Napus Var Research Articles

Could Cocropping or Successive Cropping with Cd Accumulator Oilseed Rape Reduce Cd Uptake of Sensitive Chinese Cabbage?

Oilseed rape, a Cd accumulator, is effective in the uptake of plant available Cd from the soil. We hypothesize that the efficient removal of bioavailable Cd from soil solution by the Cd-accumulator oilseed rape (Brassica napus var. Xikou Huazi) might reduce the Cd uptake of coplanted or rotated Cd sensitive Chinese cabbage (Brassica campestris var. Zhongyou 821). Xikou Huazi and Zhongyou 821 were cocultivated in uncompartmentalized pots, or pots that were divided by plastic film or mesh barriers to limit the extent of root intermingling at a Cd concentration of 60 mg kg−1 . The shoot biomass of Xikou Huazi was significantly increased when its root were permitted to intermingle with Zhongyou 821. Cocropping of Xikou Huazi with Zhongyou 821 not only increased its biomass, but also increased the Cd uptake by Xikou Huazi when there was no barrier. The results were reversed for Cd sensitive oilseed rape (Zhongyou 821) in such a system. There was no significant difference in biomass, Cd concentration, and total...

Effects of Bt transgenic Chinese cabbage pollen expressing Bacillus thuringiensis Cry1Ac toxin on the non-target insect Bombyx mori (Lepidoptera: Bombyxidae) larvae

We evaluated the effects of the pollens of transgenic Chinese cabbage ( Brassica campestris subsp. napus var. pekinensis Makino), expressing Bacillus thuringiensis Cry1Ac toxin ( Bt cabbage), on Bombyx mori larvae. Decreased survival rate and body weight of B. mori larvae were observed when fed with an artificial diet containing Bt cabbage pollens. ELISA test using Cry1Ac-antibody revealed that the Cry toxin was detected not only in the alimentary canal but also in the hemolymph and remaining body parts, suggesting that the ingested Cry1Ac protein is distributed inside the body likely through the damaged midgut epithelial membrane of B. mori. Taken together, our results suggested that Bt cabbage pollens adversely affect non-target insect B. mori larvae when consumed. Considering the low possibility of Bt cabbage pollen exposure to B. mori in the actual field condition, however, the risk would be minimal.

Work conditions for microwave applicators designed to eliminate undesired vegetation in a field

The use of electromagnetic radiation at a microwave frequency for soil preparation can be an alternative to chemical treatments. This research evaluates the work conditions of the proposed machinery in diverse inventions that have been patented in recent years, and discusses its possible use for elimination of undesired plants emerged in the field. The aim of this work is to determine the energy needed to eliminate two herbaceous species: perennial ryegrass ( Lolium perenne ), a monocotyledon seed, and oilseed rape ( Brassica napus var. oleifera ), a dicotyledon seed. The plants had been sowed in trays and had emerged up to 7 cm in height. The trays were irradiated once using a circulating array of microwave radiators for a defined time. The speed of work and the power of microwave applicators were determined for use in the field. The results show that the elimination of herbaceous species already germinated in the field is technically possible, but it requires quite a slow speed of 0.2 m s −1 and tractors with a minimum power of 48 kW. The minimum time necessary for elimination of one hectare of undesired vegetation will be 9.26 h. How these conditions can be improved is discussed in this paper.

Root Uptake of Lipophilic Zinc−Rhamnolipid Complexes

This study investigated the formation and plant uptake of lipophilic metal-rhamnolipid complexes. Monorhamnosyl and dirhamnosyl rhamnolipids formed lipophilic complexes with copper (Cu), manganese (Mn), and zinc (Zn). Rhamnolipids significantly increased Zn absorption by Brassica napus var. Pinnacle roots in (65)Zn-spiked ice-cold solutions, compared with ZnSO4 alone. Therefore, rhamnolipid appeared to facilitate Zn absorption via a nonmetabolically mediated pathway. Synchrotron XRF and XAS showed that Zn was present in roots as Zn-phytate-like compounds when roots were treated with Zn-free solutions, ZnSO4, or Zn-EDTA. With rhamnolipid application, Zn was predominantly found in roots as the Zn-rhamnolipid complex. When applied to a calcareous soil, rhamnolipids increased dry matter production and Zn concentrations in durum (Triticum durum L. cv. Balcali-2000) and bread wheat (Triticum aestivum L. cv. BDME-10) shoots. Rhamnolipids either increased total plant uptake of Zn from the soil or increased Zn translocation by reducing the prevalence of insoluble Zn-phytate-like compounds in roots.

Morphologic and Agronomic Diversity of Brassica napus Crops

A Brassica napus L. crop called nabicol traditionally has been grown by farmers in northwestern Spain for many years and is an important horticultural product during the winter season. The relationship of nabicol to other B. napus crops has been studied based on simple sequence repeat (SSR) data. However, molecular and morphologic classifications often disagree. The objectives of this research were to study the morphologic and agronomic relationships of nabicol landraces to other B. napus crops and to compare those relationships with the ones already known, based on SSR data. Thirty-five B. napus populations from different geographic origins and uses were evaluated. Data were recorded on 17 morphologic and agronomic traits. Principal component analysis and cluster analysis were performed to classify the populations. Eight principal components (94% of the total variability) were standardized to produce the Mahalanobis' generalized distances, and a cluster analysis was conducted using the unweighted pair group method with arithmetic averages. There are no major differences between B. napus var. pabularia (DC.) Rchb. (nabicol, couve-nabiça, forage rape) and B. napus var. oleifera DC. (oilseed rape), and they probably share a common origin. Rape kale (B. napus var. pabularia) and rutabaga [B. napus var. napobrassica (L.) Rchb.] cultivars are separated from the rest and probably they have an independent origin or domestication. Molecular and morphologic classifications are complementary, and both are necessary to classify germplasm correctly and to clarify genetic relationships among B. napus crops.

Genetic and molecular variability of aTurnip mosaic virus population from horseradish (Cochlearia armoracia L.)

Variability and genetic structure of a novel Turnip mosaic virus (TuMV) population from horseradish (Cochlearia armoracia L.) were examined. Over 60 horseradish plants were tested to identify a total of 28 TuMV isolates, constituting the Cochlearia ARmoracia (CAR) TuMV population. Two subgroups of the CAR TuMV isolates could be distinguished: subgroup N did not infect oilseed rape (Brassica napus var. oleifera) cv. Westar plants, while subgroup A infected these plants systemically. Two types of infection of oilseed rape plants were induced by inoculation with the CAR TuMV isolates: systemic mosaic infection and systemic necrotic lesions. The complete sequences of isolates CAR37 (subgroup N) and CAR37A (subgroup A) were determined and compared. The sequences of HC-Pro and CP genes of CAR37 and CAR37A and other isolates of TuMV from other countries were compared to provide some insight into their relatedness. CAR37A, initially regarded as a variant, proved to be very different from CAR37. Re-sequencing after repeated passages confirmed the genetic stability of both isolates.

Effects of passive heating and storage on the quality of hand-bagged and pre-packed growing media

Passive heating during storage of pre-packed growing media may reduce its quality. However, the impact of passive heating on basic chemical characteristics of growing media and plant yield are not fully understood. The objectives of this study were to investigate the effect of (i) the passive heating temperature under oxygen depleted conditions, (ii) the critical passive heating duration and (iii) the type of storage on the basic chemical composition of hand-bagged and pre-packed growing media and on yield of Chinese white cabbage ( Brassica napus var. chinensis). Six growing media at three different degrees of humification (H2–H7 on the von post humification scale) were heated for two weeks at 20, 35, 45 and 60 °C under oxygen depleted conditions prior to testing. Additionally, the growing media were heated for 2, 4, 6, 8 and 10 days at 35 °C under oxygen depleted conditions and tested directly after heating and after five months of storage. Increased heating temperatures of unlimed and unfertilized (unamended) growing media from 20 to 60 °C led to NH 4 + accumulation, but did not cause plant yield losses, if nitrogen fertilization of growing media after heating was mainly through NO 3 −. Heating of amended growing media to 35 °C for six days or longer decreased plant fresh weight more than 20%. Five months of storage after heating at 35 °C of amended growing media for zero to 10 days influenced yield slightly negatively only for one growing medium, which was based on weakly decomposed peat (H2–H3). For growing media amended prior to heating, the loss of NO 3 − explained 87% of the variation in fresh weight yield. The NH 4 +:NO 3 − ratio was a good indicator of a previous heating event. The NH 4 +:NO 3 − ratio values were fitted by a logarithmic curve to the plant fresh yield and were high significantly correlated ( r 2 = 0.75). Nitrate loss during storage of pre-packed growing media in bags was less for bags with perforations on the outside of the palette than those with perforations on the inside of the palette. Our results indicate that growing media should not be exposed to temperatures higher than 35 °C for more than six days during transport and storage.

Cellular Membranes, the Sites for the Antifungal Activity of the Herbicide Sethoxydim

The fungicidal effect of sethoxydim on the canola (Brassica napus var. Olifera) white stem rot pathogen (Sclerotinia sclerotiorum) encouraged us to conduct a series of studies on the mechanism of the antifungal activity of this herbicide commonly applied in Iranian fields under canola cultivation. Present preliminary studies on the changes in the level of Malondialdehyde (MDA) as the main product generated through peroxidation of polyunsaturated fatty acids indicated the disintegration of the fungal bilayer of plasma membrane as the result of the herbicidal treatment. Also, it was demonstrated that the amount of hydrogen peroxide in the treated samples was higher than the control samples with no herbicidal treatment. Therefore, our present results confirm the disintegration of the plasma membrane as one of the mechanism for the antifungal impact of sethoxydim. As with weed plants, the phytotoxic impact of this herbicide has been attributed to the inhibition of the first enzyme in the lipid biosynthesis pathway, acetyl-CoA carboxylase, therefore, it would be very interesting to study on this subject and the relations between the sensitivity of different fungi and their DNA and protein sequences of acetyl-CoA carboxylase.

Effect of chemical seed treatment, seeding rate and row width on plant populations and yield of canola (Brassica napus var. oleifera)

Field experiments were conducted in 2003 and 2004 at Roodebloem, representing the Rûens, in the canola production area of the Western Cape Province to determine the influence of seeding rate, row width and chemical seed treatment on the plant density (plants m−2) and yield of canola (cv. Varola 44). Untreated (control) seeds and seeds treated with Cruiser® (fludioxonil, metalaxyl and thiamethoxam) and a local mixture (SA-combination, which consist of thiram, metalaxyl, imidacloprid and iprodione) were seeded in 17 cm and 34 cm row spacings at seeding rates of 3, 5 and 7 kg ha−1. In general results showed that treated seeds tend to produce more plants m−2 and yield more than untreated seeds, while the highest seeding rate produced significantly more plants m−2, but not significantly higher yield than the lowest seeding rate at the same locality. Although row width did not have an effect on plant densities in 2003; yield was significantly lower with wider (34 cm) rows than narrow (17 cm) rows.

First Report of Bacterial Blight of Rutabaga (Brassica napus var. napobrassica) Caused by Pseudomonas syringae pv. alisalensis in California.

In 2005, commercial, organically grown rutabaga (Brassica napus var. napobrassica) in San Benito County, CA showed symptoms of a previously undescribed disease on approximately 30% of the plants. Initial symptoms consisted of small (1 to 2 mm in diameter), angular, water-soaked flecks that often were surrounded by chlorotic haloes. These flecks enlarged and coalesced into large, irregularly shaped, gray brown lesions that could be as long as 10 mm. Lesions were visible from both adaxial and abaxial leaf surfaces and generally retained the chlorotic borders. A blue-green fluorescing pseudomonad was consistently isolated from lesions on King's medium B. Eight isolates were characterized and were levan positive, oxidase negative, and arginine dihydrolase negative. Isolates did not rot potato slices but induced a hypersensitive reaction in tobacco (Nicotiana tabacum cv. Samsun). These data indicated that the bacteria belonged to Lelliot's LOPAT group 1 (2). This was confirmed with data from fatty acid methyl ester analysis (MIS-TSBA version 4.10; MIDI, Inc., Newark, DE) that showed that the isolates were highly similar (similarity = 0.922 or greater) to Pseudomonas syringae. Amplification of repetitive bacterial sequences (rep-PCR) using the BOXA1R primer and the polymerase chain reaction resulted in identical banding patterns for the rutabaga isolates and the P. syringae pv. alisalensis pathotype strain. Pathogenicity was demonstrated by growing inocula of six isolates in nutrient broth shake cultures for 48 h (24°C), adjusting the bacterial suspension to 106 CFU/ml, and misting the resulting suspensions onto rutabaga (cv. American Purple Top). Plants were enclosed in plastic bags for 24 h and then incubated in a greenhouse (24 to 26°C). Control plants were misted with sterile water and treated the same way. After 5 to 7 days, foliar symptoms similar to symptoms seen in the field developed on all inoculated plants, and reisolated bacteria were characterized and found to be P. syringae pv. alisalensis. Control plants remained symptomless. The results of two sets of pathogenicity tests were the same. To our knowledge, this is the first report of commercially grown rutabaga as a host of P. syringae pv. alisalensis and the first report of a B. napus host of this pathogen. This bacterial pathogen has previously been reported on commercial plantings of arugula (Eruca sativa), broccoli (Brassica oleracea var. botrytis), and broccoli raab (Brassica rapa var. rapa) in California and under experimental conditions it causes disease on additional hosts, including members of the Poaceae (1).

In vitro Studies on the Integrated Control of Rapeseed White Stem Rot Disease through the Application of Herbicides and Trichoderma Species

Five herbicides commonly used in rapeseed crop, canola (Brassica napus var Olifera) fields in Iran were studied with an eye to their antifungal activities against six isolates of Trichoderma species and also the phytopathogenic fungus Sclerotinia sclerotiorum. The doses tested were the same as are recommended for applications in canola crops. The results showed that the dinitro aniline herbicides (trifluralin and ethalfluralin) had the highest antifungal activities in vitro on the toxified CDA media; also three other herbicides behaved differently in relation to the fungi investigated. Cycloxydim had the most toxicity against Trichoderma sp. and sethoxydim had the least deleterious effects. But, with, Sclerotinia sclerotiorum, sethoxydim had the most toxicity together with cycloxydim with an intermediate level of anti-fungal activity between sethoxydim and haloxy fop ethoxy ethyl. This may be the first global report of the antifungal activities of the haloxy fop ethoxy ethyl, ethanol fluralin and cycloxydim.

First Report of Bacterial Leaf Spot on Leafy Brassica Greens Caused by Pseudomonas syringae pv. maculicola in South Carolina.

As of 2001, South Carolina ranked second in the United States in acreage of turnip greens (Brassica rapa) and collard (B. oleracea) and third in acreage of mustard (B. juncea). In June 2001, a leaf disease was found on turnip greens (cv. Alamo), mustard (cvs. Southern Giant Curled and Florida Broadleaf), and rape salad greens (B. napus var. napus cv. Essex) on a commercial farm in Lexington County, South Carolina. Symptoms appeared after a heavy rainstorm that included blowing sand. The disease was found in May and June 2002 on three additional farms in the same county on turnip greens cv. Topper and Royal Crown and collard cv. Top Bunch. Symptoms included small tan spots, water soaking, yellowing, and brown necrosis of leaves after spots coalesced on the lower halves of plants. Yellowing was more prevalent on older than on younger leaves. Leaf samples were collected in 2001 and 2002 from the affected hosts on the four farms. Bacterial streaming was evident from these samples and 27 strains were isolated on nutrient agar or King's medium B (KMB). All strains were gram negative and fluoresced bluegreen or yellow under UV light after 48-h growth at 28°C on Pseudomonas agar F (PAF). On the basis of LOPAT tests, the strains were identified as P. syringae (2). All 27 strains were tested for pathogenicity to rape salad greens cv. Essex and then to turnip greens cv. Topper. Plants were grown in peat-vermiculite potting mix in 10-cm-diameter pots in a greenhouse. P. syringae pv. maculicola F41, isolated from turnip in Oklahoma, and P. syringae pv. tomato F33, isolated from tomato in Oklahoma, were included as positive and negative controls along with a noninoculated control. Bacteria were grown on KMB for 48 h at 24°C, and bacterial suspensions were prepared and adjusted to 0.1 optical density at 600 nm. Three-week-old plants were held at 95 to 100% relative humidity (RH) for 48 h before they were sprayed just to runoff with inoculum and then held at 95 to 100% RH for 48 h after inoculation (4). After an additional 5 to 8 days in a greenhouse, nine strains and F41 caused symptoms on both Topper and Essex similar to symptoms observed in the field. No symptoms were observed on noninoculated plants or plants inoculated with F33. On the basis of repetitive sequence-based polymerase chain reactions with the BOXA1R primer, the DNA fingerprint of each of the nine pathogenic strains from South Carolina was nearly identical to that of F41. Bacteria isolated from inoculated, symptomatic turnip leaves had identical LOPAT and BOXA1R profiles to the corresponding original strains. Pathogenic strains had bluegreen fluorescence on PAF, whereas nonpathogenic strains fluoresced yellow. Five pathogenic strains, as well as F41, were further identified to species and pathovar with fatty acid methyl ester profiles as P. syringae pv. maculicola. To our knowledge, this is the first report of P. syringae pv. maculicola from South Carolina. Over the past 10 years, P. syringae pv. maculicola has been found in Oklahoma (4), California (1), and Ohio (3). Bacterial leaf spot has occurred yearly in South Carolina since the initial outbreaks. Currently, it is the disease that causes the greatest yield losses of leafy brassica greens in the state.

Use of near infrared spectroscopy to predict chemical parameters and phytotoxicity of peats and growing media

Abstract Fast and cost efficient tests are required for a screening of chemical parameters of peats and an estimation of a potential phytotoxicity. The objective of this study was to test the usefulness of near infrared spectroscopy (NIRS) for the quality control of peats and growing media. A population of 73 phytotoxic and non-phytotoxic peats from various stockpiles and growing media of different origins was collected and, after storage, characterised for their pH, contents of salt (estimated using the electrical conductivity), P, K, NO3− and NH4+ and their phytotoxicity using Chinese white cabbage (Brassica napus var. chinensis) as indicator. For unknown reasons, storage reduced the percentage of phytotoxic peats and growing media from 65 to 16%. Spectra of the visible and near infrared region (400–2500 nm) were obtained for all samples after drying and grinding (variant A) or in a moist state (variant B). A cross validation was carried out using a modified partial least square method which was based on the entire spectra and included the first to third derivate after base line correction. The chemical parameters pH, and contents of salt, P and K were predicted well by NIRS for both variants: the ratios of standard deviation of the laboratory results to standard error of cross validation (RSC) were greater than 2, the regression coefficients (a) of a linear regression (measured against predicted values) ranged from 0.9 to 1.1 and the correlation coefficients (r) were greater or equal to 0.9. Satisfactorily (0.8 ≤ a ≤ 1.2, r ≥ 0.8 and 1.4 ≤ RSC ≤ 2.0) assessed was the NH4+ content in variant A. Nitrate contents and phytotoxicity were predicted unsatisfactorily. However, investigating a less diverse subpopulation of 38 samples which were all growing media for plant propagation from two different origins showed a good prediction accuracy for nitrate contents (variant A) and a satisfactory one for phytotoxicity (variant B). The good and satisfactory predictions reported above indicate a marked usefulness of NIRS in the quality assessment of peats and growing media.

Can we “cultivate” erucic acid in southern Europe?

Over the last fifteen years, considerable progress has been made in the field of “green chemistry”, as regards both research aspects and market development. In particular, extraction of erucic acid (C22:1) from plants and its industrial applications have received increasing attention. At present, known species producing oils yielding large quantities of erucic acid belong, with few exceptions, to the Brassicaceae family. Among these, the two major sources of erucic acid in the world are HEAR (High Erucic Acid Rapeseed, Brassica napus var. oleifera) and crambe (Crambe abyssinica), both mainly cultivated in the USA. Their cultivation has also recently been considered and extended to southern Europe, supported by specific research projects. The quantity of erucic acid in Brassicaceae oils ranges greatly, from 55% in Crambe abyssinica to nearly zero in some varieties of Brassica napus var. oleifera. Even more differentiated and peculiar to each species and variety is adaptability to specific climatic and soil conditions. In this regard, the major limitation to the cultivation of some interesting Brassicaceae species, crambe in particular, is their poor tolerance to cold. Among Brassicaceae producing erucic acid, the less frequently cultivated species, such as Brassica juncea and B. carinata, if grown in areas with relatively mild winters, may give yields of seed and oil similar to those of the most productive rapeseed genotypes. Within this framework, in order to achieve high production of erucic acid, it is essential to identify the most productive genotypes, among available species, for each environment. In this report, seed and oil productions of some important Brassicaceae species for extraction of erucic acid, derived from 15 years of field trials in northern Italy, are discussed in relation to the possibility of autumn or spring sowing.

Response of different forms of propagules of Rhizoctonia solani AG2‐1 (ZG5) exposed to the volatiles produced in soil amended with green manures

AbstractThe sensitivity of different forms of propagules of Rhizoctonia solani anastomosis group (AG)2‐1/zymogram group (ZG)5 to volatile compounds produced in soil amended with green manure will influence the efficacy of green manures used to manage the disease. In laboratory experiments, we determined the impact of volatiles arising from residues of five species of Brassicaceae, and Avena sativa (oat), a non‐Brassicaceae species, and volatiles of pure allyl isothiocyanate (AITC) or 2‐phenylethyl isothiocyanate (2‐PEITC) in either their soluble or vapour phase on the hyphal growth of R. solani arising from different propagules. The brassicaceous species were Brassica napus var. Karoo, B. napus B1, B. napus B2, B. nigra and Diplotaxis tenuifolia (a brassicaceous weed). Colony growth and hyphal density on water agar were measured up to 7 days. The amendment of a sandy soil with green manures at a high (100 g kg−1, 10%) concentration generally suppressed the growth of the pathogen, but at a low (10 g kg−1, 1%) concentration, the amendment had little effect on the radial fungal growth of the pathogen but increased the density of hyphae through more branching. The inhibition by volatiles from the residues of Brassicaceae species at 10% concentration was stronger (82–86%) than that by volatiles from oat (64%) amendment at the same rate. Hyphae arising from sclerotia and precolonised ryegrass seed were less sensitive than hyphae growing out of potato dextrose agar plugs. This indicates that thick‐pigmented cell walls may have protected the fungus from these unfavourable conditions. Pure AITC and 2‐PEITC in the range of 0.5–2.0 mM inhibited the growth of R. solani from all forms of propagules, but hyphae originating from agar plugs were the most vulnerable compared with the two others. Thus, hyphae arising from the medulla of the sclerotia may be relatively tolerant to volatile compounds emanating from decomposing Brassica green manure amendments in the field and in vitro inhibition of the vegetative growth of the pathogen may not reflect its response to the amendments in the field.

Reuse of agricultural drainage water in central California: phytosustainability in soil with high levels of salinity and toxic trace elements

Abstract Agricultural drainage waters in the western San Joaquin Valley of Central California contained high levels of salts, boron (B) and selenium (Se). Discharge of the drainage directly into the Kesterson Reservoir was hazardous to plants and wildlife. To investigate the plausibility of using plants as recipients for disposing of poor-quality drainage-waters, multi-year field studies were conducted to reuse drainage water on plants that are salt and B tolerant, and accumulate or stabilize soluble Se from the drainage. Installation of a subsurface tile drainage system in cropping fields allowed drainage waters to be collected and subsequently reused on tolerant plants. The tested plant species included Lactuca sativa, Lycopersicon esculentum, Gossypium hirsutum L., Medicago sativa L., Brassica napus var. Hyola, Helianthus annuus, Distichlis spicata L., and Salicornia bigelovii Torr. The quality of drainage water decreased along the water reuse path, with a sulphate-dominated salinity change from 4.5 to 15.2 dS m -1 ; soluble B from 3.4 to 14.5 mg L -1 ; and soluble Se from 0.08 to 1.18 mg L -1 . Soil salinity and concentrations of B and Se increased with decreasing quality of reused drainage waters. This study demonstrated the importance of monitoring changes in soil quality for sustaining such a plant-based system.

Uranium Accumulation of Crop Plants Enhanced by Citric Acid

Citric acid was applied to soil to enhance U accumulation in four crop plants. While the highest enhanced U accumulation of aboveground tissues (a.c. 2000 mg kg(-1) dry weight) occurred in the leaves of Indian mustard (Brassica juncea), the highest enhanced U accumulation of roots (a.c. 3500 mg kg(-1) dry weight) occurred in canola (Brassica napus var. napus). Uranium translocation among tissues of test plants is in the relation of roots>shoots congruent with leaves. The flowers of sunflower (Helianthus annuus) contained similar or higher U concentrations than those found in shoots, but concentrations in seeds are close to zero. In conclusion, Indian mustard is recommended as a potential species for phytoextraction for U-contaminated soil due to its high U accumulation of aboveground biomass (a.c. 2200 microg per plant). There is no evidence that two types of soils cause a significant difference of the enhanced U accumulation (p<0.05). Results, however, indicate that additional citric acid may result in downward U migration that may contaminate groundwater. Speciation of U that is taken up by plants is also discussed in the end.

Saprophytic growth of Rhizoctonia solani Kühn AG2-1 (ZG5) in soil amended with fresh green manures affects the severity of damping-off in canola

Plants of the Brassicaceae contain glucosinolates, the hydrolysis products of which inhibit the growth of many soil-borne fungi that cause plant disease. However, amending soil with green manures of these plants gives inconsistent control of several soil-borne diseases, including those caused by Rhizoctonia solani. To identify factors that contribute to this inconsistency we investigated, in the laboratory and in pot experiments in the glasshouse, the saprophytic behaviour of R. solani AG2-1 (ZG5) in a sandy soil amended with various green manures. Fresh material from either Brassica napus var. Karoo, B. napus B1, B. napus B2, B. nigra, Diplotaxis tenuifolia (a brassicaceous weed) and the non-Brassicaceae species, oat ( Avena sativa) or lupin ( Lupinus angustifolius) was used at 10 or 100 g of fresh material kg −1 of dry soil in Lancelin sand. At 100 g kg −1 the volatiles of all green manures reduced the hyphal growth of R. solani, except for B. napus B1. D. tenuifolia at 100 g kg −1 inhibited the growth and sclerotial formation of R. solani. Most green manures at 10 g kg −1, and at 40% water holding capacity, stimulated the growth of R. solani for up to 3 months and increased the activity of other microbes. R. solani infected the brassicaceous plants when growing and colonized the residues mixed with soil at 10 g kg −1. This inoculum increased the severity of damping-off in canola, by 27%. Disease was particularly severe when the green manure species, except D. tenuifolia and oat, were grown in situ and residues returned to the pot from which they came, before sowing canola. There is a potential hazard in applying green manures of Brassica species as their residues can, under certain conditions, support the saprophytic activity of R. solani which increases damping-off in canola sown in the amended soils.

Relative longevity of Leptosphaeria maculans and associated mycobiota on canola debris

Survival of the blackleg pathogen (Leptosphaeria maculans) in canola (Brassica napus var. oleifera) stem debris was studied at three locations during two separate tests from August 1995 through October 1998. In combined isolation frequencies from both locations, L maculans decreased over time from 85.0% before burial in July to 15.4% in September and 3.4 % in December. Eleven months after initiation of this test, L maculans could not be isolated from the infected canola stem pieces. Isolation frequencies of L maculans were similiar among the three soil depths over all sampling dates at both locations. AH other fungi that were present in a preliminary assay also declined after burial. Trichoderma spp. were undetectable after initiation of the test and increased to 27.5 % on the last sampling date in July 1996. The increase of Trichoderma spp. corresponded with the decrease in isolation frequencies of L maculans and other fungi in the stem pieces. The first test differed from previous studies, consequently a second test located near Griffin, Georgia, was initiated in 1996. In the second test, the relative longevity of L. maculans was determined on intact debris (two to three times greater in size) left on the soil surface after harvest in a field using either minimum or no-tillage. Leptosphaeria maculanswas isolated from 26.4,31.2, and 20.8 % of the pieces, respectively, for May 1997, November 1997, and October 1998. Pycnidia containing viable conidia were also identified on 43.7, 26.4, and 18.0% from debris present in the D-V-8 plates even though no visible fungal colonies of L. maculans grew on the agar. The difference in relative longevity of L. maculans between the two tests was directly related to the condition and size of the canola debris. In the first test, the debris was sectioned into 10-cm pieces. These pieces were badly deteriorated and fragmented 5 months after burial. In contrast, the debris in the second test was still intact 36 months after being placed on the soil surface. This survival was because of increased debris size that resulted in reduced fragmentation from tillage. Thus, intact canola debris can serve as an inoculum source for at least three seasons or longer.

Gibberella avenacea . [Distribution map

Abstract A new distribution map is provided for Gibberella avenacea Cooke Ascomycota: Hypocreales Principal hosts: Barley ( Hordeum vulgare ), lucerne ( Medicago sativa ), oat ( Avena sativa ), pea ( Pisum sativum ), potato ( Solanum tuberosum ), rape ( Brassica napus var. napus ) and wheat ( Triticum aestivum ). Information is given on the geographical distribution in EUROPE, Austria, Belarus, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Netherlands, Norway, Poland, Portugal, Romania, Central Russia Russia, Eastern, Russian Far East, Northern Russia, Western Siberia, Serbia and Montenegro, Slovakia, Slovenia, Sweden, Switzerland, UK, Ukraine, ASIA, China, Gansu, Hubei, Jiangsu, Qinghai, Xizhang, Yunnan, Zhejiang, Republic of Georgia, India, Arunachal Pradesh, Manipur, Punjab, Uttar Pradesh, Indonesia, Iran, Iraq, Israel, Japan, Hokkaido, Honshu, Kazakhstan, Korea Republic, Lebanon, Malaysia, Sri Lanka, Taiwan, Turkey, Uzbekistan, AFRICA, Egypt, Ethiopia, South Africa, Tunisia, NORTH AMERICA, Canada, Alberta, British Columbia, Manitoba, New Brunswick, Nova Scotia, Ontario, Prince Edward Island, Quebec, Saskatchewan, Mexico, USA, California, Colorado, Connecticut, Idaho, Minnesota, Montana, Nevada, New York, North Dakota, Oregon, Texas, Washington, Wyoming, CENTRAL AMERICA &amp; CARIBBEAN, Trinidad and Tobago, SOUTH AMERICA, Argentina, Brazil, Rio Grande do Sul, Chile, Colombia, Peru, Venezuela, OCEANIA, Australia, New South Wales, Victoria, Western Australia, New Zealand, Papua New Guinea.