Progress 10/01/04 to 09/30/09
Outputs
OUTPUTS: Helix aspersa (Brown Garden Snail) is an invasive terrestrial mollusk. It is widespread in California, is a pest of many different plant species, and can damage young seedlings and foliage. We collected 350 snails in California (San Francisco, Sacramento, Davis, Woodland, San Jose, and Tulare) to identify nematodes and bacteria associated with the snails, and to determine snail tissues where nematodes and bacteria occur. We are interested in the dissemination of pathogens in cropping systems by the snails. Snails were dissected, and nematodes and bacteria were recovered from surface rinsate, the foot muscle, shell, digestive gland, stomach, heart, mantle, and feces yielding 500 individual nematodes. Nematodes and bacterial isolates were subject to PCR amplification using primers for ITS, 16S, 28S, 18S, and rpoβ. Nematodes were recovered from ca. 91% of snails and included Caenorhabditis elegans (in 60% of snails), Rhabditis terricola (32%), Aphelenchoides fragariae (44%), Xiphinema index (24%), Heterodera spp. (28%), and Aphelenchus avenae (45%). There were 25 distinct bacterial colonies isolated from organ tissues, with Serratia proteamaculans, Klebsiella terrigena, and Stenotrophomonas maltophilia recovered, and five bacteria isolated from snail slime, including Psuedomonas putida and Sphingobacterium kitahinoshimense. These associations establish the brown garden snail's role as an important phoretic host for plant pathogens, and lead us to consider the possible use of snails as sentinels for the detection of pathogens in the environment. Research results were disseminated to scientific peers in campus meetings and seminarsand Multi-State Project Meetings. PARTICIPANTS: J. Haynes, a Master's degree student at the University of California, Davis has worked on this project extensively, and her professional development was enhanced through this research in that she has obtained a position with the California Department of Food and Agriculture. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
These associations establish the brown garden snail's role as an important phoretic host for plant pathogens, and lead us to consider the possible use of snails as sentinels for the detection of pathogens in the environment.
Publications
- No publications reported this period
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Under this objective research to assess and develop measures to prevent or minimize the transmission of nematodes via irrigation water continues. Nematodes infest fields through movement by water, wind, and the movement of animals and people, or contaminated equipment. Nematodes detected in irrigation water may include Aphelenchoides spp., Meloidogyne spp., and Pratylenchus spp. Given possible requirement that run-off from irrigation water be recycled on site, we have been looking at methods for eliminating plant-parasitic nematodes from such water. We have been evaluating use of ozone and ultraviolet light as methods to treat nematodes in recycled irrigation water. During this time period we have assessed ozone treatments as a method for clarifying recycled irrigation water such as to allow subsequent treatment with ultraviolet light to eliminate plant-parasitic nematode inoculum. Ozone works as a disinfectant through oxidation and can oxidation can break down particulates that lead to low transmittance of ultraviolet light in irrigation water. We performed experiments to determine the amount of ozone exposure time is necessary to reach various transmittance levels. Depending on the exact rate of ozone application, the change in ultraviolet light transmittance varied, but at lower rates of ozone application transmittance was increased from ca. 10% to 40% after 2 to 8 hours of exposure. At the higher rates of application the transmittance of ultraviolet light could be increased from ca. 10% to 40 to 90% over a period of 6 hours. The amount of time required for maximum increase in transmittance depended upon the condition and the time of year at which the water was collected from the field. Research results were disseminated to scientific peers in campus meetings and Multi-State Project Meetings. PARTICIPANTS: J. Haynes, a Master's degree student at the University of California, Davis has worked on this project extensively, and her professional development was enhanced through this research in that she has obtained a position with the California Department of Food and Agriculture. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The research results obtained promote our progress toward the goal of disinfestation of commercial recycled irrigation water, in order to allow for recycling on site without compromising other nematode management strategies that may be in place, such as nematicide applications. The ultimate objective is to derive economically acceptable and environmentally friendly combinations of tactics that will allow for effective nematode management.
Publications
- No publications reported this period
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Progress 01/01/07 to 12/31/07
Outputs
Agricultural and nursery soils are often contaminated with nematodes through nematode-infested irrigation water. Plant-parasitic nematodes may be moved in irrigation water, and the need to recycle water may exacerbate this problem. Treatment with pulsed-ultraviolet light (PUV) is being evaluated as a non-chemical, residue-free method of controlling nematodes in water. Nematodes were exposed to a range of UV doses with a flashlamp-type (Xe-filled), non-coherent pulsed UV/Vis source operating with 200-300 J/pulse (~18% UV, ~82% visible, no IR) and 1-3 Hz (pulses per second). All exposure doses were measured with a calibrated pyroelectric joulemeter (9.02 V/Joule) and expressed as mJ/cm2/pulse. Bioassay nematodes were exposed to a range of pulses of UV/Vis light and to UV-filtered beam containing only the visible light spectrum. Nematodes were examined after exposure and 24 h post-exposure for delayed mortality. PUV at 372 mJ/cm2 immediately inactivated Meloidogyne
javanica juveniles. Inactivation of Aphelenchoides fragariae required 425 mJ/cm2, Caerhabditis elegans: 460 mJ/cm2, and Acrobeloides buetschii: 407 mJ/cm2. UV-filtered exposure experiments showed that the UV component of the emission spectrum was solely responsible for nematode mortality. Pulsed UV may be an effective for controlling nematodes in water.
Impacts
Investigations continued on the use of ozone and ultra-violet light for use in limiting or eliminating nematodes from irrigation water. At this point we are seeking a change in knowledge on the efficacy and potential for use of these techniques. The goal is the disinfestation of commercial irrigation water, in order to allow for recycling on site without compromising other nematode management strategies that may be in place, such as nematicide applications. The goal is to develop baseline data for effective treatment thresholds and assessing water quality issues.
Publications
- Haynes, J.L., Sanchez, K.R., Lagunas-Solar, M.C., Nadler, S.A., Pina, C., and E. P. Caswell-Chen. 2007. Treatment of water with pulsed ultraviolet light for inactivation of nematodes. Journal of Nematology 39:84. (Abstr.)
- Sanchez, K.R., Haynes, J.L., Moore, W.H., Pryor, A., and E. P. Caswell-Chen. 2007. Ozonation for control of nematodes in irrigation water. Journal of Nematology 39:84. (Abstr.)
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Progress 01/01/06 to 12/31/06
Outputs
Agricultural and nursery soils are often contaminated with nematodes through nematode-infested irrigation water. Ozone is a powerful oxidizing agent and has been shown to be an effective fungicidal and bactericidal agent when injected into water. We have continued to assess the potential of ozone to treat water to eliminate nematodes, and have also been pursuing use of ultraviolet light to sterilized irrigation water. Our tests of ozone treatments included injecting ozone gas into water containing nematodes using a negative pressure injector (Mazzei Corp., Bakersfield, Ca) placed in a water recirculation loop. Exposing CAENORHABDITIS ELEGANS to aqueous ozone concentrations of 0.12 ppm resulted in death of almost all nematodes by 15 minutes. We have assessed the efficacy of ozonation against other plant-parasitic nematodes using the same system and have found that the time required for nematode inactivation varied somewhat among species including HETERODERA SCHACHTII
(15-30 minutes), PRATYLENCHUS PENETRANS (15-30 minutes), PRATYLENCHUS PENETRANS (15-30 minutes), MELOIDOGYNE JAVANICA (15 to 25 minutes), M. ARENARIA (15-35 minutes), M. CHITWOODI (10-40 minutes), and M. INCOGNITA (20-55 minutes). It is likely that the short exposure times required for C. ELEGANS result because that species ingests the treated water, Dissolved ozone concentrations of 0.5 ppm could be reached in irrigation water after treatment for 80 minutes using our experimental apparatus, and these exposures were lethal to C. ELEGANS (approximately 100 percent lethality in 30 minutes) and M. JAVANICA (approximately 100 percent lethality in 85 minutes) in irrigation water. The response of APHELENCHOIDES FRAGARIAE to ozonation yielded responses similar to those of other plant parasitic forms. Continued research is planned with the bioassays using nematodes in irrigation water.
Impacts
Investigations on the use of ozone to control nematodes in irrigation water has the objective of disinfesting irrigation water in order to extend the effective period of field treatments such as nematicide applications. We are extending this research to treatments using ultraviolet light as a method for disinfesting irrigation water. We are developing baseline data for effective treatment thresholds and assessing water quality issues.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
To assess potential cover crops for use in management of sugarbeet cyst nematode (SBCN), HETERODERA SCHACHTII, we have continued greenhouse experiments on potential cover crop plants that may be useful in California rotations to reduce SBCN numbers in soil. In two separate experiments, assay plants included a mustard blend, Arugula (Nemat. Gowan), Beta 8520N (as a control), cabbage (as a control), oil seed radish, oil seed radish (Diablo Gowan), and Phoenix. Plants that supported very limited reproduction of SBCN included the oil seed radish plants and Arugula, with Pf/Pi ratios that were less than 1. Given that the nematodes infected the plants but showed limited reproduction it is possible that they may have some potential for use in California. However, the reproduction that did occur is cause for some concern relative to long term use of such plants because they may act as selection pressure for SBCN isolates capable of increased reproduction on the cover crops.
Additional trap crops were also evaluated for management of SBCN, including BRASSICA NAPUS (oilseed rape) Humus, BRASSICA JUNCEA (mustard), Horned Green, Red Giant, Erika, Green Wave, Southern Giant, Pacific Gold, ISCI 20, ISCI 61A, ISCI 61B, and ISCI 99, and SINAPIS ALBA (white mustard) Martigena and Ida Gold. Cultivars supporting the least SBCN reproduction (Pf/Pi 0.3) were Martigena, ISCI 99, ISCI 161B, and Red Giant. Evaluations of these latter cultivars is continuing. There have been numerous reports of bacteria as having potential as biocontrol agents of plant-parasitic nematodes, but none of the reports have assessed members of the genus LYSOBACTER. The LYSOBACTER are typically found in soil and water habitats, and characterized by having lytic activity against other microorganisms, including nematodes, presumably through the diverse array of antibiotics and lytic enzymes they can excrete, including chitinases, lipases and proteases. In the lab we assessed the influence of
LYSOBACTER ENZYMOGENES strain C3 (LEC3) on CAENORHABDITIS ELEGANS, SBCN, MELOIDOGYNE JAVANICA, PRATYLENCHUS PENETRANS, and APHELENCHOIDES FRAGARIAE. Exposure of C. ELEGANS to LEC3 on agar plates resulted in almost complete elimination of egg production and death of 94% of hatched juveniles after two days. Hatch of SBCN eggs was about 50% on a lawn of strain C3 on agar as compared to 80% on a lawn of E. coli. Juveniles that hatched on a plate of LEC3 on agar died due to the cuticle and body contents disintegrating. M. JAVANICA juveniles died after four days of exposure to a seven-day-old chitin broth culture of LEC3. Immersion of A. FRAGARIAE, M. JAVAINCA, AND P. PENETRANS juveniles and adults, and SBCN juveniles exposed to a nutrient broth culture of LEC3 strain C3 led to rapid immobilization and disintegration of the nematodes.
Impacts
A few isolates of Beauveria bassiana were virulent against the glassy-winged sharpshooter, a devastating insect pest of grapes and other crops because of its efficiency as a vector of Pierces disease. The use of this fungus may reduce overwintering populations of this insect.
Publications
- Kaya, H. K., Dara, S. K., and McGuire, M. R. 2005. Evaluation of some fungal pathogens fro the control of the glassy-winged sharpshooter. Proc. 2005 Pierces Dis. Res. Symp. Pp. 345-348.
- Luong, L. T. and Kaya, H. K. 2005. Sexually transmitted nematode affect spermatophylax production in the cricket, Gryllodes sigillatus. Behav. Ecol. 16: 153-158.
- Luong, L. T., and H. K. Kaya. 2005. Sexually transmitted parasites and host mating behavior in the decorated cricket. Behav. Ecol. 16: 794-799.
- Shapiro-Ilan, D. I., Fuxa, J. R., Lacey, L. A.., Onstad, D. W. and Kaya, H. K. 2005. Definitions of pathogenicity and virulence in invertebrate pathology. J. Invertebr. Pathol. 88: 1-7.
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Progress 01/01/04 to 12/31/04
Outputs
Research was conducted on the bacterium Lysobacter enzymogenes strain C3 as a potential biological control agent for plant parasitic nematodes. We changed the culture production medium from a chitin medium to a nutrient broth and found that the in vitro activity of the bacterium against a range of plant-parasitic nematodes was enhanced. Experiments were conducted to assess the influence of immersion of nematodes in cultures of the bacterium and cell-free cultures of the bacterium. The nematodes Heterodera schachtii, Meloidogyne javanica, Aphelenchoides fragariae, and Pratylenchus penetrans were assessed. Exposure to cultures derived from full-strength nutrient broth cultures resulted in the striking effect of complete dissolution of nematodes within 3 days. Although our previous research on C3 production in chitin medium revealed that C3 could exert a lethal effect on M. javanica and H. schachtii, this lytic action was not observed when the bacterium was cultured in a
chitin medium. Thus, it is clear that the medium in which the bacterium grows has a strong influence on its biological control potential. The death and disintegration of juvenile nematodes suggests activity of proteases and lipases as has been reported for this strain. We continue to evaluate strain C3 for biological control of plant-parasitic nematodes. The host status of thirteen different potential cover crop cultivars for Heterodera schachtii management in California was determined in greenhouse experiments. Two experiments were conducted to determine the host status of 13 cultivars of mustard and oil seed radish. Nine cultivars of Brassica juncea were evaluated, including the following: ISCI 20, ISCI 99, ISCI 61a, ISCI 61b, Pacific Gold, Green Wave, Southern Giant, Red Giant, and Horned Green. Two varieties of Sinapis alba were investigated: Ida Gold and Martigena. The Humus and Erika cultivars of Brassica napus were also included. Sugarbeet was used as a control. Plants were
inoculated with infective juveniles, and a single generation of progeny was counted to assess the host status of the different plants. The results varied between experiments, but all plants did support some reproduction by the nematode. Martigena, Humus, Pacific Gold, and ISCI 20 supported the least reproduction among the cultivars in one experiment, while in the other experiment southern giant supported only limited reproduction. This research is being continued.
Impacts
The bacterium Lysobacter enzymogenes strain C3 shows strong potential as a biological control agent for plant-parasitic nematodes, with activity against four plant-parasitic nematodes of importance to field and ornamental crops. The use of cover crops to shorten rotations for management of sugarbeet cyst nematode is an important alternative, and these results have been communicated to clientele in California. The fact that some nematode reproduction is supported by these cultivars raises concerns about use of these in California as part of a sugarbeet cyst nematode integrated management strategy.
Publications
- Chen, J., Yuen, G. Y., Kobayashi, D. Y. and Caswell-Chen, E. P. 2004. Lysobacter enzymogenes as an antagonist of plant-parasitic nematodes. Journal of Nematology 36:311.
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Progress 01/01/03 to 12/31/03
Outputs
Experiments continued in the field during the year to assess the efficacy of broccoli mulch as a biofumigant to manage the plant-parasitic nematode Heterodera schachtii. This research is ongoing and will conclude this year. While assessing the influence of the potential biological control bacterium L. enzymogenes strain C3 on the bacterial-feeding nematode Caenorhabditis elegans and the plant-parasitic nematodes Heterodera schachtii and Meloidogyne javanica, we observed matricidal hatching in C. elegans. We followed up with research that led to a novel interpretation that matricidal hatching promotes progeny survival by enhancing to some degree the transition to the dauer stage. This is a new hypothesis regarding nematode survival under stress and has relevance to the ecology and evolution of matricidal hatching ("bagging")in C. elegans and other nematodes.
Impacts
Approximately 25 percent of nematicides in California are for reduction of cyst nematode in Cole crops. This research may reduce pesticide use by defining biofumigation with plant biomass, or biological control possibilities. These may be alternatives to chemical control, but the nematode control reductions will likely be less than with nematicides.
Publications
- Chen, J. and Caswell-Chen, E. P. 2003. Why Caenorhabditis elegans adults sacrifice their bodies to progeny. Nematology. In press.
- Chen, J. and Caswell-Chen, E. P. 2003. The ecology of C. elegans: Phenotypic plasticity, survival, and facultative vivipary. Journal of Nematology. 35:329-330. Abstract.
- Chen, J. and Caswell-Chen, E. P. 2003. Bagging as a part of the C. elegans life cycle. Program and Abstracts of 14th International C. elegans meeting, page 192. Abstract.
- Chen, J. and Caswell-Chen, E. P. 2002. Dual modes of reproduction in Caenorhabditis elegans. Nematology 4: 202. Abstract.
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Progress 01/01/02 to 12/31/02
Outputs
Experiments continued during the year to assess the efficacy of broccoli mulch as a biofumigant to manage the plant-parasitic nematode Heterodera schachtii. Field trials were conducted to assess the efficacy of broccoli biomass to reduce nematode populations. Experiments are conducted as randomized complete blocks with 4 replications per treatment. Each harvestable plot consists of 10 feet of a single row (with 5 foot buffers on all sides of each plot to avoid edge effects and effects caused by soil movement during tillage). Treatments are: 1) control (no broccoli soil amendment, although roots of previous broccoli crop remain in place), 2) No broccoli with tarp; 3) 2x broccoli shoot residue; 4) 1X broccoli shoot residue; 5) 1x broccoli shoot residue with tarp; 6) 2x broccoli shoot residue with tarp; 7) 1x broccoli plus Telone (rate of 9 GPA-current standard practice). The basic experimental protocols are as follows: (1) The broccoli crop is planted, grown, and
harvested according to commercial scheduling; (2) Following harvest, the crop remains are mechanically chopped in situ with commercial equipment; (3) The crop residue is moved by hand among plot units as necessary to achieve appropriate treatment rates for residue (0x or 2x the biomass per unit area in the biomass production areas - 1x is normal residue and does not require movement); (4) Plots are disced and bedded with commercial scale equipment, and soil samples are collected for nematodes; (5) Fumigant and tarp are applied by hand to appropriate treatments; (6) After three weeks the tarps are pulled, soil samples collected for each treatment, and the entire area planted to broccoli; (7) At the appropriate time (depending on the time of year, the length of time to maturation will vary) the crop is harvested, yield data recorded from ten feet of a single row, and post-harvest nematode soil samples taken. This research is ongoing. We also assessed the influence of the potential
biological control bacterium L. enzymogenes strain C3 on the bacterial-feeding nematode Caenorhabditis elegans and the plant-parasitic nematodes Heterodera schachtii and Meloidogyne javanica. Exposure of C. elegans to commercial chitinase resulted in five times fewer progeny juveniles than without chitinase. Exposure of C. elegans to L. enzymogenes strain C3 on agar gave almost complete elimination of egg production and the death of 94 percent of hatched juveniles after two days. The hatch of H. schachtii eggs placed on L. enzymogenes growing on agar was about 50 percent as compared to 80 percent hatch of eggs placed on E. coli growing on agar, and hatched juveniles died as the cuticle and body contents disintegrated. Exposure of Meloidogyne javanica juveniles to a seven-day old broth culture of L. enzymogenes for four days resulted in the death of juveniles. The death and disintegration of juvenile nematodes suggests that the proteases and lipases previously reported for this strain
have activity against plant-parasitic nematodes.
Impacts
Approximately 25 percent of nematicides in California are for reduction of cyst nematode in Cole crops. This research may reduce pesticide use by defining biofumigation with plant biomass, or biological control possibilities. These may be alternatives to chemical control, but the nematode control reductions will likely be less than with nematicides.
Publications
- Westerdahl, B. B. and Caswell, E. P. 2002. Broccoli residue as a biofumigant for cyst nematode management in Cole crops. Annual report to the University of California Statewide Integrated Pest Management Program.
- Westerdahl, B. B. and Caswell-Chen, E. P. 2002. Management of cyst and root-knot nematodes in sugarbeets. Annual report for 2000-2001 to the California Beet Growers Association.
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Progress 01/01/01 to 12/31/01
Outputs
Experiments are being conducted to assess the efficacy of broccoli mulch as a biofumigant to manage Heterodera schachtii. In field trials were conducted to assess the efficacy of broccoli biomass to reduce nematode populations, with treatments 1) No broccoli soil amendment, although roots of previous broccoli crop remained in place, 2) 2x broccoli shoot residue; 3) 1X broccoli shoot residue; 4) 1x broccoli shoot residue with tarp; 5) 1x broccoli plus Telone (rate of 9 GPA); 6) 1x broccoli plus Telone (rate of 18 GPA). Broccoli amendment biomass was grown in place, chopped, and added to the soil at two rates. Three weeks after treatment application, the tarps were removed and plots were planted to a broccoli crop that was grown for approximately three months. Soil samples were collected immediately prior to biomass incorporation and also at three weeks after treatment application. Samples were processed to extract cysts, cysts were crushed to allow enumeration of eggs,
and cysts were placed on Baermann funnels as a hatching bioassay to determine egg viability. A primary finding of a summer field trial was that broccoli residue at twice normal field density reduced larval densities and also egg hatch, indicative of effective biofumigation; however a fall field experiment with cooler temperatures did not show the same reduction in hatching. The research is continuing. The influence of biological control agents on eggs and juveniles of Heterodera schachtii and Caenorhabditis elegans was investigated. During the research the reproductive pathway of C. elegans was investigated because although the development and genome of Caenorhabditis elegans have been extensively studied, many aspects of its natural life history have been surprisingly little explored. We found that in response to starvation, C. elegans changes its reproduction from ovipary to vivipary. Viviparity is induced by starving late L4s, young adults, or gravid adults, and is reversible to
oviparity by restoring food. Viviparous larvae engage in matricide by consuming the parent body contents, and the resources so obtained allow some larvae to become dauers under complete starvation. Vivipary, androdioecy, and dauer formation are life-history traits that together ensure survival of dispersal propagules under extreme food limitation.
Impacts
This research that addresses biofumigation using cole crop residues to reduce cyst nematode densities has application to nematode management. This cultural control is an alternative to chemical control, and the nematode reductions will be less than with nematicides. Effects on the soil are likely to be more complex and subtler than with the chemical approach, and will protect the environment.
Publications
- Chen, J. and Caswell-Chen, E. P. 2001. Effects of Stenotrophomonas maltophilia on Caenorhabditis elegans and Heterodera schachtii. 13th International C. elegans meeting, June 22-26, 2001. Abstr.
- Westerdahl, B. B. and Caswell-Chen, E. P. 2001. Broccoli residue as a biofumigant for cyst nematode management in Cole crops. Annual report to the University of California Statewide Integrated Pest Management Program.
- Westerdahl, B. B. and Caswell-Chen, E. P. 2001. Management of cyst and root-knot nematodes in sugarbeets. Annual report for 2000-2001 to the California Beet Growers Association.
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Progress 01/01/00 to 12/31/00
Outputs
Alternatives to nematicides are desired for use in sustainable, integrated nematode management. Biological control agents have strong potential. Nematode egg shells and fungal cell walls contain chitin, and research has shown that chitinases affects nematode egg hatch, and may suppress plant-parasitic nematodes. Accordingly, there has been increased attention given to chitinase-producing bacteria as potential agents for biological control of plant-parasitic nematodes. This is particularly important, as alternatives to nematicides are desirable. In the experiments summarized here, Stenotrophomonas maltophilia (SM) strain C3 was assessed for its possible influence on Caenorhabditis elegans (CE). The nematode was cultured on S. maltophila to assess the hypothesis that the bacteria would be consumed by the nematode, but that the chitinase produced would exert a toxic influence on the nematode. Wild-type CE strain N2 and its bacterial food, E. coli strain OP50, were
obtained from the Caenorhabditis Genetic Center at University of Minnesota, St Paul. A spontaneous rifampicin derivative (R5) of SM strain C3 was cultured on the agar surface of NGM, and a bacterial lawn was developed. Different stages of juveniles, young or gravid adults of CE were cleaned of adhering E. coli (OP50) by first placing the nematode on NGM without any bacterium. The nematode was then placed onto NGM with a lawn of SM C3. A chitinase control treatment was included. The development, reproduction, and survival of CE were examined daily or periodically using an inverted compound microscope. Nematode body length was measured to assist the identification of developmental stages of CE. A lawn of E. coli OP50 was formed on chitinase-amended NGM, and CE juveniles developed and matured to adults in chitinase-amended NGM. There was no significant difference in nematode survival between treatments with and without chitinase. A lawn of SM strain C3 was formed on NGM. It appeared that
production of chitinase and other harmful substances increased as the culture aged, suggested by quick killing of adults and the almost complete inhibition of egg production on aged cultures. Nematodes did not survive more than three days exposed to SM, regardless of the nematode life-stage. None of the young juveniles that hatched on the SM plates were able to successfully develop into normal adults.
Impacts
Because the SM has a strong negative influence on a bacterial-feeding nematode, it is possible that it will also have a negative influence on other nematodes, such as the plant-parasitic forms. Other research has shown that SM can exert a negative influence on eggs of cyst nematodes. The bacteria SM will be researched further with the aim of developing sustainable nematode management tactics.
Publications
- No publications reported this period
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Progress 01/01/99 to 12/31/99
Outputs
Previous research on this project revealed that three geographic isolates of Heterodera schachtii (SBCN) were differentially selected by oilseed radish, white mustard, cabbage, and sugarbeet. This year we continued research on these results to SBCN-resistant sugarbeets. Nematode-resistant sugarbeet lines were obtained from the USDA in Salinas, CA. The lines carry SBCN resistance derived from Beta patellaris. Specifically three lines were investigated (C603-1, N303H15, and N724), putatively NN, Nn, and N_:nn respectively (N=SBCN resistance). Because of problems with resistance transmission, it was necessary to test seedlings for the presence of the resistance gene by PCR amplification. The PCR primers for the resistance gene were derived from published sequence information for HsPro-1. The primers amplify a fragment representing an approximately 800 bp region of the resistance gene. We have conducted several experiments during 1999, wherein the resistant plants were
grown and inoculated with juveniles of a single California SBCN isolate that was in greenhouse culture at UCD for ca. 9 years. The frequency of nematodes capable of reproducing on the resistant plants was relatively low (0.1 percent, or 5 cysts resulting from an inoculum of approximately 5,000 J2). Nematodes that reproduced on the resistant beets were subsequently transferred to either resistant beets or cabbage plants, but the selected nematodes did not maintain viable populations. The data suggest that those nematodes capable of circumventing the resistance have a lower fitness. If so, it is an important finding relative to the deployment of resistance in the field. This research is ongoing.
Impacts
(N/A)
Publications
- No publications reported this period
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Progress 01/01/98 to 12/01/98
Outputs
Greenhouse and growth chamber experiments were conducted to assess the influence of plants of differing host quality on three genetically distinct isolates of HETERODERA SCHACHTII (SBCN). The four hosts were white mustard, sugarbeet, cabbage, and oilseed radish. Nematode phenotypic responses were observed in less than four generations, and included changes in morphometrics, male-to-female ratios, total number of nematodes, clutch size, and number of eggs produced. These changes were influenced both by genetic differences among nematode isolates, and the SBCN responses to different hosts. Within isolates, the body length and width of pre-infective J2 were affected by host plant. For all isolates, the ratio of males-to-females was greatest on oilseed radish. The three isolates were readily differentiated by the ratio of body length-to-body width, and by the number of males after growth on white mustard. The number of cysts, males, and eggs, and the clutch size were
affected by SBCN isolate and host. Differences in host-selected nematode populations continued to be evident 11 days and 38 days after inoculation on subsequent hosts. The results emphasize the need to understand the dynamics among hosts and nematode populations to evaluate the potential selection imposed by nematode management using resistance, crop rotation, or trap crops. Research to assess the capacity of California isolates of SBCN to parasitize SBCN-resistant sugarbeets was initiated. As, expected a few cysts were found on SBCN-resistant plants, and the nematodes will be further characterized.
Impacts
(N/A)
Publications
- CASWELL-CHEN, E. P., and WESTERDAHL, B. B. 1997. Management of sugarbeet cyst (SBCN) and root-knot nematode (RKN). 1998 Sugarbeet Res. Rev. (Ann. Prog. Rep. to Cal. Beet Growers Assoc., 1996-1997).
- KAPLAN, M. 1997. Influence of four plants of differing host quality on three genetically distinct isolates of HETERODERA SCHACHTII: A morphometric, demographic, and genetic analysis of host-induced selection. Ph.D. thesis. Univ. Calif.
- WESTERDAHL, B. B., CASWELL-CHEN, E. P. and NORRIS, R. F. 1997. Sugarbeet cyst nematode: In-field assessment of damage/economic thresholds on cole crops and reproductive potential on weeds. Ann.
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Progress 01/01/97 to 12/01/97
Outputs
The ability of four different hosts (white mustard, sugarbeet, cabbage, and oilseed radish) to select specific genotypes among three genetically distinct isolates of HETERODERA SCHACHTII (Hs) was investigated. Nematode phenotypic responses were observed in less than four generations, and included changes in morphometrics, male-to-female ratios, total number of nematodes, clutch size, and number of eggs produced. These changes were influenced both by genetic differences among nematode isolates, and nematode responses to different hosts. The isolates were differentiated by the ratio of body length-to-body width, by the number of males after growth on white mustard, and the ratio of males-to-females was greatest on oilseed radish. The number of cysts, males, eggs, and the clutch size were affected by both isolate and host. Using amplified fragment length polymorphisms (AFLP) and random amplified polymorphic DNA (RAPD) markers, genotypic differences were detected among
host-induced nematode populations. Oilseed radish resulted in the greatest number of changes in both AFLPs and RAPDs. RAPD analysis indicated that nematode population genotypes induced by growth on oilseed radish were stable after transfer from the oilseed radish back to the other hosts. The transmission of altered genetic markers revealed that oilseed radish selected certain nematode genotypes in less than four nematode generations. The damage threshold for Hs on cole crops was investigated.
Impacts
(N/A)
Publications
- KAPLAN, M. 1997. Influence of four plants of differing host quality on three genetically distinct isolates of HETERODERA SCHACHTII: A morphometric, demographic, and genetic analysis of host-induced selection. Ph.D. thesis. Univ. Calif.
- WESTERDAHL, B. B., CASWELL-CHEN, E. P. and NORRIS, R. F. 1997. Sugarbeet cyst nematode: In-field assessment of damage/economic thresholds on cole crops and reproductive potential on weeds. Ann.
- CASWELL-CHEN, E. P., and WESTERDAHL, B. B. 1997. Management of sugarbeet cyst (SBCN) and root-knot nematode (RKN). 1998 Sugarbeet Res. Rev. (Ann. Prog. Rep. to Cal. Beet Growers Assoc., 1996-1997).
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Progress 01/01/96 to 12/30/96
Outputs
The reproductive potential of HETERODERA SCHACHTII (SBCN) on weeds has not been quantified for California, so we have initiated research on weeds common in California sugarbeet and Cole crop areas. The data reveal that SBCN reproduction varies among weed species, and that cyst production and clutch size varies among weed species. It is clear that BRASSICA RAPA and BRASSICA KABER are very suitable hosts for SBCN, while CAPSELLA BURSAPASTORIS, AMARANTHUS RETROFLEXUS, and RAPHANUS RAPHANISTRUM are marginal hosts for SBCN, and PORTULACA OLERACEA and CHENOPODIUM ALBUM are poor hosts for SBCN. We have defined random amplified polymorphic DNA (RAPD) markers that allow us to distinguish MELOIDOGYNE HAPLA from M. CHITWOODI and from other common root-know nematode species, and have developed species-specific PCR primers for identification. The primers allow successful amplification of DNA from juvenile nematodes.
Impacts
(N/A)
Publications
- WILLIAMSON, V. M., CASWELL-CHEN, E. P., WESTERDAHL, B.B., WU, F. F., and CARYL, G. 1997. A PCR assay to identify and distinguish single juveniles of MELOIDOGYNEHAPLA and M. CHITWOODI. J Nematol. Accept for Pub.
- JAFFEE, B. A., CASWELL-CHEN, E. P., and WESTERDAHL, B.B. 1996. Management of sugarbeet cyst (SBCN) and root-knot nematode (RKN). Ann. Prog. Rep. to Cal. BeetGrowers Assoc., 1995-1996. pp. 1-8.
- WESTERDAHL, B. B., and CASWELL-CHEN, E. P. 1996. Sugarbeet cyst nematode: In-field assessment of damage/economic thresholds on Cole crops and reproductivepotential on weeds. Prog. Rep. to Univ. of Calif. Statewide IPM Proj. 10 pp.
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Progress 01/01/95 to 12/30/95
Outputs
The reproductive potential of HETERODERA SCHACHTII (SBCN) on weeds has not been quantified for California, and we have initiated research for weeds common to sugarbeet and cole crop areas. Preliminary data indicate that SBCN reproduction varies among weed species. SBCN numbers may appear to increase without a host. Results from microplot and growth chamber research reveals that white cysts mature to become brown cysts, egg number per cyst increases, and juveniles develop into cysts on root fragments devoid of foliage. SBCN numbers may increase during fallow periods if host root fragments are left in soil. In microplot and field experiments the damage threshold for SBCN (spring plant, fall harvest) on sugarbeets is approximately 1 egg per g of soil or less. We have defined random amplified polymorphic DNA (RAPD) markers that distinguish MELOIDOGYNE HAPLA (Mh) and M. CHITWOODI (Mc) from each other and from other root-knot nematode species were identified. Primers that
specifically amplified a DNA fragment from each species were developed. Successful amplifications from single juveniles were readily attained. A mixture of two pairs of primers in a single PCR reaction mixture was shown to identify and distinguish single juveniles of Mh and Mc.
Impacts
(N/A)
Publications
- GARDNER, J., and CASWELL-CHEN, E. P. 1996. Influence of cyst maturation on apparent population increases by HETERODERA SCHACHTII on root remnants. Fund Appl Nematol. Accept for pub.
- GARDNER, J. 1995. Influence of cyst maturation on apparent population increases by HETERODERA SCHACHTII on root remnants. M.S. Thesis. Univ. California, Davis.
- WILLIAMSON, V. M., CASWELL-CHEN, E. P., HANSON, D., and WU, F.F. 1994. PCR for nematode identification. IN: LAMBERTI, F., DEGEORGIN, C., and MCK. BIRD, D. (Eds.), Advances in Molecular Plant Nematology. pp. 119-128. Plenum Pub Corp: New Y.
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Progress 01/01/94 to 12/30/94
Outputs
My lab has been investigating HETERODERA SCHACHTII genetics, damage thresholds, and reproduction and development. A RAPD fragment (ca. 460 bp) common to all H. SCHACHTII isolates examined was cloned. DNA from many different geographic H. SCHACHTII isolates have been examined and the primers work with all of them, although product is variable among isolates. The primers allow successful DNA amplification from single juvenile nematodes. Amplification of total H. GLYCINES DNA using the primers yielded one product distinct from that of products observed for H. SCHACHTII. Attempts to use the primers to amplify DNA from 21 other nematode species did not yield products. The primers have utility for detection and identification of H. SCHACHTII. We conducted a microplot experiment to assess the damage threshold for SBCN on fall-planted beets in Northern California (planted in Nov. and harvested in Aug.). The estimated damage threshold was low, approximately 1-to-2 eggs per
gram of soil. In addition, in several microplots nematode numbers increased from undetectable levels to more than 215 eggs per ml of soil. Sugarbeet-cyst nematode numbers may appear to increase without a host. We have observed that cabbage root explants continue to respire after foliage removal, and that H. SCHACHTII continues to develop and reproduce on those roots that remain viable (as determined by measuring respiration).
Impacts
(N/A)
Publications
- No publications reported this period.
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Progress 01/01/93 to 12/30/93
Outputs
Penetration, development and reproduction of HETERODERA SCHACHTII, was observed on (BRASSICA OLERACEA), phacelia (PHACELIA TANACETIFOLIA), buckwheat (FAGOPYRUM ESCULENTUM), oilseed radish (RAPHANUS SATIVUS), and white mustard (SINAPIS ALBA). Except for Phacelia, all plants were readily penetrated by second-stage juveniles. After 38 days at 25 C, there were no cysts on phacelia cv. Angelia or on the oilseed radish cv. Nemex and Pegletta. Cyst production was < 2.5 cysts/plant on buckwheat cv. Tardo and Prego and most of the oilseed radish cv., was intermediate (5-14 cysts/plant) on the white mustard cv., and high on cabbage (20-110 cysts/plant). A subset of cv. were all susceptible to MELOIDOGYNE INCOGNITA race 3 and M. JAVANICA. Penetration of CROTALARIA JUNCEA (PI 207657 and cv. Tropic Sun), DOLICHOS LABLAB cv. Highworth and SESAMUM INDICUM, by M. JAVANICA juveniles was assessed. CROTALARIA were resistant to penetration. SESAMUM INDICUM and D. LABLAB had fewer
nematodes per cm of root than tomato, but greater nematodes per cm of root than the CROTALARIA. Growth stages of MELOIDOGYNE JAVANICA were released from roots with cellulose and pectinase. The average % recovery of stages from D. LABLAB, ELYMUS GLAUCUS, and LYCOPERSICON ESCULENTUM by digestion were: eggs=526%; J2=272%; J3=783%; J4=549%; adults=285%; and, total= 425% (as percentages of counts from stained roots spread on glass plates). A random amplified polymorphic DNA (RAPD) fragment (CA.
Impacts
(N/A)
Publications
- ARAYA, M., and CASWELL-CHEN, E. P. 1994. Host status of CROTALARIA JUNCEA, SESAMUM INDICUM, DOLICHOS LABLAB, and ELYMUS GLAUCUS to MELOIDOGYNE JAVANICA. Accepted for pub. in J. Nematol.
- GARDNER, J., and CASWELL-CHEN, E. P. 1993. Penetration, development, and reproduction of HETERODERA SCHACHTII on FAGOPYRUM ESCULENTUM, PHACELIA TANACETIFOLIA, RAPHANUS SATIVUS, SINAPIS ALBA, and BRASSICA OLERACEA. J. Nematol. 25:695-702.
- CASWELL-CHEN, E. P., WILLIAMSON, V. M., and WESTERDAHL, B. B. 1993. Applied biotechnology in nematology. Suppl. J. Nematol. 25(4s):719-730.
- ARAYA, M., and CASWELL-CHEN, E. P. 1993. Enzymatic digestion of roots for recovery of root-knot nematode developmental stages. J. Nematol. 25:590-595.
- WILLIAMSON, V. M., CASWELL-CHEN, E. P., WU, F. F., and HANSON, D. 1994. PCR for nematode identification. Accepted for pub. in: Advances in Molecular Plant Nematology (eds. LAMBERTI, F., OPPERMAN, C. H., and BIRD, D. Mk.). Plenum Press.
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Progress 01/01/92 to 12/30/92
Outputs
HETERODERA SCHACHTII and HETERODERA CRUCIFERAE are important plant-parasitic nematodes. Single, random oligo-deoxyribonucleotide primers were used to generate PCR-amplified fragments, termed RAPD (random-amplified-polymorphic DNA) markers, from genomic DNA of H. SCHACHTII and H. CRUCIFERAE. Nineteen different random primers yielded multiple RAPD fragments with size ranging from 200 to 1500 base pairs. A single RAPD fragment amplified from a California H. SCHACHTII population was cloned. The clone was used to probe a Southern blot of RAPD. The clone hybridized to several H. SCHACHTII populations, but did not hybridize to H. CRUCIFERAE or GLOBODERA TABACUM RAPD. The clone is ca. 600 bp, and is a low-copy number element of the H. SCHACHTII genome. The host status of FAGOPYRON ESCULENTUM, PHACELIA TANACETIFOLIA, RAPHANUS SATIVA, AND SINAPIS ALBA cvs. for a California population of H. SCHACHTII was investigated. Except for P. TANACETIFOLIA cv. Angelia, all were penetrated
by H. SCHACHTII juveniles. P. TANACETIFOLIA (cv. Angelia) was a nonhost, and F. ESCULENTUM (cvs. Tardo, Ultimo) was a poor host. Most cvs. of S. ALBA were poor hosts, supporting some cyst development. The R. SATIVA cvs. Adagio, Nemex, and Pegletta were nonhosts (no cyst development).
Impacts
(N/A)
Publications
- No publications reported this period.
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Progress 01/01/91 to 12/30/91
Outputs
HETERODERA SCHACHTII Schmidt and HETERODERA CRUCIFERAE Franklin are important plant-parasitic nematodes in many areas or the world. The two species are sympatric and frequently occur in the same field in California, parasitizing the same host. I have investigated the use of polymerase chain reaction (PCR) amplification of nematode DNA sequences to differentiate H. SCHACHTII and H. CRUCIFERAE and to assess genetic variability within each species. Single, random oligodeoxyribonucleotide primers were used to generate PCR-amplified fragments, termed RAPD (random-amplified-polymorphic DNA) markers, from genomic DNA of H. SCHACHTII and H. CRUCIFERAE. Each of nineteen different random primers yielded from two-to-twelve fragments whose size ranged from 200 to 1500 base pairs. Reproducible differences in fragment patterns allowed differentiation of the two species with each primer. Six different geographic populations of H. SCHACHTII were examined, and similarities and
differences among geographic populations were detected. The potential application of RAPD analysis to relationships among nematode populations was assessed through cluster analysis of six different H. SCHACHTII populations with 78 scorable markers from eleven different random primers. DNA from single cysts was successfully amplified, and genetic variability was revealed within geographic populations. The use of RAPD markers to assess genetic variability is a simple, reproducible technique that does not require radioisotopes.
Impacts
(N/A)
Publications
- CASWELL-CHEN, E.P., WILLIAMSON, V.M. and WU, F.F. 1992. Random amplified polymorphic DNA analysis of HETERODERA CRUCIFERAE and H. SCHACHTII populations. J. Nematol. In Press.
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Progress 01/01/90 to 12/30/90
Outputs
In a field experiment CHLORIS GAYANA, EROGROSTIS SPP., TAGETES SPP., and SESAMUMINDICUM reduced populations of MELOIDOGYNE INCOGNITA as compared to a host plant. Growth chamber experiments have revealed that H. CRUCIFERAE will not penetrate cabbage roots at 30 C, while H. SCHACHTII does. Penetration is more efficient and development appears more rapid in H. CRUCIFERAE than in H. SCHACHTII at 12 C. Polymerase chain reaction (PCR) amplification of nematode DNA sequences was used to assess genetic variability in H. SCHACHTII and H. CRUCIFERAE. Single random primers were used to generate RAPD markers. From two to twelve fragments with sizes ranging from 0.2 to 1.5 kb were obtained with each primer. Reproducible differences in fragment patterns between the two species have been observed. Differences among geographic populations of H. SCHACHTII have been detected using several different random primers. Several fragments that are conserved among geographic populations have
also been detected. RAPD markers from individual females have been successfully assayed. Individual females from field populations of H. SCHACHTII subject to RAPD analysis revealed intrapopulational variation.
Impacts
(N/A)
Publications
- No publications reported this period.
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