Populations of Hemicycliophora epicharoides, H. gigas, H. labiata, H. pruni, H. shepherdi, H. vidua, H. zuckermani, Gracilacus straeleni, and Paratylenchus labiosus were obtained from different geographical areas in the continental United States and characterized morphological and molecularly. Two new species of Hemicycliophorinae: Hemicaloosia uarki n. sp from Pinetree, St. Francis County, Arkansas, and Hemicycliophora wyei n. sp from Wayne County, North Carolina, are also described. Hemicaloosia uarki n. sp. is characterized by having two lip annuli separated from the rest of body and directed anteriorly, a long stylet (106-124 μm), long body length (1,081-1,326 μm) and a single lateral fields demarcated by interruptions of the body annuli. Hemicycliophora wyei n. sp. showed a lateral fields demarked by two faint lines with transverse anastomoses and/or breaks of the striae; an elongated not offset conical tail with distinct annulations and a rounded tip and long vulval lips with a vulval sleeve. The molecular characterizations of the new (H. uarki n. sp. and H. wyei n. sp.) and known species of Criconematidae using the ITS1 rDNA gene sequence and the molecular phylogenetic relationships are provided.
Gracilacus straeleni; Hemicaloosia uarki n. sp.; Hemicycliophora epicharoides; Hemicycliophora gigas; Hemicycliophora labiata; Hemicycliophora pruni; Hemicycliophora shepherdi; Hemicycliophora vidua; Hemicycliophora wyei n. sp.; Hemicycliophora zuckermani; internal transcribed spacer 1; molecular biology; morphology; Paratylenchus labiosus, phylogeny
Rhabditid nematodes are one of a few animal taxa in which androdioecious reproduction, involving hermaphrodites and males, is found. In the genus Pristionchus, several cases of androdioecy are known, including the model species P. pacificus. A comprehensive understanding of the evolution of reproductive mode depends on dense taxon sampling and careful morphological and phylogenetic reconstruction. In this article, two new androdioecious species, P. boliviae n. sp. and P. mayeri n. sp., and one gonochoristic outgroup, P. atlanticus n. sp., are described on morphological, molecular, and biological evidence. Their phylogenetic relationships are inferred from 26 ribosomal protein genes and a partial SSU rRNA gene. Based on current representation, the new androdioecious species are sister taxa, indicating either speciation from an androdioecious ancestor or rapid convergent evolution in closely related species. Male sexual characters distinguish the new species, and new characters for six closely related Pristionchus species are presented. Male papillae are unusually variable in P. boliviae n. sp. and P. mayeri n. sp., consistent with the predictions of “selfing syndrome.” Description and phylogeny of new androdioecious species, supported by fuller outgroup representation, establish new reference points for mechanistic studies in the Pristionchus system by expanding its comparative context.
gonochorism; hermaphroditism; morphology; P. boliviae n. sp.; P. mayeri n. sp.; phylogeny; Pristionchus atlanticus n. sp.; selfing syndrome; taxonomy
Globodera ellingtonae was detected in Oregon in 2008. In order to make decisions regarding the regulation of this nematode, knowledge of its biology is required. We determined the host status of a diversity of potato (Solanum tuberosum) varieties in soil-based experiments and identified hatching stimulants in in vitro hatching assays. ‘Russet Burbank,’ ‘Desiree,’ ‘Modac,’ ‘Norland,’ ‘Umatilla,’ and ‘Yukon Gold’ were good hosts (RF > 14) for G. ellingtonae. Potato varieties ‘Maris Piper,’ ‘Atlantic,’ and ‘Satina,’ all which contain the Ro1 gene that confers resistance to G. rostochiensis, were not hosts for G. ellingtonae. In in vitro hatching assays, G. ellingtonae hatched readily in the presence of diffusates from potato (PRD) and tomato (Solanum lycopersicum; TRD). Egg hatch occurred in an average of between 87% and 90% of exposed cysts, with an average of between 144 and 164 juveniles emerging per cyst, from PRD- and TRD-treated cysts, respectively. This nematode hatched rapidly in the presence of PRD and TRD, with at least 66% of total hatch occurring by day 3 of exposure. There was no dose-response of egg hatch to concentrations of PRD or TRD ranging from 1:5 to 1:100 diffusate to water. When G. ellingtonae was exposed to root diffusates from 21 different plants, hatch occurred in 0% to 70% of exposed cysts, with an average of between 0 to 27 juveniles emerging per cyst. When root diffusate-exposed cysts were subsequently transferred to PRD to test viability, root diffusates from arugula (Eruca sativa), sudangrass (Sorghum bicolor subsp. drummondii), and common vetch (Vicia sativa) continued to inhibit egg hatch compared with the other root diffusates or water in which hatch occurred readily (60 to 182 juveniles emerging per cyst). Previously known hatching stimulants of G. rostochiensis and G. pallida, sodium metavanadate, sodium orthovanadate, and sodium thiocyanate, stimulated some egg hatch. Although, Globodera ellingtonae hatched readily in PRD and TRD and reproduced on potato, the pathogenicity of this nematode on potato remains to be determined.
behavior; diffusates; Globodera; hatching; potato; resistance; tomato
Fumigation for nematode management in irrigated potato production systems of Idaho is widely practiced. Soil injection is the only labeled application method for 1,3-dichloropropene that is conventionally applied on a whole-field basis. Plant-parasitic nematode species exhibit spatially variable population densities that provide an opportunity to practice site-specific fumigation to reduce chemical usage and production costs. During 2002 to 2008, 62 fields intended for commercial potato production in eastern Idaho were sampled using a geo-referenced grid sampling system for plant-parasitic nematode population densities. In total, 4,030 grid samples were collected representing nearly 3,200 ha of commercial potato production. Collectively, 73% of the grid samples had Columbia root knot (CRN) (Meloidogyne chitwoodi) population densities below detectable levels. Site-specific fumigation is the practice of varying application rate of a fumigant based on nematode population density. In 2007, 640 ha of potato production were site-specific fumigated for CRN nematode control in eastern Idaho. On average, this practice resulted in a 30% reduction in chemical usage and production cost savings of $209/ha when 1,3-dichloropropene was used as the sole source of nematode suppression. Reductions in usage of 1,3-dichloropropene can exceed 50% if used in combination with a nonfumigant nematicide such as oxamyl. This combination approach can have production cost savings exceeding $200/ha. Based on farm-gate receipts and USDA inspections provided by potato producers from 2001 to 2011, potato tuber yield and quality have not been adversely affected using site-specific fumigation.
Columbia root-knot nematode; 1,3-dichloropropene; management; Meloidogyne chitwoodi; oxamyl; potato; site-specific precision agriculture; spatial distribution; technique
Previous reports suggest that fungivorous nematodes are the only trophic group in forest soils affected by elevated CO2. However, there can be ambiguity within trophic groups, and we examined data at a genus level to determine whether the conclusion remains similar. Nematodes were extracted from roots and soil of loblolly pine (Pinus taeda) and sweet gum (Liquidambar styraciflua) forests fumigated with either ambient air or CO2-enriched air. Root length and nematode biomass were estimated using video image analysis. Most common genera included Acrobeloides, Aphelenchoides, Cephalobus, Ditylenchus, Ecphyadorphora, Filenchus, Plectus, Prismatolaimus, and Tylencholaimus. Maturity Index values and diversity increased with elevated CO2 in loblolly pine but decreased with elevated CO2 in sweet gum forests. Elevated CO2 treatment affected the occurrence of more nematode genera in sweet gum than loblolly pine forests. Numbers were similar but size of Xiphinema decreased in elevated CO2. Abundance, but not biomass, of Aphelenchoides was reduced by elevated CO2. Treatment effects were apparent at the genus levels that were masked at the trophic level. For example, bacterivores were unaffected by elevated CO2, but abundance of Cephalobus was affected by CO2 treatment in both forests.
climate change; ecology; FACE; interaction; nematode biomass; soil function; soil productivity
Belonolaimus longicaudatus is an important parasite of both warm-season bermudagrass and winter overseed grasses used on golf courses in the southeastern United States. Field trials were conducted to study the effects of a commercial formulation of Paecilomyces lilacinus strain 251 applied to overseed grasses during the winter and early spring on population density of B. longicaudatus and bermudagrass health in late spring after bermudagrass broke dormancy. These studies found that P. lilacinus reduced numbers of B. longicaudatus in most cases, but not below damaging levels. Multiple applications of 1 × 1010 spores/m2 were generally more effective than 2 × 1010 spores/m2 in reducing nematode numbers and improving turf roots. These results indicate that application of this formulation of P. lilacinus strain 251 to overseeded turf in the spring may be a useful integrated pest management tool for B. longicaudatus on bermudagrass, but is not sufficient as a stand-alone nematode management tactic.
Belonolaimus longicaudatus; bermudagrass; biological control; Paecilomyces lilacinus, sting nematode; turfgrass
The soybean cyst nematode (SCN), Heterodera glycines, can cause significant reductions in soybean yield and quality in many parts of the world. Natural biological control may play an important role in regulating SCN population. In this study the bacterial communities associated with SCN cysts obtained from fields under different lengths of soybean monoculture were explored. Soil samples were collected in 2010 and 2011 from six fields that had been used for soybean monoculture for 2 to 41 yr. SCN population densities were determined and bacterial communities from SCN cysts were investigated by Biolog and PCR-DGGE methods. SCN population densities initially increased in the first 5 yr of soybean monoculture but then declined steeply as years of soybean monoculture increased. Catabolic diversity of bacterial communities associated with cysts tended to decline as number of years of monoculture increased. Some specific PCR-DGGE bands, mainly representing Streptomyces and Rhizobium, were obtained from the cysts collected from the long-term monoculture fields. Principal component analysis of Biolog and PCR-DGGE data revealed that bacterial communities associated with cysts could be divided into two groups: those from cysts obtained from shorter (< 8 yr) vs. longer (> 8 yr) monoculture. This research demonstrates that the composition of the bacterial communities obtained from SCN cysts changes with length of soybean monoculture; the suppressive impact of these bacterial communities to SCN is yet to be determined.
bacterial community; biodiversity; biological control; cyst; Heterodera glycines; monoculture; soybean; soybean cyst nematode
Deladenus cocophilus n. sp. was isolated from infested coconut fruits in Winder, Balochistan, Pakistan. Descriptions are given of the entomophagous (insect-parasitic females) and mycetophagous (fungus-feeding) free-living females, males, and juveniles. The new species D. cocophilus resembles those species in which the excretory pore is situated anterior to the hemizonid, namely, D. apopkaetus
Chitambar, 1991; D. leptosoma
Gagarin, 2001; D. ipini
Massey, 1974; D. laricis (Blinova and Korentchenko, 1986) Ebsarry, 1991; D. (siricidicola) canii
Bedding, 1974; D. (s) imperialis
Bedding, 1974; D. nevexii
Bedding, 1974; D. (wilsoni) proximus
Bedding, 1974; D. (s) rudyi
Bedding, 1974; D. (s) siricidicola
Bedding, 1968; D. (wilsoni) wilsoni
Bedding, 1968 and D. minimus Chizhov and Sturhan, 1998. The new species differs from D. ipini in the absence of a post uterine sac vs. present; a = 17 to 30 vs. 35 to 40; stylet = 8 to 10 vs. 11 to 12 μm and vulva-anus = 21 to 28 vs. 35 to 48 μm. From D. apopkaetus it differs in tail length in female 22 to 28 vs. 31 to 43 μm and in the male it is 24 to 32 vs. 30 to 46 μm. It differs from D. leptosoma in the c ratio in females, c = 21 to 37 vs. 16 to 22, presence of 6 lines in lateral field vs. 10 lines and slightly longer spicules 16 to 18 vs. 15 to 16 μm. From D. laricis it differs in a shorter stylet length 8 to 10 vs. 11 to 12 μm; in the c ratio in males 16 to 22 vs. 22 to 35 and hemizonid from anterior end 76 to 90 vs. 90 to 119 μm. It also differs from the following species: D. (siricidicola) canii; D. (s) imperialis; D. nevexii; D. (wilsoni) proximus; D. (s) rudyi; D. (s) siricidicola; D. (wilsoni) wilsoni and D. minimus in having shorter tail length, lower values of a,b,c ratios and a slightly anteriorly located vulva in females.
coconut; Deladenus cocophilus; Hexatylina; morphology; Nematoda; new species; Pakistan; taxonomy
The effects of a soil hardpan and Meloidogyne incognita on cotton root architecture and plant growth were evaluated in microplots in 2010 and 2011. Soil was infested with M. incognita at four different levels with or without a hardpan. The presence of a hardpan resulted in increased plant height, number of main stem nodes, and root fresh weight for cotton seedlings both years. Meloidogyne incognita decreased height and number of nodes for seedlings in 2010. Nematode infestation increased seedling root length and enhanced root magnitude, altitude, and exterior path length in 2010. This was also the case for root length and magnitude in 2011 at lower infestation levels suggesting compensatory growth. A hardpan had no consistent effect on these root parameters but increased root volume in both years. A hardpan hastened crop maturity and increased the number of fruiting branches that were produced, while M. incognita infection delayed crop development and reduced plant height and number of bolls. Both M. incognita infection and a hardpan reduced taproot length and root dry weight below the hardpan in both years. Root topological indices under all the treatments ranged from 1.71 to 1.83 both years indicating that root branching followed a herringbone pattern. The techniques for characterizing root architecture that were used in this study provide a greater understanding of changes that result from disease and soil abiotic parameters affecting root function and crop productivity.
ecology; host-parasite relationship; root-knot nematode; root topology; soil hardpan
The population of M. incognita, the root knot nematode (RKN) was found infesting five different host plants (okra, banana, sunflower, bottle gourd, and brinjal) out of 24 examined from four districts of Punjab, India (Gurdaspur, Ludhiana, Patiala, and Hoshiarpur). Morphological and morphometrical characterization indicated that in the case of mature female, the characters of body length and width, neck length, ratio ‘a’, anus to tail terminus (ATT), interphasmid distance (IPD), and perineal pattern were recorded as stable characters. These taxonomic characters can be reliable for identification. All characters of second-stage juvenile (J2) such as body length, stylet length, head to median bulb length (H-MB), distance from median bulb to excretory pore (MB-EP), tail length, anal body width (ABW), and ratios C and C’ were highly variable. Analysis of interpopulation morphometric characters of mature female of M. incognita, namely, body length, width, and ratio ‘a’ were moderately variable characters (CV 0.26% to 20%) and stylet length, neck length, length of median bulb (LMB), and width of median bulb (WMB) were highly variable (CV 1.0% to 36.1%). In the perineal pattern, the two characters ATT and IPD were moderately variable (CV 8.8% to 17.6%) and two characters, anus to vulval slit (AVS) and length of vulval slit (LVS), were highly variable (CV 2.1% to 40.5%). In J2, body length, stylet length, H-MB, MB-EP, ABW, tail length, ratios C, and C’ were highly variable characters (CV > 12%).
Female; juveniles; morphology; morphometrical; M. incognita; perineal pattern
The sedentary semi-endoparasitic nematode Rotylenchulus reniformis, the reniform nematode, is a serious pest of cotton and soybean in the United States. In recent years, interest in the molecular biology of the interaction between R. reniformis and its plant hosts has increased; however, the unusual life cycle of R. reniformis presents a unique set of challenges to researchers who wish to study the developmental expression of a particular nematode gene or evaluate life stage–specific effects of a specific treatment such as RNA-interference or a potential nematicide. In this report, we describe a simple method to collect R. reniformis juvenile and vermiform adult life stages under in vitro conditions and a second method to collect viable parasitic sedentary females from host plant roots. Rotylenchulus reniformis eggs were hatched over a Baermann funnel and the resultant second-stage juveniles incubated in petri plates containing sterile water at 30°C. Nematode development was monitored through the appearance of fourth-stage juveniles and specific time-points at which each developmental stage predominated were determined. Viable parasitic sedentary females were collected from infected roots using a second method that combined blending, sieving, and sucrose flotation. Rotylenchulus reniformis life stages collected with these methods can be used for nucleic acid or protein extraction or other experimental purposes that rely on life stage–specific data.
host-parasitic relationship; life stages; reniform nematode; Rotylenchulus reniformis; technique
Blueberry replant disease (BRD) is an emerging threat to continued blueberry (Vaccinium spp.) production in Georgia and North Carolina. Since high populations of ring nematode Mesocriconema ornatum were found to be associated with commercially grown blueberries in Georgia, we hypothesized that M. ornatum may be responsible for predisposing blueberry to BRD. We therefore tested the pathogenicity of M. ornatum on 10-wk-old Rabbiteye blueberries (Vaccinium virgatum) by inoculating with initial populations (Pi) of 0 (water control), 10, 100, 1,000. and 10,000 mixed stages of M. ornatum/pot under both greenhouse (25 ± 2°C) and field microplot conditions. Nematode soil population densities and reproduction rates were assessed 75, 150, 225, and 255, and 75, 150, 225, and 375 d after inoculation (DAI) in both the greenhouse and field experiments, respectively. Plant growth parameters were recorded in the greenhouse and field microplot experiments at 255 and 375 DAI, respectively. The highest M. ornatum population density occurred with the highest Pi level, at 75 and 150 DAI under both greenhouse (P < 0.01) and field (P < 0.01) conditions. However, M. ornatum rate of reproduction increased significantly in pots receiving the lowest Pi level of 10 nematodes/plant compared with the pots receiving Pi levels of 100, 1,000, and 10,000 nematodes 75 DAI. Plant-parasitic nematode populations were determined in commercial blueberry replant sites in Georgia and North Carolina during the 2010 growing season. Mesocriconema ornatum and Dolichodorus spp. were the predominant plant-parasitic nematodes in Georgia and North Carolina, respectively, with M. ornatum occurring in nearly half the blueberry fields sampled in Georgia. Other nematode genera detected in both states included Tylenchorhynchus spp., Hoplolaimus spp., Hemicycliophora spp., and Xiphinema spp. Paratrichodorus spp. was also found only in Georgia. In Georgia, our results indicate that blueberry is a host for M. ornatum and its relationship to BRD warrants further investigation.
blueberry; host-parasitic relationship; Mesocriconema ornatum; replant disease; ring nematode; Vaccinium spp
The reniform nematode, Rotylenchulus reniformis, is the most damaging nematode pathogen of cotton in Alabama. Soil texture is currently being explored as a basis for the development of economic thresholds and management zones within a field. Trials to determine the reproductive potential of R. reniformis as influenced by soil type were conducted in microplot and greenhouse settings during 2008 to 2010. Population density of R. reniformis was significantly influenced by soil texture and exhibited a general decrease with increasing median soil particle size (MSPS). As the MSPS of a soil increased from 0.04 mm in clay soil to > 0.30 mm in very fine sandy loam and sandy loam soils, R. reniformis numbers decreased. The R. reniformis population densities on all soil types were also greater with irrigation. Early season cotton development was significantly affected by increasing R. reniformis Pi, with plant shoot-weight-to-root-weight ratios increasing at low R. reniformis Pi and declining with increasing R. reniformis Pi. Plant height was increased by irrigation throughout the growing season. The results suggests that R. reniformis will reach higher population densities in soils with smaller MSPS; however, the reduction in yield or plant growth very well may be no greater than in a soil that is less preferential to the nematode.
Gossypium hirsutum; median soil particle size (MSPS); soil moisture; soil texture; site-specific management
The nematophagous fungus Pochonia chlamydosporia var. chlamydosporia is one of the most studied biological control agents against plant (semi-) endo-parasitic nematodes of the genera Globodera, Heterodera, Meloidogyne, Nacobbus and, more recently, Rotylenchulus. In this paper we present highlights from more than three decades of worldwide research on this biological control agent. We cover different aspects and key components of the complex plant-fungus-nematode tri-trophic interaction, an interaction that needs to be addressed to ensure the efficient use of P. chlamydosporia as a biopesticide as part of an integrated pest management approach.
biopesticides; chlamydospores; fungal biotypes; nematophagous fungus
Romanomermis iyengari and Strelkovimermis spiculatus are mermithid nematodes that parasitize mosquito larvae. We describe host penetration and emergence patterns of Romanomermis iyengari and Strelkovimermis spiculatus in laboratory exposures against Culex pipiens pipiens larvae. The mermithid species differed in host penetration behavior, with R. iyengari juveniles attaching to the host integument before assuming a rigid penetration posture at the lateral thorax (66.7%) or abdominal segments V to VIII (33.3%). Strelkovimermis spiculatus attached first to a host hair in a coiled posture that provided a stable base for penetration, usually through the lateral thorax (83.3%). Superparasitism was reduced by discriminating against previously infected hosts, but R. iyengari’s ability to avoid superparasitism declined at a higher inoculum rate. Host emergence was signaled by robust nematode movements that induced aberrant host swimming. Postparasites of R. iyengari usually emerged from the lateral prothorax (93.2%), whereas S. spiculatus emergence was peri-anal. In superparasitized hosts, emergence was initiated by males in R. iyengari and females in S. spiculatus; emergence was otherwise nearly synchronous. Protandry was observed in R. iyengari. The ability of S. spiculatus to sustain an optimal sex ratio suggested superior self-regulation. Mermithid penetration and emergence behaviors and sites may be supplementary clues for identification. Species differences could be useful in developing production and release strategies.
Culex pipiens pipiens; insect-parasitic; host emergence; host penetration; mermithid; Mermithidae; mosquito; nematode behavior; Romanomermis iyengari; Strelkovimermis spiculatus
We study and describe the life cycle of Plectus murrayi, a free-living, bacterivorous soil nematode endemic to terrestrial Antarctica. The study was performed at 15°C, a temperature identified as optimal for growth rate studies in the laboratory. Under these conditions, we observed that the first molt occurs in the egg, and second-stage juveniles hatch 12 to 14 d after egg laying. Individuals undergo three subsequent molts to become adults 23 to 26 d after hatching with a final average length of 950 μm. Egg-laying begins 41 to 43 d after hatching, resulting in an egg-to-egg life cycle ranging from 53 to 57 d under our experimental conditions. Considering that the average soil temperature during austral summers in the McMurdo Dry Valleys is only a few degrees above freezing, it is highly likely that many, if not most of these animals, require more than 1 yr to complete their entire life cycle. Our study supports other research that establishes P. murrayi as an important model organism for studying adaptation to extreme environmental stress.
Anhydrobiosis; McMurdo Dry Valleys; physiology; soil fauna
Cucumis melo var. texanus, a wild melon commonly found in the southern United States and two accessions, Burleson Co. and MX 1230, expressed resistance to Meloidogyne incognita in preliminary experiments. To characterize the mechanism of resistance, we evaluated root penetration, post-penetration development, reproduction, and emigration of M. incognita on these two accessions of C. melo var. texanus. Additionally, we evaluated 22 accessions of C. melo var. texanus for their reaction against M. incognita in a greenhouse experiment. Fewer (P ≤ 0.05) J2 penetrated the root system of C. melo var. texanus accessions (Burleson Co. and MX 1230) and C. metuliferus (PI 482452) (resistant control), 7 days after inoculation (DAI) than in C. melo ‘Hales Best Jumbo’ (susceptible control). A delayed (P ≤ 0.05) rate of nematode development was observed at 7, 14, and 21 DAI that contributed to lower (P ≤ 0.05) egg production on both accessions and C. metuliferus compared with C. melo. Though J2 emigration was observed on all Cucumis genotypes a higher (P ≤ 0.05) rate of J2 emigration was observed from 3 to 6 DAI on accession Burleson Co. and C. metuliferus than on C. melo. The 22 accessions of C. melo var. texanus varied relative to their reaction to M. incognita with eight supporting similar levels of nematode reproduction to that of C. metuliferus. Cucumis melo var. texanus may be a useful source of resistance against root-knot nematode in melon.
Cucumis melo; C. melo var. texanus; C. metuliferus, emigration; melon; Meloidogyne incognita, post-penetration development; resistance; and root-knot nematode
Pristionchus bucculentus n. sp. was isolated from a shining mushroom beetle, Episcapha gorhami, associated with white rot on a decaying log in Hokkaido, Japan. The new species is distinguished by its stomatal morphology, which includes three regularly shaped, conical left subventral denticles and a vacuolated cheilostom with weak internal sclerotization. Also distinguishing P. bucculentus n. sp. are male sexual characters, including arrangement of genital papillae, a rounded and ventrally skewed manubrium, and a gubernaculum with a large, deep posterior curvature and a short, shallow anterior curvature. Morphological and molecular evidence support the new species as being close to P. elegans, which was previously the most basal known species of the genus. Comparative morphology of basal Pristionchus species is supported by a molecular phylogeny inferred from a partial small subunit ribosomal rRNA gene and 25 ribosomal protein-coding genes. Description of P. bucculentus n. sp. provides a new point of comparison for reconstructing the evolution of stomatal characters in the comparative model system of Pristionchus.
Evolution; morphology; morphometrics; ribosomal protein genes; new species; phylogeny; stoma; taxonomy
Belonolaimus longicaudatus and Helicotylenchus pseudorobustus are among the most common nematode parasites of turfgrasses in Florida. Bermudagrass (Cynodon dactylon × C. transvaalensis) and seashore paspalum (Paspalum vaginatum) are the two turf species most commonly used on Florida golf courses. This paper explores the interactions between B. longicaudatus and H. pseudorobustus on bermudagrass and seashore paspalum hosts. Data collected from thousands of nematode samples submitted to the Florida Nematode Assay Lab over a 8-yr period revealed a negative relationship between B. longicaudatus and H. pseudorobustus on bermudagrass, but not seashore paspalum. In a multi-year field plot experiment using multiple cultivars of bermudagrass, and seashore paspalum B. longicaudatus and H. pseudorobustus were negatively related on both turf species. Greenhouse trials where multiple cultivars of both turf species were inoculated with different combinations of B. longicaudatus and H. pseudorobustus found that each nematode species was inhibitory to the other on both host species. Belonolaimus longicaudatus and H. pseudorobustus clearly impact each other on turfgrass hosts, although the mechanism of the nematode-nematode interactions is unknown.
Belonolaimus longicaudatus; bermudagrass; Cynodon dactylon; Helicotylenchus pseudorobustus; interaction; Paspalum vaginatum; seashore paspalum; spiral nematode; sting nematode; turfgrass
The soybean cyst nematode (SCN), Heterodera glycines, is a major factor limiting soybean yield. Experiments were conducted in 2009 and 2010 to determine the effects of liquid swine manure and chemical fertilizer PK on soybean and corn yields, and on SCN population in an SCN-suppressive field (S-Site) and an SCN-conducive field (C-Site) in Minnesota. The experiment was a split-plot design with crop sequences as main plots and fertilizer treatments as subplots. The 2-yr crop sequences were Sus-Sus, Res-Sus, and Corn-Sus, where Sus was SCN-susceptible soybean, and Res was SCN-resistant soybean. The fertilizer treatments were manure, PK, and a nonfertilizer as control. Manure did not reduce SCN egg population density but resulted in 31% lower SCN second-stage juvenile (J2) population density at the S-Site at 45 d after planting (DAP) in 2009. Manure also reduced spiral nematode (Helicotylenchus spp.) population density by 52% compared with PK and nonfertilizer treatments at S-Site at 45 DAP in 2009. The crop sequence of Corn-Sus and Res-Sus reduced the SCN egg and J2 but increased spiral nematode population density at both sites. An increase of 1.4 Mg/ha and 0.5 Mg/ha in yield of susceptible soybean was observed in manure and PK treatments, respectively, at the C-Site in 2009. Corn yield was 2.8 Mg/ha and 5.0 Mg/ha greater when treated with manure than nonfertilizer at the S-Site and C-Site, respectively. This study suggests that soil fertility management may be a useful strategy to alleviate the SCN damage to soybean.
Helicotylenchus; Heterodera glycines; management; nematode suppressive soil; swine manure; soybean; soybean cyst nematode
The seed gall nematode, Anguina agrostis, feeds and reproduces within the developing ovaries of bentgrass seeds and overwinters in seed galls as anhydrobiotic juveniles. These dormant juveniles can survive within the seed gall for many years. In this dehydrated state, they are more tolerant to extreme environmental conditions than are their hydrated counterparts. Nematodes in seed galls were exposed to various high temperatures (80 to 160°C) for time intervals of 5 to 30 min. Survival decreased as time and temperature increased. Remarkably, these nematodes survived exposure to 155°C for 5 min, higher than that recorded for any other metazoan. In contrast, seed galls that had been stored at room temperature and humidity for 5 yr also survived exposure to extreme temperatures; however, their survival rates were not as high as those for freshly collected galls. Juveniles within the seed gall were coiled and grouped together conforming to the shape of the seed gall. The gross morphology of the cuticle of the juveniles was very smooth and relatively undistorted by the shrinkage from the loss water from their body tissues. Wherever the nematodes were cut with a razor blade, a small amount of their contents oozed out of the opening and coalesced with that of other nearby specimens and appeared gel-like. Elucidation of the mechanisms that enable these nematodes to remain viable after exposure to extreme heat remains a mystery. Understanding the changes that occur in these nematodes as they rehydrate and return to life from an ametabolic state may have major impacts on the life sciences, including insights into the answer of the age-old question: “What is life?”
Agrostis stolonifera; ametabolic; Anguina agrostis; anhydrobiosis; desiccation; extremist; feeding site; host-parasitic relationship; longevity; survival; thermal death point; morphology; thermophilic
Resistance to Meloidogyne spp. in commonly used resistant grape rootstocks is slightly compromised at soil temperatures above 27°C. Newly released UCD-GRN series rootstocks, which have broad nematode resistance, exhibit trace infections by Meloidogyne spp. at elevated temperature. Pathotypes of M. incognita and M. arenaria that are virulent on ‘Harmony’ rootstock, as well as M. incognita Race 3, which is avirulent on ‘Harmony’, failed to produce egg masses on the UCD-GRN series rootstocks and other resistant selections at 24°C. At 27°C and above, there was increased nematode galling and egg mass production; at 30°C, egg mass production levels of M. incognita Race 3 on ‘Harmony’ were up to 12% of that on susceptible ‘Colombard’ while reproduction of the virulent pathotypes on the UCD-GRN series was less than 5% of that on ‘Colombard’. Resistance of several of the parental genotypes of the UCD-GRN rootstock series was slightly compromised at soil temperatures of 30°C and above; however, others maintained their resistance to even the virulent M. arenaria pathotype A at high temperatures. Effects of high temperature on resistance to Xiphinema index could not be assessed because of temperature sensitivity of the nematodes while resistance to Mesocriconema xenoplax was not compromised at high soil temperature. Resistance to Meloidogyne spp. in the UCD-GRN series rootstocks was not compromised when plants and nematodes were subjected to cyclical high and low temperature conditions, indicating that once initiated, the resistance mechanism is not reversed.
Broad resistance; durable resistance; host status; temperature effects
Two new species, Neotobrilus nicsmolae n. sp. and Chronogaster carolinensis n. sp. are described from a small, acidic, temperate, natural lake in North Carolina. N. nicsmolae n. sp. comes close to three members of the genus reported from North America, N. filipjevi, N. longus, and N. hopei. However, N. nicsmolae is unique with in the genus in having a combination of characters: size smaller than 1,700 μm, shorter outer labial and cephalic setae, tail shorter than 250 μm, last ventromedian supplement close (about 5 μm) to cloacal opening, spicule length of 61 to 85 μm, flagelloid sperm, and possession of subterminal setae. Assessment of relationships among clades within the Triplonchida using DNA sequences of the D2D3 expansion segment of the LSU rDNA showed that the family Trichodoridae and the genus Tripyla were recovered as monophyletic. The genus Tobrilus was recovered as monophyletic in the neighbor-joining and maximum likelihood trees, but that was not so in the maximum-parsimony tree. The separation among genera of the Trichodoridae, i.e., Trichodorus and Paratrichodorus, was not clear-cut in all phylograms. Chronogaster carolinensis n. sp. in having one ventral mucro with no spine and vacuolated lateral glandular bodies comes close to C. typica and C. ethiopica but differs from all hitherto known species in a combination of characteristics: in having long cephalic setae, long stoma, crystalloid bodies, vacuolated lateral glandular bodies, and a tail terminus with blunt ventral mucro, and its lack of lateral line.
Free-living nematode; freshwater nematode; new species; taxonomy