Inhibition of potato sprout growth by carvone enantiomers and their bioconversion in sprouts

Summary The monoterpenes (R)-(−)-carvone and (S)-(+)-carvone inhibited sprout growth in a model system consisting of sprouts growing from potato eye pieces. The sprout tissue was not necrotic after carvone treatment and the inhibition was reversible, since after treatment the sprouts showed regrowth either by continued top growth or by branching. However, the effect of both isomers on sprout growth differed, and (S)-(+)-carvone inhibited the elongation of the sprouts sooner than did (R)-(−)-carvone. This might be explained by a faster uptake of the former, since the concentration of (S)-(+)-carvone and its derivatives was twice as high during the first 4 days compared with (R)-(−)-carvone-treated sprouts. The sprouts were able to reduce (R)-(−)-carvone mainly into neodihydrocarveol, and (S)-(+)-carvone into neoisodihydrocarveol; in addition hydroxylated compounds were also detected. To whom correspondence should be addressed     

Control of Dutch elm disease by the sterol biosynthesis inhibitors fenpropimorph and fenpropidin

Sterol biosynthesis inhibitors that inhibit the yeast-hyphae conversion inOphiostoma ulmi suppressed Dutch elm disease development in two elm clones. After curative treatment with fenpropimorph-sulphate of 27 Vegeta elms which had previously been inoculated withO. ulmi, 25 trees did not show disease symptoms by the end of the second season. All 41 control trees, inoculated withO. ulmi only, were clearly diseased. In an experiment with Commelin elms three fenpropimorph salts and thiabendazole were compared. Injection of the trees three weeks after inoculation withO. ulmi gave by the end of the second season no symptoms of Dutch elm disease in any of the trees injected with fenpropimorph-phosphate or thiabendazole, and in most trees injected with fenpropimorph-acetate or-sulphate. Similar treatments with the free base of fenpropimorph and fenpropidin-sulphate were less effective due to insufficient uptake of the fenpropimorph emulsion and phytotoxicity of fenpropidin-sulphate, respectively. Injection of fenpropimorph-sulphate or thiabendazole six weeks after inoculation withO. ulmi did not result in significant differences from the control group inoculated withO. ulmi only.Fenpropimorph-phosphate and-sulphate completely suppressed Dutch elm disease upon injection of only 7.5 or 10 g per tree (average tree diameter 28 cm). Residue analyses showed only a slow decrease in concentration of the fungicide over two growing seasons and an apparent transport into the new annual ring, other prerequisites for a possible future use for control of Dutch elm disease.Samenvatting De iepeziekte kan onderdrukt worden door sterolbiosyntheseremmers die de overgang vanOphiostoma ulmi van de gistvorm in de hyfevorm remmen. Aan het eind van het tweede seizoen na een curatieve behandeling van 27 Vegeta iepen met fenpropimorfsulfaat bleken 25 bomen geen symptomen van iepeziekte te vertonen. Alle controlebomen, die alleen metO. ulmi geïnoculeerd waren, waren duidelijk ziek. In een proef met Commelin iepen werden drie fenpropimorfzouten en thiabendazool vergeleken. De zouten werden drie weken na de inoculatie metO. ulmi geïnjecteerd. Aan het eind van het tweede seizoen vertoonden geen van de bomen die met fenpropimorffosfaat of thiabendazool geïnjecteerd waren en slechts enkele bomen die met fenpropimorfacetaat of-sulfaat geïnjecteerd waren iepeziektesymptomen. Behandelingen met fenpropimorf (vrije base) en fenpropidinsulfaat werkten minder goed door de slechte opname van de fenpropimorfemulsie en de fytotoxiciteit van fenpropidin. Injectie met fenpropimorfsulfaat of thiabendazool zes weken na inoculatie leidde niet tot significante verschillen met de controlegroep die alleen metO. ulmi geïnoculeerd was.Een dosis fenpropimorffosfaat of-sulfaat van 7.5 of 10 g per boom met een gemiddelde boomdiameter van 26 cm bleek de iepeziekte volledig te kunnen onderdrukken. Uit residue-onderzoek bleek dat de concentratie van het fungicide gedurende de twee groeiseizoenen slechts langzaam afnam en dat het middel naar de nieuwe jaarring werd getransporteerd, twee voorwaarden voor een toepassing op praktijkschaal van fenpropimorf voor de bestrijding van de iepeziekte.     

Pseudomonas for biological control of dutch elm disease. I. Labeling,detection and identification of pseudomonas isolates injected into elms; comparison of various methods

To understand the mechanisms involved in biological control of Dutch elm disease byPseudomonas, data were needed on the distribution of the introduced bacteria within elm and on the development of the bacterial population over a period of time.As traditional biochemical identification techniques are not suitable for distinguishment between individualPseudomonas isolates, three alternative approaches were compared.

Pseudomonas for biological control of Dutch elm disease. III. Field trials at various locations in the Netherlands

The prophylactic effect in elm of one treatment with aPseudomonas isolate was monitored in two types of field trials. In one type only natural Dutch elm disease infections were monitored and hence large numbers of trees were necessary due to the low incidence of natural occurring infections. In the other type trees were artificially infected.The large-scale field trials in which only natural infections were monitored, were based on expected annual losses due to Dutch elm disease of approximately 2%. As a result of the Dutch sanitation program, which was based on the prompt removal of every weakened or diseased elm, the actual losses were generally threefold lower. Dutch elm disease incidence was 22–45% lower in the trees treated with aPseudomonas isolate in the year of treatment and the year after. The results of the biocontrol treatment were negatively influenced because on several locations trees were felled that showed initial signs of Dutch elm disease, which probably would have disappeared during the season.The advantage of artificial infections withOphiostoma ulmi was a reproducable development of symptoms and the possibility to maintain diseased trees, at least till the first signs of elm bark beetle breeding. For Commelin elms an increase in symptoms was observed with increasingO. ulmi dose till 3000 conidia per tree; the standard 500 000 conidia used for most experiments was well above this critical value. No decrease in effectiveness of the bacterial pre-treatment was observed with increasingO. ulmi inoculum. Different bacterial treatments suggested that injections at a smaller interval (i.e. more injections per tree) may result in a better prophylactic effect, but the significance of the correlation remained doubtful. A comparison of several elm species and clones showed the importance of the host tree. Prophylaxis as a result of one bacterial treatment was shown repeatedly in Commelin elms; the numbers of trees showing symptoms by the end of the second year were 10 to 85% lower in the bacteria-treated groups in comparison with the controls. Also in one experiment with Belgica elms prophylaxis was observed, resulting in a 84% decrease in the number of trees showing symptoms by the end of the second year after the prophylactic treatment followed by inoculation withO. ulmi. In Vegeta symptom development was only less severe and in field elms (Ulmus carpinifolia) some prophylactic effect was observed in one experiment, but no effect in two others.Samenvatting De mogelijke bescherming tegen de iepeziekte, verkregen door injectie van de boom met bacteriën van het geslachtPseudomonas, werd gemeten in twee soorten experimenten. In het ene soort werden natuurlijke infecties gemeten, waardoor grote proefgroepen nodig waren. In het andere soort werden de iepen kunstmatig geinfecteerd.De grootschalige veldexperimenten waarbij natuurlijke iepeziekte-infecties werden gemeten, waren gebaseerd op een verwachte jaarlijkse uitval van 2%. Als gevolg van de landelijke bestrijdingscampagne bleken de verliezen slechts ongeveer een derde hiervan te zijn. Er kwam minder iepeziekte voor in de metPseudomonas geïnjecteerde bomen in het jaar van injectie en in het jaar daarna. Een storende invloed op de resultaten had het effect dat ook met bacteriën geïnjecteerde bomen soms beginnende symptomen vertonen na infectie metOphiostoma ulmi, symptomen die in de loop van het seizoen soms weer verdwijnen. Als gevolg van de bestrijdingscampagne werden zulke bomen toch geveld.Het voordeel van kunstmatige infecties metO. ulmi was een voorspelbaar verloop van de symptoomontwikkeling en de mogelijkheid om zieke bomen te laten staan tot er iepespintkevers in kwamen. In Commelin iepen bleken de symptomen toe te nemen met een tot 3000 conidiën per boom toenemende dosisO. ulmi. De gebruikelijke 500000 conidiën die in de meeste experimenten werden gebruikt lagen ver boven deze kritische waarde. Er werd geen effect van een toenemende dosisO. ulmi op de effectiviteit van een bacteriebehandeling waargenomen.Uit variaties in de diverse bacteriebehandelingen kwam naar voren dat injecties met een kleinere tussenruimte (dus meer injecties per boom) mogelijk het effect verbeterden, maar de significantie van deze correlatie bleef twijfelachtig.Vergelijken van diverse iepen toont dat soort en kloon type een belangrijke rol speelt bij deze bestrijdingsmethode. Bescherming tegen de iepeziekte als gevolg van een bacteriebehandeling werd diverse malen aangetoond in Commelin iepen; het aantal bomen met iepeziekte-symptomen was aan het eind van het tweede seizoen in de met bacteriën behandelde groepen 10 tot 85 % lager dan in de controlegroepen. Ook in een experiment met Belgica iepen werd een goede bescherming gemeten. In Vegeta werd slechts een verminderde symptoomontwikkeling gemeten en in veldiepen (U. carpinifolia) werd enige bescherming gevonden in één experiment, maar geen effect in twee andere.     

Developmental horizons in the pre‐natal development of the Greater cane rat (Thryonomys swinderianus)

The Greater cane rat (GCR, Thyronomys swinderianus) is a precocial rodent predominantly found within Africa. Economic and scientific interests have led to several research efforts towards the domestication and better understanding of the biology and development of this rodent. Despite these efforts, information on the pre‐natal development of this rodent is currently lacking. This study characterises distinct developmental milestones including skin pigmentation, emergence and distributions of hairs, calvarium consistency, teeth eruption, development of appendages, sensory organs and external genitalia in the pre‐natal GCR and assesses quantitative body parameters, that is body weight, body and crown–rump lengths across its entire gestation length (gestation days [GDs] 10‐140). Using these external features, we provide baseline reference ontogenetic scales for GCR embryos and fetuses, employable for stage, age and sex estimation of the pre‐natal GCR in future studies. We observed that the first evidence of an embryo was not seen before the end of the first trimester (GD50) and that the late second trimester (GD80‐GD100) marks the transition from embryogenesis to fetogenesis in the GCR. As both events occur at a much later developmental time point when compared to precocial non‐rodents including human, sheep and pig and slightly later when compared to other precocial rodents such as guinea pig, our data provide first indication that the pre‐natal GCR development might be associated with a reproductive delay. Together, this study expands our knowledge of the development and biology of the GCR, which will improve reproductive and breeding management, and native species conservation of this hystricomorph mammal.     

In vitro evaluation of cryopreserved bovine sperm and its relation to field fertility in fixed‐time artificial insemination

This study aimed to assess characteristics of bovine cryopreserved sperm and evaluate its relation to field fertility in fixed‐time artificial insemination (FTAI). Semen samples of 16 bulls were used to inseminate 811 Nellore cows, and four of these bulls were also used to inseminate 101 Nellore heifers. Samples of the same ejaculate used for FTAI from each bull were analysed in the laboratory after thawing. Sperm motility and vigour were subjectively assessed by light microscope, and integrity of the plasma and acrosome membranes, and H₂O₂ production were evaluated by flow cytometer. Relation among sperm characteristics and pregnancy rate of cows and heifers were evaluated by univariate and multivariate logistic regression. Subjective sperm motility and vigour did not affect the probability of pregnancy in cows or heifers. In univariate analysis for pregnancy in cows, sperm traits related to acrosome injury positively affected probability of pregnancy mainly when associated with plasma membrane integrity; H₂O₂ production seems to be less important than plasma membrane integrity in affecting probability of pregnancy. In multivariate analysis, sperm traits related to injured acrosome positively affected probability of cow and heifer pregnancies while intact acrosome was negatively related to cow pregnancy. Intact plasma membrane and high H₂O₂ production were positively related to cow pregnancy but negatively related to heifer pregnancy. Results suggest that a capacitation‐like status of the acrosome may benefit probability of pregnancy in cows.