Studies on Botrytis spp. occurring on onions (Allium cepa) and leeks (Allium porrum)

Botrytis byssoidea (mycelial neck rot) was more prevalent than B. allii (sclerotial neck rot) on the leaves of field onions and the bulbs of stored onions grown in some of the areas where onions or onions and leeks had previously been grown sequentially.
B. byssoidea and B. porri were also isolated from leeks. Spores of B. allii, B. byssoidea (from onions and leeks), B. porri , and B. squamosa caused infection of seedlings of salad (green) and bulb onions.
Inoculation with B. squamosa spores caused severe infection of seedling leaves, but inoculation with mycelial discs caused little damage to onion bulb tissue. By comparison, mycelial discs of the remaining species were highly pathogenic to bulbs.
The practical implications of disease transfer of certain of these species between onions and leeks are discussed.     

Chemical weed control in transplanted onion (Allium cepa L.) in the Sudan Gezira

Unrestricted weed growth reduced the yield of transplanted onions (Allium cepa L.) by 26–48%. Hand-weeding once, 42 days after transplanting reduced the yield loss to 15%. Application of oxadiazon (1.1–1.3 kg ai ha^?1), pendimethalin (1.2–1.8 kg ai ha^?1), oxyfluorfen (0.14–0.43 kg ai ha^?1) and chlorthal-dimethyl (8.3–13.1 kg ai ha^?1) resulted in yields comparable to the hand-weeded control (82–126%). When sprayed at transplanting these herbicides gave excellent and persistent control of grasses (86–100%). However, they were less effective on broad-leaved weeds (38–94% control). Désherbage chimique de l'oignon repiqué (Allium cepa L.) dans la Gezireh soudanaise La croissance incontrôlée des mauvaises herbes réduit le rendement des oignons repiqués de 26–48%. Un désherbage manuel, 42 jours après le repiquage, ramène la baisse de rendement à 15%. L'application d'oxadiazon (1,1–1,3 kg ma ha^?1), de pendiméthalin (1,2–1,8 ka ma ha¹), d'oxyfluorfen (0,14–0,43 ka ma ha^?1) et de chlortal-diméthyle (8,3–13,1 kg ma ha^?1), a permis d'atteindre des rendements comparables aux témoins désherbés manuellement (82–126%). Lorsqu'ils ont été administrés au moment du repiquage, ces herbicides ont permis un contrôle efficace et persistant des monocotylédones (86–100%). Toutefois, ils se sont montrés moins efficaces à l'égard des dicotylédones (38–94% du témoin). Chemische Unkrautbekämpfung in verpflanzten Zwiebeln (Allium cepa L.) in der Region Gezira (Sudan) Ungehinderte Unkrautentwicklung in verpflanzten Zwiebeln (Allium cepa L.) verringerte die Ernte um 26–48%. Eine Handjätung, 42 Tage nach dem Auspflanzen, reduzierte den Ernteverlust auf 15%. Die Applikation von Oxadiazon (1,1–1,3 kg ai ha^?1), Pendimethalin (1,2–1,8 kg ai ha^?1), Oxyfluorfen (0,14–0,43 kg ai ha^?1) und Chlorthal- dimethyl (8,3–13,1 kg ai ha^?1) erbrachte Ernten, die mit denjenigen, der von Hand gejäteten Kontrollparzellen vergleichbar waren (82–126%). Diese Herbizide, zur Ausflanzzeit ausgebracht, ergaben eine ausgezeichnete und andauernde Kontrolle von Gräsern (86–100%), während die Wirkung gegen breitblättrige Unkräuter geringer ausfiel (38–94%).     

Response of onion (Allium cepa L.) plants to fertilizers, weed competition duration, and planting times in the central Jordan Valley

The competitive ability of onion with weeds and the effects of weeds on onion crop growth and yield were investigated in three field experiments carried out in the central Jordan Valley during the 1997–1998 growing season. Fertilizer application to the onion plants in the presence of weeds significantly lowered the onion yield and reduced the bulb diameter, compared to the unfertilized, weed-infested onion crop. Weed competition and onion yield reduction increased with an increase in the fertilizer rate. All weed-free treatments with or without fertilizer gave a significantly higher onion yield than any of the fertilized, weedy plots. The highest yield of onion was obtained from the weed-free plots with a moderate application of fertilizer. Weed competition reduced the growth, bulb yield, and size of onion in the plots established from bulbs, seedlings, and seeds when compared to the relevant weed-free controls. The effect increased with competition duration and was more pronounced in direct-seeded onion than in the other two types of planting material. However, onion grown from bulbs or seedlings gave better growth, bulb weight, and number and was more competitive than the direct-seeded onion. The results showed that the minimum number of days of weed competition needed for a significant reduction in onion growth was 42 days when propagated from bulbs or seedlings and 21 days after direct-seeding. Onion grown from bulbs tolerated weed competition better and produced a higher bulb yield than that obtained from direct-seeded or transplanted onion, irrespective of the planting dates. December was found to be the best planting time for onion that was grown from bulbs and seedlings, while November was the best planting time for direct-seeded onion, provided the plots were weed-free throughout the growing season.     

Solar heating of the soil for the control of pink root and other soilborne diseases in onions

The effectiveness of solar heating of the soil by means of mulching with transparent polyethylene, against soilborne pathogens of onions, was tested in two field experiments: at Yotvata (hot region) and at Gefen (cooler one). In both experiments, solar heating significantly reduced the incidence and severity of the pink root disease caused byPyrenochaeta terrestris by 73-100% during the 6-7 months of plant growth.Rhizoctonia solani, Fusarium infection, and weed populations (except forMelilotus) were also considerably reduced by this treatment. In addition, stand and plant growth were improved and yields were increased by 109-125% at Yotvata and by 59-62% at Gefen, as compared with the untreated control. Similar results were obtained when soil was moistened by sprinkler irrigation before applying the mulch or by sprinkler irrigation supplemented by drip irrigation under the mulch. Pentachloronitrobenzene did not control pink root disease.     

Seasonal dynamics of the pink root fungus (Setophoma terrestris) in rhizosphere soil: Effect of crop species and rotation

Setophoma terrestris, a ubiquitous inhabitant of soil, causes pink root rot in various crops. In the present study, the density of S. terrestris was estimated by quantitative real-time PCR in onion and non-onion fields of Hokkaido, the northernmost island of Japan. Three-year observations in monoculture and rotation fields demonstrated that the fungus grew significantly from the third year onwards, and declined in fields planted with poor hosts (e.g., sugar beet and soybean) that produced few or no chlamydospores of S. terrestris. Seasonal analysis revealed that the population of S. terrestris consistently increased when the tops of onions fell over in summer, which is when root activity declines. However, the soil inoculum potential estimated by a seedling bioassay showed distinct seasonal patterns, which rose from post-harvest in winter and remained high until the subsequent planting in spring. Detailed surveys on depth distribution in an onion field detected a high population of S. terrestris in the effective layer (10–30 cm deep) but not below the hardpan (40 cm), implying that the fungus is intimately associated with roots. These results indicate that the proliferation of the fungus is closely related to root senescence and that over-wintered propagules play an important role in primary infections, affecting disease severity. The present study shows that the temporal dynamics of S. terrestris depend exclusively on the activity of infecting roots and provides circumstantial evidence on the deleterious impact of monoculture on crop production.     

Pink root rot of squash caused by Setophoma terrestris in Japan

Pink root rot of squash (Cucurbita moschata) caused by Setophoma terrestris was found in Maebashi, Gunma Prefecture, Japan in July 2007. Cucumber grafted on the squash first developed wilt and finally blight. These symptoms followed a severe pink root rot of the squash rootstock. The fungal isolates from diseased roots were identified as S. terrestris based on morphological characteristics and nucleotide sequences. One isolate induced a similar pink root rot but not entire wilting of the cucumber vine. We propose the name “pink root rot” (koshoku-negusare-byo in Japanese) of squash for the new disease.     

Differences in resistance in onion cultivars to pink root rot disease in Iran

Forty-five onion (Allium cepa) cultivars were evaluated for disease resistance to the fungal pathogen Pyrenochaeta terrestris (pink root disease). Forty-three Iranian cultivars and two commercially exotic resistant cultivars (Texas Early Grano and Yellow Sweet Spanish) were grown in a glasshouse for two successive years (2003 and 2004) in Isfahan, Iran. Susceptibility of the cultivars was determined using a scale of 0–3. Six cultivars had significantly lower susceptibility of pink root compared to the exotic ones. High susceptibility tended to be associated with high mean scores (2–3), and the highly resistant cultivars had the lowest scores (0–1). In addition, the 45 examined cultivars were ranked from 1 to 45 according to their markedly differing reactions to P. terrestris, which differed markedly. Of 32 cultivars that were less resistant, 30 with an intermediate status or tolerance (1–2) differed considerably in their rank order. No pink root symptoms were seen in the early stages, but on blotter paper or wheat-straw agar some roots turned pink with no pycnidia formation, whereas on potato dextrose agar medium (PDA) with a few fresh healthy and sterile onion roots on the surface, mycelia and pycnidia were recovered. Variance and cluster analysis showed similar results among the cultivars with various levels of resistance, tolerance and susceptibility as determined by scoring scales.     

Natural infection of garlic (Allium sativum L.) by viruses in the Czech Republic

Journal of Plant Diseases and Protection - Garlic (Allium sativum L.) is one of the most important Allium crops. Significant yield and quality reduction due to virus infection is currently a...     

Tolerance of spring wheat (Triticum aestivum L.) to trifluralin deep-incorporated in the autumn or spring

Field experiments at Lacombe on a Ponoka loam soil (9·6% organic matter) during 1982 and 1983 investigated the tolerance of spring wheat (Triticum aestivum L.) cv. Neepawa in a weed free situation to trifluralin applied at 0·0–3·0 kg ai ha^?1 in the autumn or spring and incorporated to a depth of 10 cm. Rates of trifluralin above 1·0 kg ai ha^?1 applied in the autumn or spring reduced the percent stand of wheat compared to an untreated control. Two weeks after emergence the crop showed 37 or 47% injury indicated by delayed growth, following application at 1·0 kg ai ha^?1 in the autumn or spring, respectively. The wheat recovered throughout the course of the growing season. At harvest, trifluralin applied in the autumn or spring at rates below 1·0 kg ai ha^?1 caused a yield increase while higher rates caused a yield decrease compared to the untreated control. Spring application caused a greater yield loss than autumn application. The tolerance of spring wheat to trifluralin at rates required for weed control (1·1 kg ai ha^?1 or higher) on this soil type is marginal.     

Responses of spring barley (Hordeum vulgare L.) and spring wheat (Triticum aestivum L.) to foliar or root entry of chlorsulfuron

The objective of this study was to determine whether chlorsulfuron applied post-emergence enters more by roots or by foliage of spring barley (Hordeum vulgare L.) and spring wheat (Triticum aestivum L.). Such differences could explain observed variation in tolerance between cultivars and interactions with environmental factors. Two experiments were conducted in the glasshouse, where chlorsulfuron was applied to either foliage, soil or combined foliage and soil. In the first experiment, application of chlorsulfuron to foliage had less effect on dry matter (DM) than the combined treatment in two cultivars each of barley and wheat. Root DM was more sensitive to chlorsulfuron than shoot DM in both species. Shoot DM of wheat cv. Vulcan tended to be more sensitive to chlorsulfuron than cv. Olympic or both barley cultivars. In the second experiment, application of chlorsulfuron to foliage of two barley cultivars reduced shoot DM by 30–40%, compared with about 70% after soil or combined applications. Root DM was more sensitive than shoot DM, with reductions of 80% after soil or combined applications, and about 50% after foliar application. Root entry of chlorsulfuron in barley thus leads to greater crop injury from the herbicide than foliar entry, and this may explain why rain soon after application leads to more injury from the herbicide. If no rain follows application, uptake of chlorsulfuron primarily by foliage may still reduce barley root growth in some circumstances, which will impair the ability of plants to take up nutrients and water, and the consequences for grain yield will be most severe in drought conditions. Differences in root or foliar entry did not explain culti-var differences in tolerance to chlorsulfuron measured previously in the field. Réponses de l'orge de printemps (Hordeum vulgare L.) et du blé de printemps (Triticum aestivum L.) au chlorsulfuron appliqué par voie foliaire ou racinaire Le but de cette étude était de déterminer si la pénétration du chlorsulfuron appliqué en post levée se fait principalement par les racines ou le feuillage de l'orge de printemps (Hordeum vulgare L.) et du blé de printemps (Triticum aestivum L.). De telles différences pourraient expliquer des variations de tolérance entre variétés et l'effet de facteurs de l'environnement. Deux expériences ont été menées en serre, où le chlorsulfuron était appliqué sur le feuillage, sur le sol ou sur les deux à la fois. Dans la première expérience, sur deux variétés d'orge et deux variétés de blé, l'application de chlorsulfuron sur le feuillage avail moins d'effet sur la production de matière sèche (MS) que le traitement combiné. Chez les deux espèces, la production de MS était plus affectéd dans les racines que dans les parties aériennes. La production de MS par les parties aériennes était plus touchée par le chlorsulfuron chez la variété de blé Vulcan que chez la variété Olympic et chez les deux variétés d'orge. Dans la seconde expérience, l'application de chlorsulfuron sur le feuillage des deux variétés d'orge réduisait la MS des parties aériennes de 30–40%, contre 70% par un traitement sur le sol ou par des applications combinées. Dans les racines, la production de MS était plus affectée que dans le feuillage, avec des réductions de 80% lors de traitements sur le sol ou combinés et environ 50% lors de traitements foliaires. Le chlorsulfuron était plus phytotoxique à l'égard de l'orge quand il pénétrait par les racines que par le feuillage. Ceci pourrait expliquer qu'une pluie survenant peu de temps après le traitement occasionne plus de phytotoxicité. S'il ne pleut pas après le traitement, l'absorption de chlorsulfuron, qui se produit principalement par le feuillage, peut toutefois sous certaines conditions réduire la croissance racinaire de l'orge. La capacité des plantes à absorber les nutriments et l'eau est diminuée, avec pour conséquence que les effets sur le rendement en grain sont plus importants en cas de stress hydrique. Les différences d'absorption racinaire ou foliaire n'expliquent pas les différences de tolérance au chlorsulfuron constatées précédemment au champ entre variétés. Reaktion von Sommergerste (Hordeum vulgare L.) und Sommerweizen (Triticum aestivum L.) auf Blatt- und Wurzelaufnahme von Chlorsulfuron Ziel dieser Untersuchung war es, festzustellen, ob im Nachauflauf angewandtes Chlorsulfuron mehr über die Wurzeln oder über das Blatt von Sommergerste (Hordeum vulgare L.) und Sommerweizen (Triticum aestivum L.) aufgenommen wird. Solche Unterschiede könnten die unterschiedliche Toleranz von Sorten und Interaktionen mit Umweltfaktoren erklären. Bei 2 Gewächshausversuchen, wobei Chlorsulfuron auf das Blatt und/oder den Boden ausgebracht wurde, hatte bei je 2 Gersten- und Weizensorten die Blattapplikation eine geringere Wirkung auf die Trockenmasse-(TM-)Bildung als die kombinierte Ausbringung. Bei beiden Arten war die Wurzel-TM-Bildung empfindlicher als die Sproß-TM-Bildung, wobei diese sich bei der Weizensorte ‘Vulcan’ empfindlicher als bei ‘Olympic’ und den beiden Gerstensorten erwies. Im 2. Versuch verminderte sich nach der Blattapplikation von Chlorsulfuron bei den Gerstensorten die Sproß-TM um 30 bis 40%, nach Boden- oder kombinierter Anwendung um 70%. Die Wurzel-TM-Büdung war (wiederum) mit 80% Verminderung nach Boden- oder kombinierter und 50% nach Blattapplikation empfindlicher als die Sproß-TM-Bildung. Die Aufnahme von Chlorsulfuron über die Wurzeln führt bei Gerste also zu stärkeren Schäden als über das Blatt, womit erklärbar wird, warum das Herbizid bei Regen kurz nach der Anwendung phytotoxischer ist. Wenn nach der Anwendung kein Regen fällt, kann nach Blattaufnahme das Wurzelwachstum unter bestimmten Umständen trotzdem beeinträchtigt sein, wodurch die Wasser- und Nährstoffaufnahme abnimmt, und die Konsequenzen für den Kornertrag werden unter trockenen Bedingungen am stärksten. Aufgrund der Unterschiede der Wurzel- oder Blattaumahme ließen sich die in der Praxis beobachteten Sortenunterschiede der Toleranz gegenüber Chlorsulfuron nicht erklären.     

Cultivar Resistance to Anthracnose Disease of Cowpea (Vigna unguiculata (L.) Walp.) caused by Colletotrichum destructivum O'Gara

The infection process of Colletotrichum destructivum, a hemibiotrophic anthracnose fungus, was studied by light microscopy in two cowpea (Vigna unguiculata) cultivars which differ in disease reaction type. Large, multilobed, intracellular infection vesicles, followed by necrotrophic, radiating, secondary hyphae were produced in tissues of the susceptible cv. IT82E-60. In the resistant cv. TVx3236, both the production of appressoria and their melanisation were impaired, resulting in reduced penetration. Where penetration occurred, the initially-infected epidermal cells underwent a hypersensitive response, restricting the growth of multilobed vesicles and thereby blocking the destructive necrotrophic phase of disease development. The phytoalexins kievitone and phaseollidin accumulated earlier and more rapidly in stem tissues of the resistant cultivar, associated with the appearance of delimited, necrotic spots on inoculated surfaces. In contrast, delayed and slower accumulation of these compounds occurred in the compatible interaction, together with the development of typical spreading, water-soaked, anthracnose lesions.     

Metabolic effects in rapeseed (Brassica napus L.) seedlings after root exposure to glyphosate

Metabolic effects in rapeseed (Brassica napus L.) seedlings after root exposure to sublethal concentrations of glyphosate were examined in order to evaluate the possibilities of using a response pattern in plants as a measure of exposure to glyphosate through the growth media, more sensitive than the well-known biomarker shikimate. Rapeseed seedlings were grown in hydroponic nutrient solutions containing varying sublethal concentrations of glyphosate (1–50 μM). After 9 days of glyphosate exposure, the shoots of the seedlings were analysed with respect to the effects on selected metabolites downstream from the primary affected metabolite shikimate, which accumulated linearly in response to glyphosate exposure (from 0 to ∼126 μmol/g DW). The selected metabolites analysed, comprising the free amino acids, and the glucosinolates derived therefrom, showed complex patterns in response to glyphosate exposure. Most noteworthy was though that they responded at the lowest concentrations of exposure to glyphosate (1 μM), where no visual effects, decrease in shoot DW or shikimate could be detected, indicating that a biomarker response more sensitive than that of shikimate can be established for plants exposed to glyphosate.     

Spoilage of stored onion (Allium cepa L. var Cepa) by Pseudomonas aeruginosa (Schroeter) Migula in Lowland Papua New Guinea

Abstract

Biochemical and pathogenicity studies of bacterial isolates from onions with discoloured internal tissues indicated the fluorescent pseudomonad Pseudomonas aeruginosa (Schroeter, 1872) Migula, 1900 to be the causal agent and that a site of injury was necessary for infection to take place. It is postulated that in the field a likely mode of infection would be through the necks of onion bulbs which are damaged during or after harvest.     

Factors contributing to enhanced pink snow mould resistance of winter rye (Secale cereale L.) – Pivotal role of crowns

Frost tolerance, resistance to Microdochium nivale and associated biochemical changes were investigated in leaves and crowns of six winter rye inbred lines. Investigated lines differed in their susceptibility to snow mould but not in frost tolerance. It was shown that winter rye resistance is linked to defence response in crowns expressed by higher activity of antioxidant enzymes – CAT, SOD and total peroxidases – on the 1st day after inoculation and β-d-glucosidase activation during the course of pathogenesis. It could be postulated that changes in leaves are attributed to reaction to cold while changes in crowns are attributed to pathogen reaction.     

杂草稻落粒粳种子的耐冷性评价

采用低温处理方法评价了杂草稻落粒粳（Orayza sativaL.）种子的耐冷潜力。浸种0~48 h,落粒粳种子平均含水量为17.038%,显著低于栽培稻春江11的20.533%和赣早籼的20.180%,落粒粳颖壳具有比两种栽培稻更强的水分阻隔能力。在相同含水量条件下,经过低温-20℃处理3 h和28℃条件下培养4 d的落粒粳种子发芽率显著高于春江11和赣早籼,落粒粳种子具有更强的耐冷能力。     

Metabolic effects in rapeseed (Brassica napus L.) seedlings after root exposure to glyphosate

Metabolic effects in rapeseed (Brassica napus L.) seedlings after root exposure to sublethal concentrations of glyphosate were examined in order to evaluate the possibilities of using a response pattern in plants as a measure of exposure to glyphosate through the growth media, more sensitive than the well-known biomarker shikimate. Rapeseed seedlings were grown in hydroponic nutrient solutions containing varying sublethal concentrations of glyphosate (1-50 μM). After 9 days of glyphosate exposure, the shoots of the seedlings were analysed with respect to the effects on selected metabolites downstream from the primary affected metabolite shikimate, which accumulated linearly in response to glyphosate exposure (from 0 to ∼126 μmol/g DW). The selected metabolites analysed, comprising the free amino acids, and the glucosinolates derived therefrom, showed complex patterns in response to glyphosate exposure. Most noteworthy was though that they responded at the lowest concentrations of exposure to glyphosate (1 μM), where no visual effects, decrease in shoot DW or shikimate could be detected, indicating that a biomarker response more sensitive than that of shikimate can be established for plants exposed to glyphosate.     

Phytotoxic activity of root absorbed glyphosate in corn seedlings (Zea mays L.)

Growth chamber experiments were conducted in order to study the absorption, translocation and activity of glyphosate when applied to roots with aqueous solution avoiding any glyphosate–substrate interaction. Corn seedlings at the first leaf stage were set up in individual graduated cylinders containing different solutions of ¹⁴C-glyphosate (0–30 mg ae kg⁻¹). After 26 h of root exposure, plants were transferred to fresh nutrient solution and grown for the next 5 days. After harvest, plants were separated into seed, root, mesocotyle, coleoptile, cotyledon, first leaf and all new leaves (apex), and quantified ¹⁴C radioactivity contained in each part. Glyphosate uptake was only 11% of the theoretical mass flow into the plant. The amount of glyphosate translocated from roots was positively correlated with plant uptake ( P  < 0.01). Total plant fresh weight presented a logistic response to glyphosate amounts, including a growth stimulant effect (hormesis), when plants absorbed less than 0.6 µg. The treated plants presented a normal pattern of glyphosate allocation, with the apex the principal sink, accumulating more than 38% of mobilized glyphosate. When corn plants absorbed more than 0.6 µg they showed a decrease in growth. The relatively high glyphosate quantities allocated in the new leaves showed the relevance of the symplastic pathway in the translocation process for root absorbed glyphosate.     

Evaluation of cultural practices (surface burning,deep ploughing,organic amendments) for management of rice root-knot nematode in rice - onion cropping system and their effect on onion (Allium cepa L.) yield

Rice hull burning (RHB) is a traditional cultural practice of many onion growers in San Jose City, Nueva Ecija, Philippines, mainly for weed control and increased yield. The resulting carbonized rice hull (ash) is incorporated into the soil during land preparation before transplanting of onion. Studies to evaluate the effect of RHB on the population of the rice root-knotnematode, Meloidogyne graminicola, and onion yield were conducted in a farmer's field naturally infested with the pathogen. Burning of 15-cm-deep rice hulls significantly reduced the nematode populations in the soil and increased onion yield. Increasing the thickness of rice hulls burned to 30 cm deep resulted in a yield increase of 44.2% over no RHB and 11.9% over 15-cm-deep rice hulls, while the yield increase with 15-cm-thick hulls was 28.8% over no RHB. Plots that received rice hulls 30 cm deep also produced 37.7% more large bulbs for export than those plots that received 15-cm-deep hulls, and 151.7% more than those plots with no RHB. Deep ploughing did not significantly affect nematode populations compared with standard ploughing. Organic amendment did not contribute to an increase in onion yield and has no effect on the population of rice root-knot nematode.     

Damage to Rumex crispus L. and Rumex obtusifolius L. caused by the rust fungus Uromyces rumicis (Schum.) Wint.

Rumex crispus L. and R. obtusifolius L. were infected by the rust fungus Uromyces rumicis (Schum.) Wint. Infections caused severe damage to R. crispus. Rusted plants always had a reduced number of leaves and the significant loss of dry weight of roots and leaves amounted to a minimum of 55% compared with controls. Less damage was caused to R. obtusifolilus, but a significant loss of root and leaf dry weight was also observed. These findings support earlier suggestions in the literature that U. rumicis may be able to play a role in controlling docks, which are common weeds in pastures. Effets pathogènes de la rouille Uromyces rumicis (Schum.) Wint. sur Rumex crispus L. et Rumex obtusifolius L. Des Rumex crispus L. et R. obtusifolius L. ont été infectés par la rouille Uromyces rumicis (Schum) Wint. Les infections ont provoqué des dommages importants chez R. crispus. Les plantes infectées avaient toujours un nombre de feuilles réduit, et subissaient au niveau des racines et des feuilles une perte significative de poids sec d'au moins 55% par rapport aux témoins. Les dommages subis par R. obtusifoliusétaient moins importants, mais une perte significative de poids sec des racines et des feuilles a également été observée. Ces résultats confirment la possibilité déjä suggérée dans la littérature que U. rumicis peut être capable de jouer un rôle dans le contrôle des Rumex, qui sont des mauvaises herbes communes dans les prairies. Ueber Schäden an Rumex crispus L. und R. obtusifolius L., verursacht durch den Rostpilz Uromyces rumicis (Schum.) Wint. Rumex crispus L. und R. obtusifolius L. wurden mit dem Rostpilz Uromyces rumicis (Schum.) Wint. infiziert. Die Infektionen verursachten an R. crispus starke Schädigungen. Befallene Pflanzen wiesen eine reduzierte Anzahl Blätter auf. Die signifikante Verringerung des Trockengewichtes von Wurzeln und Blättern betrug mindestens 55% im Vergleich zu unbefallenen Kontrollen. An R. obtusifolius waren die Schäden geringer; aber auch in diesem Fall wurde eine signifikante Reduktion der Trockengewichte von Wurzeln und Blättern beobachtet. Diese Befunde bestätigen frühere Literaturangaben, wonach U. rumicis bei der Bekämpfung von Rumex-Arten, die verbreitete Unkräuter auf Weiden sind, eine Rolle spielen könnte.     

Uptake and efflux of chlorimuron ethyl by excised soybean (Glycine max (L.) Merr.) root tissue†

Chlorimuron ethyl uptake into excised soybean root tissue was investigated using ¹⁴C-labelled herbicide. Chlorimuron ethyl accumulated in the root tissue, reaching a maximum concentration after 2 h and then declining over the next 2 h. The herbicide did not accumulate against a concentration gradient. The tissue concentration was linearly correlated with the external herbicide concentration. The Q₁₀ between 15 and 25°C was 1.6. Addition of KCN and anoxia reduced uptake. The efflux of ¹⁴C that had accumulated in root tissue segments occurred in two phases: a rapid phase with a T½ value of 6.3 min and a slower phase with a T½ value of 172 min. Chlorimuron ethyl uptake and efflux in excised soybean root tissue closely resembled that previously observed in velvetleaf, a sensitive weed species.