Progress 10/01/03 to 09/30/09
Outputs
OUTPUTS: Over the course of this project, experiments have been conducted in field, microplot, greenhouse and laboratory environments evaluating the host status of popular cultivars of soybean, cotton, rice, sugarcane, tomato, bell pepper, and eggplant to indigenous populations of plant parasitic nematodes. In other research, new and more environmentally-responsible materials such as Agri-Terra (Cal-Agri Products, LLC of California), Oraphyte (Nuvilex Corp. of New Jersey), and the bacterial sting nematode parasite, Pasteuria penetrans (Pasteuria Bioscience, LLC of Florida) have been evaluated for management of nematode populations and communities that are economically importance in Louisiana. Oral presentations of research findings have been made at nine professional meetings here in North America and Hawaii and abroad in South America, Europe, Asia, Africa and Australia. Contributions have been made annually to the Louisiana Plant Disease Control Guide, and presentations have been made at meetings of local producer organizations and turf management workshops. One M.S. (J.D. Bruce) and one Ph.D. student (M.J. Pontif) have received degrees. One educational multimedia production (18 months in production) was completed and critically reviewed by an international panel of 18 veteran nematologists in 2009. This production, entitled, "Introduction to Nematodes" is authored by E.C. McGawley and two of his former students (Drs. C. Overstreet and M.J. Pontif). It will be posted on the internet for free download (in Spanish and in English) worldwide from the websites of The Society of Nematologists (http://www.nematologists.org/) and The Organization of Nematologists of Tropical America (http://www.ontaweb.org/). PARTICIPANTS: Individuals: Principal investigator on the Louisiana portion of this regional project was E.C. McGawley. Other individuals who worked on the project were graduate students J.Bruce and M.J. Pontif (Research Associate and graduate student). J. Bruce conducted research on the egg biology of reniform nematode (Rotylenchulus reniformis) and M.J. Pontif assisted in all research activities and also conducted research on the impact of root leachates from weeds on the eclosion of eggs of reniform nematode. Partner Organizations: Other academic institutions participating ion this project were: Auburn University, University of Arkansas, University of Georgia, University of Minnesota, Mississippi State University, North Carolina State University, Clemson University, Texas A&M University, University of Florida and the University of Tennessee. Collaborators at LSU: Professors J.W. Hoy, J. Boudreaux, C. Overstreet and R. Bracy. Training or professional development: annual seminars at Southeastern Louisiana University on plant pathology and nematology impact on agriculture and career opportunities. TARGET AUDIENCES: Target audiences: soybean and cotton producers in Louisiana and soybean, cotton and peanut producers in Texas and Georgia. Efforts: Annual federal CRIS report entries, individual publications in professional and producer directed and extension publications. PROJECT MODIFICATIONS: None
Impacts
Information on the diversity, distribution and impact of plant parasitic nematodes is an essential consideration in any plant production/protection system. Over the duration of this project, survey data have documented a marked shift in the overall distribution of and damage attributable to the soybean cyst nematode, Heterodera glycines. Similarly, survey activities have shown a tremendous increase in the distribution of the reniform nematode, Rotylenchulus reniformis. This pathogen is now widespread throughout the cotton and soybean production areas of Louisiana and all popular cultivars of both crops are susceptible to damage. Additionally, this nematode also causes significant damage to most vegetable crops, especially tomato, eggplant and cucumber. Root knot nematodes, which include primarily Meloidogyne incognita, but also M. arenaria and M. javanica remain serious pests of a wide range of crops in Louisiana. Unlike that for reniform nematode, there is satisfactory resistance to root-knot nematode available in most major crops. The greatest damage from root knot nematode, M. incognita in particular, results from its' interaction with root-infecting fungi in cotton. Research with new, environmentally responsible, chemistry for nematode management conducted during the tenure of this project demonstrated that less toxic materials can be successfully used against plant parasitic nematodes.
Publications
- Robinson, A. F., Akridge, J. R., Bradford, J. M., Cook, C. G., Gazaway, W. S. McGawley, E. C., Starr, J. L., and Young, L. D. 2006. Suppression of Rotylenchulus reniformis 122-cm Deep Endorses Resistance Introgression in Gossypium. Journal of Nematology 38: 195-209.
- McGawley, E. C., Pontif, M. J., Bruce, J. B., and Overstreet, C. 2006. Efficacy of Agri-Terra Against Nematodes Associated With Major Crop Species in Louisiana. Journal of Nematology 38: 282.
- Robinson, A. F., R. Akridge, J. M. Bradford, C. G. Cook, W. S. Gazaway, T. L. Kirkpatrick, G. W. Lawrence, G. Lee, E. C. McGawley, C. Overstreet, B. Padgett, R. Rodriguez-Kabana, A. Westphal, and L. D. Young. 2005. Vertical Distribution of Rotylenchulus reniformis in cotton fields. Journal of Nematology 37 (3): 265-271.
- McGawley, E. C., M. J. Pontif, C. Overstreet, and J. B. Sumner. 2005. Chemical Management of Nematodes in Louisiana: 2000-2004 Field and Microplot trials with Rice, Soybean, Sugarcane, Cotton and assorted Vegetables. Proceedings of the Society of Nematologists Forty-fourth Annual Meeting. P. 52.
- McGawley, E. C., and Pontif, M. J. 2006 Chemical Management of Nematodes in Louisiana: 2000-2005 Field and Microplot Trials With Cotton, Soybean, Sugarcane, Rice, Assorted Vegetables and Turf. Nematropica 36:134.
- Overstreet, C., McGawley, E. C., Burris, E., Cook, D., Padgett, G. B., and M. Wolcott, M. 2006. Progress in Field Mapping Nematode Populations and Potential Uses of Electrical Conductivity to Create Management Zones. Nematropica 36:139.
- McGawley, E.C. 2007. Management of Nematode Parasites of Major Crops in Louisiana with Agri-Terra. Proceedings of the 2007 Annual International Research Conference on Methyl Bromide Alternatives and Emissions Reductions. 13: 1-4.
- McGawley, E.C., M.J. Pontif and C. Overstreet. 2008. Management options for plant parasitic nematodes of turf. Proceedings of the 24th Australian Turfgrass Conference; pp. 45-47.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: From support of this project, my lab successfully submitted two abstracts and one manuscript for the International Nematology Congress in Australia and the International Congress of Plant Pathology in Italy. Data from this project were also presented to members of the Louisiana/Mississippi Turf Association and to nematologists in the Southern Regional Nematology Project. PARTICIPANTS: Principal Investigator: Edward C. McGawley, Ph.D. Partner Organizations:Society of Nematologists and American Phytopathological Society TARGET AUDIENCES: The target audience for the project research outputs are other researchers, agricultural producers and agricultural policy makers PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Reniform, root knot and soybean cyst are the most economically important nematodes in agriculture in Louisiana. A total of five pathotypes of reniform nematode have been characterized in microplot trials. Survey activity combined with greenhouse race analysis tests indicate that races three and five of soybean cyst nematode are the most common. Meloidogyne incognita is the most common species of root knot nematode on cotton and soybean, and M. graminicola is the most common species on recreational turf. Experiments conducted under laboratory conditions with morning glory, hemp sesbania and johnsongrass weeds document the production of compounds which inhibit the hatching of eggs of reniform nematode.
Publications
- Pontif, M.J. and E.C. McGawley 2008. The Influence of Morningglory (Ipomoea lacunosa), Hemp Sesbania (Sesbania exaltata), and Johnsongrass (Sorghum halepense) on Reproduction of Rotylenchulus reniformis with emphasis on the eclosion and hatching of eggs. Nematropica 38:23-35.
- McGawley, E.C., M.J. Pontif and C. Overstreet. 2008. Management options for plant parasitic nematodes of turf. Proceedings of the 24th Australian Turfgrass Conference; pp. 45-47.
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Progress 01/01/07 to 12/31/07
Outputs
Research with Rotylenchulus reniformis and three weed species, pitted morningglory, hemp sesbania and johnsongrass, has resulted in the partial characterization of root leachates which inhibit egg hatch and thereby reduce nematode reproduction and damage potential.
Impacts
Microplot studies were conducted to evaluate the effects of LA 887 cotton, Pioneer 96B1 soybean and three endemic weed species, pitted morningglory (Ipomoea lacunosa), hemp sesbania (Sesbania exaltata), and johnsongrass (Sorghum halepense), on reproduction of the reniform nematode, Rotylenchulus reniformis. Over two trials, the co-culture of cotton with any of the three weeds suppressed numbers of reniform nematode juveniles in soil. When grown singly, reniform nematode reproductive values after 60 days on cotton averaged 69.0, while those for morningglory, hemp sesbania, and johnsongrass averaged 42.0, 23.5, and 18.0, respectively. Reproductive values for cotton co-cultured with morningglory averaged 38.7. Those for the cotton-hemp sesbania and cotton-johnsongrass combinations averaged 23.5 and 26.2, respectively. Reniform reproduction data for soybean cultured alone or with the three weeds in two trials showed reduced reproduction of reniform nematode only in the
presence of johnsongrass. In greenhouse trials, reniform reproduction on cotton and soybean plants irrigated with leachates from the roots of morningglory, hemp sesbania and johnsongrass was reduced significantly. Laboratory experiments conducted in which eggs of reniform nematode were exposed to 0.45 micron filtered leachates from roots of the three weeds showed significantly reduced hatch relative to that observed with the control, distilled water. Hence, it can be concluded that reduced reproduction of the nematode is accounted for in large measure by root leachates which retard egg hatch.
Publications
- McGawley, E.C. 2007. Proceedings of the XVI International Plant Protection Congress. A summary of six years of greenhouse, microplot and field experimentation with a new in-furrow, at-planting material for the management of plant parasitic nematodes of major agricultural crops in the southern United States. Pages 12-19.
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Progress 01/01/06 to 12/31/06
Outputs
Populations of Rotylenchulus reniformis from Alabama, Georgia, Hawaii, Louisiana, Mississippi, and Texas were employed in laboratory studies of egg production and hatch. A total of 36 vials, six for each nematode population, containing 10 grams of sterile soil were prepared and a single tomato seedling transplanted into each. After 72 hours, the seedlings in each vial were inoculated with 100 juvenile nematodes collected from single egg mass populations maintained under greenhouse conditions. After 39 days, the vials were soaked in water to remove the plants. In order to ensure uniformity of observations, one replication of each population was processed on each of five consecutive days. The soil was rinsed off of the roots and the tops were severed 1 cm above the soil line and discarded. The root system was placed into a 90 mm Petri dish containing enough water to cover the roots. The numbers of egg masses per plant were determined at 40X on a dissecting microscope.
Micrographs were taken of 25 egg masses from each population. Openlab, an image analysis computer application, was then used to calculate the volume of each egg mass. The number of eggs per egg mass were then counted, and the sizes, lengths and widths, of 80 eggs per population determined. There were significant differences among populations in the number of egg masses per root system. The populations separated into two groups, with populations from Mississippi, Alabama and Louisiana having significantly greater numbers than those from the other three states. Although there are no significant differences in the numbers of eggs per egg mass among the populations, the greater numbers of egg masses per plant could account for the differences in reproduction and subsequent pathogenicity among the populations. Further studies are in progress to determine whether or not there are differences in egg development and or hatch among these populations of reniform nematode.
Impacts
The reniform nematode, Rotylenchulus reniformis, is currently the most economically important plant parasitic nematode in the southeastern United States. Management of this nematode will require improved plant cultivars and more effective nematicides. Additionally, all populations of this nematode are not equal in their reproduction on and damage to important crops such as cotton and soybean. Differences in egg production and viability among populations appears to be a major factor governing population dynamics of the nematode. A new experimental nematicide, Agri-Terra, produced by Cal-Agri Products of Los Angeles, California has shown great efficacy against this nematode in five years of field evaluations.
Publications
- Robinson, A. F., Akridge, J. R., Bradford, J. M., Cook, C. G., Gazaway, W. S. McGawley, E. C., Starr, J. L., and Young, L. D. 2006. Suppression of Rotylenchulus reniformis 122-cm Deep Endorses Resistance Introgression in Gossypium. Journal of Nematology 38: 195-209.
- Bruce, J. M. and E. C. McGawley. 2006. Egg Biology, Reproduction and Ecology of Rotylenchulus Reniformis Isolates. Journal of Nematology 38: 264.
- Pontif, M. J., and McGawley, E. C. 2006. Impact of Three Weed Species on the Reproduction of Rotylenchulus Reniformis on Cotton and Soybean. Journal of Nematology 38: 287.
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Progress 01/01/05 to 12/31/05
Outputs
Nine populations of the reniform nematode, Rotylenchulus reniformis (Rr) from Louisiana (LA), Alabama (AL), Arkansas (AR), Florida (FL), Georgia (GA), Hawaii (HI), Mississippi (MS), Texas (two locations, TX1 and TX2) and Puerto Rico (PR) were employed in studies of reproductive potential and pathogenicity. Single egg masses (SEM) representative of each population were dissected from tomato roots, transferred to the tip of a sterile toothpick, and placed into a depression in sterile soil in a 19 x 66 mm glass vial containing one established tomato seedling. After eight weeks, SEM derived populations were transferred to 10-cm diameter clay pots and maintained under greenhouse conditions for use as inoculum in subsequent studies. In laboratory studies, the morphological measurements and comparisons necessary to confirm the species of reniform nematode as R. reniformis are facilitated by the use of Openlab, a scientific imaging software application. Using a digital video
camera attached to a microscope, this image analysis program allows the researcher to capture, measure, and archive both video and still photographs of specimens. Once calibrated, images can be analyzed to produce counts and linear and spatial measurements of specimens. Images of at least 25 individual pre-infective females per population were obtained and body length, distance from head to vulva, and stylet measurements were archived for comparison with published values for R. reniformis. All populations examined were R. reniformis. After one generation, 23-30 days, numbers of egg masses per root system averaged 34.5, 26.5, 26.2, 19.0, 5.1, 3.6, and 2.7 respectively for populations from MS, AL, LA1, LA2, GA, TX2, and PR. In the same order, eggs per egg mass averaged 92, 83, 87, 78, 72, 72, and 71. Significant differences in the numbers of egg masses per plant combined with significant differences in eggs per egg mass among population probably accounts in part for differences in
pathogenicity among these populations.
Impacts
Rotylenchulus reniformis is the most economically important plant parasitic nematode in the southeastern United States. Currently there is no commercial resistance to this nematode available to cotton and soybean producers. Significant differences in the numbers of egg masses per plant combined with significant differences in eggs per egg mass among population probably accounts in part for differences in pathogenicity among these populations.
Publications
- EGG BIOLGY AND REPRODUCTION OF ROTYLENCHULUS RENIFORMIS ISOLATES FROM THE SOUTHERN UNITED STATES. Sumner, J. B. and E. C. McGawley. Department of Plant Pathology and Crop Physiology, LSU AgCenter, Baton Rouge, LA, 70803. Proceedings of the Society of Nematologists Forty-fourth Annual Meeting, July 9- 13, 2005. pg. 71
- IMPACT OF THREE WEED SPECIES ON REPRODUCTION OF ROTYLENCHULUS RENIFORMIS ON COTTON AND SOYBEAN. Pontif, M. J. and E. C. McGawley. Department of Plant Pathology and Crop Physiology, LSU AgCenter, Baton Rouge, LA, 70803. Proceedings of the Society of Nematologists Forty-fourth Annual Meeting, July 9- 13, 2005. pg. 61
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Progress 01/01/04 to 12/31/04
Outputs
A microplot trial with Stoneville LA887 cotton was conducted using populations of the reniform nematode, Rotylenchulus reniformis, from Louisiana, Mississippi, Texas, Hawaii, and Arkansas. At harvest, 122 days after planting, there were marked differences in the numbers of juveniles in soil, the numbers of eggs per gram of root, as well as dry weights of tops and roots. Among the five reniform nematode populations, the numbers of juveniles per 250 cubic centimeters of soil ranged from 2134 for the Arkansas population to 4532 for the Louisiana population; eggs per gram of root ranged from 47 for the Hawaii population to 464 for the Arkansas population. Weights of tops and roots were reduced significantly below those of controls by populations from all states except Hawaii. Subsequent studies were conducted under lab conditions to evaluate the role of egg biology in population development of these geographic isolates of reniform nematode. Over the course of two
preliminary trials, hatch of eggs of isolates from 10 major cotton-producing parishes of Louisiana were determined in soil and in water. In the first trial, the percent egg hatch in water and soil, respectively, averaged 90 percent and 93 percent for the Catahoula parish isolate and 58 percent and 45 percent for the Avoyelles isolate. In trial two, the Opelousas isolate had the highest percent egg hatch, which was 91 percent in water and 94 percent in soil. The Evangeline isolate had the lowest percent egg hatch in water, which averaged 58 percent. The Avoyelles isolate had the lowest percent egg hatch in soil, which averaged 57 percent. Reproductive and genomic differences in populations of Rotylenchulus reniformis, are being studied among seven populations collected from Alabama, Arkansas, Florida, Hawaii, Louisiana, Mississippi, and Texas. Eight soybean lines (Lee 74, Peking, Plant Introductions (PIs) 88788, 90763, 209332, 437654, 89772, and Cloud) were each inoculated with 1,000
vermiform stages of the nematode. After 30 days, the number of eggs per egg mass and egg masses per plant were determined. Across the eight lines, the number of eggs per egg mass ranged from 0 to 66, while the number of egg masses ranged from 0 to 64. The Alabama population did not reproduce on Peking, Plant Introductions 90763, 437654 and 89772, while the Arkansas population reproduced on every line. Analysis of genomic differences among populations is based on examination of the two intergenic spacer regions (ITS1 and ITS2) by polymerase chain reactions (PCR) and restriction fragment length polymorphism (RFLP). Nematode genomic DNA is extracted from 10 swollen females dissected from tomato roots. A fragment with the size of approximately 1100 base pairs has been produced from every population.
Impacts
Rotylenchulus reniformis is rapidly becoming the most economically important plant parasitic nematode in the southeastern United States. Currently there is very little, if any, commercial resistance to this nematode available to cotton and soybean producers. If, as we hypothesize, there are distinct pathotypes of this nematode found in nature, it is essential that a scheme for their identification be developed. Our research with the whole organism and its biology, as well as our molecular studies, is aimed at developing methods to distinguish between and among populations of the nematode. Research such as this will allow plant breeders to develop crop cultivars effective against the most common regional populations of the nematode.
Publications
- Carter-Wientjes, C.H., J.S. Russin, D.J. Boethel, J.L. Griffin and E.C. McGawley. 2004, Feeding and Maturation by Soybean Looper (Lepidoptera: Noctuidae) Larvae on Soybean Affected by Weed, Fungus, and Nematode Pests. Journal of Economic Entomology: 14-20.
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