The southern root-knot nematode, Meloidogyne incognita, is the most damaging pathogen of cotton in the United States, and both resistance and tolerance to M. incognita could be valuable management approaches. Our objectives were to evaluate advanced cotton breeding lines for resistance and tolerance to M. incognita and to determine if a relationship between resistance and tolerance exists. Reproduction of M. incognita was evaluated on 17 breeding lines, a susceptible control (Delta and Pine Land DP5415), and a resistant control (M-120) in two greenhouse trials with six replications in a randomized complete block design. Two-week-old seedlings were inoculated with 8,000 M. incognita eggs and assessed for egg production 8 weeks later. Reproduction on the resistant control was only 10% of that on the susceptible control. Eight breeding lines supported 45% to 57% less (P <= 0.05) nematode reproduction than the susceptible control, and none of them were as resistant as M-120. Yield was determined in 2001 and 2002 in fumigated (1,3-dichloropropene at 56 liters/ha) and nonfumigated plots in a strip-plot design with three replications in a field naturally infested with M. incognita. Yield suppression caused by nematode infection differed among genotypes (P ≤ 0.05 for genotype × fumigation interaction). Six genotypes in 2001 and nine in 2002 were tolerant to M. incognita based on no difference in yield between the fumigated and nonfumigated plots (P ≥ 0.10). However, only three genotypes had no significant yield suppression in both years, of which two also were resistant to M. incognita. Regression analysis indicated that yield suppression decreased linearly as nematode resistance increased.
Gossypium hirsutum; Meloidogyne incognita; nematode management; southern root-knot nematode
We investigated the effects of Heterodera glycines cyst components and surface disinfestants on hatching of H. glycines eggs in vitro. Eggs were incubated in either H. glycines cyst wall fragments, cyst wall and egg rinsate, egg homogenate, or control solutions of soybean root diffusate, sterile distilled water, or zinc sulfate. Hatch in cyst wall and egg rinsate, and egg homogenate, was greater (α = 0.05) than hatch in sterile distilled water; however, it was not different from hatch in zinc sulfate according to Dunnett's test. Hatch in cyst wall fragments was similar to hatch in sterile distilled water. To determine whether surface disinfestants affected hatch, eggs were treated first with chlorhexidine diacetate, mercuric chloride, sodium hypochlorite, or streptomycin sulfate and then incubated in H. glycines egg homogenate, soybean root diffusate, sterile distilled water, or zinc sulfate. Hatch of eggs treated with chlorhexidine diacetate, mercuric chloride, and streptomycin sulfate was reduced (α = 0.05), and hatch of eggs treated with sodium hypochlorite was increased (α = 0.05) relative to hatch of nontreated eggs in all incubation solutions except zinc sulfate according to Dunnett's Test. Hatch in zinc sulfate was similar among all surface disinfestants except mercuric chloride, where hatch was reduced relative to hatch of nontreated and other surface disinfestant-treated eggs.
chlorhexidine diacetate; cyst; egg hatch; hatch inhibitor; hatch stimulator; Heterodera glycines; mercuric chloride; sodium hypochlorite; soybean cyst nematode; soybean root diffusate; streptomycin sulfate; surface disinfestation
A mixed population of Meloidogyne arenaria race 1 and M. javanica race 3 is reported on peanut from a field in Levy County, Florida. Confirmation of M. javanica on peanut is based on esterase and malate dehydrogenase isozyme patterns resolved on polyacrylamide slab gels following electrophoresis, and perineal patterns. Up to 29% of 290 individual females collected from peanut roots in the field in autumn 2002 showed a typical esterase J3 phenotype for M. javanica. This is the third report of M. javanica infecting peanut in the United States.
Arachis hypogaea; electrophoresis; esterase phenotype; host race; malate dehydrogenase phenotype; Meloidogyne arenaria; Meloidogyne javanica; nematode; peanut; root-knot nematode
It has been hypothesized Rotylenchulus reniformis (Rr) has a competitive advantage over Meloidogyne incognita (Mi) in the southeastern cotton production region of the United States. This study examines the reproduction and development of Meloidogyne incognita (Mi) and Rotylenchulus reniformis (Rr) in separate and concomitant infections on cotton. Under greenhouse conditions, cotton seedlings were inoculated simultaneously with juveniles (J2) of M. incognita and vermiform adults of R. reniformis in the following ratios (Mi:Rr): 0:0, 100:0, 75:25, 50:50, 25:75, and 0:100. Soil populations of M. incognita and R. reniformis were recorded at 3, 6, 9, 14, 19, 25, 35, 45, and 60 days after inoculations. At each date, samples were taken to determine the life stage of development, number of egg masses, eggs per egg mass, galls, and giant cells or syncytia produced by the nematodes. Meloidogyne incognita and R. reniformis were capable of initially inhibiting each other when the inoculum ratio of one species was higher than the other. In concomitant infections, M. incognita was susceptible to the antagonistic effect of R. reniformis. Rotylenchulus reniformis affected hatching of M. incognita eggs, delayed secondary infection of M. incognita J2, reduced the number of egg masses produced by M. incognita, and reduced J2 of M. incognita 60 days after inoculations. In contrast, M. incognita reduced R. reniformis soil populations only when its proportion in the inoculum ratio was higher than that of R. reniformis. Meloidogyne incognita reduced egg masses produced by R. reniformis, but not production of eggs and secondary infection.
antagonism; competition; concomitant infections; cotton; Gossypium hirsutum; Meloidogyne incognita; Reniform nematode; root-knot nematode; Rotylenchulus reniformis; sequential infections
Evolutionary relationships based on nucleotide variation within the D3 26S rDNA region were examined among acollection of seven Meloidogyne hapla isolates and seven isolates of M. arenaria, M. incognita, and M. javanica. Using D3A and D3B primers, a 350-bp region was PCR amplified from genomic DNA and double-stranded nucleotide sequence obtained. Phylogenetic analyses using three independent clustering methods all provided support for a division between the automictic M. hapla and the apomictic M. arenaria, M. incognita, and M. javanica. A nucleotide sequence character distinguishing M. hapla from the three apomictic species was a 3-bp insertion within the interior of the D3 region. The three apomictic species shared a common D3 haplotype, suggesting a recent branching. Single M. hapla individuals contained two different haplotypes, differentiated by a Sau3AI restriction site polymorphism. Isolates of M. javanica appeared to have only one haplotype, while M. incognita and M. arenaria maintained more than one haplotype in an isolate.
evolution; Meloidogyne arenaria; M. hapla; M. incognita; M. javanica; phylogeny; rDNA; reproductive modes; root-knot nematodes; speciation
Two new parthenogenetic species of Longidorus were found in Arkansas. Longidorus grandis n. sp. is characterized by its body (5.80-8.24 mm), slightly offset head, head width 20-27 µm, odontostyle 86-100 µm, guide ring 26-35 µm posterior to the anterior end, short conoid to mammiliform tail. Longidorus grandis n. sp. is similar to L. vineacola Sturhan &Weischer, 1964; L. lusitanicus Macara, 1985; L. edmundsi Hunt &Siddiqi, 1977; L. kuiperi Brinkman, Loof &Barbez, 1987; L. balticus Brzeski, Peneva &Brown, 2000; L. closelongatus Stoyanov, 1964; and L. seinhorsti Peneva, Loof &Brown, 1998. Longidorus paralongicaudatus n. sp. is characterized by its body length (2.60-5.00 µm), anteriorly flattened and offset head region 13-18 µm wide, odontostyle length 92-127 µm, guide ring 21-30 µm posterior to the anterior end, tail elongate-conical, and c' = 1.2-2.6. Longidorus paralongicaudatus n. sp. most closely resembles L. longicaudatus Siddiqi, 1962; L. socialis Singh &Khan, 1996; L. juvenilis Dalmasso, 1969; and L. curvatus Khan, 1986.
Arkansas; Longidorus grandis n. sp.; Longidorus paralongicaudatus n. sp; morphology; new species; SEM; taxonomy
Meloidogyne haplanaria n. sp. is described and illustrated from specimens parasitizing peanut in Texas. The perineal pattern of the female is rounded to oval with a dorsal arch that is high and rounded except for striae near the vulva, which are low with rounded shoulders. The striae are distinctly forked in the lateral field, and punctations often occur as a small group near the tail tip and singly within the whole perineal pattern. The female stylet is 13-16 µm long and has broad, distinctly set-off knobs. The excretory pore opens 40-118 µm from the head, approximately halfway between the anterior end and the metacorpus. Males are 1.2-2.4 µm in length and have a high, wide head cap that slopes posteriorly. The labial disc and medial lips are partially fused to form an elongated lip structure. In some specimens the labial disk is distinctly separated from the lips by a groove. The stylet is 17-22 µm long and has wide knobs that are rounded and distinctly set off from the shaft. Mean second-stage juvenile length is 419 µm. The head region is not annulated, and the large labial disc and crescent-shaped medial lips are fused to form a dumbbell-shaped head cap. The stylet is 9-12 µm long and has rounded, posteriorly sloping knobs. The slender tail, 58-74 µm long, has a distinct, inflated rectum and a slightly rounded tip. The hyaline tail terminus is 11-16 µm long. The isozyme phenotypes for esterase and malic dehydrogenase do not correspond to any other recognized Meloidogyne species. Tomato and peanut are good hosts; corn and wheat are very poor hosts; and cotton, tobacco, pepper, and watermelon are nonhosts.
esterase phenotype; malate dehydrogenase phenotype; scanning electron microscopy; taxonomy
Meloidogyne javanica isolates were collected from nine districts of Uttar Pradesh. These isolates showed pathogenic variability when inoculated on the pepper cultivars California Wonder and Suryamukhi Green. Meloidogyne javanica that infected Suryamukhi Green but not California Wonder were designated as pepper race 1 and the populations that infected both the cultivars were designated pepper race 2. Race 1 was more frequent than race 2 in Almora, Pauri Garhwal, Basti, Gorakhpur, and Deoria, whereas race 2 was more frequent than race 1 in the Dehradun, Farrukhabad, Hardoi, and Sitapur districts. The overall frequencies were 70% and 30% for race 1 and race 2, respectively, in the study area.
Capsicum annum cultivars; isolate; Meloidogyne javanica; race; root-knot nematode; pathogenic variability; pepper
The effects of perennial peanut (Arachis glabrata) ground cover on the nematode community in a citrus orchard were examined. Samples were taken from two different ground cover treatments (perennial peanut or bare ground) at each of three distances from the tree trunk. Richness, measured as total numbers of nematode genera per sample, and total numbers of nematodes were greatest in the perennial peanut treatment (P < 0.05). Abundance of many genera of bacterivores, fungivores, and omnivores were increased by the perennial peanut ground cover. Total numbers of plant parasites were greater in perennial peanut treatments on three of the five sampling dates (P < 0.05), mainly due to trends in numbers of Mesocriconema. Distance from a tree trunk and the interaction of ground cover treatments and proximity to a tree trunk were most influential for Belonolaimus and Hoplolaimus. Although differences among treatments were observed for nematode genera and trophic groups, ecological indices were not consistently sensitive to treatments. Among several ecological indices evaluated, richness was most often affected by ground cover treatment.
Arachis glabrata; Belonolaimus; citrus; ecological indices; Hoplolaimus; Mesocriconema nematode community; perennial peanut; plant-parasitic nematodes
The activity of an ethanolic rhizome extract of Artemisia vulgaris against hatching, mortality, host plant infectivity, and galling of the root-knot nematode Meloidogyne megadora was investigated. The extract inhibited egg hatch (50% inhibition by 2.35mg/ml) and caused second-stage juvenile mortality (50% lethality at 12 hours' exposure to 55.67 mg/ml), both in a dose-dependent manner. Nematode infectivity on Phaseolus vulgaris 'Bencanta Trepar', a susceptible host, decreased in a dose-responsive manner (50% inhibition at 6.28 hours exposure to extract). When applied directly to the soil, the extract reduced root galling on a susceptible host in a dose-dependent manner (50% inhibition by 32.36 mg/ml). After dilution in distilled water, the extract did not lose activity when stored in the dark at 25°C for 15 days.
Artemisia vulgaris; botanical-nematicide; Meloidogyne megadora; mugwort; root-knot nematode; toxicity
Three described species of root-knot nematode parasitize peanut (Arachis hypogaea): Meloidogyne arenaria race 1 (Ma), M. hapla (Mh), and M. javanica (Mj). Peanut cultivars with broad resistance to Meloidogyne spp. will be useful regardless of the species present in the field. The objective of this study was to determine whether peanut genotypes with resistance to M. arenaria originating from three different breeding programs were also resistant to M. hapla and M. javanica. The experiment used a factorial arrangement (completely randomized) with peanut genotype and nematode population as the factors. The five peanut genotypes were 'COAN' and AT 0812 (highly resistant to Ma), C209-6-13 (moderately resistant to Ma), and 'Southern Runner' and 'Georgia Green' (susceptible to Ma). The four nematode populations were two isolates of Ma (Gibbs and Gop) and one isolate each of Mh and Mj. On COAN or AT 0812, both Ma and Mj produced <10% of the eggs produced on Georgia Green. On the peanut genotype C209-6-13, Ma and Mj produced about 50% of the eggs produced on Georgia Green. None of the resistant genotypes exhibited a high level of resistance to Mh. The lack of resistance to Mh in any cultivars or advanced germplasm is a concern because the identity of a Meloidogyne sp. in a particular peanut field is generally not known. Breeding efforts should focus on moving genes for resistance to M. hapla into advanced peanut germplasm, and combining genes for resistance to the major Meloidogyne spp. in a single cultivar.
Arachis hypogaea; Meloidogyne arenaria; M. hapla; M. javanica; peanut; reproduction; resistance; root-knot nematode
Alternatives to reduce or modify nematicide use for minimizing groundwater contamination in Easter lily were explored in two field trials. Alternatives to standard 1,3-dichloropropene (1,3-D) plus phorate injection in the first trial were: (i) delaying applications until after winter rains, (ii) removing roots from planting stock, (iii) 1,3-D via drip irrigation, (iv) a chitin-urea soil amendment, (v) the registered insecticide disulfoton, and (vi) several nonregistered nematicides. None of the treatments equaled the standard treatment. In the second trial, potential benefits of adding a systemic nematicide, oxamyl (OX), or a fungicide, metalaxyl (MX), to the standard treatment were explored. Preplant drip irrigation applications of metam sodium (MS), sodium tetrathiocarbonate (ST), and emulsifiable 1,3-D were evaluated alone and in combination with postplant applications of OX and MX. Several drip-applied treatments performed comparably to the standard treatment with respect to the most important criteria of crop quality, bulb circumference. Metam-sodium in combination with either or both OX and MX, 1,3-D plus OX and MX, and ST plus OX and MX provided the best results.
easter lily; lesion nematode; Lilium longiflorum; nematicide; nematode; Pratylenchus penetrans
Longidorus paravineacola n. sp., described herein, was found in a survey of longidorids of Arkansas. It is a parthenogeneticspecies characterized by its long body (6.68-9.85 mm); slightly expanded and rounded head, head width 21-27 µm; odontostyle length 95-114 µm; guide ring 28-37 µm posterior to the head end; short rounded tail, and c' = 0.6-1.0. Longidorus paravineacola n. sp. is similar to the amphimictic species L. vineacola Sturhan &Weischer, 1964; L. balticus Brzeski, Peneva &Brown, 2000; L. kuiperi Brinkman, Loof &Barbez, 1987; and parthenogenetic species L. crassus Thorne, 1974, which also occurred in the type locality.
hierarchical cluster analysis; Longidorus paravineacola; L. vineacola; morphology; species; SEM; taxonomy
Intracellular bacteria of the genus Wolbachia are among the most abundant endosymbionts on the planet, occurring in at least two major phyla-the Arthropoda and Nematoda. Current surveys of Wolbachia distribution have found contrasting patterns within these groups. Whereas Wolbachia are widespread and occur in all three major subphyla of arthropods, with estimates placing them in at least several million arthropod species, the presence of nematodes carrying Wolbachia is currently confined to the filariids, in which they occur at appreciable frequencies. It has been hypothesized that Wolbachia entered the ancestor of modern-day filariids in a single acquisition event, and subsequently cospeciated with their filariid hosts. To further investigate this hypothesis, we examined the broader distribution of Wolbachia in nematodes using a polymerase chain reaction (PCR) assay in a diverse set of nonfilariid species. The assay consisted of three different types of PCR screens on adults of 20 secernentean nematode species (14 rhabditids, 2 strongylid parasites of vertebrates; 1 diplogasterid; 3 cephalobid relatives, 1 myolaim, and 1 filariid) and two adenophorean species (plectids). Two PCR screens were specific to the 16S rDNA and ftsZ protein coding gene of Wolbachia; and the third screen was specific to the 18S rDNA of the nematodes. Based upon our results, we conclude that Wolbachia are absent in all 21 non-filariid species encompassing all the major groups of the Secernentea and two species of Adenophorea, from which the Secernentea derived. The absence of Wolbachia in these non-filariids is consistent with the hypothesis that Wolbachia entered the nematode phylum once, in an ancestral lineage of extant filariids.
endosymbiont; filaria; nematode; rhabditid; Wolbachia
Fine structure of the stoma, including the cheilostom, gymnostom, and stegostom of Bunonema sp. and Teratorhabditis palmarum was compared with Caenorhabditis elegans to consider fine structural characters that may be phylogenetically informative. The stegostom, enclosed by the anterior end of the pharynx, includes a triradiate lumen surrounded by radial cells (interradial or pairs of adradial cells) repeated in the dorsal and subventral sectors; in Rhabditina, typically the stegostom includes anteriorly two sets of epithelial and posteriorly two sets of muscular radial cells. These muscle cells are anteriorly m1 and posteriorly m2. In Bunonema sp., unlike T. palmarum and C. elegans, the stegostom has a third set of interradial epithelial cells. In Bunonema sp., m1 is expressed by three interradial cells, whereas in T. palmarum and C. elegans m1 is three pairs of adradial muscle cells (i.e., six cells). In all three taxa m2 is expressed as three pairs of adradial muscle cells. Posterior processes of adjacent adradial cells fuse, and closely apposed nuclei may present a figure-eight shape. However, in Bunonema the three interradial m1 cells each have a long posterior process enclosing two separate round nuclei. In combination with additional characters, these diverse stoma features may prove phylogenetically informative. Specifically, the radial epithelial cells of the stegostom appear to be a synapomorphy consistent with a bunonemid-diplogastrid-rhabditid clade, whereas a thickening in the dorsal sector of the stoma cuticle lining is interpreted as a synapomorphy supporting a bunonemid-diplogastrid clade.
Bunonema sp.; Caenorhabditis elegans; cell fusion; DAPI; Diplogastrina; fine structure; nuclei; SEM; TEM; Teratorhabditis palmarum
Arginine kinase (AK) is a phosphagen kinase that plays a key role in energy mobilization in invertebrates. Alignment of expressed sequence tags (ESTs) for soybean cyst nematode (SCN) (Heterodera glycines) produced two separate contiguous sequences (contigs) and three singletons encoding peptides with high similarity to AKs. One contig, Hg-AK1, had 244 ESTs in the alignment whereas the other, Hg-AK2, had only three; nonetheless, the consensus sequence for Hg-AK1 was missing much of the 5' end. Polymerase chain reaction (PCR) was used to prepare clones that were then sequenced to obtain full-length sequences for both Hg-AK1 and Hg-AK2. Hg-AK1 has an open reading frame of 1080 nucleotides (nt) encoding a protein of 360 amino acids (aa) with a predicted molecular weight of 40 kDa. The open reading frame for Hg-AK2 is 1221 nt, 407 aa, and 46 kDa with a 71% aa identity with Hg-AK1. Semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) indicated that Hg-AK1 and Hg-AK2 are expressed constitutively throughout the SCN life cycle. Phylogenetic analysis of peptide sequences for near full-length nematode contigs and other AKs in the Swisspro database indicates that the nematode AKs evolved from a single gene after divergence of insects and nematodes.
arginine kinase; gene expression; Glycine max; Heterodera glycines; soybean; soybean cyst nematode
A new species of the genus Nothacrobeles is described from natural areas (a salt lake) in the Southeast Iberian Peninsula. Nothacrobeles lanceolatus sp. n. is characterized by its body length, two rows of cuticular punctations per annulus, labial probolae bifurcate with divergent prongs, pharyngeal corpus 2.4 to 3.5 times isthmus length, spermatheca length, postuterine sac 0.5 to 1.1 times the corresponding body diameter ratio, female tail conical and bearing a spindle-shaped or conical mucro with acute terminus, phasmid at 8 to 17 µm posterior to the anus, male tail conical with acute mucro, spicules length, and gubernaculum length. In addition, Nothacrobeles cf. lunensis and Zeldia punctata are studied. Cervidellus capricornis is transferred to genus Nothacrobeles. A key to species of Nothacrobeles is also provided.
cephalobs; description; key; morphology; Nothacrobeles; SEM; Spain; taxonomy; Zeldia
The objective of this study was to determine the effect of egg age and pre-colonization of cysts by a saprophytic or parasitic fungus on parasitism of Heterodera glycines eggs by other parasitic fungi. In agar and in soil tests, fungi generally parasitized more eggs in early developmental stages than eggs containing a juvenile. The effect of pre-colonization of cysts by a fungus on parasitism of eggs by other fungi depended on the fungi involved. In most cases, pre-colonization of cysts by an unidentified, saprophytic fungal isolate (A-1-24) did not affect parasitism of eggs in the cysts subsequently treated with other fungi. However, pre-colonization of cysts by A-1-24 reduced fungal parasitism of eggs in cysts subsequently treated with Cylindrocarpon destructans isolate 3. In agar tests, pre-colonization of cysts by Chaetomium cochliodes, a saprophytic or weakly parasitic fungus, reduced parasitism of eggs in cysts subsequently treated with Verticillium chlamydosporium Florida isolate, Fusarium oxysporum, Fusarium solani, ARF18, and another sterile fungus. However, in soil tests, pre-colonization of cysts by C. cochliodes had no effect on parasitism of eggs by subsequent fungal parasites. In another test, parasitism of eggs by V. chlamydosporium in cysts was not affected by pre-colonizing fungi C. destructans, F. oxysporum, and F. solani but was reduced by Mortierella sp., Pyrenochaeta terrestris, and C. cochliodes. Parasitism of eggs in cysts by ARF18 was reduced by pre-colonizing fungi C. destructans, F. oxysporum, F. solani, P. terrestris, and C. cochliodes but not Mortierella sp.
biological control; cysts; cyst nematode; eggs; Heterodera glycines; nematophagous fungi; soybean cyst nematode
Steinernematid nematodes were evaluated against the three major cruciferous insect pests: the imported cabbageworm Artogeia rapae, the diamondback moth Plutella xylostella, and the cabbage looper Trichoplusia ni. LC50 values of S. carpocapsae All, S. feltiae UK, S. feltiae 27, and S. riobrave 335 were 18.2, 3.6, 5.7, and 8.3 on A. rapae L2; 24.5, 2.3, 6.0, and 15.5 on P. xylostella L3; and 10.1, 4.7, 9.5, and 7.8 on T. ni L2, respectively. Insect mortality from the nematode species and isolates was modulated by temperature. Maximum mortality (100%) was recorded for A. rapae L2 from S. riobrave at 30 °C, 95.8% from S. feltiae, and 91.7% from S. feltiae 27 at 25 °C and 75.7% from S. carpocapsae at 30 °C. Mortality of A. rapae L2 increased with contact time to nematode. Mortality of 76% and 78% was achieved for S. carpocapsae and S. feltiae, respectively, after 12-hour exposure. Susceptibility of A. rapae, P. xylostella, and T. ni larvae to entomopathogenic nematodes increased with larval age development. The addition of adjuvants - Corn Oil (0.9%, 1.8%, 3.6%), Leafshield (3.0%, 6.0%, 12.0%), Seaweed (0.1%) and Agral (0.05%) - significantly increased the density and survival rate of S. carpocapsae on cabbage leaves compared to water only. At 20 °C and 70% relative humidity (RH), survival rates of S. carpocapsae All, S. feltiae UK, and S. riobrave 335 on cabbage leaves were 43%, 2%, and 0% after 4 hours following application. Under field conditions, foliar applications of S. carpocapsae provided 35.3% and 33.0% control of A. rapae (L3-L5) on Brussels sprouts and broccoli in 1996 and 24.9%, 19.4% and 14.9% on Brussels sprouts, broccoli, and cauliflower, respectively, in 1999. Based on our field results, foliar applications of S. carpocapsae do not provide an acceptable level of A. rapae control under Quebec's environmental conditions.
Artogeia rapae; cabbage looper; diamondback moth; entomopathogenic nematodes; foliar application; imported cabbageworm; Plutella xylostella; Trichoplusia ni
Belonolaimus longicaudatus is a serious problem on bermudagrass, a common warm-season turfgrass, in Florida. The cancellation of organophosphate nematicides necessitates that new management tools be identified for use on sports turf. Postplant application of 1,3-dichloropropene (1,3-D) on bermudagrass was evaluated for management of B. longicaudatus on golf course fairways and driving ranges. A series of 10 experiments were conducted to evaluate the effectiveness of 1,3-D in reducing population densities of B. longicaudatus and enhancing bermudagrass recovery from nematode damage. In 5 of 10 experiments, 1,3-D injected at 46.8 liters/ha was effective in reducing population densities of B. longicaudatus (P < 0.05) compared to untreated plots 2 to 4 weeks after treatment. One month after treatment, population densities of B. longicaudatus ranged from 59% to 97% of those in untreated plots. Nematode suppression generally lasted 2 months or less. Turf visual performance was improved following injection with 1,3-D (P < 0.05) over untreated plots when other factors were not limiting. Turf root development also was enhanced following injection with 1,3-D. Postplant injection of 1,3-D could be a useful nematode management tool for certain sports turf applications.
Belonolaimus longicaudatus; bermudagrass; Cynodon dactylon; Cynodon hybrids; 1,3-dichloropropene; nematicide; nematode; nematode management; soil fumigation; sting nematode; turf
Effect of sunn hemp (Crotalaria juncea) hay amendment on nematode community structure in the soil surrounding roots of yellow squash (Cucurbita pepo) infected with root-knot nematodes was examined in two greenhouse experiments. Soils were from field plots treated long-term (LT) with yard-waste compost or no yard-waste compost in LT experiment, and from a short-term (ST) agricultural site in ST experiment. Soils collected were either amended or not amended with C. juncea hay. Nematode communities were examined 2 months after squash was inoculated with Meloidogyne incognita. Amendment increased (P < 0.05) omnivorous nematodes in both experiments but increased only bacterivorous nematodes in ST experiment (P < 0.05), where the soil had relatively low organic matter (<2%). This effect of C. juncea amendment did not occur in LT experiment, in which bacterivores were already abundant. Fungivorous nematodes were not increased by C. juncea amendment in either experiment, but predatory nematodes were increased when present. Although most nematode faunal indices, including enrichment index, structure index, and channel index, were not affected by C. juncea amendment, structure index values were affected by previous soil organic matter content. Results illustrate the importance of considering soil history (organic matter, nutrient level, free-living nematode number) in anticipating changes following amendment with C. juncea hay.
community structure indices; Cucurbita pepo; Meloidogyne incognita; organic amendments; squash; sunn hemp
Oxycom applications increased plant growth and population levels of Meloidogyne incognita on susceptible tomato. A single Oxycom drench at 2,500 ppm applied 7 days prior to inoculation with M. incognita provided remediation of plant growth measured 63 days later. This occurred without reducing nematode population levels. Follow-up drenches at 2,500 ppm at 10-day intervals stunted shoots and roots (P = 0.05). The same application rates at 20-day intervals did not reduce plant growth. Plants receiving multiple drenches had more galls (P = 0.05), females, and second-stage juveniles (J2) per root system compared to plants receiving only the single treatment. Foliar mass and height of plants treated with a single pre-inoculation Oxycom drench were indistinguishable from plants without nematodes. Oxycom treatments activated signaling pathways for plant defense as confirmed by detection of elevated defense gene transcripts in root tissues. The finding of increased reproduction of root-knot nematode without loss of plant growth is consistent with the definition of induced tolerance. Frequency, rate, and timing of applications need further study with other nematodes and various field settings.
Ethylene; growth stimulation; induced resistance; MAPK activation; nematodes; salicylic acid; tolerance
Johnson and Wood constructed recombinant inbred strains of Caenorhabditis elegans with life spans ranging from 10 to 31 days. Using these strains, we have demonstrated previously that hyperoxia and methyl viologen inhibited development at rates inversely correlated with life span. The growth rates of the short-lived recombinant inbred strains were more profoundly inhibited by oxidative stress than were those of the long-lived strains. Here we report a positive correlation between life span and catalase levels in these same strains. Specifically, when compared to short-lived strains at 10 days after fertilization, the long-lived strains possessed higher levels of total enzymatic catalase. Northern blots indicated a similar relationship between life span and clt-1mRNA (the cytosolic catalase). This suggests that at least some of the polygenes that influence life span are also responsible for regulating gene expression of catalase, an important defense component against oxidative stress.
aging; catalase; Caenorhabditis elegans; life span; oxidative stress; recombinant inbreds