2018 Journal of nematology  
The free living soil nematode C. elegans is uniquely known to have certain fatty acids composition particularly very high level of the polyunsaturated fatty acids, specifically C:20 with 1,2,3,4, and 5 double bonds which exist mostly in the triacylglycerol (triglycerides) and phospholipids. Exposure to mercury (Hg) compounds from environmental and food sources are a significant threat to public health. Organomercuric compounds such as phenyl mercuric acetate (PMA), an herbicide, can cause
more » ... l damage to the nervous system. C. elegans studies showed that chronic exposure to mercury compounds induces neuron degeneration likely due to the increase in reactive oxygen species (ROS). The nematode C. elegans is a major model organism in environmental toxicology, developmental biology, neurobiology, host pathogen interactions, aging research, and pharmacology. Experimental advantages of the C. elegans model include a fast reproductive cycle, a transparent body, known cell lineages, and a fully sequenced genome. Furthermore, its hermaphroditic nature (self-fertilization) allows raising a large number of homozygous animals in short time, and the presence of males allows mutations to be moved between strains. The full developmental cycle of C. elegans from eggs to fertile adults takes about 2-3 days at 20 °C, and can be cultured easily and inexpensively in the laboratory. When C. elegans were chronically exposed to sub lethal doses of phenyl mercuric acetate for a complete lifecycle, the exposure was resulted in no death, however it quantitatively reduced the triacylglycerols with the polyunsaturated double bonds. These types of polyunsaturated fatty acids are related to neurobehavioral and neurosignaling of the worm. It was evident that the exposed nematodes had a higher level of reactive oxygen species (ROS) relative to the control, which may be related to the reduction of the polyunsaturated triacylglycerols concentration. Triacylglycerols were extracted from freeze-dried nematodes using chloroform and methanol 2:1 (v/v). The crude lipid extracts were purified using thin layer chromatography to select only the neutral triacylglycerols. The qualitative and quantitative chemical analysis of triacylglycerols composition was determined using high-resolution accurate mass Liquid Chromatography/Mass Spectrometry Quadruple Time of Flight Agilent System (LCMSQTOF), using Masshunter B07 software for data interpretation. The destruction of the polyunsaturated triacylglycerols was recovered and restored when the Selenium was included in a bioassay, and revealed the ability of Selenium to counteract the effects of PMA induced lipid profiling of C. elegans. The results were replicated three times. Root-knot nematodes (RKN; Meloidogyne spp.) are among the most damaging pests to tomato production in the United States and worldwide, with damage ranging from 25-100% yield loss. Host resistance conferred by the Mi gene in tomato is effective against some species of RKN (e.g. M. incognita, M. javanica and M. arenaria); however, there are virulent species and lines including. M. hapla and M. eterolobii that break Mi-mediated resistance. Triggering innate plant immunity using chemical elicitors is a proven strategy to combat plant pathogens and we believe this method may augment or supplement Mi-resistance in tomato against virulent RKN infection. Nicotinamide adenine dinucleotide (NAD) is one such chemical elicitor that regulates plant defense responses to different biotic stresses. In this study, we investigated the role of NAD in the context of induced tomato innate immunity and RKN pathogenicity in two tomato cultivars; VFN and Rutgers, with and without Mi, respectively. Single soil drench application of NAD 24 hours before nematode inoculation significantly induced defense response pathways, reduced infective-juveniles penetration, and increased plant mass in both cultivars. Importantly, we observed no direct toxic effects of NAD on nematode viability and infectivity. The results presented here suggest that NAD induces resistance against RKN pathogenicity in presence or absence of tomato Mi gene, likely through accumulation of tomato basal defense responses rather than direct effect on the infective-juveniles behavior. ENHANCING THE BIOLOGICAL CONTROL POTENTIAL OF ENTOMOPATHOGENIC NEMATODES: PROTECTION FOM DES-ICCATION. Acar, Ismet, and B. Sipes. Department of Plant and Environmental Protection Sciences, University of Hawaii, Honolulu, HI 96822. Entomopathogenic nematodes (EPNs) are obligate parasites of insects. EPNs have a broad host range, are easily mass reared, and kill insects within 48 hours. EPNs are safe for vertebrates, plants, and nontarget organism. On the other hand, EPNs have disadvantages that make them less effective against foliar insect pest. EPNs are sensitive to desiccation, ultraviolet (UV) radiation and high temperatures. Our goal is to improve the efficacy of aboveground application EPNs by protecting them against desiccation and UV radiation. Barricade is a proprietary fire-protection product that prevents desiccation. One thousand IJ of Steinernema feltiae were exposed to Barricade gel at 0, 0.5, 1, 2 and 3% aqueous concentrations for 8 hours and evaluated for mortality. All EPNs were alive, infected, and killed all mealworms within 48 hours after of exposure to the different Barricade solutions. In the next experiment, 1000 IJ of S. feltiae were placed in 0, 0.5, 1, 2, or 3% Barricade solutions and exposed to sunlight for 1, 2, 3, 4, 5 and 6 hours. A similar experiment was conducted in a dark incubator at 25°C. At each hour, moving EPN were counted, and all EPN inoculated onto mealworms. Barricade gel protected the EPNs for up to 4 hours in direct sun. Number of live EPNs gradually decreased from 85% at 1 hour to 35% after 4 hours and to 22% after 6 hours exposure. EPNs that survived desiccation killed inoculated mealworm within 48 hours. Barricade gel at 1% and 2% provided greater protection (P < .001) in the controlled incubator than in direct sunlight. Protection lasted up to 6 hours in the incubator. Barricade gel at 1% afforded better protection for EPNs (P < .001) exposed to direct sun compared to other Barricade concentrations. EPNs viability can be enhanced with Barricade. Effects of cover crops on soybean cyst nematode (SCN; Heterodera glycines) host range and population reduction were evaluated under greenhouse and microplot conditions. To evaluate the host range, twenty-one cover crops/cultivars and two susceptible soybeans (Barnes and Sheyenne) were planted in small 'cone-tainers' , each containing about 100 cm 3 of soil naturally infested with each of two SCN populations (HG type 0 and 7) and kept in a growth chamber at 27 o C for 35 days. After 35 days, white females were extracted from roots and soil of individual plants and counted under microscope to estimate female index (FI = average number of SCN females on each crop/ average number of SCN females in susceptible check Barnes, x100). Out of the twenty-one crops, SCN populations did not reproduce (FI = 0) on 13 crops suggesting non-hosts. However, the SCN reproduced on eight crop species and cultivars; Austrian winter pea, crimson clover, forage pea, field peas (Aragorn and Cooper), hairy vetch, and turnips (Pointer and Purple Top) with FIs of less than 10, suggesting them as poor-hosts for at least one of the SCN populations. The hosting abilities of those crops were further confirmed by artificial inoculation using the two SCN populations. The results showed similar responses for SCN reproduction except for turnip (Pointer) and field pea (Aragorn), with at least one of the SCN populations having FIs slightly greater than 10. To evaluate the ability of population reduction, ten cover crops including annual ryegrass, Austrian winter pea, carinata, faba bean, foxtail millet (Dixie), radish (Daikon), red clover (Allington), sweet clover, turnip (Pointer), and winter rye (Dylan) were evaluated further in microplot experiments in the years of 2016 and 2017. Crops were planted in early August and grown in large plastic pots; each containing 5 kg of SCN infested soil from each field under natural conditions. The experimental design was Randomized Complete Block Design with five replications for each treatment. After 75 days of growth in the external environments, soil samples were collected from each pot, nematode were extracted, and SCN eggs were counted to determine the Reproductive Factor (RF: final/initial SCN egg number). The nematode population reduction by each crop was also determined as a percentage of density reduction (PR = (Initial -final density)/ initial density, x 100%) of SCN by each crop. All tested cover crops except Austrian winter pea had significantly (P < 0.0001) lower RF for SCN populations (RF: 0.33 to 0.56) compared to the controls, non-planted control and susceptible soybean (Barnes) (RF: 0.92 to 2.43) in both years. The population reductions of SCN by the cover crops ranged from 44 to 67%. Annual ryegrass and radish consistently reduced more SCN numbers than others with an average PR of 65 and 67%, respectively, for both years. The results suggested that most cover crops reduced the SCN populations in controlled microplot conditions, and can be used for managing SCN as well as understanding the mechanisms of SCN population reductions by cover crops. Organismal growth and development relies on gene transcription and protein synthesis, requiring vast amounts of phosphorus (P) that is primarily sequestered in the sugar-phosphate backbone of ribosomal RNA. Thus, the availability of elemental phosphorus is one of the most limiting factors to organismal growth and development. We hypothesized that nematode populations evolve adaptive responses to phosphorus limitation that are associated with life history traits and that these adaptations are reflected in their genome architecture. Comparing populations of the same species (Scottnema lindsayae, Plectus murrayi) from nearby P-rich and P-poor soil ecosystems, we found that compared to populations in P-rich environments, nematodes in P-poor environments have 1) less somatic P, 2) larger body size at maturity, 3) lower rates of gene expression, and 4) fewer copies of rDNA in their genome. Experimental evolution assays conducted in the laboratory revealed that after as few as 30 or as many as 120 generations Caenorhabditis elegans and P. murrayi growing in P-poor media evolved 1) slower growth rates, 2) delayed reproduction, 3) longer reproductive cycles, 4) larger body size, 5) decreased rates of transcription, and 6) decreased rRNA gene copy number. We suggest that rapid loss of rRNA gene copies from the genome is a plastic adaptive solution for regulating the sequestration of environmental phosphorus into RNA for efficient growth and development in environments that are highly phosphorus limited. These findings have important implications on the evolution of organismal life history traits and ultimately the development of trophic complexity in terrestrial ecosystems. Biological and ecological studies often produce non-normal count data that do not satisfy the assumptions to which parametric data analyses such as the analysis of variance (ANOVA) could be applied. For decades, square root and logarithmic transformation methods have been the recommended frameworks to 'normalize' count data and make them amenable to parametric statistical tests. While log-scale data transformation [log(count+constant)] is a common practice among biologists and ecologists, there is, however, no practical justification given for its persistent use. There has been a shift, in recent years, towards embracing model-based method such as the generalized linear models (GLM) or generalized linear mixed models (GLMMs) in the analysis of count data. By contrast, the GLM/GLMM-based analysis approach to count data estimates fixed and random effects parameters on the Poisson/negative binomial scale, which are the probability distributions that led to the data. In this study, we (1) reanalyzed nematode count data from a publication of the second author and (2) conducted a simulation experiment to investigate the performances of the different techniques of analyzing count data. The simulation followed the outline given in Stroup 'Generalized Linear Mixed Models: Modern Concepts, Methods and Applications' , using two treatment groups. Our simulated count data -1000 repetitions -were generated through a Poisson random number generator without and with random effects. Data were analyzed with a normal, lognormal, Poisson or negative binomial distribution function in SAS PROC GLIMMIX (SAS/ STAT 14.1), calculating both least square means and the variance of a mean; for a Poisson-distributed data the variance must be equal the mean. As expected the mean and variance of the 1000 repetition, analyzed using the Poisson distribution functions, were very close to the simulated value. If the same data were analyzed using a normal distribution function the estimated mean was close to the simulated value, PLANT-PARASITIC NEMATODES ON SUGARBEET IN NORTH
doi:10.21307/jofnem-2018-057 pmid:31094163 pmcid:PMC6909347 fatcat:lut4vex74vgqfl5hivg27wvqg4