Morphological and molecular characterization of Paractinolaimus sahandi n. sp. (Nematoda: Actinolaimidae) from the Sahand Mountains in Iran.

Paractinolaimus sahandi n. sp., found in wet soil samples collected from the rhizosphere of grasses of Sahand Mountains, Iran, is described. This new species is characterized by its long body (3.5-4.7 mm), high a value (74.5-88.5), anterior location of posterior subventral nuclei, occupying 62.5-68.0% of glandularium distance, the presence of 1-4 pre- and 1-3 post-vulval papillae and numerous tiny, not innervated papillae in front and behind the vulva in the outer layer of cuticle; common functional males in the population, with 62.5-81.3 µm long spicules and 15-17 ventromedian supplements. The new species, which is the only one in the genus showing the advulval cuticular tiny papillae and is unusually slender, is compared to four species of Paractinolaimus, namely P. macrolaimus, P. longidrilus, P. spanithelus and P. rafiqi. The ribosomal 18S rDNA (1246 bp sequenced) and 28S rDNA D2/D3 region (844 bp sequenced) of P. sahandi n. sp. were sequenced for molecular characterization. Sequences of the 18S and 28S D2/D3 of P. sahandi n. sp. have distinct differences from those of the only sequenced P. macrolaimus, with 6 bp differences in 18S and 38 bp differences and five gaps in 28S. This is the first report of the occurrence of members of Actinolaimidae in Iran.

First Record of Trichodorus primitivus and Morphological and Molecular Identification of Longidorus elongatus from Canada.

During July 2008, sandy loam soil samples were collected near the rhizosphere of Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) at a depth of 15 to 20 cm from Caledonia Park, Toronto, Canada. Samples were suspended in water and nematodes were collected on sieves with 250- and 74-µm openings. Among the nematodes recovered were one species of Longidorus Micoletzky, 1922 (4) and one species of Trichodorus Cobb, 1913. The Trichodorus species (2), was identified as T. primitivus (de Man, 1880) Micoletzky, 1922, in which females have rod-like sclerotized pieces parallel to the vagina lumen, each with dimensions of 3.1 × 1.2 µm and at a distance of 2 to 3 µm from each other; and males have spicules with a wide nonoffset capitulum and very narrow blade, three ventromedian cervical papillae (CP), and three precloacal supplements with the anterior one at the level of the capitulum of retracted spicules. Males showed unusual variation in the position of CP2 (i.e., posterior to the onchiostyle region, except for one specimen with CP2 located within the posterior onchiostyle region, which is typical for the species). The morphometric data for nine males are: L, 665 to 805 µm; a, 23.0 to 27.5; b, 3.7 to 5.2; c, 46 to 56; onchiostyle, 47 to 52 µm; and spicules, 32.5 to 40.5 µm. Measurements for 13 females are: L, 630 to 775 µm; a, 20.5 to 24.8; b, 3.5 to 5.5; c, 75.5 to 158.5; and V, 54 to 61%. To our knowledge, this is the first report of T. primitivus in Canada. According to Chen et al. (1), the Longidorus species was identified as L. elongatus (de Man, 1876) Micoletzky, 1922 (3). The morphometric data for females (n = 13) are: L, 5.1 to 6.0 mm; a, 78.5 to 106.5; b, 11.5 to 13.5; c, 86.0 to 120.5; V, 45.5 to 53.0%; odontostyle, 79 to 91 µm; odontophore, 57.5 to 66.5 µm; and tail length, 44.5 to 59.0 µm. Males were not found. Four juvenile stages were identified. J1 (n = 2) with a body length of 1.1, 1.2 mm and replacement/functional odontostyle 59, 59/53.5, 54.5 µm, J2 (n = 2) with L: 1.7, 2.0 mm and replacement/functional odontostyle 62.5, 68.0/58.7 µm, 59.0, J3 (n = 2): L: 2.8, 3.0 mm and replacement/functional odontostyle 76.5, 77/66.5, 67.0 µm and J4 (n = 2) with L: 3.6, 3.8 mm and replacement/functional odontostyle 87.0, 90.5/75.0, 77.5 µm. Due to large morphometric overlap in Longidorus species identification, 2,472 bp of the near full-length 18S and the internal transcribed spacer 1 region of rDNA (Accession No. GU199044) were sequenced. The Blastn search of the partial 18S revealed 100% identity with a population of L. elongatus from Scotland (GenBank No. AY687992, 1,707 bp compared), 99% identity (3 bp difference, 1,707 bp compared) with a population of L. elongatus from Iran (EU503141) and 99% identity (4 bp difference, 1,707 bp compared) with a population of L. elongatus (AF036594, sample location unknown). A Blastn search of the 18S and ITS region revealed only 1 to 3 bp differences with two populations of L. elongatus from Switzerland (AJ549986 and AJ549987) and a population of L. elongatus (AF511417) from Scotland. These molecular data further confirmed the identity of the population from Canada to be L. elongatus. References: (1) Q. Chen et al. Fundam. Appl. Nematol. 20:15, 1997. (2) W. Decraemer. Kluwer Academic Publishers, Dordrecht, the Netherlands, 1995. (3) J. G. de Man. Tijdschr. Ned. Dierk. Ver. 2:78, 1876. (4) H. Micoletzky. Archiv. Naturgesch. 87:1, 1922.

Secondary structure models of D2-D3 expansion segments of 28S rRNA for Hoplolaiminae species.

The D2-D3 expansion segments of the 28S ribosomal RNA (rRNA) were sequenced and compared to predict secondary structures for Hoplolaiminae species based on free energy minimization and comparative sequence analysis. The free energy based prediction method provides putative stem regions within primary structure and these base pairings in stems were confirmed manually by compensatory base changes among closely and distantly related species. Sequence differences ranged from identical between Hoplolaimus columbus and H. seinhorsti to 20.8% between Scutellonema brachyurum and H. concaudajuvencus. The comparative sequence analysis and energy minimization method yielded 9 stems in the D2 and 6 stems in the D3 which showed complete or partial compensatory base changes. At least 75% of nucleotides in the D2 and 68% of nucleotides in the D3 were related with formation of base pairings to maintain secondary structure. GC contents in stems ranged from 61 to 73% for the D2 and from 64 to 71% for the D3 region. These ranges are higher than G-C contents in loops which ranged from 37 to 48% in the D2 and 33-45% in the D3. In stems, G-C/C-G base pairings were the most common in the D2 and the D3 and also non-canonical base pairs including A•A and U•U, C•U/U•C, and G•A/A•G occurred in stems. The predicted secondary model and new sequence alignment based on predicted secondary structures for the D2 and D3 expansion segments provide useful information to assign positional nucleotide homology and reconstruction of more reliable phylogenetic trees.

Phylogenetic Analysis of the Hoplolaiminae Inferred from Combined D2 and D3 Expansion Segments of 28S rDNA.

DNA sequences of the D2-D3 expansion segments of the 28S gene of ribosomal DNA from 23 taxa of the subfamily Hoplolaiminae were obtained and aligned to infer phylogenetic relationships. The D2 and D3 expansion regions are G-C rich (59.2%), with up to 20.7% genetic divergence between Scutellonema brachyurum and Hoplolaimus concaudajuvencus. Molecular phylogenetic analysis using maximum likelihood and maximum parsimony was conducted using the D2-D3 sequence data. Of 558 characters, 254 characters (45.5%) were variable and 198 characters (35.4%) were parsimony informative. All phylogenetic methods produced a similar topology with two distinct clades: One clade consists of all Hoplolaimus species while the other clade consists of the rest of the studied Hoplolaiminae genera. This result suggests that Hoplolaimus is monophyletic. Another clade consisted of Aorolaimus, Helicotylenchus, Rotylenchus, and Scutellonema species. Phylogenetic analysis using the outgroup species Globodera rostocheinsis suggests that Hoplolaiminae is paraphyletic. In this study, the D2-D3 region had levels of DNA sequence divergence sufficient for phylogenetic analysis and delimiting species of Hoplolaiminae.

Longidorus ferrisi n. sp. from California Citrus.

In October 1999, the authors received fixed specimens of a species of Longidorus from Howard Ferris found about the roots of a citrus tree in Oakville, Napa County, CA. After determining it to be new a species, we requested additional specimens. The samples contained roughly equal numbers of males and females. Longidorus ferrisi n. sp. is most similar to L. elongatus, but can be distinguished by a greater c-ratio (111-187 vs 73-141), a lesser c´ (0.7-1.1 vs 1.0-1.3), a more offset head, a more posterior guide ring (35-40 vs 30-33 µm), the presence of sperm in the uterus in mature females, and the approximate 1:1 ratio of females to males. Other similar species include L. artemisiae, L. crassus, L. glycines, and L. milanis. Longidorus ferrisi n. sp. differs from L. artemisiae by a lesser a-ratio (74-102 vs 109-155), a lesser c´ value (0.7-1.1 vs 1.0-1.6), a more posterior guide ring (35-40 vs 27-34 µm), a longer odontostyle (91-108 vs 84-98 µm), a wider lip region (16-19 vs 14-17 µm), wider mid-body (53-69 vs 41-52 µm), and longer spicules (57-65 vs 39-49 µm). The new species differs substantially from L. crassus by its lip shape and the presence of males, and differs from L. glycines by a shorter body (4.33-5.97 vs 6.14-8.31 mm), a lesser c´ value (0.7-1.1 vs 0.9-1.4), a narrower lip region (16-19 vs 20-23 µm), wider mid-body (53-69 vs 39-57 µm), longer spicules (53-69 vs 45-53 µm), and fewer supplements (7-11 vs 11-17). Longidorus ferrisi n. sp. differs from L. milanis by a longer body (4.33-5.97vs 3.00-4.90 mm), a greater c value (111-187 vs 86-130), a wider mid-body (53-69 vs 43-56 µm), a different head shape, and longer spicules (53-69 vs 41-54 µm). The nuclear 18S ribosomal DNA sequence of this species revealed that this species is unique with respect to all sequenced Longidorus species.

Xiphinema bernardi n. sp. (Nematoda: Longidoridae) from the Great Smoky Mountain National Park.

In October 1985 during a survey of fauna of the Great Smoky Mountains National Park, Ernest Bernard recovered a limited number of specimens of a non-described species of Xiphinema (Nematoda: Longidoridae) and sent them to the senior author. The species is distinct from other species by its large size and having Z-organs in the genital tract. During July 2006, Dr. Bernard's survey crew took samples in the area where the species was first found and was successful in finding it again. Without Dr. Bernard's efforts, this species could not have been described and thus the new species is named X. bernardi n. sp. in his honor. Several female and juvenile specimens of the new species were recovered in a sample from a mixed forest of maple, hemlock, and silverbell. It is distinct from all others in Xiphinema group 4 species (with Z-organs) by having a longer total stylet length, 259.8 to 284.2 µm vs < 253 µm for all other species in this group. Xiphinema bernardi n. sp. is distinctive because of its long body length (4.45 to 6.00 mm), tail shape, and c' ratio. Of the group 4 species, it most closely resembles X. phoenicis. Second, third and fourth stage juvenile descriptions and morphometrics are included. The polytomous key code for X. bernardi n. sp. is A4-B1-C6-D56-E56-F(4)5-G4-H2-I34-J5-K?-L1. Molecular approaches using the internal transcribed spacer 1 sequences of nuclear ribosomal DNA suggested that X. bakeri and X. diversicaudatum are the most closely related species from the species examined.

Genetic variation of Hoplolaimus columbus populations in the United States using PCR-RFLP analysis of nuclear rDNA ITS regions.

Hoplolaimus columbus is an important nematode pest which causes economic loss of crops including corn, cotton, and soybean in the Southeastern United States. DNA sequences of the ITS1-5.8S-ITS2 region of ribosomal DNA from H. columbus were aligned and analyzed to characterize intraspecific genetic variation between eleven populations collected from Georgia, Louisiana, North Carolina, and South Carolina. In comparative sequence analysis with clones from either one or two individuals obtained from the eleven populations, we found variability existed among clones from an individual and that clonal diversity observed from within individuals was verified by PCR-RFLP. PCR-RFLP analysis with Rsa I and Msp I restriction enzymes yielded several fragments on 3.0% agarose gel that corresponded to different haplotypes in all populations and the sum of digested products exceeded the length of undigested PCR products, which revealed that ITS heterogeneity existed in a genome of H. columbus. This indicates that heterogeneity may play a role in the evolution of this parthenogenetic species.

Molecular Characterization of a Xiphinema hunaniense Population with Morphometric Data of all Four Juvenile Stages.

A population of Xiphinema hunanienseWang and Wu, 1992 with all four juvenile stages was found in the rhizosphere of Pinus sp. in Hangzhou, Zhejiang, China. Morphometrics of 18 females and 35 juveniles of this population are given herein. Detailed morphology and morphometrics of the four juvenile stages are provided. Further comparisons based on morphometrics of the population with previous studies of the females and the first-stage juveniles of X. hunaniense with X. radicicola are given, and morphological variation in X. hunaniense populations are discussed. A revised polytomous key code of Loof and Luc (1990) for X. hunaniense identification is provided, i.e., A1- B4- C4- D4/5- E1- F2(3)- G2- H2-I3- J4- K2- L1. In addition, the sequence of the D2 and D3 expansion region of the 28S rRNA gene was analyzed and compared with sequences of closely related species downloaded from the NCBI database. Cluster analysis of sequences confirmed and supported the species identifications.

Morphological Observation on Longidorus crassus Thorne, 1974 (Nematoda: Longidoridae) and Its Intraspecies Variation.

Longidorus crassus is a common species and widely distributed in Arkansas. It was also identified for the first time in samples from Alabama, Iowa, Kansas, Nebraska, South Carolina, Wisconsin, and Canada. It is a parthenogenetic species, but a few males were found and were described herein for the first time. Four developmental juvenile stages were identified. A high degree of intraspecies variation was observed among different populations of this species. Twenty-three populations of L. crassus found in Arkansas were studied for their variability using standard measurements, mean comparison, and coefficient of variation. Most of the Arkansas populations have a smaller body than the paralectotypes. Populations Long-63 and Long-88 are close to the paralectotype population. Two populations, Long-10 and Long-80, are different from each other and all other populations. The majority of morphometric characters of this species do not have a normal distribution pattern as they have a high degree of variability within and between populations. The means of many morphometric characters strikingly differ between populations. Hierarchical cluster analysis based on female morphometric character means including body length, distance from vulva opening to anterior end, head width, odontostyle length, esophagus length, body width, tail length, and anal body width were used to examine the morphometric relationships and create dendrograms for 23 Arkansas populations and the lectotype population.

Morphological and Molecular Characterization of Longidorus americanum n. sp. (Nematoda: Longidoridae), a Needle Nematode Parasitizing Pine in Georgia.

We describe and illustrate a new needle nematode, Longidorus americanum n. sp., associated with patches of severely stunted and chlorotic loblolly pine, (Pinus taeda L.) seedlings in seedbeds at the Flint River Nursery (Byromville, GA). It is characterized by having females with a body length of 5.4-9.0 mm; lip region slightly swollen, anteriorly flattened, giving the anterior end a truncate appearance; long odontostyle (124-165 microm); vulva at 44%-52% of body length; and tail conoid, bluntly rounded to almost hemispherical. Males are rare but present, and in general shorter than females. The new species is morphologically similar to L. biformis, L. paravineacola, L. saginus, and L. tarjani but differs from these species either by the body, odontostyle and total stylet length, or by head and tail shape. Sequence data from the D2-D3 region of the 28S rDNA distinguishes this new species from other Longidorus species. Phylogenetic relationships of Longidorus americanum n. sp. with other longidorids based on analysis of this DNA fragment are presented. Additional information regarding the distribution of this species within the region is required.

Longidorus biformis n. sp. and L. glycines n. sp. (Nematoda: Longidoridae): Two Amphimictic Species from Arkansas.

Two new amphimictic species of Longidorus were found in Arkansas. Longidorus biformis n. sp., found in the rhizosphere of hardwood trees along streams in sandy soil in 14 Arkansas locations, is characterized by its long body (5.42-9.50 mm), wide expanded flattened head end, head width 20.0 to 26.0 microm, odontostyle 96 to 125 microm, guide ring 29 to 38 microm posterior to the anterior end, elongate conoid tail, and c' = 0.9-2.1. Females with 2 to 11 vetromedian supplement-like structures were found in 2 of 14 populations of this new species. Longidorus biformis n. sp. is closest to L. seinhorsti Peneva, Loof &Brown, 1998 and L. closelongatus Stoyanov, 1964. Among North American species it is closest to L. glycines n. sp. A distinguishing feature of L. biformis n. sp. is the presence of supplement-like organs in some females. Longidorus glycines n. sp., found in soybean microplots at the Main Research Station, Fayetteville, Arkansas, is characterized by its long body (6.14-8.31 mm), wide offset flattened head end, head width 20.3 to 23.3 microm, odontostyle 87.3 to 99.5 microm, guide ring 22.3 to 26.4 microm posterior to the anterior end, short conoid tail with rounded terminus, and c' = 0.9-1.4. Longidorus glycines n. sp. is closest to L. lusitanicus Macara, 1985. Among North American species it is close to L. biformis n. sp., L. breviannulatus Norton and Hoffman, 1975, and L. crassus Thorne, 1964. Both new species are believed to have four juvenile stages; the first stage was not found for L. biformis n. sp.

Phylogenetic Relationships and Genetic Variation in Longidorus and Xiphinema Species (Nematoda: Longidoridae) Using ITS1 Sequences of Nuclear Ribosomal DNA.

Genetic analyses using DNA sequences of nuclear ribosomal DNA ITS1 were conducted to determine the extent of genetic variation within and among Longidorus and Xiphinema species. DNA sequences were obtained from samples collected from Arkansas, California and Australia as well as 4 Xiphinema DNA sequences from GenBank. The sequences of the ITS1 region including the 3' end of the 18S rDNA gene and the 5' end of the 5.8S rDNA gene ranged from 1020 bp to 1244 bp for the 9 Longidorus species, and from 870 bp to 1354 bp for the 7 Xiphinema species. Nucleotide frequencies were: A = 25.5%, C = 21.0%, G = 26.4%, and T = 27.1%. Genetic variation between the two genera had a maximum divergence of 38.6% between X. chambersi and L. crassus. Genetic variation among Xiphinema species ranged from 3.8% between X. diversicaudatum and X. bakeri to 29.9% between X. chambersi and X. italiae. Within Longidorus, genetic variation ranged from 8.9% between L. crassus and L. grandis to 32.4% between L. fragilis and L. diadecturus. Intraspecific genetic variation in X. americanum sensu lato ranged from 0.3% to 1.9%, while genetic variation in L. diadecturus had 0.8% and L. biformis ranged from 0.6% to 10.9%. Identical sequences were obtained between the two populations of L. grandis, and between the two populations of X. bakeri. Phylogenetic analyses based on the ITS1 DNA sequence data were conducted on each genus separately using both maximum parsimony and maximum likelihood analysis. Among the Longidorus taxa, 4 subgroups are supported: L. grandis, L. crassus, and L. elongatus are in one cluster; L. biformis and L. paralongicaudatus are in a second cluster; L. fragilis and L. breviannulatus are in a third cluster; and L. diadecturus is in a fourth cluster. Among the Xiphinema taxa, 3 subgroups are supported: X. americanum with X. chambersi, X. bakeri with X. diversicaudatum, and X. italiae and X. vuittenezi forming a sister group with X. index. The relationships observed in this study correspond to previous genera and species defined by morphology.

Cluster analysis of longidorus species (nematoda: longidoridae), a new approach in species identification.

Hierarchical cluster analysis based on female morphometric character means including body length, distance from vulva opening to anterior end, head width, odontostyle length, esophagus length, body width, tail length, and tail width were used to examine the morphometric relationships and create dendrograms for (i) 62 populations belonging to 9 Longidorus species from Arkansas, (ii) 137 published Longidorus species, and (iii) 137 published Longidorus species plus 86 populations of 16 Longidorus species from Arkansas and various other locations by using JMP 4.02 software (SAS Institute, Cary, NC). Cluster analysis dendograms visually illustrated the grouping and morphometric relationships of the species and populations. It provided a computerized statistical approach to assist by helping to identify and distinguish species, by indicating morphometric relationships among species, and by assisting with new species diagnosis. The preliminary species identification can be accomplished by running cluster analysis for unknown species together with the data matrix of known published Longidorus species.

Distribution and Morphology of Longidorus breviannulatus Norton &Hoffman, 1975 and Longidorus fragilis Thorne, 1974 (Nematoda: Longidoridae) from North America.

In a survey of ecotypes for longidorids, primarily from the rhizosphere hardwood trees growing in sandy soil along stream banks, 828 soil samples were collected from 37 Arkansas counties in 1999-2001. Eight populations of Longidorus breviannulatus were identified from the Arkansas survey samples. A total of 19 populations from California, Illinois, Iowa, Kansas, Michigan, Nebraska, New Jersey, New York, and Wisconsin were identified from the collection of the second author. A few males were found in New York and Nebraska populations and are described herein. Seven populations of L. fragilis were identified in the Arkansas survey samples, and one population was found from Indiana. Four juvenile stages of L. fragilis are present, and data are given for them herein.

Stepwise and canonical discriminant analysis of longidorus species (nematoda: longidoridae) from arkansas.

During a 1998-to-2001 survey from Arkansas, nine distinct species of Longidorus were found including five new species. Morphometrics of these nine species were used in a stepwise and canonical discrimination to select a subset of characteristics that best identified each species. Student's t test was applied to compare Longidorus breviannulatus Norton &Hoffman, 1975; L. crassus Thorne, 1974; L. diadecturus Eveleigh &Allen, 1982; L. fragilis Thorne, 1974; L. biformis Ye &Robbins, 2004; L. glycines Ye &Robbins, 2004; L. grandis Ye &Robbins, 2003; L. paralongicaudatus Ye &Robbins, 2003; and L. paravineacola Ye &Robbins, 2003 to examine interspecies variation and test for the most useful morphometric characters in species discrimination. Most of the morphometric characters were useful to differentiate species, but species identification could not be based on a single character because the morphometric character ranges often overlap. Stepwise discriminant analysis indicated that the guide ring position, head width, tail length, body length, odontostyle length, and anal body width were the most important variables. These were used to generate canonical variables in discriminating the species. The first three canonical variables accounted for 95% of the total variance. The scatterplots by the first three canonical variables grouped and separated the Longidorus species from Arkansas. Stepwise and canonical discriminant analyses were useful for examining the groupings and morphometric relationships of the nine Longidorus species.

Longidorus grandis n. sp. and L. paralongicaudatus n. sp. (Nematoda: Longidoridae), Two Parthenogenetic Species from Arkansas.

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 microm, odontostyle 86-100 microm, guide ring 26-35 microm 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 microm), anteriorly flattened and offset head region 13-18 microm wide, odontostyle length 92-127 microm, guide ring 21-30 microm 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.

Longidorus paravineacola n. sp. (Nematoda: Longidoridae), a New Species from Arkansas.

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 microm; odontostyle length 95-114 microm; guide ring 28-37 microm 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.

Host suitability of soybean cultivars and breeding lines to reniform nematode in tests conducted in 2001.

Reproduction of reniform nematode Rotylenchulus reniformis on 139 soybean lines was evaluated in a greenhouse in the summer of 2001. Cultivars and lines (119 total) were new in the Arkansas and Mississippi Soybean Testing Programs, and an additional 20 were submitted by C. Overstreet, Louisiana State Extension Nematologist. A second test of 32 breeding lines and 2 cultivars from the Clemson University soybean breeding program was performed at the same time under the same conditions. Controls were the resistant cultivars Forrest and Hartwig, susceptible Braxton, and fallow infested soil. Five treatment replications were planted in sandy loam soil infested with 1,744 eggs and vermiform reniform nematodes, grown for 10 weeks in 10 cm-diam.- pots. Total reniform nematodes extracted from soil and roots was determined, and a reproductive factor (final population (Pf)/ initial inoculum level (Pi)) was calculated for each genotype. Reproduction on each genotype was compared to the reproduction on the resistant cultivar Forrest (RF), and the log ratio [log(RF + 1) is reported. Cultivars with reproduction not significantly different from Forrest (log ratio) were not suitable hosts, whereas those with greater reproductive indices were considered suitable hosts. These data will be useful in the selection of soybean cultivars to use in rotation with cotton or other susceptible crops to help control the reniform nematode and to select useful breeding lines as parent material for future development of reniform nematode resistant cultivars and lines.

Host suitability in soybean cultivars for the reniform nematode, 2000 tests.

In greenhouse pot experiments during summer 2000, 118 soybean cultivars were tested to determine their suitability as hosts for the reniform nematode, Rotylenchulus reniformis. The cultivars included 115 new entries into the Arkansas and Mississippi soybean variety testing programs and three entries submitted by an extension nematologist from Texas. Also included in the tests were the R. reniformis-resistant cultivars Forrest and Hartwig, the susceptible cultivar Braxton, and fallow R. reniformis-infested soil that served as controls. Total number of eggs and nematodes extracted from both the soil and roots from each pot and reproductive indices (Pf/Pi) were calculated for each cultivar. The ratio of the Pf/Pi of each cultivar to the Pf/Pi of Forrest (RF), and the log ratio[log(10) (RF + 1)], are reported. Cultivars with reproductive indices that were greater than the reproductive index on Forrest were considered to be suitable hosts for R. reniformis. These data will be useful in the selection of soybean cultivars to use in rotation with cotton or other susceptible crops to help control the reniform nematode.