Robert Carver, Mcgawley, Edward C.
INVESTIGATOR: McGawley, E. C.
Plant Pathology & Crop Physiol
LOUISIANA STATE UNIVERSITY
BATON ROUGE, LOUISIANA 70893
IMPROVED MANAGEMENT OF PLANT-PARASITIC NEMATODES THROUGH MODERN DIAGNOSTIC TOOLS AND INCREASED USE OF HOST RESISTANCE
CLASSIFICATION HEADINGS: R212 . Pathogens and Nematodes Affecting Plants; S3130 . Nematodes; F1120 . Nematology
NON-TECHNICAL SUMMARY: The scientific literature of plant nematology and pathology is replete with testaments to the local, national and international economic impact of crop losses caused by plant-parasitic nematodes. The most recent global impact estimate for nematode-related damage, from 2008, indicates an annual loss of $157 billion. Across major agricultural regions and crops within the continental United States, the annual loss caused by plant-parasitic nematodes is seven to ten percent, an estimate that translates into tens of millions of dollars. In the South, where there is great crop diversity and where winter conditions are relatively mild, losses probably exceed these estimates because of the widespread occurrence of the three most damaging nematode species in the world: the root-knot nematode, Meloidogyne spp.; the soybean cyst nematode, Heterodera glycines; and the reniform nematode, Rotylenchulus reniformis. Both classical and advanced molecular research methodologies will be used by nematologists involved in this project to develop methods to minimize the negative impact of nematodes in agriculture. Outcomes of this research will likely involve plant cultivars with improved genetic resistance to nematodes as well as more efficacious and environmentally responsible materials, both biological and non-biological, for nematode management.
OBJECTIVES: Facilitate and improve identification of nematode species and races.
APPROACH: The maintenance of a current census of nematode associations with crop species of agricultural importance in Louisiana will be a major facet of this objective. This activity is important because over 85 percent of the 3,000 or so root-parasitic nematodes known to science have very wide host ranges, great persistence, and low mortality during the relatively mild winters of the South in general and Louisiana in particular. Survey time expenditure will parallel major changes in crop cultivars and cultivation practices but will require about 10% of our total effort. Reniform nematode, Rotylenchulus reniformis, is now and has during the last four to five years become firmly established as the most economically important nematode species in Louisiana and most of the South. Soil and root samples representative of the major crops and production areas in the state are monitored on a continuous basis by traveling to the major production areas and collecting samples, a minimum of 10 sites for soybean and sugarcane, three to five for corn and 10-20 for cotton as part of our expanded concentration on reniform nematode in recent years. Nematode populations are separated from soil and root material using established extraction procedures. After initial crude separation by tissue maceration or soil centrifugation, laboratory manipulation is employed to isolate individual species and establish greenhouse cultures. Laboratory activities include microscopic enumeration, observation and measurement for generic and species identification. For the root-knot nematode, Meloidogyne spp., identification of species (M. incognita, M. arenaria, M. hapla and M. javanica) and races involves the preparation and observation of perineal patterns of females, the electrophoresis of macerated preparations of the females and observations of diagnostic banding patterns on acrylamide gel and greenhouse-based host range assays. For the soybean cyst nematode, Heterodera glycines, which currently is dramatically reduced in both distribution and importance in Louisiana, classical race identification tests (that do not require controlled temperature conditions) are conducted on a limited basis, perhaps five to ten per year. For reniform nematode, populations from Louisiana and most southern states have been established from single egg-mass cultures and are maintained in the greenhouse for use in a range of studies that include microplot-based studies evaluating the pathogenicity of isolates on cotton and soybean and greenhouse-based studies designed to develop a set of host differentials employing either multiple soybean cultivars, multiple cotton cultivars or multiple plant cultivars .
KEYWORDS: host resistance, nematode management, reniform nematode, root-knot; nematode, soybean cyst nematode.
PROGRESS: 2010/01 TO 2010/12
OUTPUTS: E.C. McGawley attended and participated in a workshop on this bacterial parasite of nematodes at the national meeting of the Society of Nematology in Boise, Idaho, during 2010. National and international plant pathology and nematology meetings, at which multiple research and teaching presentations were made, were also attended. PARTICIPANTS: Participants in this project are members of Southern Regional nematology project S-1046. Additionally, Drs. Charles Overstreet and Michael J. Pontif are involved in all aspects of research conducted in the lab of E.C. McGawley. TARGET AUDIENCES: Target audience includes plant protection scientists, agricultural producers and commercial producers of plant protection chemicals and biocontrol agents. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
IMPACT: 2010/01 TO 2010/12
During 2010, full-season field and 60-day-duration greenhouse trials were conducted in cooperation with Pasteuria Bioscience, Inc. to evaluate the efficacy of their product as a seed treatment, a soil-surface-applied and a soil-incorporated material. The field trial with Pasteuria-treated cotton (DP0912 B2RF) seed was established at the LSU AgCenter Ben Hur Research Farm in Baton Rouge, La., on a 0.5-acre site that has been used for cotton production for the last 8 years. Soil at this site is naturally infested with the reniform nematode, Rotylenchulus reniformis. Reniform nematode population levels at planting were uniformly distributed across the field and averaged 2,715 individuals per 250cc of soil. At midseason, population levels of R. reniformis, were reduced significantly, relative to the nontreated control, by both 1X and 2X rates of Pasteuria. At harvest, populations of reniform associated with the 2X seed treatment rate were also reduced significantly below that of the nontreated control. Moreover, this reduced population level of reniform nematode was associated with a significant increase in yield. In the greenhouse trial, soil surface application of Pasteuria versus soil incorporation was compared. During the 50-day period in which reniform nematodes were present on plants, populations associated with the "untreated control" increased from 500 to an average of 17,638 individuals per pot, a reproductive value (final population level divided by infestation level) of 25.3. As a soil-surface application at rates of 50, 100, 200 and 300k/cc of soil, Pasteuria resulted in significantly reduced population levels of reniform nematode with reproductive values of 20.4, 21.9, 18.6 and 16.9, respectively. When uniformly incorporated into the total soil volume, reproductive rates for the reniform population were again significantly reduced and averaged 21.1, 26.1, 16.9 and 23.0 for the 50, 100, 200 and 300k/cc rates, respectively. Numbers of soil stages of reniform nematode with attached Pasteuria ranged from 4-11 of 20 specimens examined with the surface-application treatment and from 5-9 of 20 specimens with the incorporation treatment. The numbers of attached spores per individual nematode visible at a magnification of 630X ranged from 8 to more than 50 per reniform individual.
PUBLICATIONS (not previously reported): 2010/01 TO 2010/12
1. Navas, A., P. Flores-Romero, S. Sanchez-Moreno, J.A. Camargo and E.C. McGawley. 2010. Effects of Heavy Metal Soil Pollution on Nematode Communities After the Aznalcollar Mining Spill. Nematropica 40:13-30.
2. McGawley, E.C., R.M. Steckler and N. Nakada. 2010. Agri Terra: colloidal ingredient synergy and environmental responsibility. Proceedings: 13th Congress of the Mediterranean Phytopathological Union (20-25 June, 2010; Rome Italy), 483-484.
3. Overstreet, C, E.C. McGawley, C. Hollier, D. Ferrin and R. Singh. 2010. Current Strategies for Sampling Plant Parasitic Nematodes in Field Crops. Louisiana Plant Pathology Disease Identification and Management Series.
Name: McGawley, E. C.