feldversuchen in den Jahren 1968 und 1969 mit den gleichen Pr?paraten verglichen, als die trockenen Sommer Gew?hr boten, dass die Knollen auf dem Feld ungef?hr ebenso stark schorfig waren wie jene im Glashaus. Die Ergebnisse beider Methoden stimmten bei der Schorfkontrolle gut überein und, was erstaunlicher war, auch in Bezug auf Einfluss der Chemikalien, auf den Ertrag (Tabelle 1). Jede signifikante Zu-oder Abnahme im Schorfbefall oder im Ertrag im Glashaus (P≤0,05) stimmte überein mit einem entsprechenden signifikanten Einfluss auf dem Feld; dagegen traten nicht alle im Feldversuch festgestellten Schwankungen auch im Glashaus auf.

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Résumé Les conditions nécessaires pour l'infection des tubercules par la gale commune (Streptomyces scabies) sont le renflement des stolons d'une variété susceptible pour devenir de petits tubercules, un sol chaud et sec infecté de gale d'un pH>5,5. Les principes d'une méthode de serre pour tester les produits chimiques de lutte contre la gale, principes qui réalisent les conditions ci-dessus, sont les suivants. Des pots d'argile sont remplis de trois couches de sol d'égale épaisseur. La couche inférieure consiste en compost de rempotage. Les couches moyenne et supérieure, qui sont séparées l'une de l'autre par un, filet circulaire de ‘Terylene’, sont consituées de sol provenant d'un champ uniformément infesté et non stérilisé, auquel les produits chimiques à tester sont ajoutés suivant les nécessités (habituellement à 50 ppm). Un simple germe bien enraciné (var.Majestic ouMaris Piper) est planté dans la couche supérieure de chaque pot (Fig. 1). Les pots (20 par traitement) sont placés au hasard dans une serre à 20°C (jour) et 15°C (nuit). Les pots sont arrosés abondamment pendant les 10 premiers jours, mais, par après, ils re?oivent seulement 50 ml par jour, et par pot, dans la soucoupe. Après les 10 jours suivants, on subtitue à l'eau 50 ml de la solution de Hoagland et cela, trois fois par semaine. Les racines traversent rapidement le filet pour atteindre le mélange nutritif humide de la base, mais les stolons ne le traversent pas; les tubercules sont formés dans le sol sec près de la surface et, dans le sol non traité, sont presque toujours sévèrement infectés de gale. A la récolte (8–10 semaines, après la mise en pot) les tubercules sont pesés et l'infection de gale appréciée. On a comparé les résultats obtenus avec sept produits chimiques avec les résultats des mêmes produits obtenus dans les champs en 1968 et 1969, années où les conditions de sécheresse faisaient que les tubercules des champs étaient approximativement aussi sévèrement atteints de gale que ceux des serres. Les résultats des deux méthodes s'accordent bien pour le contr?le de la gale et, ce qui est plus surprenant, pour les effects des produits chimiques sur la production (Tableau 1). Chaque augmentation ou diminution significative de gale ou de production en serre (P≤0,05) est égale à un effet significatif correspondant dans le champ, quoique l'opposé ne soit pas toujours vrai.

     

Decreased common scab incidence after foliar sprays of daminozide

Summary In four small trials in two fields infested withStreptomyces scabies, potato foliage (cv. Maris Piper) was sprayed with solutions of the growth retardant daminozide in May–June. The sprays roughly halved the amount of scab in one field but were less effective in the other. The decrease in scab was not influenced by changes in daminozide concentration (3–10 g litre), by varying the timing of single sprays (mainly in June) or by spraying more than once. Yields of tubers were unaffected.     

Fructokinase,Fructans, Intestinal Permeability,and Metabolic Syndrome: An Equine Connection?

Fructose is a simple sugar present in honey and fruits, but can also exist as a polymer (fructans) in pasture grasses. Mammals are unable to metabolize fructans, but certain gram-positive bacteria contain fructanases and can convert fructans to fructose in the gut. Recent studies suggest that fructose generated from bacteria or directly obtained from the diet can induce both increased intestinal permeability and features of metabolic syndrome, especially the development of insulin resistance. The development of insulin resistance is driven in part by the metabolism of fructose by fructokinase C in the liver, which results in oxidative stress in the hepatocyte. Similarly, the metabolism of fructose in the small bowel by intestinal fructokinase may lead to increased intestinal permeability and endotoxemia. Although speculative, these observations raise the possibility that the mechanism by which fructans induce laminitis could involve intestinal and hepatic fructokinase. Further studies are indicated to determine the role of fructanases, fructose, and fructokinase in equine metabolic syndrome and laminitis.     

RAPD-based assessment of genetic relationships among and within American ginseng (Panax quinquefolius L.) populations and their implications for a future conservation strategy

American ginseng (Panax quinquefolius) is a native North American medicinal plant that is becoming increasingly vulnerable despite government harvest restrictions. To better understand the genetic diversity and gene flow of American ginseng, we studied RAPD variation in cultivated and wild populations. Classical and Bayesian analogues of genetic diversity statistics were estimated in seven wild and two cultivated populations. The wild populations were more highly structured (G _stβ  = 0.41) than the cultivated populations (G _stβ  = 0.24). The genetic diversity within populations ranged from H _eβ  = 0.05 to 0.38. Based on genetic pairwise distances, six of the wild populations clustered with the locally-derived cultivated population, while one wild population was more similar to the non-local cultivated population than the local populations. This wild population was highly diverse (P = 1.0; U = 1.0) suggesting that it was supplemented from exotic seed. A set of eight RAPD markers was identified that differentiated plants of local and non-local origin. As a conservation strategy, we recommend that regional gene banks be established based on molecular and geographic diversity to preserve the locally adapted germplasm. These regional gene banks would serve as a conservation tool and also provide a source of genes for genetic improvement of cultivated ginseng.     

Genetic relationship between the adult plant resistance gene Lr12 and the complementary gene Lr31 for seedling resistance to leaf rust in common wheat

A resistant phenotype similar to that conferred in wheat by the complementary genes Lr27  +  Lr31 was produced in the progeny of intercrosses of cultivars carrying Lr27 and a line possessing Lr12 . This confirms that Lr12 is either completely linked with Lr31 or is the same gene. On the basis of these findings and that Lr31 is located on chromosome 4BS, it is concluded that Lr12 must also be located on 4BS. Adult-plant genetic tests confirm that the Australian wheat cultivar Timgalen carries Lr12 , and stocks with Lr12 alone were established from this cultivar.     

Generation of Paramoeba perurans clonal cultures using flow cytometry and confirmation of virulence

Amoebic gill disease (AGD) in farmed Atlantic salmon is caused by the amoeba Paramoeba perurans. The recent establishment of in vitro culture techniques for P. perurans has provided a valuable tool for studying the parasite in detail. In this study, flow cytometry was used to generate clonal cultures from single‐sorted amoeba, and these were used to successfully establish AGD in experimental Atlantic salmon. The clonal cultures displayed differences in virulence, based on gill scores. The P. perurans load on gills, determined by qPCR analysis, showed a positive relationship with gill score, and with clonal virulence, indicating that the ability of amoebae to proliferate and/or remain attached on gills may play a role in virulence. Gill scores based on gross signs and histopathological analysis were in agreement. No association between level of gill score and specific gill arch was observed. It was found that for fish with lower gill scores based on histopathological examination, gross examination and qPCR analysis of gills from the same fish were less successful in detecting lesions and amoebae, respectively.     

Field trials of chemicals for control of common scab by soil treatment

Summary In six field trials, sixteen chemicals were compared against common scab, with quintozene as standard, by application to soil before planting. Captafol was as effective as quintozene, and did not decrease yield, but the closely related chemicals captan and folpet were ineffective. The other chemicals, of which over half were dihydroxybenzenes or dithiocarbamates, also failed to decrease scab. or decreased yield, or both.