Location: Crop Protection and Management Research2013 Annual Report
1a. Objectives (from AD-416):
1. Identify and characterize nematode resistance genes and improve host-plant resistance to nematodes in cotton and peanut. 1.a. Characterize and improve resistance to root-knot and reniform nematodes in cotton. 1.b. Identify resistance/susceptibility to the lesion nematode in peanut. 2. Develop integrated strategies and control options for managing nematodes in cotton and peanut. 2.a. Enhance the efficacy and consistency of biological control of nematodes. 2.b. Identify new cultural control options for managing nematodes in cotton and peanut. 2.c. Develop integrated approaches for managing nematodes.
1b. Approach (from AD-416):
Field and greenhouse experiments will be conducted to improve management of plant-parasitic nematodes in cotton and peanut. Host-plant resistance to nematodes is the cornerstone of our nematode management strategy. We will work cooperatively with plant breeders to develop cultivars and germplasm with desirable agronomic traits and a high level of nematode resistance. Plant material will be selected for resistance using traditional and marker-assisted selection. However, we cannot rely exclusively on host-plant resistance for managing nematodes. We will also investigate ecologically-based control strategies that can be integrated with resistant cultivars to increase the durability of resistance and control a broader spectrum of nematode pathogens. Biological control organisms are being marketed for use in cotton and peanut, and also occur naturally in fields. We will explore the effect of crop production practices (tillage, fumigation, cultivar, and cover crops) on these antagonistic organisms with the goal of conserving or enhancing their activity against nematodes. We will identify crops that can be grown in rotation with cotton and peanut that will reduce populations of root-knot nematode either by producing toxic metabolites (high residue rye) or by limiting nematode reproduction (sorghum for bioenergy use). Our integrated management approach will also include increasing plant tolerance to nematode damage by applying cytokinin to seedlings. Finally, we will combine the most effective and economical control options from earlier years of the project to test different integrated management programs for plant-parasitic nematodes in the southeastern United States.
3. Progress Report:
A field study is underway to evaluate the influence of tillage and fumigation with 1,3-dichloropropene on abundance of the nematode parasite Pasteuria penetrans. We have collected soil from this field site and determined the abundance of P. penetrans spores in the different treatments. We have also set up a greenhouse study to determine reproductive potential of the southern root-knot nematode in the different treatments. This is the 2nd year of a multi-year study. We completed two greenhouse trials to determine whether the efficacy of Paecilomyces lilacinus (a fungal pathogen of nematodes marketed as NemOut) could be enhanced by planting a winter cover crop. We found that nematode suppression by the fungus averaged 36% in fallow soil and 63% in soil that had a rye cover crop. We attempted to set up a third trial in the greenhouse, but we had poor growth of the cover crop. We will repeat it again this winter. The first year of a field study is underway to determine whether high residue rye can suppress populations of M. incognita prior to planting cotton. We have killed the rye that was planted last fall and planted cotton in the late spring. Greenhouse testing of sorghum entries to evaluate their suitability as a host for Meloidogyne incognita, the cotton root-knot nematode, is substantially completed. Preliminary tests had found levels of nematode reproduction ranging from almost none to extremely high, and our recent tests have verified those results. These findings were the catalyst for a new, collaborative project to identify DNA markers for nematode resistance genes in sorghum. Research is ongoing to evaluate the effect of both highly resistant and highly susceptible genotypes on nematode reproduction and on damage caused to the crop in the field. A study evaluating cytokinin, a plant hormone that increases root growth, for its ability to reduce the damage caused to cotton by M. incognita has largely been completed. Cytokinin was shown by others to increase root system size in non-irrigated cotton in arid climates thereby increasing yields by drought tolerance, but increased root size was not seen in irrigated cotton. Increasing the size the root system could also make the plants more tolerant of nematode parasitism. We found no effect on cotton yield of cytokinin application in non-irrigated cotton in Georgia, and we conclude that in most years natural rainfall in Georgia will be sufficient to minimize any benefit from cytokinin.
1. Winter cover crops could enhance biological control of nematodes in cotton. The fungus Paecilomyces lilacinus is sold commercially throughout the world to control plant-parasitic nematodes. An ARS researcher in Tifton, GA demonstrated in a greenhouse study that when annual rye or clover were grown prior to planting cotton, suppression of root-knot nematodes by P. lilacinus was greater than in cotton after fallow. Removing the surface residue of the cover crop negated the benefit to biological control suggesting that the residue creates an environment that is more conducive to the fungus. This research demonstrates that planting cover crops can not only reduce soil erosion, but also improve biological control of plant-parasitic nematodes.
Timper, P., Bouton, J. 2012. Variable response of non-ergot-producing strains of Neotyphodium coenophialum in tall fescue to lesion nematodes. In: Young, C.A., Aiken, G., McCulley, R., Strickland, J.R., Schardl, C.L., editors. Epichloae, endophytes of cool season grasses: Implications, utilization and biology. 1st edition. Ardmore, OK: The Samuel Roberts Noble Foundation. p. 40-43.