A Multiplex Real-Time PCR Assay Differentiates Four Xanthomonas Species Associated with Bacterial Spot of Tomato

Bacterial spot of tomato, a major problem in many tomato production areas, is caused by Xanthomonas euvesicatoria, X. vesicatoria, X. perforans, and X. gardneri. In order to detect and identify the bacterial spot pathogens, we evaluated a region of hrpB operon as a source for primers and probes for real-time polymerase chain reaction (PCR). A 420-bp fragment of the hrpB7 gene was amplified by PCR from 75 strains representing the four species. The PCR products were sequenced and phylogenetic analysis revealed that hrpB7 is highly conserved within each species, with a single-nucleotide polymorphism (SNP) among the X. vesicatoria strains. X. euvesicatoria and X. perforans varied by two SNP. Four probes and two primer sets were designed to target the four bacterial spot pathogens based on their hrpB7 gene sequences. In order to simultaneously detect the four bacterial spot pathogens, the four probes and two primer sets were optimized for a multiplex real-time TaqMan PCR assay. The optimized multiplex assay was determined to be highly specific to the four bacterial spot pathogens. Because the optimized multiplex assay facilitated the identification of each bacterial spot pathogen from pure cultures and infected plant tissue, it holds great potential as a diagnostic tool.

Belonolaimus longicaudatus: An Emerging Pathogen of Peanut in Florida

Sting nematode (Belonolaimus longicaudatus) is an economically important ectoparasitic nematode that is highly pathogenic on a wide range of agricultural crops in sandy soils of the southeastern United States. Although this species is commonly found in Florida in hardwood forests and as a soilborne pathogen on turfgrasses and numerous agronomic and horticultural crops, it has not been reported infecting peanut. In the summers of 2012 and 2013, sting nematode was found infecting three different peanut cultivars being grown on two separate peanut farms in Levy County, FL. The damage consisted of large irregular patches of stunted, chlorotic plants at both farms. The root systems were severely abbreviated and there were numerous punctate-like isolated lesions observed on pegs and pods of infected plants. Sting nematodes were extracted from soil collected around the roots of diseased peanut over the course of the peanut season at both farm sites. Peanut yield from one of these nematode-infested sites was 64% less than that observed in areas free from sting nematodes. The morphological characters of the nematode populations in these fields were congruous with those of the original and other published descriptions of B. longicaudatus. Moreover, the molecular analyses based on the sequences of D2/D3 expansion fragments of 28S rRNA and internal transcribed spacer (ITS) rRNA genes from the nematodes further collaborates the identification of the sting nematode isolates as B. longicaudatus. The sequences were deposited in GenBank (accession no. KF963097, KF963098 for ITS, and KF96399, KF963100 for D2-D3). The results of the phylogenetic analysis using the sequences of these isolates from peanut compared with those of other isolates from Florida suggests that the sting nematode from both peanut farms are genetically close to B. longicaudatus populations occurring in the state. Peanut plants inoculated with both nematode isolates showed punctate-like isolated lesions on pods and pegs, and an abbreviation of their root systems, whereas those symptoms were not observed on noninoculated peanut plants. To our knowledge, this is the first report of large-scale field damage caused by sting nematode infecting peanut grown under field conditions in Florida.

Molecular Detection of the Laurel Wilt Fungus, Raffaelea lauricola

The laurel wilt disease fungus, Raffaelea lauricola, is killing redbay trees, spreading rapidly in the U.S. southeastern coastal plain forest, and posing a serious threat to the avocado industry in Florida. A molecular tool is urgently required to facilitate detection of this pathogen. The 5' region of the large ribosomal RNA (28S) gene is highly variable among Raffaelea spp. and ideal for this purpose but amplification of this sequence from R. lauricola has been difficult. Different amplification conditions were tested and a high-fidelity polymerase chain reaction (PCR) procedure utilizing a dNTP mix containing 7-deaza-dGTP was found to reliably amplify 28S sequences from R. lauricola. Sequencing the amplified products or cloned inserts also turned out to be difficult and required using a custom-blended sequencing mix containing 1 M betaine, 5% dimethyl sulfoxide, and dGTP-BigDye v3.1. Three GC-rich stem and loop or cruciform secondary structures were discovered, which may have interfered with amplification. This improved protocol made it possible to partially characterize the internal transcribed spacers sequence from R. lauricola, which also has interfering secondary structures. A TaqMan real-time PCR assay was designed using the species-specific 28S sequences and this allowed detection of R. lauricola from wood tissues or cultures. Wood tissues from symptomatic redbay, avocado, and sassafras trees in Florida were screened using this TaqMan assay and several were found to test positive for R. lauricola. Results were further confirmed by performing Koch's postulates for avocado specimens collected from commercial grooves.

Transcriptome sequencing and annotation of the predatory mite Metaseiulus occidentalis (Acari: Phytoseiidae): a cautionary tale about possible contamination by prey sequences

Next-generation sequencing was applied to the transcriptome of the phytoseiid Metaseiulus occidentalis to characterize gene expression in all life stages reared under different conditions to optimize the recovery of as many genes as possible. One production and one titration run produced a total of 862,069 reads (average size: 314.87 bp), which generated 255.6 Mbp of sequences on the GS-FLX Titanium sequencing platform. After removal of putative prey sequences 850,543 reads were used in NewBler and PTA assemblies to produce 74,172 non-redundant sequences, including 30,691 contigs and 43,481 singlets with 11,994 contigs consisting of more than 500 bp and 37,278 sequences >300 bp, constituting 48.7 % of all sequences. There were 25,888 hits with the NCBI non-redundant database and 15,376 unique transcripts. There were 26,225 hits with the Ixodes scapularis genome and 6,634 unique transcripts. There were 22,225 hits with the RefSeq of Homo sapiens with 6,465 unique transcripts, and 23,656 hits with the RefSeq of Drosophila melanogaster with 9,216 unique transcripts. Selected ESTs corresponding to genes of interest were analyzed including those related to transposable elements, GPCRs, Sox transcription factors, diapause and foraging behavior, and pesticide resistances. Novel and important genes appear to have been discovered that provide insight into the evolution, biology, and physiology of this important predator of pest mites in agriculture and will be useful in analyzing complete genome sequences of this natural enemy.

First Report of Guignardia citricarpa Associated with Citrus Black Spot on Sweet Orange (Citrus sinensis) in North America

In March 2010, citrus black spot symptoms were observed on sweet orange trees in a grove near Immokalee, FL. Symptoms observed on fruit included hard spot, cracked spot, and early virulent spot. Hard spot lesions were up to 5 mm, depressed with a chocolate margin and a necrotic, tan center, often with black pycnidia (140 to 200 μm) present. Cracked spot lesions were large (15 mm), dark brown, with diffuse margins and raised cracks. In some cases, hard spots formed in the center of lesions. Early virulent spot lesions were small (up to 7 mm long), bright red, irregular, indented, and often with many pycnidia. In addition, small (2 to 3 mm), elliptical, reddish brown leaf lesions with depressed tan centers were observed on some trees with symptomatic fruit. Chlorotic halos appeared as they aged. Most leaves had single lesions, occasionally up to four per leaf. Tissue pieces from hard spots and early virulent spots were placed aseptically on potato dextrose agar (PDA), oatmeal agar, or carrot agar and incubated with 12 h of light and dark at 24°C. Cultures that grew colonies within a week were discarded. Fourteen single-spore cultures were obtained from the isolates that grew slower than the Guignardia mangiferae reference cultures, although pycnidia formed more rapidly in the G. mangiferae cultures (1). No sexual structures were observed. Cultures on half-PDA were black and cordlike with irregular margins with numerous pycnidia, often bearing white cirrhi after 14 days. Conidia (7.1 to 7.8 × 10.3 to 11.8 μm) were hyaline, aseptate, multiguttulate, ovoid with a flattened base surrounded by a hyaline matrix (0.4 to 0.6 μm) and a hyaline appendage on the rounded apex, corresponding to published descriptions of G. citricarpa (anomorph Phyllosticta citricarpa) (1). A yellow pigment was seen in oatmeal agar surrounding G. citricarpa, but not G. mangiferae colonies as previously reported (1,2). DNA was extracted from lesions and cultures and amplified with species-specific primers (2). DNA was also extracted from G. mangiferae and healthy citrus fruit. The G. citricarpa-specific primers produced a 300-bp band from fruit lesions and pure cultures. G. mangiferae-specific primers produced 290-bp bands with DNA from G. mangiferae cultures. The internally transcribed spacer (ITS) of the rRNA gene, translation-elongation factor (TEF), and actin gene regions were sequenced from G. citricarpa isolates and deposited in GenBank. These sequences had 100% homology with G. citricarpa ITS sequences from South Africa and Brazil, 100% homology with TEF, and 99% homology with actin of a Brazilian isolate. Pathogenicity tests with G. citricarpa were not done because the organism infects immature fruit and has an incubation period of at least 6 months (3). In addition, quarantine restrictions limit work with the organism outside a contained facility. To our knowledge, this is the first report of black spot in North America. The initial infested area was ~57 km². The disease is of great importance to the Florida citrus industry because it causes serious blemishes and significant yield reduction, especially on the most commonly grown 'Valencia' sweet orange. Also, the presence of the disease in Florida may affect market access because G. citricarpa is considered a quarantine pathogen by the United States and internationally. References: (1) R. P. Baayen et al. Phytopathology 92:464, 2002. (2) N. A. Peres et al. Plant Dis. 91:525, 2007 (3) R. F. Reis et al. Fitopath Bras. 31:29, 2006.

First Report of a 16SrIV-D Phytoplasma Associated with Texas Phoenix Palm Decline on Pigmy Date Palm (Phoenix roebelenii) in Florida

The pigmy date palm (Phoenix roebelenii O'Brien) is used as an ornamental in Florida and is popular and lucrative within the nursery trade. Severe decline of several pigmy date palms was observed at a residence in Hillsborough County, FL. Several other palm species, including P. canariensis (Canary Island date palm), P. sylvestris (wild date palm), P. dactylifera (date palm), Syagrus romanzoffiana (queen palm), and Sabal palmetto (cabbage palm), in Florida are known to be affected by Texas Phoenix palm decline (TPPD), a disease associated with a phytoplasma subgroup strain 16SrIV-D (2,3). Moreover, the location of the affected pigmy date palms was in the proximity of many other diseased cabbage palms that were identified in previous surveys and subsequently rogued. Genomic DNA was extracted from 100 mg of ground-up palm trunk tissues containing phloem cells with a DNeasy Plant Mini kit column (QIAGEN Inc., Valencia, CA) from four specimens. A high-fidelity PCR (Hf-PCR) procedure was used in preference to standard PCR because it was 10,000 to 100,000 times more sensitive (1,4). The Hf-PCR (50 μl) utilized two DNA polymerases; Taq (five units) and ACCUZYME (one unit), 350 μM dNTP, a buffer (50 mM Tris pH 9.2, 16 mM ammonium sulfate, and 1.75 mM magnesium chloride), a higher concentration of primers (200 pM) (2,3), and palm DNA templates (>10 ng) or no DNA negative control. Hf-PCR was performed using three linked profiles: (i) 94°C (2 min) (1 cycle); (ii) 94°C (10 s), 50°C (30 s) for P1m/P7 or 57°C for LY16Sf/LY16Sr and 68°C (2 min) (10 cycles); and (iii) 94°C (10 s), 50°C (30 s) for P1m/P7 or 57°C for LY16Sf/LY16Sr and 68°C (2 min plus 20 s added for every consecutive cycle) (20 cycles) (1). The genomic DNA extracted from P. roebelenii specimens was used as template for amplification by Hf-PCR. Expected 1.8- and 1.4-kb DNA bands for each primer combination were readily amplified. The Hf-PCR products were sequenced (GenBank Accession No. JF791816) and a BLAST search revealed a 100% similarity with a phytoplasma subgroup strain 16SrIV-D (EF042899 and AF434989), which is known to cause severe palm decline (TPPD) in other hosts (2,3). To our knowledge, this is the first report of TPPD from P. roebelenii, and therefore, expands the host range of this pathogen. In areas where TPPD is present, the landscape industry may need to identify alternative nonhost palm species or resistant varieties for disease management. References: (1) W. M. Barnes. Proc. Natl. Acad. Sci. USA 91:2216, 1994. (2) N. A. Harrison et al. Plant Dis. 86:676, 2002. (3) N. A. Harrison et al. Ann. Appl. Biol. 153:85, 2008. (4) A. Jeyaprakash and M. A. Hoy. Insect Mol. Biol. 9:393, 2000.

Symbionts, including pathogens, of the predatory mite Metaseiulus occidentalis: current and future analysis methods

Metaseiulus (= Typhlodromus or Galendromus) occidentalis (Nesbitt) (Acari: Phytoseiidae) is an effective natural enemy of pest mites in a variety of crops around the world, although it is considered to be endemic in the western USA. A broad understanding of much of its biology, ecology, behavior, and genetics has been obtained over the past 60 years, but the role(s) symbionts play, which includes pathogens and other microorganisms, remains to be resolved fully. Until molecular tools became available, analysis methods were limited primarily to microscopic observations; some viruses and rickettsia-like organisms were observed infecting 'diseased' M. occidentalis, but it is not clear which one(s) was the causal agent(s) of the disease(s). Subsequent to the development of the polymerase chain reaction (PCR) and genome sequencing, we identified putative gut symbionts and reproductive tract symbionts in M. occidentalis, as well as a microsporidian pathogen. A new phylogenetic analysis of the Bacteroidetes-Flavobacterium group suggests the unnamed Bacteroidetes in M. occidentalis is associated with the digestive tract. However, much of our current information about the role these microorganisms play in the biology of M. occidentalis is based on correlation, lacking the strength of fulfilling Koch's postulates. We also currently lack any knowledge of the importance of these microorganisms under field conditions. In the future, it should be possible to learn what role(s) these organisms play in the biology of this important predator using metagenomics approaches to analyze the transcriptome and to determine their relative abundance within their hosts with the quantitative PCR. We have just begun to resolve these relationships.

Morphological and molecular characterization of a new microsporidian species from the predatory mite Metaseiulus occidentalis (Nesbitt) (Acari, Phytoseiidae)

A new microsporidian species is described from the predatory mite Metaseiulus (formerly Typhlodromus or Galendromus) occidentalis (Nesbitt) (Acari, Phytoseiidae). The ultrastructure of this new species is presented together with the first molecular characterization for a microsporidium of mites. All stages of this new microsporidium are haplokaryotic and develop in direct contact with the host-cell cytoplasm. Sporogony is disporoblastic and spores are formed in eggs, immature stages, and adults of M. occidentalis. There are two morphological classes of spores, one with a short polar filament (3-5 coils) that measured 2.53 x 1.68 microm and one with a longer polar filament (8-9 coils) that measured 3.14 x 1.77 microm. Horizontal transmission of this new species occurs by cannibalism of eggs and other stages and perhaps involves the spores with the long polar filament. Spores with the short polar filament may play a role in autoinfection and vertical (transovarial) transmission that is highly efficient in transferring the microsporidium from adults to progeny. Analysis of the small subunit ribosomal DNA indicated that this species from M. occidentalis is most closely related to the Nosema/Vairimorpha clade of microsporidia. A conflict between the morphological and molecular data is discussed. The species is compared to previously described microsporidia of arachnids resulting in creation of Oligosporidium occidentalis n. sp. in the family Unikaryonidae.

Long PCR improves Wolbachia DNA amplification: wsp sequences found in 76% of sixty-three arthropod species

Bacteria belonging to the genus Wolbachia are associated with a variety of reproductive anomalies in arthropods. Allele-specific polymerase chain reaction (= Standard PCR) routinely has been used to amplify Wolbachia DNA from arthropods. While testing the two-spotted spider mite Tetranychus urticae and other arthropods known to be infected with Wolbachia, Standard PCR frequently produced false negatives, perhaps because the DNA from the arthropod host interfered with amplification by Taq DNA polymerase. Long PCR, which uses two enzymes (Taq and Pwo), consistently amplified Wolbachia DNA and a sensitivity analysis indicated that Long PCR was approximately six orders of magnitude more sensitive than Standard PCR in amplifying plasmid DNA spiked into insect genomic DNA. A survey indicated that 76% of sixty-two arthropod species and two subspecies in thirteen orders tested positive for the Wolbachia wsp sequence by Long PCR, which is considerably higher than the rate of 16.9% obtained previously for the ftsZ sequence using Standard PCR (Werren, J.H., Windsor, D. and Gao, L. (1995a) Proc R Soc Lond B 262: 197-204). A subsample of Long PCR products from fourteen arthropod species and two subspecies were sequenced, both directly and after cloning. Two A- and eleven B-Wolbachia strains were detected and their wsp sequences displayed a maximum of 23.7% sequence divergence at this locus. Two new groups (named Fus and Ten) were identified in addition to nineteen reported earlier (Zhou, W., Rousset, F. and O'Neill, S.L. (1998) Proc R Soc Lond B 265: 1-7; van Meer, M.M.M., Witteveldt, J. and Stouthamer, R. (1999) Insect Mol Biol 8: 399-408), because they displayed more than 2.5% sequence divergence from other Wolbachia wsp sequences. PCR products from seventeen of twenty-nine (59%) arthropod species analysed could not be sequenced directly due to apparent infection by multiple Wolbachia strains. The wsp sequences cloned from two such species (Plutella xylostella and Trichoplusia ni) indicated both A- and B-Wolbachia were present in a single individual. Hence, superinfection also may be more widespread than the 1.2% incidence previously estimated.

Saccharomyces cerevisiae pms2 mutations are alleles of MLH1, and pms2-2 corresponds to a hereditary nonpolyposis colorectal carcinoma-causing missense mutation

A number of mutant Saccharomyces cerevisiae strains having phenotypes consistent with defects in DNA mismatch repair have been described, but not all have been extensively characterized. In this study we demonstrate that the pms2-1 and pms2-2 alleles arise from missense mutations in the MLH1 gene which inactivate MLH1. One of these alleles, pms2-2, causes the same amino acid substitution in a highly conserved region of the known MutL homologs as that caused by a proposed missense mutation observed in a Swedish hereditary nonpolyposis colorectal carcinoma kindred. This observation supports the functional significance of missense mutations found in hereditary nonpolyposis colorectal carcinoma kindreds and indicates that in some cases S. cerevisiae can serve as a useful model system for the analysis of such mutations.

An ankyrin-related gene (unc-44) is necessary for proper axonal guidance in Caenorhabditis elegans

Caenorhabditis elegans unc-44 mutations result in aberrant axon guidance and fasciculation with inappropriate partners. The unc-44 gene was cloned by transposon tagging, and verified by genetic and molecular analyses of six transposon-induced alleles and their revertants. Nucleotide sequence analyses demonstrated that unc-44 encodes a series of putative ankyrin-related proteins, including AO49 ankyrin (1815 aa, 198.8 kD), AO66 ankyrin (1867 aa, 204 kD), and AO13 ankyrin (< or = 4700 aa, < or = 517 kD). In addition to the major set of approximately 6 kb alternatively spliced transcripts, minor transcripts were observed at approximately 3, 5, 7, and 14 kb. Evidence is provided that mutations in the approximately 14-kb AO13 ankyrin transcript are responsible for the neuronal defects. These molecular studies provide the first evidence that ankyrin-related molecules are required for axonal guidance.

Complete sequence of a mariner transposable element from the predatory mite Metaseiulus occidentalis isolated by an inverse PCR approach

Degenerate primers designed and synthesized based on two conserved regions of the mariner transposase open reading frame were used to amplify a 454 bp DNA fragment from M. occidentalis. Two inverse primers were then synthesized and used to amplify flanking genomic DNA fragments from M. occidentalis by a ligation-mediated inverse PCR. The complete mariner element (Moc1) was 1284 bp long, including the imperfect 28 bp inverted terminal repeat sequences, and shared 59% similarity to an active 1286 bp long D. mauritiana mariner element (Mos1). Insertions, deletions and substitutions were observed in the Moc1 sequence at several positions. No intact open reading frame was detected and the Moc1 element is considered inactive. Stringent Southern blot hybridizations revealed at least twelve copies of mariner sequences similar to Moc1 in the colonies tested.

Mutagenesis of yeast MW104-1B strain has identified the uncharacterized PMS6 DNA mismatch repair gene locus and additional alleles of existing PMS1, PMS2 and MSH2 genes

The haploid yeast Saccharomyces cerevisiae MW104-1B strain was disomic for chromosome III (n + 1) and carried DNA mismatches at three different heteroallelic loci; leu2 (leu2-1/leu2-27), thr4 (thr4-1/thr4-16) and his4 (his4-4/his4-519) (Williamson, 1984). We mutagenized the MW104-1B strain and identified seven mutant isolates that display elevated mitotic/meiotic prototrophs due to mismatch repair failures at heteroallelic loci. Three mutants (pms1, pms2 and pms3) isolated earlier from MW104-1B were shown to correct in vitro constructed plasmids with defined DNA mismatches (G/T, A/C, G/G, etc.) poorly (Kramer et al., 1989a). Complementation tests were performed by crossing all seven new mutant isolates to pms1 and pms2 mutants and assaying for mutant phenotype in the diploids. Four mutant isolates failed to complement the two known pms alleles (pms1-1 and pms2-1). Two other mutant isolates complemented the pms1-1 and pms2-1 alleles, but failed to complement each other and were named as the pms5-1 allele of an uncharacterized gene (PMS5). One other mutant isolate complemented the pms1-1, pms2-1 and pms5-1 alleles and was named as the pms6-1 allele of another uncharacterized gene (PMS6). Subsequently, the pms5-1 mutant allele was shown to be complemented by a plasmid borne yeast MSH2 gene, implying that it is an allele of MSH2 (PMS5). The human homologs (hMSH2 and hMLH1) of two yeast DNA mismatch repair genes (MSH2 and MLH1) have been cloned recently and shown to be responsible for hereditary nonpolypnosis colon cancer (HNPCC) (Fishel et al., 1993; Leach et al., 1993; Bronner et al., 1994; Papadopoulos et al., 1994).

Multicopy CUP1 plasmids enhance cadmium and copper resistance levels in yeast

A 3.3 kb fragment of yeast genomic DNA was isolated by screening a genomic library constructed in the high copy number 2 micron plasmid YEp351 vector for clones capable of enhancing the degree of resistance of Saccharomyces cerevisiae strain MW3070-8B to cadmium. The insert contained two complete copies of the CUP1 gene open reading frame (183 bp), including the upstream promoter sequences (450 bp) with two conserved metal responsive cis-acting elements. Northern analysis showed that addition of cadmium (0.02 microM) or copper (50 microM) to overnight liquid cultures of yeast induced expression of CUP1 transcripts from both chromosomal and plasmid-borne gene copies. The cloned 3.3 kb DNA in a high copy number plasmid restored copper resistance to the sensitive strain LS70-3B delta, deleted for the CUP1 gene (cup 1 delta), but failed to restore cadmium resistance. Thus, CUP1 gene expression in yeast appears to be influenced differently by cadmium and copper ions. Resistance to heavy metal poisoning resulted from enhanced gene product levels attributable to amplification of the CUP1 gene as well as to increased transcriptions. Two distinct gene product levels mediate cadmium and copper resistance; a higher gene product level was required to confer cadmium resistance.

The C. elegans unc-104 gene encodes a putative kinesin heavy chain-like protein

Mutations in the unc-104 gene of the nematode C. elegans result in uncoordinated and slow movement. Transposon insertions in three unc-104 alleles (e2184, rh1016, and rh1017) were used as physical markers to clone the unc-104 gene. DNA sequence analysis of unc-104 cDNAs revealed an open reading frame capable of encoding a 1584 amino acid protein with similarities to kinesin heavy chain. The similarities are greatest in the amino-terminal ATPase and microtubule-binding domains. Although the primary sequence relatedness to kinesin is weak in the remainder of the molecule, the predicted secondary structure and regional isoelectric points are similar to kinesin heavy chain.

Control of Root-knot Nematodes on Tomato by Lectins

Significant control of tomato root knot was achieved by applications of the lectins Concanavalin A (Con A) and Limax flavus agglutinin in greenhouse, growth chamber, and microplot trials. Four consecutive weekly applications at lower concentrations of Con A yielded better control than single applications at a higher total concentration. The present state of knowledge on binding of Con A to soil nematodes and the in vitro effect of this lectin in chemotactic behavior are discussed. The mode of action of Con A on root-knot control is unknown.

Fluorescent and Ferritin Labelling of Cuticle Surface Carbohydrates of Caenorhabditis elegans and Panagrellus redivivus

Caenorhabditis elegans and Panagrellus redivivus were investigated for surface carbohydrates using fluorescent-labelled and ferritin-labelled lectins. Rhodamine-labelled Concanavalin A was specifically located in the cephalic region of both species. Rhodamine-labelled wheat germ agglutinin was located over the entire cuticle of P. redivivus but was absent on C. elegans. Rhodamine-labelled peanut agglutinin and Limax flavus agglutinin did not label nematodes of either species. Galactose and sialic acid were not detected on either species, whereas mannose-glucose residues were specifically localized in the head areas of both species. No detectable N-acetylglucosamine occurred on C. elegans, but it was evenly distributed over the cuticle surface of P. redivivus.

Caenorhabditis elegans: comparisons of chemotactic behavior from monoxenic and axenic culture

Significant differences in chemotactic response of Caenorhabditis elegans were demonstrated for nematodes from monoxenic culture as compared to nematodes from axenic culture. These results support those of a previous study in which large differences in growth, development, behavior, and longevity were shown for C. elegans in comparative assays of the monoxenic and axenic regimes.

Control of Root-Knot Nematodes on Tomato by the Endoparasitic Fungus Meria coniospora

The endoparasitic nematophagous fungus Meria coniospora reduced root-knot nematode galling on tomatoes in greenhouse pot trials. The fungus was introduced to pots by addition of conidia at several inoculum levels directly to the soil or addition of nematodes infected with M. coniospora to the soil; both methods reduced root galling by root-knot nematodes. These studies represent a part of a recently initiated effort to evaluate the potential of endoparasitic nematophagous fungi for biocontrol of nematodes.

Differential Adhesion and Infection of Nematodes by the Endoparasitic Fungus Meria coniospora ( Deuteromycetes )

The conidia of the endoparasitic fungus Meria coniospora ( Deuteromycetes ) had different patterns of adhesion to the cuticles of the several nematode species tested; adhesion in some species was only to the head and tail regions, on others over the entire cuticle, whereas on others there was a complete lack of adhesion. After adhesion, the fungus usually infected the nematode. However, adhesion to third-stage larvae of five animal parasitic nematodes, all of which carry the cast cuticle from the previous molt, did not result in infection. M. coniospora infected animal parasitic nematodes when this protective sheath was removed. Seven preparations of sialic acid ( N -acetylneuraminic acid) gave three types of response in adhesion-infection of nematodes: (i) a significant reduction in conidial adhesions; (ii) no interference with adhesion, but a 10-day delay in infection; and (iii) a delay in infection by 2 to 3 days. The current results support previous findings indicating involvement of sialic acids localized on nematode cuticles in recognition of prey by M. coniospora.

Caenorhabditis elegans: lectin-mediated modification of chemotaxis

Binding of the lectins concanavalin A (Con A) and limulin to Caenorhabditis elegans wild type resulted in consistent, reproducible, partial inhibition of chemoattraction to sterile filtrates of Escherichia coli. Normal chemotaxis resumed within 8 hr following treatment with these lectins. Competitive displacement of Con A or limulin by flooding with the specific sugars resulted in rapid resumption of normal chemotactic behavior. The experimental protocol for Con A applied to three age groups (newly hatched larvae, young adults, and old adults) showed the same response for all groups tested. Two mutant C. elegans with morphological defects in the cephalic chemosensilla showed the same inhibition of chemotactic response after exposure to Con A, and rapidly resumed normal behavior after competitive displacement of the lectin. Limulin and Con A did not affect nematode growth, development, or longevity, demonstrating that the observed results were not attributable to toxic effects. These results and other experimental evidence support the premise that behavioral modification was caused by functional impairments caused by Con A and limulin to chemoreceptors located on sensory dendrites of the cephalic sensilla.

Caenorhabditis elegans and Panagrellus redivivus: enzyme-mediated modification of chemotaxis

Treatment with mannosidase or sialidase completely inhibited chemotactic responses of Caenorhabditis elegans wild type, C. elegans mutants CB1377 (daf-6)X and CB1379 (che-3)I, and Panagrellus redivivus to a source of attractants. Trypsin (EC3.4.21.4) caused a partial reduction in the level of chemoresponse. Normal chemotaxis was renewed within 20 hr following exposure to the enzymes. Other enzymes tested had no effect. Experimental and supporting evidence is presented that behavioral modification resulted from functional impairments to receptors located within chemosensory sensilla.