Chinese Cabbage Leaf Research Articles

Feeding Activity and Survival of Slugs, Deroceras reticulatum, Exposed to the Rhabditid Nematode, Phasmarhabditis hermaphrodita: A Model of Dose Response

Abstract The slug, Deroceras reticulatum (Stylommatophora: Limacidae), was exposed to different concentrations of infective dauer juveniles of the rhabditid nematode Phasmarhabditis hermaphrodita, in a two-stage bioassay, at 10°C. Slugs were exposed in groups of 10 or 12 to nematodes in plastic boxes filled with soil aggregates for 3 or 5 days and then transferred individually to petri dishes each containing a disk of Chinese cabbage leaf as food. Subsequently, slug food consumption and survival were measured for 10 to 13 days. Models were developed to describe the way that exposure to the nematode caused inhibition of slug feeding followed by death. Both effects were related to nematode concentrations and time after exposure to the nematode. Following exposure to high concentrations (300,000 dauer juveniles per box), slugs were killed rapidly, within a few days after the end of the exposure period. Following exposure to low concentrations of nematodes (7000 or 15,000 per box), substantial numbers of slugs survived until the end of the bioassay, but feeding activity by these slugs was strongly inhibited. It is suggested that inhibition of slug feeding is important for the success of this nematode as a biocontrol agent.

Slugs (Deroceras reticulatum and Arion ater agg.) Avoid Soil Treated with the Rhabditid Nematode Phasmarhabditis hermaphrodita

A series of experiments was done to determine whether the pest slugs Deroceras reticulatum and Arion ater agg. (Mollusca: Gastropoda: Stylommatophora) could detect the presence of and avoid soil treated with the parasitic nematode Phasmarhabditis hermaphrodita (Nematoda: Rhabditidae). One-half of the surface area of moist soil in experimental boxes was treated with infective juveniles of P. hermaphrodita at a density of 120/cm2. The other half of each box was left untreated. Five discs of Chinese cabbage leaf were placed in each half of each box. Slugs (D. reticulatum or A. ater agg.) were added to each box and food consumption and resting sites were recorded over a 12-day period. Both slug species were more likely to rest and feed on untreated soil than on nematode-treated soil. A series of boxes was also prepared with one-half untreated and the remaining half treated with 1, 4, 12, 38, or 120 nematodes/cm2. Slugs were less likely to rest or feed in the treated half of boxes containing 38 or 120 P. hermaphrodita/cm2 but showed no preference between the untreated and the nematode-treated soil at lower nematode densities. A final experiment showed that there was little movement of P. hermaphrodita from the treated half to the untreated half of each box.

Evaluation of Spinning Disc Technology for the Application of Entomopathogenic Nematodes against a Foliar Pest

Two spinning disc spray application systems, the Micron Herbaflex and Micron Ulva+, were assessed for their potential for the application of infective juveniles (IJs) of entomopathogenic nematodes (EPNs) against larvae of the diamondback moth (DBM),Plutella xylostella.The effect of initial concentration of IJs on subsequent infection was examined for three species of EPNs:Steinernemasp. (M87),Steinernemasp. (SSL85), andHeterorhabditissp. Increasing the concentration of IJs generally resulted in a significant increase in both DBM mortality and the mean number of nematodes per larva following spray application with the Micron Herbaflex sprayer. Application with the Micron Ulva+ was examined using two different initial concentration of IJs, which generally resulted in an increase in DBM mortality and intensity of infection. The effect of changing the flow rate to the Ulva+ was also examined. This generally resulted in increased DBM mortality as flow rate was increased but there was little change in the mean number of nematodes per host larva. The effect of addition of a number of adjuvants to the spray solution on subsequent infection showed that DBM mortality by the IJs was not significantly affected but that the mean number of nematodes infecting was significantly enhanced by some of the adjuvants. Desiccation survival studies with IJs ofHeterorhabditissp. following application with both sprayers onto Chinese cabbage leaf discs, with or without the addition of an adjuvant, showed that the survival time of 50% of IJs was over 3 h. Infection of DBM larvae was also assessed following desiccation on Chinese cabbage leaf discs. High levels of infection were attainable, in terms of resultant DBM mortality, for at least 150 min following spray application.

Changes in Various Ingredients, <i>Escherichia coli</i>, Taste and Texture of Blade Vegetables as a Result of Low Temperature Steam-Heating Process

To research wider uses of the low temperature steam heating process, blade vegetables were heated by steam of temperature adjusted from 55°C to 80°C for 5-30 min. The treated vegetables were used for analysis of various ingredients, measurement of color tone and texture, and evaluation of taste. To determine possible sterilizing effect of the process on E. coli, broccoli soaked in nutrient broth with the germ was treated at 60 and 65°C. The breaking stress of Chinese cabbage leaf stalk increased when treated for 30 min at 60°C. The color tone of leaves heated for 10 min at 65°C scarcely changed during storage for 48h at 5°C. The E. coli adhering to broccoli declined from 10 CFU/g to <30 CFU/g after steaming for 5 min at 60°C. The desirability of cabbage steamed for this same period and temperature showed little difference from the fresh sample. Total vitamin C in both Chinese cabbage and cabbage steamed for 5 min at 60°C remained over 90%, while there was augmentation of the γ-amino butyric acid in the samples at this temperature. The water soluble pectin in Chinese cabbage at 60°C decreased and NaOH soluble pectin increased. Consequently, we would like to propose that the low temperature steam heating process is a very useful way to prepare blade vegetables, because the color tone and taste of the treated samples were almost the same as those of the fresh sample, and E. coli was sterilized if condition of treatment were adequate.

Role of Erwinia carotovora subsp. carotovora Sprayed on Leaves of Chinese Cabbage as a Source of Inoculum for Soft Rot.

The role of the soft rot bacterium, Erwinia carotovora subsp. carotovora (Jones) Bergey et al., as a source of inoculum for soft rot of Chinese cabbage was examined by spraying a rifampicin-resistant strain (RRS) on spring and summer-sown Chinese cabbage (cv. Matsushima-kohai W-1116) leaves. The organism was then suspended in sterilized water at a concentration of 106cfu/ml and 2.0ml per plant was sprayed on the leaves at 20, 33, 47 and 60 days after seeding. In addition, 2.0ml/plant of the suspension at 108, 106, 104, 102 or 100cfu/ml were sprayed on the leaves at 45 days after seeding, respectively. The RRS sprayed on leaves of Chinese cabbage survived until harvest, but most of the plants were diseased, at 50-60 days after seeding both in the sprayed and control plants. Disease severity did not differ between the sprayed and control plants in the spring- and the summer-seeded crops except for the middle growing stage of the spring crop. The RRS from soft, rotten petioles and rhizosphere soil of diseased plants were reisolated by dilution plating onto modified Drigalski's medium containing rifampicin (RMDM). The RRS was predominantly reisolated from rotten tissues and rhizospheres of the diseased plants, irrespective of the spraying time and concentration of the used strain. Naturally occurring soft rot bacteria were detected on leaf surfaces of the plant at a population level of 105-106cfu/g of fresh tissue at 76 days after seeding in the spring crop and at 33 days after seeding in the summer crop. Soft rot bacteria artificially sprayed on leaves of Chinese cabbage survived until harvest and played a role as a source of inoculum for soft rot disease of Chinese cabbage in the field.

Leaf and head rot of Chinese cabbage - a new field disease caused by Pythium tracheiphilum Matta

A new disease has arisen in field grown Chinese cabbage (Brassica campestris ssp. pekinensis) in Denmark. The soil-borne causal agent was shown to be Pythium tracheiphilum Matta, a little known pathogen of lettuce. Until now, outbreaks of the disease in Chinese cabbage were generally attributed to Phytophthora porri Foister, since symptoms of the disease in the field resemble those caused by Ph. porri in Chinese cabbage in cold stores. In some severely affected crops harvest losses in 1994, directly attributable to P. tracheiphilum, were estimated to about 50%, corresponding to a market value of up to $ US 20000 per ha. Outbreaks of the disease coincide with the heading of the crop, while juvenile plants or seedlings are apparently not attacked. It appears that the outer leaves are infected directly from the soil. Mainly above ground parts are affected and colonized by the pathogen, and indications of infection via the root system have not been observed. This is the first record of P. tracheiphilum as a pathogen of Chinese cabbage.

Behavioural evidence for detection of the repellent polygodial by aphid antennal tip sensilla

Abstract. Close‐up video was used to record responses of the aphid Myzus persicae (Sulzer) (Homoptera: Aphididae) to the plant‐derived repellent polygodial. When 0.1% (±)‐polygodial was painted onto one half of a Chinese cabbage leaf disc, and the other half treated with the ethanol solvent, apterous adult aphids avoided walking onto the polygodial‐treated area during 15 min access periods. Similarly, when the rim of a small plastic Petri dish was treated with polygodial, aphids took significantly longer to walk off the base of the dish and onto the rim, compared with insects in solvent‐treated control dishes. Analysis of video‐recordings indicated that aphids were repelled following contact of antennal tips with the polygodial‐treated areas of leaf or plastic. In contrast, aphids with both antennal tips surgically removed showed no apparent response to polygodial treatment of leaf or plastic surfaces. Aphids were placed between polygodial‐ and solvent‐treated angled glass cover slips to enable unilateral presentation of polygodial on either the left or right side of the insects. Most aphids with antennae intact moved away from the polygodial‐treated side, but removal of both antennal tips again negated the response. When the tip was removed from only one antenna, and the other remained intact, unilateral presentation caused a repellent response only if polygodial occurred on the same side as the intact antenna. Presentation of polygodial on both sides of aphids (bilaterally) caused no response if both antennal tips were intact or removed, but aphids with only one antennal tip removed were repelled from the side where the antenna remained intact. The results indicate that aphids detect polygodial upon contact with sensilla located on the antennal tips, and that the repellent response occurs as a negative chemotropotaxis following unilateral stimulation of these sensilla. Contact between the antennal tips and glass substrates was demonstrated using a fluorescent pigment.

Effects of the antifeedant polygodial on plant penetration by aphids, assessed by video and electrical recording

AbstractAdult apterous Myzus persicae (Sulz.) discriminated within 2 min between mature Chinese cabbage (Brassica pekinensis L.) leaf halves treated with (±)‐polygodial solution and solvent alone, and walked off leaf areas treated with polygodial faster than off the solvent‐treated areas. However, when aphids were attached to a fine gold wire and stylet penetration of cabbage leaves was recorded electrically, polygodial treatment did not affect the number or duration of electrically‐recorded penetrations, time taken to initiate a first penetration, or total penetration time. As the tethering of aphids causes behavioural restrictions which may negate the response to polygodial, indications of stylet penetration by freely‐moving insects were sought. Simultaneous electrical recording and video monitoring showed that stylet penetration duration could be accurately inferred from antennal and body movements, enabling assessment of penetration times without attachment to the wire tether. When freely‐moving M. persicae were video recorded during 15 min access to cabbage seedlings, polygodial treatment again had no apparent effect on stylet penetration. However, when aphids were presented with a choice of polygodial‐ and solvent‐treated sides of floating mature cabbage leaf discs, video recordings revealed that the insects spent less time and made fewer penetrations on the polygodial‐treated side. In addition to this rapid repellent effect, prolonged exposure to polygodial also produced behavioural changes. After being held for 24 h on polygodial‐treated leaves or green paper prior to behavioural examination, aphids penetrated seedlings fewer times but for longer periods. The relevance of the results to virus transmission studies is discussed.

野菜軟腐病菌のハクサイ葉上における動態について

ハクサイ葉上における軟腐病菌の分布を知るため希釈平板法,土壌増菌法の改良法(直接法,間接法)により検討した。ハクサイの栽培過程において,生育初期でハクサイ葉の下部および上部にまで軟腐病菌の存在が認められた。また,播種時に菌量が少ない場合でも,土砂飛散によりハクサイ葉上の下部では,生育初期から軟腐病菌の存在が認められた。希釈平板法では検出できない場合でも,増菌法では検出でき,植物体上部においても20葉期前後から結球期以降に至るまで本病原細菌が存在することが,明らかになった。

Turnip Mosaic Virus Strains in Cruciferous Hosts in Taiwan

Turnip Mosaic Virus Strains in Cruciferous Hosts in Taiwan

Length requirements for tRNA-specific enzymes and cleavage specificity at the 3' end of turnip yellow mosaic virus RNA.

This paper describes the minimum length of the turnip yellow mosaic virus (TYMV) RNA necessary to fulfill the tRNA-like properties of the viral RNA: 50 to 75 nucleotides and 86 nucleotides from the 3' end of TYMV RNA are sufficient for adenylation and valylation respectively by the Escherichia coli system. The size of the tRNA-like fragments obtained in vitro in the presence of an E. coli, a reticulocyte or a chinese cabbage leaf extract has also been determined. Among the major fragments liberated from the 3' end of TYMV RNA by the three systems are fragments of 117 and 112 nucleotides. In addition, the E. coli extract liberates fragments of 139 and 61 nucleotides, and the reticulocyte lysate fragments of 109, 94, 84, 73 and 46 nucleotides. The cleavage of the viral RNA by several systems in vitro to yield RNA fragments encompassing the tRNA-like sequence suggests that such fragments might also be liberated in vivo.

The Synthesis of Polyamines from Methionine in Intact and Disrupted Leaf Protoplasts of Virus-Infected Chinese Cabbage

In exploring the role of the chloroplast in the multiplication of turnip yellow mosaic virus, the biosyntheses of the major viral polyamine, spermidine, as well as that of the tetramine, spermine were studied. The synthesis of these polyamines from [2-(14)C]methionine in protoplasts of Chinese cabbage leaf cells derived from healthy plants or those infected by turnip yellow mosaic virus were examined. Populations of protoplasts of infected leaves are homogeneous with respect to containing chloroplast aggregates in contrast to those of healthy leaves. Protoplast preparations have been shown to incorporate methionine into protein, spermidine, and spermine more rapidly than do fresh leaf discs, which also show a very slow utilization of labeled arginine and ornithine into polyamine.Protein synthesis is similar for 4 hours in both healthy and infected protoplasts. Accumulation of labeled spermidine stops after 2 hours in healthy protoplasts but continues in the infected protoplasts. Much of the newly synthesized protein and spermidine is present in the easily sedimentable fraction of the readily disrupted protoplasts.Disrupted and diluted protoplasts have a decreased ability to metabolize methionine to protein and spermidine. The residual synthetic activity is essentially entirely in the easily sedimentable fraction. However, this fraction is unable to synthesize spermine, an activity found in protoplasts and disrupted protoplasts. Disrupted protoplasts contain spermidine synthase (EC 2.5.1.16) and about a quarter of this activity is present in a low-speed sedimentable fraction containing the chloroplasts. The protoplast system is suitable for an analysis of polyamine synthesis in turnip yellow mosaic virus infection and appears particularly suitable for study of the distribution of the enzymes involved.

Effect of Phosphate Buffer on the Development of Soft Rot on the Leaf of Chinese Cabbage inoculated with Erwinia carotovora var. carotovora

Effect of Phosphate Buffer on the Development of Soft Rot on the Leaf of Chinese Cabbage inoculated with <i>Erwinia carotovora</i> var. <i>carotovora</i>

Effects of N6-benzyladenine on nucleotides in chinese cabbage leaf discs

Floating Chinese cabbage leaf discs in the presence or absence of N 6-Benzyladenine did not affect the amount of AMP in the discs suggesting that at least in this system cytokinins do not inhibit the activity of a 5′(3′)-ribonucleotide phosphohydrolase.

Inhibition of turnip yellow mosaic virus synthesis by pyrimidine analogues.

The pyrimidine analogues 2-thiouracil, 2-thiouridine, 6-azauracil and 6-azauridine all inhibited the synthesis of turnip yellow mosaic virus (TYMV) and increased the synthesis of empty virus protein shells in infected Chinese cabbage leaf discs. Uracil and uridine reversed these effects. 2-Thiouracil also reduced the UTP pool in TYMV infected leaf discs. The results are consistent with the suggestion that these analogues or their in vivo derivatives affect virus synthesis by inhibiting the biosynthesis of uridylic acid, possibly by inhibiting orotidylic acid decarboxylase.

Effects of kinetin on phosphorylation of leaf membrane proteins

Isolated Chinese cabbage leaf membranes were phosphorylated by membrane-associated protein kinase(s) in the presence or [γ- 32P] ATP. Membrane-associated 3 2P radioactivity appeared to be bound to membrane proteins. Both smooth cell membranes and chloroplast lamellae reacted with ATP. Phosphorylation of the membranes was inhibited by Ca 2+ and partially inhibited by kinetin or 6-benzyladenine. The possibility that cytokinin effects on membrane phosphorylation might increase ion availability was investigated in vivo. It was found that Ca 2+ could substitute for kinetin in the leaf disc expansion assay.

The sequence of early cytological changes in Chinese cabbage leaf cells following systemic infection with turnip yellow mosaic virus

The invasion of small systemically infected Chinese cabbage leaves by turnip yellow mosaic virus (TYMV) has been followed by electron microscopy. The presence of small peripheral vesicles in the chloroplasts was used as a marker of infection by the virus. A plasmolysis procedure which induced virus particles to form crystalline arrays with little damage to chloroplast membranes was used to detect the presence of complete virus. Infection spreads out from the small veins of the leaf at about 4 μm/hr. This is equivalent to about 1 cell in 3 hr. Using the vein as a marker for the origin of the infection, we have been able to distinguish seven cytological stages in the establishment of infection. These stages fall into two phases. In the first phase, comprising the first two stages, only scattered peripheral vesicles are present in the chloroplasts. In the second phase the number of vesicles is approximately doubled by the rapid appearance of clustered vesicles. At the beginning of the second phase endoplasmic reticulum (ER) appears closely apposed over parts of the chloroplast surface. Beneath these areas, the clustered vesicles appear. The ER then disappears, and electron lucent zones appear over the clustered vesicles. Arrays of virus particles in plasmolysed tissue are first seen at the fourth stage. At this stage these arrays are always associated with the electron lucent areas, which presumably have some role in virus synthesis or assembly. The last three stages involve clumped chloroplasts. The electron lucent material appears to be involved in the clumping process.

Evidence for TYMV-induced RNA and DNA synthesis in the nuclear fraction from infected Chinese cabbage leaves

Radioactively labeled nucleic acids prepared from the nuclear fraction from Chinese cabbage leaf tissue infected with turnip yellow mosaic virus (TYMV) contained two components not present in equivalent material from healthy leaves. One of these components had the properties expected for a virus-specific double-stranded RNA; the other contained DNA, with properties expected for DNA-RNA hybrids. In leaf tissue supplied with 3H-thymidine this DNA reached maximal labeling much more rapidly than the rest of the DNA.

Leaf ontogeny and virus replication in Brassica pekinensis infected with turnip yellow mosaic virus

The ontogeny of the Chinese cabbage leaf is described in relation to infection by turnip yellow mosaic virus (TYMV) and the development of the mosaic disease. The islands of tissue in the first few leaves to show mosaic symptoms arise from clusters of several hundred cells. These clusters of cells must be formed by cell-to-cell spread of a particular strain of the virus after it has initially infected one or a few cells in the developing leaf. In a fully infected plant, virus is present in the apical dome plus the first one or two alaminate primordia. Thus, in later leaves showing mosaic patterns many of the islands of tissue probably consist of the progeny of single cells. In the developing leaf changes in concentration and amount of TYMV follow a similar pattern to that shown by 83S ribosomes. A sensitive serological procedure is described for assaying TYMV (0.1–1.0 μg) from single apices.

Evidence for the intracellular site of double-stranded turnip yellow mosaic virus RNA

Cell-free extracts containing nuclei and chloroplasts were prepared from turnip yellow mosaic virus-infected Chinese cabbage leaves from plants previously treated with 32P-orthophosphate. After fractionation by sedimentation into discontinuous sucrose density gradients, the 32P-labeled double-stranded viral RNA in the extracts distributed as did the chlorophyll-containing chloroplast fractions rather than the DNA-containing nuclei. The results support our previous suggestion that double-stranded turnip yellow mosaic virus RNA is associated with the chloroplast fraction from virus-infected Chinese cabbage leaf, and not with nuclei.