Brief Summary of Minutes of Annual Meeting

The project has four objectives. Many aspects of the work conducted and accomplishments of the project are in response to grower inquiries. The project activities are diverse and cover a wide range avenues - made possible by the very multi-state nature of the regional project. Project scientists are involved in research spanning the basic to the applied. Our accomplishments will be organized and reported under each of the four project objectives. Defining nematode genetic variability Managing pests with high genetic variability, which includes many plant-parasitic nematodes, diverse agro-ecosystems has many challenges. One aspect of variability is fecundity or the reproductive potential of the nematodes. An other aspect is the consistency between laboratory/greenhouse behavior and field behavior of the nematodes. The reproductive potential of Meloidogyne hapla from mineral soil was higher than those from muck soil, and was positively correlated with the soil pH from where the nematodes came. As measured by nematode community structure indices, a muck soil had better nutrient availability and energy channels than a loamy sand soil. Difference in reproductive potential between the loamy sand and the muck soil nematode populations suggests that nematode adaptation may need to be considered in identifying nematode populations. The fecundity of Meloidogyne incognita host race 3 derived from a single, field-isolated population that was subsequently cultured on yellow nutsedge (Cyperus esculentus = YNS), purple nutsedge (C. rotundus = PNS), or chile pepper (Capsicum annuum cv. NM 6-4) and then tested on chile was not affected by inoculum source. However, inoculum from YNS or PNS resulted in lower levels of reproduction on chile than did inoculum that had been produced on chile. Plant species within a host/weed pest complex influence nematode virulence among species, as does weed/crop competition. Greenhouse screening to identify resistance to nematodes like Heterodera glycines, the soybean cyst nematode (SCN), is expected to be consistent and representative of field conditions. Comparison of reactions over time can be problematic because breeding lines are transient in testing programs. Of 186 soybean lines compared in the uniform and preliminary IVS from 2004 through 2006 only three lines were present for all 3 years and just seven lines were present for 2 years. Comparison of these lines found consist ratings in 90% of the lines over time. A comparative mitochondrial genomics study has shed understanding on the molecular evolutionary mechanisms giving rise to the unusual structural features found within the mitochondrial genome of the mosquito parasitic nematode Romanomermis culicivorax. Multiple mitochondrial DNA haplotypes of Thaumamermis cosgrovei, parasites of the isopod Armadillidium vulgare, are maintained in local isopod populations with a magnitude and frequency of mtDNA haplotype variation unprecedented among metazoan mitochondrial genomes. Genetic analysis revealed that multiply infected hosts are the result of co-parasitization by members of the same maternal lineage, and not the result of spatially and temporally independent infections. A novel mermithid nematode mtDNA haplotype within A. vulgare was found and identified as an Agamermis sp. based on both morphological and molecular phylogenetic analyses. Complete sequences of mitochondrial geneomes frm T. cosgrovei, Agamermis sp., and the mosquito mermithid nematode Sterlkovimermis spiculatus have been determined and compared to Romanomermis revealing a number of unusual features of mermithid mitochondrial genomes. Mermithids have frequent and large-scale size polymorphism, lengthy repeating sequences, inversion of repeating units, extensive duplication of coding genes, and rapid rearrangement. Characterization and analysis of mermithid mitochondrial genomes has also expanded our understanding of the differences between mtDNAs from the Chromodorea and the Enoplea. In contrast to the recurrent mitochondrial gene syntenic relationshiops typifying the Chromodorea, remarkably divergent mitochondrial gene orders are observed at all taxonomic levels (subfamily, genus, species) among the Enoplea. To place Enoplean mtDNA in a phylogenetic context, a molecular framework was constructed from selected mermithid species based on 18S nuclear rDNA sequences. This effort provided the first molecular phylogeny for this nematode family. Topology of the molecular framework is reminiscent of the only previously hypothesized systematic treatment for mermithids, based exclusively on morphology and life history traits. The molecular phylogeny was instrumental in identifying a new mermthid parasite, Allomermis solenopsi, of the fire ant Solenopsis invicta. Determining nematode fitness and adaptability Plant-parasitic nematodes are surprisingly adaptable creatures, surviving long distance transport and what might be considered severe environmental conditions. This adaptability of plant-parasitic nematodes increases challenges producers face in controlling them. Nematodes may be transported in agricultural irrigation water which poses serious control/production challenges when recycled water is used. Ozone and pulsed-ultraviolet light (PUV) are two possible treatments to rid the water of nematodes. Ozone, a powerful oxidizing agent, was equilibrated at concentrations of 0.08, 0.18, 0.215, and 0.38 ppm. The survival of Caenorhabditis elegans, Aphelenchoides fragariae, Heterodera schachtii, and Meloidogyne species differed. A. fragariae became inactive in 20 min at a CT value 7.8 ppm/min and M. incognita in 15 min at a CT value 3.6 ppm/min. The CT values required to consistently obtain 90% kill ranged from 2-8 ppm/min, regardless of nematode species. Higher exposure CT values were required for inactivation in recycled irrigation water. M. javanica became inactive in 75 min at a CT value of 12 ppm/min and C. elegans in 30 min at a CT value of 1.5 ppm/min. Nematodes were exposed to a range of UV doses. PUV at 372 mJ/cm2 immediately inactivated M. javanica juveniles. Inactivation of A. fragariae required 425 mJ/cm2, C. elegans: 460 mJ/cm2, and Acrobeloides buetschii: 407 mJ/cm2. Because nematodes vary in their response to a host, resistance and tolerance to plant-parasitic nematodes in crop plants is important to understand. Ten alfalfa genotypes were screened for tolerance to the lesion nematode, Pratylenchus penetrans. Ts5000 had increased fresh and dry weight of shoot and root followed by the lowest level of P. penetrans populations. The reproduction of M. hapla differs on oil radish and arugula cultivars. Among those tested, Lebanese (Racola, 91.4%) and oil radish (Defender, 95.0%) had the highest nematode reproduction. In another study, using the cultivars Comet, Defender, and Accent as green manures increased total potato tuber yield compared to fallow. Tests in Michigan with oilseed radish, Raphanus sativus, used as a trap, cover, or biofumigant, demonstrated potential for managing M. hapla. However, exploiting the multi-purpose traits of oilseed radish requires careful understanding of M. haplas reproductive fitness in the prevailing soil conditions. When populations of M. hapla were tested in muck, loamy sand and sandy soils, they completed their life cycle in oilseed radish in approximately 500 degree days (DD, base 10oC). Thus, suggesting that oilseed radish cultivars that are hosts to M. hapla may be best used as trap crops and plants destroyed before the nematode completes a life cycle. The host status of M. incognita on pearl and ornamental millet (Pennisetum glaucum), giant bermudagrass (Cynodon dactylon), and switch grass (Panicum virgatum), potential rotation crops with vegetables and cotton in New Mexico, were evaluated. All except ornamental millet supported less nematode reproduction than the best sorghum-sudangrass cultivars examined in 2006, with pearl millet and switch grass showing the greatest promise as candidates for suppression of M. incognita and potentially the root-knot nematode/nutsedge pest complex. Certain ornamental annuals and medicinal plants are do not seem to be good hosts to M. incognita and might provide organic vegetable producers with alternative rotation crops for root-knot nematode suppression. Plant-parasitic nematodes can be introduced into new areas and new infestations are always discovered. It is important to identify this infestations, their extent, and the biology of the nematodes. Potato cyst nematodes Globodera rostochiensis and G. pallida are significant economic threats to food production, so a comprehensive statewide detection survey documented the absence of G. rostochiensis in Idaho but confirmed the presence of G. pallida in Idaho. Relatively low levels of infestation of the previously established Northern root knot nematode, Meloidogyne hapla (0.6%), and the Columbia root knot nematode, M. chitwoodi (2.9 %), were found in Idaho. In 2006, a Cactodera population was discovered on corn in Tennessee. Tests have revealed that this cyst nematodes host range is centered on corn with little to no reproduction on other grasses and no reproduction on dicots tested. A survey for distribution of the nematode is ongoing. An infestation of the soybean cyst nematode, H. glycines, was identified on Kauai in Hawaii. The infestation was limited in distribution to an area of intense soybean production. A population of root-knot nematode infecting Citrus × paradisi, grapefruit, has been tentatively identified as Meloidogyne javanica. The nematode is reproducing well (3000 to 5250 J2/250 cc soil) on citrus with galling clearly visible on the citrus roots as well as nearby koa (Acacia koa). Females inside the galls were large and plump but their egg masses seemed to contain fewer eggs than would be expected on a good host like tomato. Designing and developing integrated management strategies for plant-parasitic nematodes Rotations and host-plant resistance continue to provide appropriate levels of nematode control and offer sustainable long-range solutions for nematode control. In Arkansas, a rotation study of 3 soybean resistance sources; Soybean cyst nematode resistance from Peking (Minokin), PI-88788 (Ag5501), and PI-437654 (Anand) have been rotated after each of the other resistant varieties and grown each year with no rotation as checks along with susceptible Hucheson with and without nematicide. In 2007, Anand showed decreases in SCN numbers, whereas Minokin and Hucheson increased in all their plots. AG 5501 gave mixed results. The field was originally tested as SCN race 6. In a second rotation using Roundup Ready and the resistance sources PI88788 (Ag 5501), SO2-3934-RR a recently released line form Missouri with PI-437654 resistance, and HBK R 4946 CX with Cystex resistance, all resistant lines reduced nematode populations compared to 2006. In Idaho, a long term crop rotation indicated that sugar beet yield increased with green manure crops of Defender and Comet oil raddish compared to fallow. Short term rotation study showed that there was a significant increase in beet yield in the green manure planted plots as compared to fallow. Maximum yield (T/A) was with the Luna (37.0) planted plots followed by the Defender(36.0) plots. When host-plant resistance is not available in a crop it is now possible to employ genetic engineering to incorporate nematode resistance into the plant. Protease inhibitors (cystatins) have been incorporated into anthuruim, coffee, and pineapple. In anthurium, burrowing nematode reproduction and body volume was reduced in putatively cystatin-transformed plants compared to the wild-type plants. The addition of cystatin to coffee via bombardment reduced root-knot nematode population by over 70% in the transgenic plants. Pineapple transgenic with a cystatin gene has greater resistance to root-knot nematode infection that the wild type pineapple. Control of plant parasitic nematodes and enhancement of beneficial free living nematodes is essential to quality crop production and protection of the environment in the USA. Columbia root-knot nematode, Meloidogyne chitwoodi, management in potato has relied on soil fumigants and non-fumigant nematicides alone or in combination. Bionematicides and trap crop/green manures on their own and in combination with reduced rates of nematicides have been tested against M. chitwoodi, Pratylenchus penetrans, and Paratrichodorus allius. Brassica trap crops in combination with half the recommended rate of the fumigant Telone, reduced populations of M. chitwoodi from 700 nematodes/250cc soil to zero, below the economic threshold of 1 nematode/250cc soil; and reduced P. penetrans and P. allius below economic thresholds as well. In contrast, the combination treatments did not reduce the beneficial free-living nematode populations. The tentative cost of growing and incorporating trap crops/green manures in combination with reduced rates of nematicides was approximately half the present commercial cost of fumigants. Green manure crops can be successful but requires different management strategies in different climatic environments. In long, warm production areas, such as those that occur in the Columbia Basin of Oregon and Washington, season length is long enough that a short season crop such as wheat or sweet corn can be followed by green manure crops planted in late summer and incorporated in late fall. While this strategy can reduce populations of M. chitwoodi substantially, the long growing season and warm soil temperatures during the following potato crop permit the small populations that remain to increase sufficiently to still cause tuber damage. In areas with short, cool growing seasons, such as those that occur in the San Luis Valley (SLV) of Colorado, season length is not long enough for a green manure crop to be planted after a grain crop. High nematode control costs relative to crop value, low grain prices, and water shortages led to grower interest in growing green manure crops during the summer instead of a grain crop to reduce water use, improve soils, and reduce nematode control costs. In long season areas, green manure crops need to be augmented with other strategies such as reduced nematicide applications or by proceeding the green manure crops with a poor or non-host rotation crop. In short season areas, green manure crops appear to be sufficient to control M. chitwoodi without other strategies to augment suppression. Trace amounts of tuber infection were found when tubers were incubated, so green manure crops should not be the sole control for potato intended for seed or export. The biocontrol agent Muscodor albus which produces fumigants with nematicidal properties resulted in nematode mortality of 82.9% for P. allius, 82.1% for P. penetrans, and 95% for M. chitwoodi compared to mortality in the nontreated controls of 9%, 7%, and 3.9% respectively. Green manures are not the only sustainable nematode control option being evaluated by the project. The effects of animal wastes like dried-screened poultry litter and beef manure at 0, 5, and 10 t/a on SCN reproduction are being evaluated.. SCN reproduction was significantly lower in both beef manure treatments and the poultry litter at 10 t/a than the control treatment with no animal waste. Producers still often seek a quick fix to nematode diseases, like those provided by chemical applications. Chancellor and the WD at the applied rate significantly increased the total potato tuber yield and reduced the percent of nematode infected tubers. The new product STAN was not as effective as Temik in controlling damage from the sugar beet cyst nematode. Efforts are also being directed at developing predictive tools to aid in controlling nematodes. A fertilizer-use efficiency (FUE) model (which describes an integrated approach to distinguishing agronomic, ecological, and economic implications of nematode management practices) has improved with the incorporation of a daily nematode population density (DNPD = (Sum of nematode population density per unit of root plus soil from planting to end of sampling date) / the number of days from planting to last sampling date). Among other aspects, DNPD can be used to test for correlations with physiological changes overtime. Relating yield and/or physiological measurements data to DNPD is a step towards developing measurable nematode threshold levels over a growing season rather than at one point in time. Visual indicators can also have a roll in assessing potential nematode damage. In a rotation test of chile pepper and non-dormant, M. incognita-resistant alfalfa (cultivar Mecca II), nutsedge counts in fields infested with the M. incognita-nutsedge pest complex can be used as a visual predictor of J2 populations, unless the number of nutsedge plants is very low. Implementing rapid information transfer to stakeholders Research results were disseminated to different user groups through multiple venues during 2006-2007. Scientific peers were updated and informed of new discoveries through presentations at annual professional meetings and at commodity meetings. Discoveries and accomplishments were published in a variety of peer-reviewed and popular outlets. Results were transferred to agricultural producers, crop consultants, and county agents at through formal presentations at conferences and field days with oral and poster presentations.

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