Nematropica

Carta, L. K., A. M. Skantar, and Z. A. Handoo. 2001. Molecular, morphological and thermal charac- ters of 19 Pratylenchus spp. and relatives using the D3 segment of the nuclear LSU rRNA gene. Nem- atropica 31:195-209. Gene sequences are provided for the D3 segment of the large subunit rRNA gene in Pratylenchus agilis , P. hexincisus , P. teres , and P. zeae. They were aligned with the closest comparable previously pub- lished molecular sequences and evaluated with parsimony, distance and maximum-likelihood meth- ods. Different outgroups and more taxa in this study compared to a previous D3 tree resulted in improved phylogenetic resolution. Congruence of trees with thermal, vulval and lip characters was evaluated. A tropical clade of Pratylenchus with 2 lip annules was seen in all trees. Maximum-Parsimony and Quartet-Puzzling Maximum-Likelihood trees, with ambiguously-alignable positions excluded and Radopholus similis as an outgroup, had topologies congruent with species possessing 2, 3 or 4 lip annules. An updated sequence for Pratylenchus hexincisus indicated it was an outgroup of P. penetrans , P. arlingtoni , P. fallax and P. convallariae . Pratylenchus zeae was related to P. neglectus in a Neighbor-Join- ing tree, but was equivocal in others. The relatives of P. teres were P. neglectus and Hirschmanniella belli rather than morphometrically similar P. crenatus . The P. agilis sequence is more closely related to the nearly identical sequences of P. pseudocoffeae and P. brachyurus , than to that of P. scribneri , which is a species closely related morphologically.

The esophagus of the juvenile stage of Rotylenchus magnus jaeni Castillo et al., 1994 exhibits a long pharyngeal overlap and esophageal glands with seven nuclei, as reported for the adult stage of this subspecies. Nuclei of esophageal glands are about the same size, but vary in their arrangement among specimens. The large number of esophageal gland nuclei and long pharyngeal overlap of R magnus suggest that this species is more evolved than the other Rotylenchus species which have shorter pharyngeal overlap and esophageal glands with only three nuclei. Morphometrics and morphology of an Italian population of Rotylenchus agnetis Szczygiel, 1968 from the rhizosphere of Ruscus aculeatus L. did not differ from those reported for other populations from other countries. However, females of this population showed a large annulus at the tail terminus.

Two formulations of a water-soluble, iodophor were evaluated as potential alternatives to methyl bromide soil fumigation by assessing their effects on growth, disease and yield of tomato. Three field trials evaluating Plantpro 45 and Plantpro 20EC were conducted in 2001 at two locations in central Florida. Plantpro 45 and Plantpro 20EC were applied through two drip irrigation lines and methyl bromide was shank applied in the bed. Methyl bromide treated soil consistently produced plants with increased shoot height, shoot weight, and root weight early in the season, healthier root condition and lower gall ratings throughout the season, and greater yields compared to both Plantpro formulations in two of three experiments. Both Plantpro formulations resulted in root-knot nematode populations in soil similar to the nontreated control soil in all studies. In fall experiments at both locations, plants in methyl bromide treated soil had less galling at the end of the season than both Plantpro formulations.

Pathogenicity tests were performed to determine resistance in the wild tomato Solanum huaylasense to four populations of Meloidogyne spp. The S. huaylasense accession LA1358, the root-knot nematode resistant tomato cultivar 'Anairis' and the susceptible tomato cultivar 'Bodar' were assessed against three Miavirulent populations of either Meloidogyne arenaria , M. incognita or M. javanica , and to one naturally Mivirulent population of M. javanica . The relationship between the final and initial population, calculated as the number of eggs per plant (final population) divided by the initial juvenile inoculum, was used as the dependent variable to determine variability in the reproduction of the four Meloidogyne populations tested. Reproduction of M. arenaria was similar on S. huaylasense accession LA1358 and cultivar 'Anairis'. Reproduction of M. incognita on accession LA1358 did not differ statistically from the resistant or susceptible tomato cultivars. Reproduction of the Mi -avirulent population of M. javanica on accession LA1358 did not differ from the susceptible cultivar 'Bodar', and the Mi -virulent M. javanica population reproduced similarly on accession LA1358 and both cultivars. This is the first report on a nematode-species specific resistance in the newly described species of S. huaylasense. Identification of novel root-knot nematode resistance genes in wild Solanum species is the first step for the deployment of new resistance genes in tomato cultivars to preserve durability of plant resistance to root-knot nematodes.

A survey was conducted in 14 major alfalfa producing counties of Colorado (USA) to determine the distribution of Ditylenchus dipsaci and Aphelenchoides ritzemabosi Both nematodes were found in six counties while neither was found in three. D. dipsaci occurred exclusively in three counties, and only A. ritzemabosi was found in two others. In addition to the sun-ev, the response of four cultivars of alfalfa (Pioneer 5312, Pioneer 5364, Pioneer 5454, and Ranger 5-1153) to both nematodes was evaluated in greenhouse experiments, where a mixture of both nematodes was used as innoculum. Under these conditions, the four entries showed a high percentage of symptomatic plants, with symptoms ranging from slight to severe stem swelling and distortion. A field study designed to evaluate the effect of Furadan 4F as a means of nematode control showed that this pesticide is ineffective on established alfalfa.

Meyer, S. L. F, D. P. Roberts, D. J. Chitwood, L. K. Carta, R. D. Lumsden, and W. Mao. 2001. Applica- tion of Burkholderia cepacia and Trichoderma virens , alone and in combinations, against Meloidogyne in- cognita on bell pepper. Nematropica 31:75-86. Bell pepper ( Capsicum annuum L.) seeds and seedlings were treated with three potentially benefi- cial microbes, applied alone and in combinations, to compare effects of these formulations on root- knot nematode ( Meloidogyne incognita ) populations and on plant growth in the greenhouse. Individ- ual treatments (applied as seed coatings and seedling drenches) were formulations of Burkholderia ce- pacia strains Bc-2 and Bc-F, and of Trichoderma virens strain Gl-3. Combination treatments were Bc- F+Gl-3, Bc-2+Gl-3, Bc-F+Bc-2, and Bc-F+Bc-2+Gl-3. At transplanting, pepper seedlings were each inoc- ulated with 10 000 M. incognita eggs or left uninoculated, and harvested 10 weeks later. Nonviable mi- crobe formulations of each individual strain were also applied; these were tested only on nematode- inoculated plants. No treatment consistently affected plant growth. Numbers of eggs + second-stage juveniles (J2) per g root were significantly lower with the Bc-2, Bc-F, and Gl-3 treatments than in the untreated controls, and highest with the nonviable Gl-3 treatment. This indicates that the viable prep- arations suppressed M. incognita numbers on pepper under the greenhouse test conditions. Impor- tantly, the egg + J2 numbers recorded from combination treatments were not significantly different from untreated controls, suggesting that strain combinations decreased biocontrol effectiveness rel- ative to applications of individual microbes.

The growth, development, and nematode susceptibility of various rootstock genotypes grafted to a commercial bell pepper variety scion were evaluated in a series of greenhouse experiments. Nine rootstocks including 'Caribbean Red Habanero', 'PA-136', 'Keystone Resistant Giant', 'Yolo Wonder', 'Carolina Wonder', 'Charleston Hot', 'Mississippi Nemaheart', 'Carolina Cayenne', and 'Charleston Belle', were grafted to the commercial variety 'Aristotle' as a scion, and inoculated with Meloidogyne incognita . 'Aristotle' ungrafted and 'Aristotle' self-grafted plants were included as controls. Graft compatibility was assessed by measuring plant growth, while nematode infestation was assessed using a gall index, and extraction and quantification of juveniles from roots and soil. Stem weight of the scion 'Aristotle' was impacted by the use of different rootstocks, and root weight of the rootstocks varied, however, no rootstock/scion incompatibility occurred. The rootstocks 'Charleston Hot', 'Carolina Wonder', 'Charleston Belle', 'Mississippi Nemaheart' and 'Carolina Cayenne' were consistently resistant to galling by M. incognita in all experiments, while 'Aristotle' ungrafted, 'Aristotle' self-grafted, 'PA-136', and 'Caribbean Red Habanero' were consistently susceptible to galling. Cultivars 'Yolo Wonder' and 'Keystone Resistant Giant' varied in their responses, with reduced galling in one experiment. Grafting a commercial bell pepper variety scion on nematode resistant rootstock has potential to reduce damage caused by M. incognita and contribute to root-knot nematode management as a component in sustainable crop production systems.

The D2-D3 and ITS regions of rDNA from 33 Florida populations of Belonolaimus spp. were sequenced and subjected to phylogenetic analysis. Our objective was to derive a theoretical evolutionary framework for interpreting phenotypic differences as they relate to the taxonomy of the genus. The most striking aspect of the phylogenetic analysis is that none of the three nominal species (B. longicaudatus, B. euthychilus, and B. gracilis) are monophyletic. Additionally, two taxa appear to have discordant ITS and LSU sequences. Three major clades of B. longicaudatus exhibited discernible, overlapping, geographic foci from east to west across the peninsula. Morphological character states considered important for species identification (stylet:tail ratio > or < unity; absence or presence of lip constriction) were paraphyletic; however, these characters may be valid if different quantitative states are used (e.g., stylet:tail ratio > or < a value somewhat greater than 1.0; degree of lip constriction). We were unable to identify suites of morphological/morphometric character states that discriminated between the molecular-derived clades of B. longicaudatus. The large number of autapomorphies for the relatively conserved D2-D3 region both between and within the nominal species reinforces previous observations that the genus Belonolaimus is far more complex than currently recognized.

A survey was conducted in Samsun (Middle Black Sea Region), Turkey to study the occurrence of plant-parasitic nematodes associated with cabbage varieties (Brassica oleracea). A total of 101 soil and root samples containing mixed populations of 10 genera and 11 species belonging to 7 families of the order Tylenchida were analyzed. Lesion (Pratylenchus thornei), spiral (Helicotylenchus sp.) and cyst forming (Heterodera cruciferae and Heterodera mediterranea) nematodes were the most frequently encountered nematode plant pests. Cyst forming nematodes were detected in 45 (45%) soil samples collected from 101 cabbage fields. The majority of these samples 78% (35) were infested with Heterodera cruciferae and 20% (9) with H. mediterranea and a single sample had a mixed population of both H. mediterranea and H. cruciferae. This survey yielded the first report of H. mediterranea in Turkey and the first record of white and red head cabbages being hosts for this and two lesion nematodes (Pratylenchus thornei and P. neglectus).

The effect of the interaction between Meloidogyne incognita and Pratylenchus vulnus on nematode reproduction and vegetative growth of Lovell peach was studied in field microplots. Pratylenchus vulnus suppressed the population density of M. incognita second-stage juveniles, whereas the presence of M. incognita did not affect the population density of P. vulnus in soil. Above-ground tree growth, as measured by trunk diameter 12 and 24 months following inoculation, was reduced in the presence of M. incognita . Differences in root growth as related to nematode treatment were detected 26 months after inoculation. Root growth was reduced in the presence of the two nematode species together than P. vulnus alone, but not when compared to M. incognita alone. There was a greater negative impact on vegetative growth of peach seedlings growing in M. incognita-infested soil than in P. vulnus-infested soil.

Postprint (published version)

A survey was carried out in August, 1995 in five wilayats of Dhofar Governorate in the Sultanate of Oman. A total of 125 soil samples collected from 12 vegetable, 11 tree fruit and eight field crops were examined, and 17 genera of plant-parasitic nematodes were recorded, of which 8 genera and 11 species are reported for the first time in the region. The economically important nematode genera found were Helicotylenchus, Hoplolaimus, Meloidogyne, Pratylenchus, Radopholus, Rotylenchulus, Tylenchorhynchus and Tylenchulus. Helicotylenchus multicinctus, Meloidogyne incognita, M. javanica, Pratylenchus jordanensis, and Rotylenchulus reniformis were the most frequently observed and widely distributed nematode species on several vegetable and tree fruit crops, whereas Radopholus similis was often recorded on banana. The other nematode genera recorded were Aphelenchoides, Boleodorus, Criconemella, Hemicriconemoides, Hemicycliophora, Longidorus, Paratylenchus, Psilenchus and Xiphinema.

Soybean cyst nematode (SCN, Heterodera glycines) represents one of the most serious threats to predictable soybean yield in the United States. Originally discovered in North Carolina during 1954, intraspecific SCN population variability was soon noted. To reduce SCN crop damage, multiple agricul-ture techniques have been exploited. Of these, resistant varieties and rotation to non host crops have been the most effective in reducing the SCN egg population density. However, no single strategy is effective due to variation in SCN populations, lack of complete resistance, and economics of non host crop production. Although it is well accepted that dissimilarities in virulence phenotypes are not associated with any morphological distinctions, knowledge of biochemical characterization of SCN populations is lacking. Therefore, the protein profiles of eggs from four SCN populations were differentiated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Out of 25 protein bands ranging in molecular weight from 40 to 200 kDa, no differences were observed among any of the populations. These results suggest that eggs from SCN populations differing in virulence phenotypes have similar proteins at the resolution of SDS-PAGE.

The phylogenetic relationships of eight Meloidogyne species and twelve isolates from Brazil and other countries were investigated using sequence data of the D2/D3 expansion segments of the large subunit of ribosomal DNA. The phylogenetic procedures used were maximum parsimony, maximum likelihood and neighbor-joining, using different mathematical alignment algorithms as implemented in TreeAlign and ClustalX, and different tree construction methods of TreeAlign and PAUP*. The results obtained with ClustalX alignments are robust and supported by high bootstrap values, suggesting a strong phylogenetic signal, as also supported by the obtained values of skewness parameter g1. Although the consensus topology of trees derived from TreeAlign alignments is more poorly resolved, the topologies obtained with different algorithms and software are congruent in dividing the species into two clusters: a heterogeneous grouping of M. chitwoodi, M. exigua (three isolates), M. graminicola and M. trifoliophila; and a much less divergent cluster with M. arenaria (race 2), M. incognita, M. konaensis and M. paranaensis (three isolates). The phylogenetic usefulness of the D2/D3 region clearly depends greatly on the evolutionary rates within the investigated lineages. For the Meloidogyne isolate study presented here, the D2/D3 region seems to be a more appropriate marker for relationships between species groups than between individual species

The suitability of onion (Allium cepa cv. Sweet Vidalia) as a host for Meloidogyne incognita, M. arenaria, and M. javanica was evaluated. The effect of M. incognita on yield and economic return of direct-seeded and transplanted onions also was evaluated. Nematode reproduction was evaluated in two greenhouse trials with six replications each. All three nematode species increased with final egg counts of 19,300 for M. incognita, 32,100 for M. arenaria, and 40,350 for M. javanica in the first trial and 167,200 for M. incognita, 71,600 for M. arenaria, and 101,950 for M. javanica in the second trial. Final egg counts were similar (P ≥ 0.05) among the three species in the first trial, but M. incognita produced more eggs (P ≤ 0.05) than M. arenaria in the second trial. The application of 1,3-D in direct-seeded onions increased the weight (kg/ha) of large and colossal sizes in both seasons and the weight of small and medium sizes in 2002-2003. In transplanted onions, the weight of colossal onions was increased in 2001-2002, but weights were unaffected in 2002-2003. Onion is a good host for all three Meloidogyne species tested, and M. incognita can reduce yields and economic return when onions are direct-seeded. Transplanted onions in this study did not suffer economic loss.

Surveys were conducted in Batinah, Dhahira, Interior Jabal Akhdar, and Sharqia regions and Dhofar and Musandam governorates of the Sultanate of Oman during cropping seasons from 1990-97, to study the occurrence, population density, and distribution of root-lesion nematodes. Twelve species of Pratylenchus were recorded in association with 31 plant families that included 21 vegetable crops, 19 tree fruit crops, 16 field crops, two ornamentals and 14 weeds. Eleven known species of Pratylenchus are reported in the country for the first time. Among them P. jordanensis was the most frequently observed nematode species occurring in association with 37 crops and 14 weed species and found widely distributed in all the regions. Pratylenchus neglectus was die second most frequently recorded species in association with 24 plant species. Pratylenchus brachyurus, P. coffeae, P. scribneri, and P. zeae were the other economically important nematode species observed in the country.

Four field trials were conducted in northern Florida to determine the feasibility of at plant applications of 1,3-dichloropropene (1,3-D) on cotton compared to the currently recommended preplant applications for management of Rotylenchulus reniformis. The 1,3-D was injected 30-cm-deep into a sandy loam soil with a single in-row chisel at rates of 16, 32, and 48 kg a.i./ha 7 to 13 days preplant or at cotton planting. In the absence of damaging initial populations of plant-parasitic nematodes, phytotoxicity in the cotton was not observed in the at plant 1,3-D treatments, and they caused only small reductions in plant stand, plant height, or yield compared with the preplant 1,3-D treatments or untreated controls. In two tests where high initial populations of R. renifomis were present, postharvest nematode population densities did not differ among any of the treatments. However, plant stands, heights and yields were increased by all rates and application timing of 1,3-D compared to control plots. Data from these tests indicate that 1,3-D may be applied at planting of cotton resulting in only limited phytotoxicity but producing comparable yields to the standard preplant treatment in R. reniformis-infested soil. Further tests are necessary under a wider range of soil types and environmental conditions before this method of application can be widely recommended.

Twelve tobacco (Nicotiana tabacum L.) nematicide field trials were conducted over ten years in north-central Florida, U. S. A., on sites containing fine sandy soil. In each of these trials, 1,3-dichloropropene (1,3-D), fenamiphos 3 SC and a control were utilized. The 1,3-D treatments were applied with a single chisel in the row at rates between 68 and 102 kg a.i./ha. Fenamiphos was applied broadcast at 6.7 kg a.i. in 185 L water/ha and double disc-incorporated. Plots were two rows wide (1.12 m wide/row) and 6.1 m long. Tests were arranged in a randomized complete block design with six replicates. Tobacco leaves were harvested 3-4 times upon maturity and cured weights recorded. Root-gall index ratings were made at or near final harvest from four plants in each plot and rated on a 0-4 scale where 0 = 0 and 4>76% of the root system galled. Compared to untreated controls, 1,3-D treatments increased yield of cured tobacco by 943 kg/ha providing added gross average value of $3134 (U.S.)/ha at average prices paid to Florida growers in 1995. Average cured yield increase of tobacco in the fenamiphos treatments was 646 kg/ha, providing an enhanced value of $1983/ha. Root-gall index ratings averaged 3.2 for the control and 1.0 and 1.1 for the 1,3-D and fenamiphos treatments, respectively. Fenamiphos and 1,3-D have performed consistently over the years in the deep sands where tobacco is grown in Florida, with 1,3-D providing greater yield and economic benefits.

A three-year nematicide study in north Florida, involving four separate cotton field trials, was conducted in loamy sand soils infested with Rotylenchulus reniformis. Cotton lint yield responses and post-harvest soil infestation levels of R. reniformis were evaluated after treatment with four single chisel application rates of 1,3-dichloropropene (1,3-D: 16, 32, 48, and 64 kg a.i./ha) and six rates of aldicarb (0.50, 0.84, 1.01, 1.18, 1.51, and 2.02 kg a.i./ha) placed in a 15-cm-wide band. All rates of 1,3-D increased (P≤0.05) lint yields of cotton in three of the four trials compared to the non-treated controls. Post-harvest soil populations of R. reniformis were reduced by 1,3-D treatments in only one of the tests. Aldicarb increased cotton yield (P≤0.05) at all rates in one test, and at one rate in a second test. Soil populations of R. reniformis were reduced in only one aldicarb treatment in one of the tests. Average cotton yield across treatments increased by 139 kg/ha with 1,3-D and 72 kg/ha with aldicarb, compared to non-treated controls. Lack of significant correlations among rates of 1,3-D or aldicarb and cotton lint yield indicated lower rates of the materials used in these tests were as effective as higher rates to manage R. reniformis.

The effects of 1,3 dichloropropene and rootstocks alone and in combination on Tylenchulus semipenetrans population densities and tree growth were evaluated during three years in a nematode-infested citrus orchard. The experiment was a 2 x 2 factorial with six replications. One factor was fumigation and the second, citrus nematode resistant and susceptible rootstocks. Soil population densities of the citrus nematode remained below detectable levels in fumigated plots planted with the resistant rootstock Cleopatra mandarin X Poncirus trifoliata 03.01.5 throughout the study. The nematode was not recovered from fumigated plots with Carrizo citrange until after the third year, when it appeared sporadically in some of the plots. The nematode was not recovered from citrus roots of either rootstock in fumigated plots. In non-fumigated plots, the resistant rootstock suppressed nematode reproduction. The number of juveniles per 250 cm3 soil, females per gram of root, and eggs per gram of root were 8, 6, and 0.3%, respectively, compared to Carrizo citrange by the third year. The trunk diameter of Orogrande mandarin scion was greater on the resistant than on the susceptible rootstock in non-fumigated plots, but there was no difference in fumigated plots. Fumigation with 1,3 D combined with the resistant rootstock 03.01.5 retarded nematode reinfestation for at least three years. Also, 1,3 D delayed reinfestation of the plots with the susceptible rootstock. The resistant rootstock suppressed nematode reproduction, and the growth rate of the nematode on this rootstock was slower than on the susceptible one.

Replicated fumigation field trials were conducted at separate sites in Florida. One site was naturally infested with Meloidogyne incognita and the other with Rotylenchulus reniformis. The fumigant, 1,3-dichloropropene (1,3-D), was applied at rates of 16, 32, and 48 kg a.i./ha at 92, 63, 36, and 2 days before planting (DBP) Delta Pine 458BR cotton at the M incognita site and at 69, 37, 12, and 0 DBP at the R. reniformis site. All treatments were replicated six times. Yields in the non-treated controls at the M. incognita site averaged 349 kg/ha of cotton lint whereas those across rates and timing in the 1,3-D treatments averaged 504 kg/ha. All 1,3-D treatments significantly reduced post-harvest numbers of M. incognita (12 J2/100 cm3 soil across rates and timing) compared with the non-treated controls (460 J2). At the R. reniformis site, the non-treated controls averaged 353 kg lint/ha while 1,3-D treatment across rates and timing averaged 450 kg/ha. Post-harvest R. reniformis soil population densities of all nematode stages were not influenced by treatment (3048/100 cm3soil from non-treated and 3040 in the 1,3-D treatments across rates and timing). Since there were no significant negative effects from timing of application, these studies indicate that profitable applications of 1,3-D may be accomplished earlier and later than the current application recommendation of 10-21 days before planting.