The incidence of Meloidogyne incognita and Rotylenchulus reniformis on cotton was determined in 1989-92 from 1,089 soil samples collected from 31 counties that account for nearly 60% of the 2.2 million hectares planted to cotton in Texas. Meloidogyne incognita was commonly found in the Southern High Plains and Brazos River Valley regions of Texas (57% and 34%, respectively, of samples) but was found in less than 8% of samples from the Central Blacklands, Coastal Bend, Low Plains, or the Upper Gulf Coast regions. Rotylenchulus reniformis was widely distributed in the Brazos River Valley (24% of samples) and found occasionally in the Upper Gulf Coast (8% of samples). Meloidogyne incognita was found only rarely in soils with greater than 40% clay content, whereas Rotylenchulus reniformis was frequently found in finely textured soils but was less common in soils with greater than 40% sand content. In samples infested with M. incognita or R. reniformis, population densities of these species were at least 10-fold greater than population densities of other plant-parasitic species present in the sample. Root-knot and reniform nematodes were not found together in high population densities (>100 individuals/500 cm³) in the same sample.
cotton; Gossypium hirsutum; incidence; Meloidogyne incognita; nematode; reniform nematode; root-knot nematode; Rotylenchulus reniformis; soil texture; survey
Fields in a concentrated area of soybean production in South Carolina were chosen for soil sampling to determine the distribution of plant-parasitic nematodes. Five hundred sampling sites were distributed over 19 counties according to county soybean acreage. Helicotylenchus and Scutellonema were identified most frequently from soil samples; together, these genera occurred in over 70% of the samples. Pratylenchus and Paratrichodorus were each observed in more than 60% of fields. Meloidogyne spp. were found in 27% of the fields and Hoplolaimus columbus in 14%. Rotylenchulus reniformis and Belonolaimus sp. each occurred in less than 10% of the fields. Tylenchorhynchus and Mesocriconema (Criconemella) were each present in over 40% of the fields, but numbers from each field were low. Of the fields sampled, 14% contained Heterodera glycines. Of these, 47% were race 14 and 32% were race 3. Races 9, 6, and 10 were also observed.
Belonolaimus; Criconemella; Glycine max; Helicotylenchus; Heterodera glycines; Hoplolaimus columbus; Meloidogyne; Mesocriconema; nematode; Paratrichodorus; Pratylenchus; race; Rotylenchulus reniformis; sampling; Scutellonema; soybean; survey; threshold; Tylenchorhynchus
Various crops were tested in greenhouse and field trials for their potential utility in the rotation sequence in the potato cropping system in Meloidogyne chitwoodi-infested soils of the Klamath Basin in northeastern California and southern Oregon. Two Solarium accessions from the International Potato Center in Peru were potential sources of resistance to M. chitwoodi. Cultivars of barley, oat, rye, wheat, and white lupine were maintenance hosts, supporting the nematode population at its current level without substantial increase or decline. Poor to nonhosts to race 1 of the nematode included cultivars of alfalfa, amaranth, oilseed radish, oilseed rape, and safflower. These crops have potential for inclusion in the cropping system but are subject to various constraints, including frost sensitivity and availability of markets. Sugarbeet, a new crop in the area, is a maintenance or better host of M. chitwoodi. Potato, tomato, and sunflower are excellent hosts.
alfalfa; amaranth; cereal; maintenance host; Meloidogyne chitwoodi; nematode; nonhost; oilseed radish; oilseed rape; poor host; potato; Pratylenchus neglectus; safflower; sugarbeet; sunflower; tomato
Twenty-three precommercial field corn lines (Zea mays) were screened in the greenhouse and in vitro for the ability to support reproduction of Heterodera zeae. Although H. zeae reproduced on all corn lines, reproduction was only 0.4 to 4.5% on the five least suitable corn lines in greenhouse tests compared with the susceptible check line Pioneer brand 3184. The least suitable experimental line supported an average of 30 cysts plus females after 8 weeks growth, whereas the susceptible check, Pioneer brand 3184, averaged 8,183 cysts plus females per pot. Reproduction of H. zeae in in vitro root cultures of the 23 lines and susceptible check cultivar, Iochief, was too low to be of any value in detecting resistance to this nematode under the conditions of these tests.
corn cyst nematode; corn; greenhouse; Heterodera zeae; in vitro; nematode; reproduction; resistance; Zea mays
Effects of tillage and crop rotation on nematode densities in tropical corn (Zea mays cv. Pioneer X304C) were examined in a factorial experiment with two rotation crops and two tillage practices (no-till vs. conventional-till), conducted in each of three seasons (1990-1992) in north Florida. The rotation treatments consisted of sorghum (Sorghum bicolor cv. DeKalb BR64) or soybean (Glycine max) grown during the 1989 season. Densities of Meloidogyne incognita (race 1) remained lower throughout the growing season in corn following sorghum than in corn plots following soybean. This effect was observed clearly even in the third consecutive corn crop. In 1990, densities of Criconemella spp. were initially higher in plots planted to sorghum the previous year, but by the end of the subsequent corn crop, no differences were evident. Paratrichodorus minor and Pratylenchus spp. (primarily P. scribneri) were mostly unaffected by the crop rotation treatments, but in a few instances, Pratylenchus spp. densities were higher in conventional than in no-till plots. In general, tillage had little effect on densities of most nematodes examined, and rotation appears to be more important than tillage for managing plant-parasitic nematodes under these conditions.
corn; Criconemella spp.; crop rotation; cropping systems; cultural practices; Glycine max; Meloidogyne incognita; nematode; Paratrichodorus minor; Pratylenchus scribneri; sorghum; Sorghum bicolor; soybean; tillage; Zea mays
Nematode-resistant tropical legumes are effective in reducing populations of plant-parasitic nematodes when used in rotation systems. Mixed cropping is a common practice of many small farmers in Central America, but little is known about the effects of tropical legumes on nematode communities under these systems. To examine the effects of intercropping on the nematode fauna associated with squash (Cucurbita pepo) and cucumber (Cucumis sativa) in Honduras, two field experiments were conducted to compare nematode density and diversity in soil under cucurbits grown as a monocrop with that in soil under cucurbits intercropped with alfalfa (Medicago sativa) or hairy indigo (Indigofera hirsuta). A parallel series of field tests compared soil nematode communities associated with a cucurbit monocrop and a cucurbit intercropped with marigold (Tagetes patula), which may decrease nematode populations through the production of toxic root exudates. Among all four tests, over a period of 90 days, there were no consistent differences in densities of various nematode genera or trophic groups in intercropped versus monocropped plants, nor were there consistent differences in community diversities among treatments.
agroecology; cropping system; ecology; intercropping; mixed cropping; nematode; nematode community
Laboratory studies were conducted to evaluate effects of selected herbicides on hatching of free eggs of the soybean cyst nematode, Heterodera glycines. The herbicides used were Atrazine (atrazine), Basagran (bentazon), Bladex (cyanazine), Blazer (acifluorfen), Command (clomazone), Lasso (alachlor), Sonalan (ethalfluralin), and Treflan (trifluralin). Treatments comprised two concentrations of commercial herbicide formulations and deionized water and 3.14 mM zinc sulfate as negative and positive controls, respectively. Eggs were extracted from females and cysts, surface disinfested, and incubated in herbicide or control solutions at 25 ± 2 C in darkness. Hatched second-stage juveniles were counted every other day for 24 days. Hatching of H. glycines eggs in 50 and 500 μg/ml Blazer was 42 to 67% less than that in deionized water and 6l to 78% less than that in zinc sulfate solution. Zinc sulfate significantly increased hatching activity in 50 μg/ml but not 500 μg/ml Blazer. The other herbicides tested at various concentrations had no significant effect on egg hatching. The specific component of Blazer inhibiting egg hatching is unknown. Suppression of hatching by Blazer indicates that this postemergence soybean herbicide may have a potential role in managing H. glycines.
acifluorfen; alachlor; atrazine; bentazon; clomazone; cyauazine; ethalfluralin; Glycine max; hatching; herbicide; Heterodera glycines; nematode; soybean cyst nematode; trifluralin
The development of Bursaphelenchus xylophilus in pine wood infested with and free of Monochamus carolinensis was investigated. Formation of third-stage dispersal juveniles occurred in the presence and absence of pine sawyer beetles. The proportion of third-stage dispersal juveniles in the total nematode population was negatively correlated with moisture content of the wood. Formation of nematode dauer juveniles was dependent on the presence of the pine sawyer beetle. Dauer juveniles were present in 3 of 315 wood samples taken from non-beetle-infested Scots pine bolts and 81 of 311 samples taken from beetle-infested bolts. Nematode densities were greater in wood samples taken adjacent to insect larvae, pupae, and teneral adults compared with samples taken from areas void of insect activity. Nematodes recovered from beetle larvae, pupae, and teneral adults were mostly fourth-stage dauer juveniles, although some third-stage dispersal juveniles were also recovered. Dauer juvenile density was highest on teneral adult beetles.
Bursaphelenchus xylophilus; dauerjuvenile; Monochamus carolinensis; nematode; pine sawyer; pinewood nematode
Chitinases are enzymes that hydrolyze the N-acetylglucosamine polymer chitin, and they occur in diverse plant tissues over a broad range of crop and noncrop species. The enzymes may be expressed constitutively at low levels but are dramatically enhanced by numerous abiotic agents (ethylene, salicylic acid, salt solutions, ozone, UV light) and by biotic factors (fungi, bacteria, viruses, viroids, fungal cell wall components, and oligosaccharides). Different classes of plant chitinases are distinguishable by molecular, biochemical, and physicochemical criteria. Thus, plant chitinases may differ in substrate-binding characteristics, localization within the cell, and specific activities. Because chitin is a structural component of the cell wall of many phytopathogenic fungi, extensive research has been conducted to determine whether plant chitinases have a role in defense against fungal diseases. Plant chitinases have different degrees of antifungal activity to several fungi in vitro. In vivo, although rapid accumulation and high levels of chitinases (together with numerous other pathogenesis-related proteins) occur in resistant tissues expressing a hypersensitive reaction, high levels also can occur in susceptible tissues. Expression of cloned chitinase genes in transgenic plants has provided further evidence for their role in plant defense. The level of protection observed in these plants is variable and may be influenced by the specific activity of the enzyme, its localization and concentration within the cell, the characteristics of the fungal pathogen, and the nature of the host-pathogen interaction. The expression of chitinase in combination with one or several different antifungal proteins should have a greater effect on reducing disease development, given the complexities of fungal-plant cell interactions and resistance responses in plants. The effects of plant chitinases on nematode development in vitro and in vivo are worthy of investigation.
antifungal protein; biotechnology; chitinase; disease resistance; enzyme; fungus; genetic engineering; hydrolase; nematode
The reproduction of isolates of five plant-parasitic nematode species on the winter rapeseed cultivars Bridger, Gorzanski, H-47, Lindora, and Viking was evaluated. Each cultivar was a good host for Helicotylenchus pseudorobustus, Meloidogyne hapla, and M. incognita, All rapeseed cultivars were poor hosts for Pratylenchus scribneri, in comparison with a susceptible reference host. Heterodera glycines females rarely developed on any cultivar, but low numbers of juveniles invaded roots and males occasionally reached maturity.
Brassica napus; canola; Helicotylenchus pseudorobustus; Heterodera glycines; host range; Metoidogyne hapla; Meloidogyne incognita; nematode; population dynamics; Pratylenchus scribneri; rapeseed; susceptibility; winter annual
Attachment of relatively low numbers of endospores from two isolates of Pasteuria spp. to several species of nematodes was consistently achieved in 2-5 minutes with a centrifugation technique. The rate of attachment of Pasteuria penetrans at 10⁴ endospores/0.1 ml/tube to second-stage juveniles (J2) of Meloidogyne javanica, M. incognita race 1, M. incognita race 3, and M. arenaria races 1 and 2 in two tests averaged 4.4, 5.2, 0.1, 0.3, and 0 endospores per J2, respectively. The rate of attachment Pasteuria sp. at 10³ endospores/0.1 ml/tube to individuals of Hoplolaimus galeatus, Belonolaimus longicaudatus, M. arenaria race 1, M. javanica, and M. incognita race 1 in two tests averaged 0.8, 0.04, 0, 0, and 0 endospores per nematode, respectively. The rate of attachment of P. penetrans to M. javanica at 10³, 10⁴, or 10⁵ endospores/0.1 ml/tube from two tests averaged 1.0, 5.7, and 28.3 endospores per J2, respectively. All of the J2 had endospores attached following centrifugation in tubes with 10⁴ and 10⁵ endospores/0.1 ml/tube.
bacterium; biological control; centrifugation; endospore; Meloidogyne arenaria; M. incognita; M. javanica; method; nematode; Pasteuria penetrans; Pasteuria sp.
The effect of simulated rainfall frequency on the pathogenicity of Pratylenchus zeae and P. brachyurus was studied in four greenhouse experiments. Corn and grain sorghum were watered at different intervals during predetermined cycles to create a gradient of water-stressed plants. Each experiment included nematode and uninoculated treatments. Growth reaction of plants to different frequencies of watering was significant but was not affected by the presence of nematodes. Pratylenchus zeae numbers differed among watering regimens on corn but not on sorghum. Numbers of P. brachyurus did not differ among watering regimens on corn or sorghum. Both lesion nematode species were harmful to corn, but sorghum increased plant growth in response to P. brachyurus. It is concluded that water stress is not the only environmental factor that influences the pathogenicity of these two species on corn and sorghum.
corn; grain sorghum; nematode; Pratylenchus brachyurus; Pratylenchus zeae; Sorghum bicolor; water stress; Zea mays
The efficacy of 1,3-dichloropropene (1,3-D) applied with one or two chisels was determined for control of Rotylenchulus reniformis on pineapple. The soil was fumigated with 1,3-D at 157 liters/ha with either a single chisel 46 cm deep or two chisels 41 cm deep in replicated experiments conducted in four commercial fields. Soil samples were collected before fumigation and 45 days afterward from three depths and three positions. The three depths were 0-15, 16-30, and 31-45 cm; and the three positions were the center of the bed, plant line, and interbed area. The single-chisel injection was comparable to the two chisels in percentage control of R. reniformis. Satisfactory control was achieved in three fields (percentage reduction from untreated = 79, 81, and 83) but not in the fourth field. The highest level of control was at the lowest soil depth (31-45 cm) nearest the points of injection. Among the sampling positions, control in the interbed area was generally the lowest. A single-chisel injection may be recommended because of the slightly enhanced control.
Ananas comosus; 1,3-dichloropropene; fumigation; nematicide; nematode; pineapple; reniform nematode; Rotylenchulus reniformis
A summer-planted crop of alyceelover significantly (P < 0.05) increased the soil abundance of Meloidogyne arenaria race 2 juveniles by 3.7-fold when measured in the following spring. Maize, sorghum, and soybean had no significant effects on residual nematode numbers over the same period. Summer plantings of aeschynomene, cotton, hairy indigo, tespedeza, millet, peanut, and sorghum-sudangrass were as efficient as fallow in reducing root-knot nematode population levels. Soybean yields (averaging 2,156 kg/ha) were significantly increased over that of monocultured soybean (1,179 kg/ha) when grown in soil previously fallowed or planted to aeschynomene, hairy indigo, peanut, and sorghum. No significant differences in yields were achieved from soybean when grown in soil previously cropped to alyceclover, cotton, lespedeza, maize, or sorghum-sudangrass. Nematode numbers, which average 2,140 juveniles/100 cm³ soil following the second year of cropping with soybean, were not related to previous cropping history and had increased an average of 9.3-fold over the course of the study.
aeschynomene; alyceclover; cotton; fallow; hairy indigo; lespedeza; maize; Meloidogyne arenaria race 2; millet; nematode; peanut; root-knot galling; rotation; sorghum; sorghum-sudangrass; soybean; yield
Genetically engineered resistance against plant virus diseases has been achieved by transforming plants with gene constructs that encode viral sequences. Several successful field trials of virus-resistant transgenic plants have been carried out. Specific features of virus infection make it possible to interfere with different steps of the infection and disease cycle by accumulating products of chimeric genes introduced into transgenic plants. In this paper we describe the most common methods of producing virus-resistant transgenic plants and discuss the possibility of applying the concept of pathogen-derived resistance to non-viral pathogens.
genetic engineering; pathogen-derived resistance; plant virus; resistance; virus
Twenty-two graminaceous plant cultivars were evaluated in the greenhouse for host suitability for three South Carolina isolates of Meloidogyne arenaria race 2 (Ma-R2) designated as Florence, Govan, and Pelion, a Florida isolate of M. arenaria race 1 (Ma-R1), and a South Carolina M. incognita race 3. Host suitability was determined by calculating egg mass index (EMI) reproduction factor (RF) (final egg numbers/initial egg numbers), and number of eggs per gram fresh root. Corn hybrids Pioneer 3147 and Northrup King 508 and oat cv. Florida 502 were nonhosts to all nematode isolates, as no egg masses or eggs were found in roots grown in infested soils. Oat cv. Coker 716 and grain sorghum cvs. Cherokee, Northrup King 2660, and Pioneer 8333 were poor hosts (RF < 1). Good (RF = 1.1-5.0) or excellent (RF > 5.0) hosts for both Ma-R1 and three Ma-R2 isolates included the following: barley cvs. Boone, Keowee, and Redhill; corn hybrid Pioneer 3389; oat cvs. Brooks and Coker 820; rye cvs. Bonel, Florida 401, and Wrens Abruzzi; triticale cvs. Beagle 82 and Florida 201 ; and wheat cvs. Coker 983, Florida 302, and Williams. All cultivars except Coker 716 oat were good or excellent hosts of M. incognita.
barley; corn; host; Meloidogyne arenaria; Meloidogyne incognita; nematode; oat; resistance; root-knot; rye; sorghum; triticale; wheat
The effects of six geographic isolates of Pratylenchus vulnus on the growth of GF-677 peach-almond hybrid and M-26 apple rootstocks were determined under greenhouse conditions. Plantlets were obtained from micropropagated plant material, and nematode isolates were reared in monoxenic cultures. All isolates suppressed growth on GF-677 compared with the uninfected controls. Isolate PvRO-S from Spain affected top weight of GF-677 more adversely than PvAT-F from France. Final population densities (Pf) of all P. vulnus on GF-677 were greater than 14.7 times the initial densities (Pi). They increased 61.5-fold on plants infected by PvWA-U from the United States. PvWA-U-, PvAT-F, and geographic undetermined PvU-UK isolates did not affect the growth of M-26 apple rootstock compared with PvAP-S, PvRO-S (both from Spain), and PvWA-A from Argentina isolates, which severely suppressed shoot growth of this rootstock. On M-26, Pf of the more parasitically fit isolates PvWA-A, PvAP-S, and PvRO-S were greater than those of nondamaging PvWA-U, PvAT-F, and PvU-UK isolates (>41.4 vs. <14.7 times the Pi). PvWA-U and PvAT-F reproduced more on GF-677 than on M-26 (>28.6 vs. <6.5 times the Pi). Isolate PvRO-S reproduced well and was quite destructive on both rootstocks. Results confirm the existence of strains with different damage potentials among geographically separated populations of P. vulnus.
host response variability; Malus silvestris M-26; nematode reproduction; Pratylenchus vulnus; Prunus persica × P. amygdalus GF-677; root-lesion nematode
The interaction between Meloidogyne incognita and Criconemella xenoplax on nematode reproduction and growth of Lovell peach was studied in field microlots and the greenhouse. Meloidogyne incognita suppressed reproduction of C. xenoplax in both field and greenhouse experiments. Tree growth, as measured by trunk diameter, was reduced (P ≤ 0.05) in the presence of M. incognita as compared with C. xenoplax of the uninoculated control trees 26 months following inoculation. A similar response regarding dry root weight was also detected in greenhouse-grown seedlings after 5 months. The presence of C. xenoplax did not affect Lovell tree growth. A synergistic effect causing a reduction (P ≤ 0.05) in tree growth was recorded 26 and 38 months following inoculation. The presence of M. incognita increased levels of malonyl-1-aminocyclopropane-1-carboxylic acid content in leaves of trees grown in field microplots 19 months after inoculaoon. Meloidogyne incognita appears to be a more dominant parasite than C. xenoplax on Lovell peach.
concomitant infection; Criconemella xenoplax; interaction; Meloidogyne incognita; nematode; population dynamics; peach; Prunus persica; ring nematode; root-knot nematode; synergism
The effect of aldicarb and fenamiphos on Tylenchulus semipenetrans population densities and on orange yield was investigated during a 3-year (1986-88) field trial in Italy. Rates were 10 and 20 kg a.i./ha as an early spring single application, 5 kg a.i./ha in spring and 5 kg after flowering, and 5 kg a.i. in spring followed by 2.5 kg/ha after flowering and 2.5 kg/ha in early autumn. Rates and times of application of the two nematicides did not affect numbers of females of T. semipenetrans on the roots but suppressed (P = 0.05) egg, male, and second-stage juvenile population densities from October 1986 to 1988. Yield of fruit was not affected by any treatment during 1986-87. Yield was increased (P = 0.05) in 1988 by i) a single application of 20 kg a.i./ha aldicarb, ii) 10 kg a.i./ha fenamiphos, and iii) an application of 5 kg a.i. aldicarb/ha in spring, followed by two more applications of 2.5 kg/ha each in June and September. Fruit size was not affected by the nematicide treatments. Concentrations of fenamiphos and its metabolites, in rind and pulp, were below 0.02 ppm.
aldicarb; citrus nematode; Citrus sinensis; control; fenamiphos; nematicide; nematode; orange; residue; Tylenchulus semipenetrans
Two Rotylenchulus reniformis populations (North Carolina and Georgia) were compared on sweetpotato and tomato. 'Beauregard' sweetpotato and 'Better Boy' and 'Marion' tomato were excellent hosts for both R. reniformis populations. On Beauregard sweetpotato, the two populations did not differ in fecundity; however, on both tomato cultivars, the Georgia population reproduced at a higher rate than the North Carolina population (P ≤ 0.05). Meloidogyne javanica reproduction was higher (P ≤ 0.05) on Marion than on Better Boy. Neither population of reniform nematodes suppressed shoot growth of tomato or sweetpotato at any Pi (initial population density). Both populations of R. reniformis, however, restricted storage-root growth of Beauregard sweetpotato but enhanced shoot growth. When the Georgia population was evaluated in microplots with Pi levels of 0, 20,000, or 40,000 R. reniformis/500 cm³ soil, total fruit weights of Better Boy tomato were not affected. In the greenhouse, Marion tomato fresh shoot and fruit growth (weights) was suppressed by M. javanica, but Better Boy was not affected. Root necrosis increased linearly with Pi on Beauregard sweetpotato grown in the greenhouse and became more pronounced as numbers of R. reniformis increased, regardless of the population. The cultivars of tomatoes evaluated were tolerant to the two populations ofR. reniformis in a sandy soil and exhibited no root necrosis. Marion tomato was highly susceptible to M. javanica, while Better Boy was tolerant.
Ipomoea batatas; Lycopersicon esculentum; Meloidogyne javanica; nematode; reniform nematode; root-knot nematode; Rotylenchulus reniformis; sweetpotato; tomato; yield
A population of Acrobeloides nanus in Australia is described and illustrated, based on light and scanning electron microscopy. Embryogenesis from egg laying to hatching is followed over a wide range of temperatures. At 15 C, hatching occurs in about 125 hours and at 35 and 37.5 C after about 40 hours. At 40 C, egg development ceases early in cleavage. The capacity of A. nanus to develop over such a range of temperatures, and its anhydrobiotic capabilities, are discussed in relation to its survival and wide distribution in Australia.
Acrobeloides nanus; Cephalobidae; description; egg laying; embryogenesis; hatching; light microscopy; morphology; nematode; oviposition; scanning electron microscopy
Developmental stages of Meloidogyne javanica were successfully released from roots by treatment with commercially available cellulase and pectinase. The average percentage recovery of nematode developmental stages from Dolichos lablab, Elymus glaucus, and Lycopersicon esculentum were as follows: eggs = 526%, J2 = 272%, J3 = 783%, J4 = 549%, adult females = 285%, and total = 425%, expressed as percentages of the counts obtained from stained roots spread on glass plates. Root digestion was more accurate and sensitive in detecting low numbers of nematodes in roots than was the glass plate method. No simple linear, quadratic, or cubic relationship was found between the two methods that would allow a conversion factor to be developed.
cellulase; demography; developmental stage; digestion; enzyme; extraction; Meloidogyne javanica; nematode; pectinase; root maceration
Proteinaceous components of freshly formed gelatinous matrix (GM) of the root-knot nematode Metoidogyne javanica were analyzed. Under reducing conditions, the prominent protein fragments had molecular weights of 26 to 66 kDa and 150 to >200 kDa, and most were glycosylated. Most of the fragments were digested by proteinase K, and fewer by trypsin. The lectins soybean agglutinin (SBA), Ulex europaeus agglutinin, and wheat germ agglutinin labeled the higher molecular weight bands (i.e., >200 kDa). SBA labeled additional protein fractions between 26 and 66 kDa. Although Bandeiraea simplicifolia lectin and Concanavalin A did not label bands on the Western blot, they did label the GM in the dot blot technique. Analysis of amino acids and amino sugars in the GM revealed an unusually high amount of ammonia and galactosamine moieties.
gelatinous matrix; glycoprotein; lectin; Meloidogyne javanica; nematode; protein
The interaction between Arabidopsis thaliana and the bacterium Pseudomonas syringae is being developed as a model experimental system for plant pathology research. Race-specific ("gene-for-gene") resistance has been demonstrated for this interaction, and pathogen genes that determine avirulence have been isolated and characterized. Because certain lines of both Arabidopsis and soybean are resistant to bacteria carrying the avirulence genes avrRpt2 and avrB, extremely similar pathogen recognition mechanisms are apparently present in these two plant species. Isogenic bacterial strains that differ by the presence of single avirulence genes are being used to analyze plant resistance. Plant resistance genes have been identified in crosses between resistant and susceptible lines. The extensive map-based cloning tools available in Arabidopsis are being used to isolate these resistance genes. In a related project, ethylene-insensitive Arabidopsis mutants are being used to examine the role of ethylene in disease development. Ethylene apparently mediates symptom formation in susceptible plants and is not required for resistance, suggesting possible strategies for enhancement of disease tolerance in crops.
Arabidopsis thaliana; avirulence; bacterium; ethylene; Glycine max; Pseudomonas syringae; resistance; tolerance
The degradation of fenamiphos, fenamiphos sulfoxide, and fenamiphos sulfone was determined in a greenhouse experiment using autoclaved and nonautoclaved soil from field plots treated or not treated with fenamiphos. Fenamiphos degradation and formation of fenamiphos sulfoxide was faster in uonautoclaved soil than in autoclaved soil. In nonautoclaved soil, previous exposure to fenamiphos was associated with increased rate of degradation of fenamiphos snlfoxide. Fenamiphos total toxic residue degraded more rapidly in nonautoclaved soil previously exposed to fenamiphos than in nonautoclaved soil never exposed to fenamiphos. This accelerated degradation was due to more rapid degradation of fenamiphos sulfoxide and appears to be biologically mediated.
accelerated degradation; degradation; enhanced degradation; fenamiphos; fenamiphos sulfone; fenamiphos sulfoxide; metabolite; microbial degradation; nematicide; nematode; pesticide degradation