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Stephanie G. Harvey, Heather N. Hannahan and Carl E. Sams

Allyl isothiocyanate (AITC) is the predominant isothiocyanate produced by damaged tissues of Indian mustard (Brassica juncea (L) Czerniak). This study investigated Indian mustard and AITC mediated suppression of mycelial growth and sclerotial germination of Sclerotium rolfsii Saccardo, a common soilborne pathogen. Indian mustard (IM) treatments of 0, 0.1, 0.2, 0.6, 1.0, 2.0, 4.1, 5.1, 10.2, 20.4, 40.8, 81.6, and 163.3 g·L-1 (weight of reconstituted mustard per liter of air) were evaluated for suppression of mycelial growth. Treatment effect was evaluated by measuring the radial growth of mycelia. Sclerotia were placed in culture tubes containing 18 g autoclaved soil and covered with an additional 5 g soil. AITC at concentrations of 0, 4.0, 16.0, 64.0, 256.0, 1024.0, or 4096.0 μmol·L-1 was injected into the tubes. Treated sclerotia were removed from tubes and plated on potato dextrose agar to determine viability. Mycelial growth was inhibited with IM treatments (P < 0.01). Inhibiting concentrations (IC) of IM for mycelial growth inhibition of 50% and 90% were 0.7 and 1.0 g·L-1, respectively, with death resulting with >2 g·L-1. Inhibition attributable to AITC alone was lower than that achieved by IM producing equivalent amounts of AITC. Germination of sclerotia was negatively correlated with AITC concentration (r = 0.96; P < 0.01). The IC50 and IC90, of AITC were 249.0 and 528.8 μmol·L-1, respectively, at 42 hours. The lethal concentration for sclerotia was not reached; only suppression occurred at the highest treatment concentrations. Sclerotium rolfsii mycelia were sensitive to the IM volatiles and were suppressed at low concentrations. Sclerotia were more resistant than the mycelia and required higher concentrations of AITC to suppress germination.

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David A. Bender, William P. Morrison and Raymond E. Frisbie

A system of intercropping cabbage (Brassica oleracea var. capitata L.) with Indian mustard [Brassica juncea (L.) Czern.] to reduce pesticide applications was evaluated over three cropping seasons. Insects were monitored in nonintercropped cabbage, cabbage plots surrounded by Indian mustard, and the Indian mustard intercrop. Insecticide applications were made to individual plots based on specific treatment thresholds for lepidopterous insects and accepted pest management practices for other insects. Intercropping had no significant effect on the number of lepidopterous larvae in cabbage. Indian mustard did not appear to preferentially attract lepidopterous insects, but was highly attractive to hemipterans, especially harlequin bugs [Murgantia histrionica (Hahn)]. In one season with heavy harlequin bug pressure, intercropping with Indian mustard eliminated two insecticide applications to cabbage. Intercropping cabbage with Indian mustard does not appear to be an economical pest management practice under normal pest pressures in West Texas.

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David A. Bender and William P. Morrison

Indian mustard (Brassica juncea) has been reported to be a preferred host for diamondhack moth (Plutella xylostellu) and other insect pests when interplanted with cabbage (Brasssica oleracea var. capitata). A cabbage-Indian mustard companion planting study was conducted to determine the seasonal occurrence of cabbage insects and the potential for using a trap-crop system to reduce insecticide applications to cabbage in West Texas. Three-row plots of cabbage 9 m long were transplanted with and without sequentially seeded borders of Indian mustard in three seasons. Harmful and beneficial insects were counted at roughly weekly intervals. Insecticides were applied when insect populations in individual plots reached predetermined thresholds. Indian mustard did not appear to be more attractive than cabbage to lepidopterous pests, but did preferentially attract hemipterans, particularly harlequin bugs (Margantia histrionica). The mustard trap crop eliminated two insecticide` applications in one trial by reducing harlequin bug pressure on the cabbage.

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David A. Bender and William P. Morrison

Indian mustard trap crops have successfully reduced pesticide use on commercial cabbage in India. Diamondback moth has been a serious pest of cabbage in Texas and has demonstrated resistance to most classes of insecticides. Use of a trap crop could fit well in an integrated management program for cabbage insects, Three-row plots of spring and fall cabbage were surrounded by successive single-row plantings of Indian mustard in trials at Lubbock, Texas to determine the efficacy of interplanting for reducing insecticide applications. Insects in the cabbage and Indian mustard were counted twice weekly, and insecticides were applied selectively when economic thresholds were reached. Indian mustard was highly attractive to harlequin bugs, and protected intercropped spring cabbage. Cabbage plots without mustard required two insecticide applications to control the infestation. False chinch bugs were also highly attracted to Indian mustard. Lepidopterous larvae, including diamondback moth, did not appear to be attracted to the trap crop. Indian mustard trap crops reduced insecticide applications to spring cabbage but had no positive effect on fail cabbage.

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Ksenija Gasic and Schuyler S. Korban

Phytochelatins (PCs) are heavy metal binding peptides that play important roles in sequestration and detoxification of heavy metals in plants. To develop transgenic plants with increased tolerance and/or accumulation of heavy metals from soil, an Arabidopsis thaliana FLAG–tagged AtPCS1 cDNA encoding phytochelatin synthase (PCS) under the control of a 35S promoter was expressed in Indian mustard (Brassica juncea). Four transgenic Indian mustard lines, designated pc lines, with different levels of AtPCS1 mRNA accumulation and correspondent AtPCS1 protein levels were selected and analyzed for tolerance to cadmium (Cd) and zinc (Zn). Heavy metal tolerance was assessed by measuring root length of 10-day-old seedlings grown on agar medium supplemented with different concentrations of Cd (0, 100, 150, and 200 μm CdCl2) and Zn (200, 400, 600, and 800 μm ZnCl2). All transgenic lines showed significantly longer roots when grown on a medium supplemented with 100 μm CdCl2. No significant differences were observed between transgenic lines and wild type when plants were grown on higher levels of Cd. This indicated that only partial tolerance to Cd was observed in these transgenic lines. Similarly, partial tolerance for Zn was also observed in these transgenic lines, but up to levels of 400 μm ZnCl2. Expression levels of AtPCS1 protein were not related to tolerance responses for either Cd or Zn stresses in transgenic lines.

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Ryan R.P. Noble, C.S. Charron and C.E. Sams

The development of alternative methods for control of soilborne pathogens is imperative since the U.S. Clean Air Act bans the use of methyl bromide after 2005. One possibility is to exploit the pesticidal properties of compounds released by macerated Brassica tissues. In this study, masked chaffer beetle larvae were placed in sealed 473-mL jars with 335 g of soil amended with 1%, 2%, 4%, or 8% (g·g–1) Brassica tissue. The most prevalent volatile toxic compound of Brassica juncea (PI 458934) is allyl isothiocyanate (AITC). AITC production was measured in the jars at 0.25, 4, 8, 24, and 48 h using a solid-phase microextraction device (SPME) and gas chromatography. After 7 days, larvae mortality was determined. Control treatments included untreated soil, soil amended with 8% tomato plant tissue, soil amended with pure AITC, and untreated soil with an atmosphere of ≈20% O2 and 0% CO2 changing over 48 h to 2% O2 and 20% CO2. AITC levels were positively correlated to larvae mortality. The estimated lethal concentration for 50% kill (LC50) was 3.6 μg AITC/L soil atmosphere. AITC levels may be influenced by Brassica mass added, soil bulk density, and environmental factors including temperature and moisture. B. juncea has a high tissue AITC concentration. However, the mass of Brassica tissue required for insecticidal application against Cyclocephala sp. is also high, between 4% and 8% of soil mass. Development and selection of Brassica species that produce higher concentrations of isothiocyanate would increase the effectiveness of Brassica biofumigation as an alternative to methyl bromide for controlling soilborne insects.

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Andrew J. Price, Craig S. Charron, Arnold M. Saxton and Carl E. Sams

A study was conducted to quantify volatiles generated from Indian mustard (Brassica juncea L. Czerniak) tissue incorporated into soils under controlled conditions. Mustard residues were incorporated into noncovered and covered soils that varied by texture, temperature, moisture, pH, or sterility (autoclaved or nonautoclaved). Sandy loam soil had 38% more allyl isothiocyanate (AITC) than clay loam soil. AITC concentration in 45 °C soil was 81% higher than in soil at 15 °C, and 56% higher in covered compared to noncovered treatments. The microbial catabolism of AITC was suggested by the result that AITC concentration in autoclaved soils was over three times that measured in nonautoclaved soils. The highest AITC level detected (1.71 μmol·L–1) occurred in the autoclaved covered soil. Several factors also influenced CO2 evolution. At 30 or 45 °C, CO2 concentration was at least 64% higher than at 15°C. The covered soil had over twice the CO2 found in the noncovered soil, and the nonautoclaved soil treatment yielded twice the CO2 measured in the autoclaved soil. There were no main effect differences among soil moisture, soil pH, and soil texture treatments for CO2 concentrations. This information could be helpful in defining ideal soil conditions for field scale experiments. Additionally, this study demonstrates a sampling technique for testing fumigation potential of biofumigation and solarization systems that may have the potential to replace methyl bromide.

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Valtcho D. Zheljazkov and Tess Astatkie

phytoextraction seem to be Indian mustard [ Brassica juncea (L.) Czern.], clary sage ( Salvia sclarea L.), garden sage ( Salvia officinalis L.), lavender ( Lavandula angustifolia L.), sunflower ( Helianthus annuus L.), scented geranium ( Pelargonium sp

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D. Grant McCarty II, Sarah E. Eichler Inwood, Bonnie H. Ownley, Carl E. Sams, Annette L. Wszelaki and David M. Butler

control”); 3) fallow with dried molasses added for ASD treatment; 4) ASD treatment with a commercial mixture (‘Caliente 61’) of Indian mustard ( Brassica juncea L.) and white mustard ( Sinapis alba L.) seeded in a 1:1 mixture with arugula ( Eruca sativa

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Susan L.F. Meyer, Inga A. Zasada, Shannon M. Rupprecht, Mark J. VanGessel, Cerruti R.R. Hooks, Matthew J. Morra and Kathryne L. Everts

tomato seedlings transplanted into soil amended with seed meals of indian mustard (InM), yellow mustard (YeM), mixtures of these mustard seed meals, linseed meal, or untreated with meal. All amendments were applied at a final total rate of 0.25% dry