Showing papers on "Meloidogyne incognita published in 1989"

Impact of Paecilomyces lilacinus Inoculum Level and Application Time on Control of Meloidogyne incognita on Tomato.

Abstract: Microplot experiments were conducted to evaluate the effects of inoculum level and time of application of Paecilomyces lilacinus on the protection of tomato against MeIoidogyne incognita. The best protection against M. incognita was attained with 10 and 20 g of fungus-infested wheat kernels per microplot which resulted in a threefold and fourfold increase in tomato yield, respectively, compared with tomato plants treated with this nematode alone. Greatest protection against this pathogen was attained when P. lilacinus was delivered into soil 10 days before planting and again at planting. Yield was increased twofold compared with yield in nematode-alone plots and plots with M. incognita plus the fungus. Percentages of P. lilacinus-infected egg masses were greatest in plots treated at midseason or at midseason plus an early application, compared with plots treated with the fungus 10 days before planting and (or) at planting time.

Effects of Meloidogyne incognita and Fusarium oxysporum f. sp. vasinfectum on plant mortality and yield of cotton.

Abstract: At initial populations of Fusarium of 23-42×10 3 colony-forming units per gram of soil and initial populations of Meloidogyne of 10-50 eggs and juveniles per 100 cm 3 , a significant Fusarium×nematode interaction was observed No interaction was observed at lower nematode populations or at higher populations of Fusarium Populations of Meloidogyne had significant effects on cotton growth measured qualitatively as a growth index; the growth index was increased by low initial nematode populations and reduced by high initial nematode populations

Influence of Glomus intraradices and Soil Phosphorus on Meloidogyne incognita Infecting Cucumis melo.

Abstract: The interaction among Glomus intraradices, Meloidogyne incognita, and cantaloupe was studied at three soil phosphorus (P) levels in a greenhouse. All plants grew poorly in soil not amended with P, regardless of mycorrhizal or nematode status. In soil amended with 50 mug P /g soil, M. incognita suppressed the growth of nonmycorrhizal plants by 84%. In contrast, growth of mycorrhizal plants inoculated with M. incognita was retarded by only 21%. A similar trend occurred in plants grown in soil with 100 mug P /g soil. Mycorrhizal infection had no effect on the degree of root-knot gall formation and did not affect the number of nematode eggs per egg mass. Mineral levels in plant shoots generally declined as soil P levels increased and were not significantly influenced by G. intraradices or M. incognita.

Influence of Environmental Factors on the Hatch and Survival of Meloidogyne incognita.

Abstract: The influence of soil temperature and moisture on Meloidogyne incognita (Kofoid and White) Chitwood was examined in relation to hatching and survival of second-stage juveniles (J2). Nematodes were cultured on cotton (Gossypiurn hirsutum L. cv. Acala SJ2) under field conditions to provide populations similar to those found in the field in late autumn. Egg masses were placed in a temperature range (9-12 C and 21 C), and hatch was measured over a period equivalent to 20 degree days 10 C (DD10). Hatch occurred below the reported 18 C activity threshold, was restricted below 12 C, and was inhibited below 10 C. Soil moisture influence on hatch was measured by placing egg masses in Hesperia sandy loam and subjecting them to suction pressures ranging from -1.1 bars to -4 .5 bars. Suction potentials of less than -2 bars reduced hatch and less than -3 bars inhibited hatch. J2 were placed in sandy loam soil with soil moisture near field capacity, and their motility was measured over a period of 500 DD10. In the absence of a host, more than 90% of J2 became nonmotile over this period. Key words: cotton, cultural management, Gossypium hirsutum, hatch, Meloidogyne incognita, soil moisture, soil temperature, survival.

Interactions of vesicular-arbuscular mycorrhizal fungi, root-knot nematode, and phosphorus fertilization on soybean

Abstract: Maximum growth and yield occurred at P fertilization rates of 50-150 μg/g, regardless of whether plants were uninoculated or were inoculated with Gigaspora margarita, Glomus etunicatum, or M. incognita or coinoculated with either endophyte and the nematode. Growth and yield were stimulated by mycorrhizae at the lowest P rate. M. incognita had no effect on root colonization by VAM fungi, but at the lowest P rates, the nematode stimulated sporulation by G. margarita and suppressed sporulation by G. etunicatum

Resistance to Meloidogyne incognita in Trifolium interspecific hybrids and species related to white clover

Abstract: Eight species of Trifolium and seven interspecific hybrids of Trifolium related to white clover (T. repens L.) were evaluated for resistance to the southern root-knot nematode, M. i. (...) Due to its cross-fertility and high level of resistance, Trifolium nigrescens may be a valuable source of resistance to M. i. for white clover.

Growth of Isolates of Paecilomyces lilacinus and Their Efficacy in Biocontrol of Meloidogyne incognita on Tomato.

Abstract: The potential of 13 Paecilomyces lilacinus isolates from various geographic regions as biocontrol agents against Meloidogyne incognita, the effects of temperature on their growth, and the characterization of the impact of soil temperature on their efficacy for controlling this nematode were investigated. Maximum fungal growth, as determined by dry weight of the mycelium, occurred from 24 to 30 C; least growth was at 12 and 36 C. The best control of M. incognita was provided by an isolate from Peru or a mixture of isolates of P. lilacinus. As soil temperatures increased from 16 to 28 C, both root-knot damage caused by M. incognita and percentage of egg masses infected by P. lilacinus increased. The greatest residual P. lilacinus activity on M. incognita was attained with a mixture of fungal isolates. These isolates effected lower root-galling and necrosis, egg development, and enhanced shoot growth compared with plants inoculated with M. incognita alone. Key words: bioassay, biocontrol, Meloidogyne incognita, Paecilomyces lilacinus, residual effect.

Surface Carbohydrates of Plant Parasitic Nematodes

Abstract: Anguina tritici, Aphelenchus avenae, Bursaphelenchus lignicolus, Longidorus elongatus, L. macrosoma, Meloidogyne incognita, Pratylenchus penetrans, Tylenchorhynchus claytoni and Radopholus similis were screened with rhodamine conjugated lectins from Arachis hypogaea (PNA), Canavalia ensiformis (Con A), Limax flavus (LFA), Triticum vulgare (WGA) and Ulex europaeus (UEA-I). Following blocking experiments with appropriate complementary sugars, N-acetylglucosamine residues were found on the head, amphids or amphidial exudates of A. tritici, R. similis and T. claytoni. D-glucose and or D-mannose residues were found in the same regions of B. lignicolus, M. incognita and P. penetrans as well as galactose residues on M. incognita. N-acetylglucosamine was localised at pore openings of L. elongatus, L. macrosoma and R. similis and was found distributed over the entire body of A. tritici. Both Longidorus species also labelled for galactose residues at the sides of the anterior end. All lectins were rapidly taken into the body of A. avenae and appeared as non-specific labelling in lipid droplets.

Influence of Four Nematodes on Root and Shoot Growth Parameters in Grape

Abstract: Two grape cultivars, susceptible French Colombard and tolerant Rubired, and four nematodes, Meloidogyne incognita, Pratylenchus vulnus, Tylenchulus semipenetrans, and Xiphinema index, were used to quantify the equilibrium between root (R) and shoot (S) growth. Root and shoot growth of French Colombard was retarded by M. incognita, P. vulnus, and X. index but not by T. semipenetrans. Although the root growth of Rubired was limited by all the nematodes, the shoot growth was limited only by X. index. The R:S ratios of Rubired were higher than those of French Colombard. The reduced R:S ratios of Rubired were primarily an expression of reduction in root systems without an equal reduction in shoot growth, whereas in French Colombard the reduced R:S ratios were due to a reduction in both shoot growth and root growth and to a greater reduction in root growth than shoot growth. All nematodes reproduced equally well on both cultivars. Both foliage and root growth of French Colombard were significantly reduced by M. incognita and P. vulnus. Nematodes reduced the shoot length by reducing the internode length. Accumulative R:S ratios in inoculated plants were significantly smaller than those in controls in all nematode treatments but not at individual harvest dates. Bud break was delayed by X. index and was initiated earlier by P. vulnus and M. incognita. All buds in nematode treatments were less vigorous than in controls.

In Vitro Inhibition of Root-Knot Nematode Meloidogyne Incognita By Sesame Root Exudate and Its Amino Acids

Abstract: Root exudates and extracts from in vitro grown seedlings of sesame showed an inhibitory effect on egg hatch and juvenile penetration by root-knot nematode, Meloidogyne incognita. Analysis of root exudates of sesame showed seven free amino acids, i.e. aspartic acid, glutamic acid, valine, proline, serine, glycine and leucine, whereas the exudates of okra had ten free amino acids, viz., glycine, serine, leucine, isoleucine, alanine, arginine, glutamic acid, glutamine, lysine and cystine. Three sugars viz. fructose, glucose and sucrose were found in sesame root exudates and extracts. Commercial amino acids both singly, and in combination inhibited egg hatching. The significance of this work in the development of nematicides is discussed.

Progression of Root-knot Nematode Symptoms and Infection on Resistant and Susceptible Cottons.

Abstract: Progressive development in cotton root morphology of resistant A623 and susceptible M-8 cotton (Gossypium hirsutum L.) lines following infection by the root-knot nematode Meloidogyne incognita was studied in glass front boxes. Symptom development and radicle growth were observed; degree of galling, gall and egg mass diameter, and number of eggs per egg mass were recorded; and root segments were examined histologically. Small cracks caused by M. incognita appeared in the root epidermis and cortex soon after the cotyledons expanded on day 4. The cracks were longer and wider and extended through the cortex when the first true leaf became visible at day 8. Galls had formed on taproots by this time. When exposed to M. incognita, A623 had faster radicle growth (22%), fewer and smaller cracks in the root epidermis and cortex, fewer and smaller root galls, one-twelfth as many egg masses, and one-fourth as many eggs per egg mass as M-8. Root cracking, galling, and giant cell formation are major effects of M. incognita that may predispose cotton roots to pathogens resulting in synergistic interactions and diseases.

Impact of Meloidogyne incognita on Physiological Efficiency of Vitis vinifera.

Abstract: Four-week-old French Colombard plants rooted from green cuttings were inoculated with 0, 1,000, 2,000, 4,000, or 8,000 Meloidogyne incognita second-stage juveniles and maintained at 25 C night and 30 C day. Leaf area and dry weight and the rates of photosynthesis, stomatal conductance, and internal leaf COs concentration were measured at intervals up to 59 days after inoculation. Nematode stress dosage, measured as the product of cumulative number of juveniles and females and their total energy (calories) demand, was up to 3.4 kcal and accounted for up to 15% of the energy assimilated by the plants. There was a decline in the rate of leaf area expansion and leaf, stem, shoot, root (excluding nematode weight), and total plant dry weight with increasing nematode stress. Root weight including nematodes was not affected. Total respiration, plant pho- tosynthesis, energy assimilated into plant tissue and respiration, and gross production efficiency decreased significantly with nematode stress. Photosynthetic rate, transpiration rate, stomatal con- ductance, and internal COs concentration were not affected. This study demonstrates that the energy demand for growth and reproduction of M. incognita accounts for a significant portion of the total energy entering the plant system. As a result, less energy is partitioned into leaf area expansion which, in turn, affects the energy entering the system and results in decreased productivity of nematode-infected grape vines. Root-knot nematodes can directly or in- directly affect host physiological processes and productivity. Their high reproduction capacity and obligate parasitism diverts a significant proportion of the photosyn- thate material from the host (11). Their ability to disrupt the vascular tissue alters the translocation of water and solutes to the shoots. These processes can be classi- fied as direct effects. This parasitism in- directly influences the mechanisms of the photosynthetic apparatus and other phys- iological processes such as CO2 exchange which, in turn, affect the total energy avail- able to the plant and the partitioning of photosynthate into leaves, stems, and roots. Several studies have shown the effects of nematodes on photosynthesis, nutrient up- take, and related physiological processes and the consequent impact on host pro- ductivity of annual crops (10,14,18). In an earlier paper (13) we addressed growth, reproduction, and energy requirements of Meloidogyne incognita in grape vines. In a host-parasite interaction, however, it is necessary to understand the relationship between the nematode energy demand and the efficiency of host physiological pro- cesses in compensating for this demand. Furthermore, such physiological informa- tion may be used for application in nema- tode management (2). The objectives of this study were to determine the effect of M. incognita (Kofoid and White) Chitwood on 1) total energy entering the plant sys- tem, 2) partitioning of the energy within the plant, and 3) the relationship between nematode energy demand and the impact on the productivity of a susceptible grape, Vitis vinifera L. cv. French Colombard.

Survival of Paecilomyces lilacinus in Selected Carriers and Related Effects on Meloidogyne incognita on Tomato.

Abstract: Laboratory and microplot experiments were conducted to determine the influence of carrier and storage of Paecilomyces lilacinus on its survival and related protection of tomato against Meloidogyne incognita. Spores of P. lilacinus were prepared in five formulations: alginate pellets (pellets), diatomaceous earth granules (granules), wheat grain, soil, and soil plus chitin. Fungal viability was high in wheat and granules, intermediate in pellets, and low in soil and chitin-amended soil stored at 25 ± 2 C. In 1985 P. lilacinus in field microplots resulted in about a 25% increase in tomato yield and 25% gall suppression, compared with nematodes alone. Greatest suppression of egg development occurred in plots treated with P. lilacinus in pellets, wheat grain, and granules. In 1986 carryover protection of tomato against M. incognita resulted in about a threefold increase in tomato fruit yield and 25% suppression of gall development, compared with plants treated with nematodes alone. Higher numbers of fungus-infected egg masses occurred in plots treated with pellets (32%) than in those treated with chitin-amended soil (24%), wheat (16%), granules (12%), or soil (7%). Numbers of fungal colony-forming units per gram of soil in plots treated with pellets were 10-fold greater than initial levels estimated at planting time in 1986. Key words: biological control, Lycopersicon esculentum, Meloidogyne incognita, Paecilomyces lilacinus, root-knot nematode, tomato.

Effects and dynamics of a nematode community on maize.

Abstract: Relationships between nematode density and yield and between final and preplant population levels were examined in small maize plots on sandy soils in north-central Florida. Plant-parasitic nematodes present in the community included Belonolaimus longicaudatus, Criconemella sphaerocephala, Meloidogyne incognita, Paratrichodorus minor, Pratylenchus brachyurus, and a Xiphinema sp. Plant growth--including stand count, grain yield, stalk weight, and size of young plants--often was inversely correlated (P ≤ 0.05) with densities of B. longicaudatus and occasionally with P. brachyurus, but not with densities of other species or with a range of soil variables. More severe losses in grain yields from B. longicaudatus occurred in 1987 than in 1988, although mean preplant nematode densities in February were similar in both years (4.4 vs. 3.9/100 cm³ soil). Final population densities of most nematode species were linearly related (P ≤ 0.05) to densities measured at planting or earlier. These relationships were stronger (higher r²) with the ectoparasites B. longicaudatus and C. sphaerocephala than with the endoparasites M. incognita and P. brachyurus. No significant correlations were found between population densities of different nematode species.

Root Tissue Response of Two Related Soybean Cultivars to Infection by Lectin-treated Meloidogyne spp.

Abstract: Treatment of second-stage juveniles (J2) of Meloidogyne incognita race 1 and M. javanica with soybean agglutinin, Concanavalin A, wheat germ agglutinin, Lotus tetragonolobus agglutinin, or Limax flavus agglutinin or the corresponding competitive sugars for each of these lectins did not alter normal root tissue response of soybean cultivars Centennial and Pickett 71 to infection by M. incognita race 1 or M. javanica. Giant cells were frequently induced in Centennial and Pickett 71 roots 5 and 20 days after inoculation of roots with untreated J2 of a population of M. incognita race 3. Treatment of J2 of M. incognita race 3 with the lectins or carbohydrates listed above caused Centennial, but not Pickett 71, root tissue to respond in a hypersensitive manner to infection by M. incognita race 3. Penetration of soybean roots by J2 of Meloidogyne spp. was strongly inhibited in the presence of 0.1 M sialic acid. Treatment of J2 with sialic acid was not lethal to nematodes, and the inhibitory activity of sialic acid was apparently not caused by low pH. These results suggest that carbohydrates may influence plant-nematode interactions.

The Fusarium oxysporum F. sp. Coffeae-Meloidogyne incognita Complex in 'Bourbon' Coffee

Abstract: The interaction of Fusarium oxysporum f. sp. coffeae with Meloidogyne incognita on Coffea arabica was studied in the greenhouse. Coffee seedlings were either not inoculated, inoculated with the fungus alone, the fungus and the nematode simultaneously, or the fungus 2 or 4 weeks after the nematode. Chlorosis, root necrosis, wilting, and stunting were greater in plants inoculated with the fungus 4 weeks after the nematode. Similar but less severe symptoms were observed in plants to which the fungus was added 2 weeks after the nematode. Significant differences among treatments were found in height and dry weight of roots and shoots. Histological studies of root sections revealed giant cell development and hyphal penetration of giant cells, xylem vessels, and the female nematode.

Relative resistance of six cowpea cultivars as affected by the concomitance of two nematodes and a fungus

Abstract: Cowpea cultivars that were resistant or moderately resistant against individual pathogens lost their resistance in the presence of the other pathogens except cv lC-503 (moderately resistant to Meloidogyne incognita) Cv S-488 (resistant to Rotylenchulus reni/ormis) did not remain resistant in the presence of M incognita though it did not lose its resistance in the presence of Rhizoctonia solani Similarly, the resistance of cv CO-4 to R solani broke down in the presence of M incognita but not in the presence of R reni/ormis Both R reni/ormis and M incognita, when present in association with R solani, broke the resistance of cv lC-244 against R solani The moderately resistant response of cvs RC-8 and EC-4213A to R reni/ormis and their complete resistance against R solani broke down when simultaneously inoculated with both the nematode species or R solani with either R reni/ormis or M incognita

Suitability of small grains as hosts of meloidogyne species.

Abstract: Seven cultivars of wheat, five of oat, one of rye, and four of barley were tested as hosts for Meloidogyne incognita, M. javanica, or M. arenaria under greenhouse conditions where soil temperature ranged from 21 to 34 C. Reproduction rates of all nematode species were high on all cultivars, except M. javanica and M. arenaria on 'Brooks' and 'Florida 501' oat. Meloidogyne incognita and M. javanica produced more eggs on roots of 'Rutgers' tomato than on cultivars of wheat, oat, rye, or barley.

Identification of New Sources of Resistance to Root‐knot Nematodes in Phaseolus

Abstract: Common bean lines PI 165426 and Alabama no 1 were found to be resistant to M incognita Race 2, 3 and 4 but were susceptible to M incognita Race 1 and to M arenaria Breeding lines A252, A315, A328, A443 and A445 were resistant to M javanica and M incognita Race 1 Resistance in the A lines was found to be derived from two common bean landraces, G1805 and G2618 The resistance was also effective against M arenaria The repary bean accession PI 310606 was found to have good resistance to all nematode isolates tested We postulate that resistance derived from G1805 and G2618 may be under different genetic control than that in PI 165426 and Alabama no 1

Fenóis, peroxidase e polifenoloxidase na resistência do cafeeiro a Meloidogyne incognita

Abstract: Seedlings of two coffee cultivars were inoculated with the nematode Meloidogyne incognita: cv. Mundo Novo (susceptible) of Coffea arabica and cv. Apoata (resistant) of C. canephora. During the larval penetration and adult female phases of the parasite, evaluations were made on phenol content, peroxidase and polyphenoloxidase activities. In the two evaluations, no differences were observed in roots and shoots growth among inoculated and non inoculated seedling. For both cultivars, only in the first phase infected seedlings showed an increase in phenols as compared to their counterparts not inoculated. However, phenol values were higher in the second than in the first phase. The cv. Mundo Novo had always higher phenols content than Apoata. Only inoculated seedlings of the cv. Mundo Novo showed an increase of peroxidase activities in the first phase; but, both cultivars presented higher peroxidase activities in the second phase as compared to the first. Apoata seedlings had always higher peroxidase and polyphenoloxidase activities than Mundo Novo. Infected seedlings of the cv. Apoata showed in the first phase, only, an increase in polyphenoloxidase activity. Thin-layer chromatograms of phenolic extracts did not present any difference among inoculated and non-inoculated seedlings. Twenty three spots on the chromatograms were common to both cultivars, except that Apoata had a further nine spots not found in Mundo Novo and the later had a further eleven not found in the former.

Organic amendments for control of root-knot nematode (Meloidogyne incognita) on ginger

Abstract: Poultry manure and sawdust (24, 36 or 48 tlha) were incorporated into soil with urea (0–1800 kg nitrogenlha) and their effects on yield of ginger and populations of Meloidogyne incognita were compared with those of nematicide programmes involving ethylene dibromide andlor fenamiphos. The pre-plant nematicide treatments proved inadequate but improved nematode control was achieved when these treatments were followed by postplant applications of fenamiphos. Total yields in soil amended with poultry manure or sawdust plus urea were greater than in non-amended soil and equal to or greater than those in the best nematicide treatments. The yield increase for poultry manure appeared to be due in part to its beneficial effects on soil fertility. Both amendments provided good control of root-knot nematodes, with significantly fewer rhizomes being discarded at late harvest from the amendment treatments than from the untreated and some nematicide-treated plots. Addition of the highest rates of urea to soil produced ammonium-nitrogen concentrations of more than 1000 μ/g soil, but no measurable effect on root-knot nematode populations or the degree of nematode damage.

Evaluation of control of Meloidogyne incognita and Nacobbus aberrans on tomato by two leguminous plants.

Abstract: SUMMARY When the leguminous plant Concanavalia enszformis and tomato were cocultivated in greenhouse pot tests, a reduction in galling caused by Meloidogyne incognita and Nacobbus aberrans was observed. The leguminous plant Mucuna deetingiana generally gave a lesser degree of control of root-knot under the same conditions, as did treatments with powdered, ground beans of the two legumes. The effects of the several treatments on plant growth were inconsistent. The lectin Con A was demonstrated in water in which C. ensiformis had been grown. The passage of this lectin from C. ensiformis into the soi1 is proposed as an explanation for the observed reduction in root-knot symptoms on tomato.

Effect of Carbamate, Organophosphate, and Avermectin Nematicides on Oxygen Consumption by Three Meloidogyne spp.

Abstract: Second-stage juveniles (I2) of Meloidogyne arenaria consumed more oxygen (P = 0.05) than M. incognita J2, which in turn consumed more than M. javanica J2 (4,820, 4,530, and 3,970 [mu]l per hour per g nematode dryweight, respectively). Decrease in oxygen consumption depended on the nematicide used. Except for aldicarb, there was no differential sensitivity among the three nematode species. Meloidogyne javanica had a greater percentage decrease (P = 0.05) in oxygen uptake when treated with aldicarb, relative to the untreated control, than either M. arenaria or M. incognita. Meloidogyne javanica J2 had a greater degree of recovery from fenamiphos or aldicarb intoxication, after subsequent transfer to water, than did M. incognita. This finding may relate to differential sensitivity among Meloidogyne spp. in the field. Degree of respiratory inhibition and loss of nematode motility for M. javanica after exposure to the nematicides were positively correlated (P = 0.05). Key words: aldicarb, avermectin, carbamate, carbofuran, ethoprop, fenamiphos, Meloidogyne arenaria, Meloidogyne incognita, Meloidogyne javanica, organophosphate, oxamyl, oxygen, root-knot nematode.

Nematode Population Density Increase on Cover Crops of Rye and Vetch

Abstract: Population densities of plant-parasitic nematodes were monitored for two seasons in plots with winter cover crops of rye (Secale cereale) or hairy vetch (Vicia villosa) on sandy soils in north central Florida. The ranges in nematode densities observed in the plots permitted derivation of linear relationships between final population densities (Pf) after 3 and 5 months and initial population densities (Pi) before planting of cover crops in October or November. More consistent linear relationships (P 0.05) were obtained for Belonolaimus longicaudatus and Criconemella sphaerocephala than for Meloidogyne incognita and Pratylenchus brachyurus. In most instances, population densities were maintained by the cover crops, with Pf Pi. However, maintenance of a rye cover crop for almost 5 months resulted in increased B. longicaudatus densities, with Pf or Pi or 3 Pi, depending on the season.

Preferred Temperature of Meloidogyne incognita

Abstract: In laboratory thermal gradients, newly hatched infective juveniles of the plant-parasitic root-knot nematode Meloidogyne incognita migrated toward a preferred temperature that was several degrees above the temperature to which they were acclimated After shifting egg masses to a new temperature, the preferred temperature was reset in less than a day Possible functions of this type of thermotaxis are discussed, including the use of thermal gradients around plant roots to locate hosts and to maintain a relatively straight path while ranging in the absence of other cues (a collimating stimulus)

Resistance to Meloidogyne spp. in Allohexaploid Wheat Derived from Triticum turgidum and Aegilops squarrosa.

Abstract: Expression of resistance to Meloidogyne incognita and M. javanica from Aegilops squarrosa was studied in a synthetic allohexaploid produced from Triticum turgidum var. durum cv. Produra and Ae. squarrosa G 3489. The reproductive rate of different races of M. incognita and M. javanica, expressed in eggs per gram of fresh root, was low (P < 0.05) on the synthetic allohexaploid and the resistant parent, Ae. squarrosa G 3489, compared with different bread and durum wheat cultivars. Reproduction of race 2 and race 3 of M. incognita and an isolate of M. javanica was studied on the synthetic allohexaploid and seven cultivars of T. aestivum: Anza, Coker 747, Coker 68-15, Delta Queen, Double Crop, McNair 1813, and Southern Bell. The latter six cultivars are grown in the southeastern United States and reportedly were resistant to M. incognita. Significant differences (P < 0.05) were detected in nematode reproduction on the seven bread wheat cultivars. Reproduction of M. incognita race 3 and M. javanica was highest on Anza. Reproductive rates on the six southeastern United States bread wheat cultivars varied both within and among nematode isolates. The lowest reproductive rates of the three root-knot isolates were detected in the synthetic allohexaploid.

The control of Meloidogyne incognita on tomato using avermectin B1 as a root dip.

Abstract: L'immersion de racines des semis de tomates dans une solution d'avermectine B1 a 1 mg/litre reduit le nombre de galles et de nematodes sur les racines des plantes traitees jusqu'a 20 jours. Le traitement differe l'invasion des racines traitees et le developpement des nematodes est retarde. L'efficacite du traitement decroit avec le temps, probablement a cause de la disparition du produit

A simple animal can use a complex stimulus pattern to find a location: Nematode thermotaxis in soil

Abstract: Newly hatched infective juveniles of the plant-parasitic nematode Meloidogyne incognita have recently been found to migrate in very shallow thermal gradients to a preferred temperature that is several °C above the temperature to which they were acclimated. Possible functions of this unusual behavior were explored by computer modeling of the movement of such nematodes in the dynamic thermal environment typical of soil. Reliable estimates were available for all the required parameters. The model predicts that, as the diurnal temperature fluctuations at the surface penetrate into the soil, a nematode located below the surface will move upward during part of the day and downward during the rest of the day. However, the distances moved upward and downward do not balance and there is a net change in depth over a period of days. The net change is upward or downward depending on the physiological parameters of the nematode and its depth. Using the best estimates available for the parameters, it is predicted that nematodes starting at any depth between 0 and 15 cm would move toward an intermediate depth of about 5 cm. It is hypothesized that, in the absence of chemical cues, this response leads the nematodes toward a level that is optimal for locating the roots of host plants. This suggests that simple organisms may make use of much more complex stimulus patterns than was previously realized.

Effects and dynamics of a nematode community on soybean.

Abstract: The relationships between densities of all members of a plant-parasitic nematode community and yield of 'Davis' soybean and between final and preplant population levels were examined in small plots on sandy soils in north-central Florida. Plant-parasitic nematodes present in the community included Belonolaimus longicaudatus, Criconemella sphaerocephala, Meloidogyne incognita, Paratrichodorus minor, Pratylenchus brachyurus, and Xiphinema sp. Plant growth, including stand count, soybean yield (kg/ha), and size of young plants, was occasionally inversely correlated (P