Brief Summary of Minutes of Annual Meeting

Plant-parasitic nematodes continue to cause substantial yield loss in many crops. Control is often difficult because of underlying genetic variability. Several approaches, including host-plant resistance, nematicide application, and biologically means, can be employed to control these pests. This project has demonstrated the potential success of each method. Host-plant resistance has been demonstrated in sugar beet, cowpea, lima beans, and taro. Syngenta sugarbeet cultivars HM 1334 and 'Nematop' were resistant to H. schachtii. In an increasing number of soybean fields, host-pant resistance is not protecting from the risk of yield loss. Despite this trend, few soybean lines coming through the USDA Southern Regional Program are resistant to any of the standard soybean cyst nematode races. Natural host plant resistance genes are valuable in crop plants as effective and safe approaches to managing nematodes. Genetic variability in nematodes for ability to reproduce on resistant plants is being characterized to help guide decisions on use of resistant crop varieties and to give direction to plant breeding programs for grain legumes. Cowpea and lima beans can best be protected with resistance genes against nematode reproduction and nematode galling. Every thing old is new again for chemical nematode control. Whereas old organophosphate nematicides are leaving the market, equally old product are finding renewed utility. This project has demonstrated the Abamectin seed treatments can be effective in reducing damage caused by nematodes. Ozone is a powerful oxidizing agent and has been shown to be an effective fungicidal and bactericidal agent when injected into water. Caenorhabditis elegans exposed to aqueous ozone concentrations of 0.12 ppm killed almost all nematodes within 15 minutes. The efficacy of Vydate can be improved by exploiting nematode development and behavior. Biological control with cover crops, fungi, and bacteria. Cover crops were tested for their ability to control damage to sugar beet, potato, and taro. Green manures of 'Defender' and 'Comet' radishes were effective against M. chitwoodi. Chitinolytic microflora may contribute to biological control of plant-parasitic nematodes by causing decreased egg viability through degradation of eggs. Some cover crops that are appropriate for one rootknot nematode may not be so good for a different species of rootknot nematode. In tropical systems, sorghumXsudan grass hybrids appear to be best for M. javanica. Lysobacter enzymogenes strain C3 killed Caenorhabditis elegans, Heterodera schachtii, Meloidogyne javanica, Pratylenchus penetrans, and Aphelenchoides fragariae in in vitro experiments. Tungus Hirsutella minnesotensis suppressed populations of M. hapla populations from 5 states by 61-98%. Weeds are often overlooked as inoculum sources, however their potential to increase nematode damage has been reconfirmed. Yellow nutsedge is a host for M. hapla and the previously?established association between nutsedges and M. incognita appears to extend to other species of Meloidogyne. Nematode genetics play a key role in plant parasitic nematodes interactions with the host. Consequently, understanding nematode genetics will allow us to develop better controls. Populations of M. hapla differ in their pathogenecity based on the environment from where they originate. Whether or not there are intra?population genetic differences or how much the differences in soil conditions contributed to the results are yet to be determined. Wild-type strains of C. elegans may not always be so "wild." C. elegans is not common in California soil, compost piles, garden soils high in organic matter, mushrooms, or surface layers of forest floors. They are found associated with snails. The nature of the snail-nematode interaction, and the genetics, ecology and demography of wild isolates are being investigated. Over 400 partial 18S sequences have been added to GenBank and others laboratories by this project. The 3' barcode used to establish that litter, soil, and understory habitats have a large proportion of unique nematode sequences and nematode diversity is greatest in the litter. In the coming year, our project activities will continue to focus on evaluation of plant germplasm for sources of resistance to nematodes, identifying sustainable . We will be conducting experiments to determine the genetic variation underlying observed nematode behavior. We will be investigating new methods to control nematodes which exploit the underlying variation in nematodes and there interactions with plants. We will undertake efforts to draft proposals to fund ongoing and new research endeavors.