Showing papers on "Meloidogyne incognita published in 1988"

Effects of rhizobacteria on root-knot nematodes and gall formation

Abstract: Three hundred and fifty-four randomly selected bacteria from plant rhizospheres, when tested for activity against Meloidogyne incognita, caused a wide range of effects from a reduction to an increase of root galling on tomato and cucumber in greenhouse tests Results were highly variable, even with strains that previously had given significant differences A bioassay, based on selecting bacterial strains that produced nematicidal compounds in vitro, proved to be a better and more rapid means of identifying promising nematode antagonists About 1% of more than 5,000 bacteria isolated from rhizospheres of different plants produced detectable compounds that affected the vitality of second-stage juveniles of M incognita in an in vitro test Twenty percent of these subsequently reduced the number of galls on cucumber in a soil-free pouch system when applied as a seed treatment Selected strains were applied as a drench to nonsterile soil infested with M incognita White clover plants growing in bacteria-treated soil had fewer galls and larger root systems Both plant top and root weights were significantly greater compared with the nontreated control

Pasteuria thornei sp. nov. and Pasteuria penetrans sensu stricto emend., mycelial and endospore-forming bacteria parasitic, respectively, on plant-parasitic nematodes of the genera Pratylenchus and Meloidogyne.

Abstract: Descriptions are presented of two members of the Pasteuria penetrans group of mycelial and endospore-forming bacteria, parasitic on plant-parasitic nematodes. In one case, the epithet P. penetrans sensu stricto emend. has now been limited to members of this group with cup-shaped sporangia and ellipsoidal endospores, parasitic primarily on the root-knot nematode Meloidogyne incognita. The second organism, with rhomboidal sporangia and nearly spherical endospores, which is parasitic primarily on the root-lesion nematode Pratylenchus brachyurus, is assigned to P. thornei sp. nov. An updated and emended description is offered of the genus Pasteuria Metchnikoff 1888 emend. The relationships are analysed among these two nematode parasites and the type species of this genus, P. ramosa Metchnikoff 1888, a parasite of cladoceran invertebrates. Because none of these microbes has been publicly reported to have been cultivated axenically, these relationships are based mainly on morphological, developmental, and pathological criteria.

A method for staining nematode secretions and structures.

Abstract: Soybean cultivars grown in pots in the greenhouse were tested for resistance by inoculation with Meloidogyne incognita or one of six races of Heterodera glycines. Selected cultivars were tested against each nematode isolate. The numbers of cultivars tested against each H. glycines race and the numbers resistant and (or) moderately resistant were as follows: Race 2 - 114 tested, 1 resistant and 9 moderately resistant; race 3 - 170 tested, 56 resistant and 17 moderately resistant; race 4 - 89 tested, 1 resistant and 13 moderately resistant; race 5 - 106 tested, 4 moderately resistant; race 6 - 95 tested, 10 resistant and 25 moderately resistant; race 14 - 81 tested, 2 resistant and 10 moderately resistant. No cultivar was resistant to all races. Meloidogyne incognita was tested on 139 cultivars; 50 were resistant.

Potential of crops uncommon to alabama for management of root-knot and soybean cyst nematodes.

Abstract: Vigna unguiculata, Cassia fasiculata, and Sesamum indicum did not support Meloidogyne arenaria, M. incognita, or Heterodera glycines race 4 in greenhouse studies with soils from peanut and soybean fields. Fagopyron eseulentum, Cyamopsis tetragonoloba, and Cucurbita pepo were hosts to the two Meloidogyne spp. but were nonhosts to H. glycines. Meloidogyne arenaria and M. incognita galled but reproduced poorly in the roots of three types of Amaranthus cruentus, and low densities of these two Meloidogyne spp. (< 10 second-stage juveniles/100 cm³ soil) occurred in soil cultivated with this crop. In a field study no juveniles of M. arenaria determined at peanut harvest were recovered from plots with Ricinus communis, Gossypium hirsutum, Aeschynomene americana, C. fasiculata, or S. indicum. Peanut plots averaged 120 juveniles/100 cm³ soil. Application of aldicarb (12 kg a.i./ha broadcast) in peanut resulted in an average of 27 juveniles/100 cm³ soil. Several crops were as effective as aldicarb treatment for reducing soil juvenile population densities of M. arenaria.

Histology of the Interactions of Paecilomyces lilacinus with Meloidogyne incognita on Tomato.

Abstract: Excised tomato roots were examined histologically for interactions of the fungus Paecilomyces lilacinus and Meloidogyne incognita race 1. Root galling and giant-cell formation were absent in tomato roots inoculated with nematode eggs infected with P. lilacinus. Few to no galls and no giant-cell formation were found in roots dipped in a spore suspension of P. lilacinus and inoculated with M. incognita. Numerous large galls and giant cells were present in roots inoculated only with M. incognita. P. lilacinus colonized the surface of epidermal cells as well as the internal cells of epidermis and cortex. The possibility of biological protection of plant surfaces with P. lilacinus against root-knot nematodes is discussed.

Compariso n of Pasteuria penetrans from Meloidogyne incognita with a Related Mycelial and Endospore-forming Bacterial Parasite from Pratylenchus brachyurus1

Abstract: Major distinctions exist between members of the Pasteuria penetrans group occurring on the root- lesion nematode, Pratylenchus brachyurus, and the root-knot nematode, Meloidogyne incognita. These dissim- ilarities include highly restricted nematode host ranges, differences in the bacterial life stages in relation to those of the host nematodes, and disparities in ultrastructural morphology of their mature sporangia and endospores. The several stages of the bacterial parasite of the root-lesion nematode (RLP) occur in all the nematode's larval stages. The mature RLP sporangia are rhomboidal, and average 2.40 ± 0.24 ^m in diameter and 2.15 ± 0.19 nm in height. The endospores within the RLP sporangia are ellipsoidal or almost spherical, narrowly elliptic in section, having axes averaging 1.08 ± 0.21 by 1.29 ±0.1 4 ^m. By contrast, the mature bacterial stages from the root-knot nematode (RKP) occur only in the adult female nematode and not in the larvae. The RKP sporangia are cup-shaped, and average 3.42 ±0.18 ^m in diameter and 2.48 ± 0.22 pm in height. The RKP endospores, also ellipsoidal but broadly elliptic in section, have axes averaging 1.10 ± 0.11 by 1.42 ± 0.12 nm. These several differences strongly suggest that these 2 members of the P. penetrans group belong in separate taxa. Considerable morphological diversity was also evident from light-microscopic examination of members of the P. penetrans group occurring in archival nematode material (genera Dolichodorus, Heterodera, Hoplolaimus, Meloidogyne, Pratylenchus, Tylenchorhynchus, and Xiphinemd) from the USDA Nematode Collection.

Growth and Energy Demand of Meloidogyne incognita on Susceptible and Resistant Vitis vinifera Cultivars.

Abstract: Food (energy) consumption rates ofMeloidogyne incognita were calculated on Vitis vinifera cv. French Colombard (highly susceptible) and cv. Thompson Seedless (moderately resistant). One-month-old grape seedlings in styrofoam cups were inoculated with 2,000 or 8,000 M. incognita second-stage juveniles (J2) and maintained at 17.5 degree days (DD - base 10 C)/day until maximum adult female growth and (or) the end of oviposition. At 70 DD intervals, nematode fresh biomass was calculated on the basis of volumes of 15-20 nematodes per plant obtained with a digitizer and computer algorithm. Egg production was measured at 50-80 DD intervals by weighing 7-10 egg masses and counting the number of eggs. Nematode growth and food (energy) consumption rates were calculated up to 1,000 DD based on biomass increase, respiratory requirements, and an assumption of 60 % assimilation efficiency. The growth rate of a single root-knot nematode, excluding egg production, was similar in both cultivars and had a logistic form. The maximum fresh weight of a mature female nematode was ca. 29-32 [mu]g. The total biomass increase, including egg production, also had a logistic form. Maximum biomass (mature adult female and egg mass) was 211 [mu]g on French Colombard and 127 [mu]g on Thompson Seedless. The calculated total cost to the host for the development of a single J2 from root penetration to the end of oviposition for body growth and total biomass was 0.535 and 0.486 calories with a total energy demand of 1.176 and 0.834 calories in French Colombard and Thompson Seedless, respectively. Key words: grape, Meloidogyne incognita, nematode energy demand, nematode growth, Vitis vinifera.

Nematicidal effects of some Fusarium toxins

Abstract: Interaction among Fusarium diseases and plant parasitic nematodes on cultivated crops have mainly been studied with particular attention to their interrelationships in the rhizosphere of the host plants, to the enhancement of Fusarium wilt in the presence of nematodes or to the break-down of resistance produced by the nematode attack (Powell, 1971; Orion and Hoestra, 1974; Palmer and MacDonald, 1974; Pitcher, 1974; Nordmeyer and Sikora, 1983; Mai and Abawi, 1987). Factors affecting the behaviour of these pathogens in nature often give rise to a complex of results that cannot be completely evaluated without considering the occurrence of all the variables involved. Some nematological experiments consider the ability of Fusarium spp. to produce toxic compounds and their effect on the different life stages of many species of plant parasitic and saprophytic nematodes (Krizkova et aI., 1979; Mani and Sethi, 1984). All these findings mainly indicate that some unidentified toxins, sugars or aminoacids, probably present in the filtrates used, were responsible for the death of the nematodes. The ability shown by several species and strains of Fusarium spp. to produce mycotoxins (Maras as et al., 1984), could play an important role in affecting nematode behaviour or interfering with the life stages. The present investigation was undertaken to determine the effect of some Fusarium toxins on the hatching of eggs of the root-knot nematode Meloidogyne incognita (Kofoid et White) Chitw.

Toxicity of Different Plant Parts of Tagetes Lucida to Plant Parasitic Nematodes

Abstract: Water extracts of different parts of marigold (Tagetes lucida) were highly deleterious to Meloidogyne incognita, Rotylenchulus reniformis, Tylenchorhynchus brassicae, Hoplolaimus indicus, Helicotylenchus indicus and Tylenchus filiformis, however, to varying extent. The nematode mortality increased with increase in the concentration of the extracts and the exposure period. Juvenile hatching of M. incognita was also greatly inhibited by the extracts. Inhibition in the hatching increased with increase in the concentration of the extracts. Flower extracts caused greatest nematode mortality and inhibition in juvenile-hatching followed by seed, leaf and root extracts.

Interactions Between Meloidogyne incognita and Pratylenchus brachyurus on Soybean.

Abstract: Interactions among Meloidogyne incognita, Pratylenchus brachyurus, and soybean genotype on plant growth and nematode reproduction were studied in a greenhouse Coker 317 (susceptible to both nematodes) and Gordon (resistant to M incognita, susceptible to P brachyurus) were inoculated with increasing initial population densities (Pi) of both nematodes individually and combined M incognita and P brachyurus individually usually suppressed shoot growth of both cultivars, but only root growth on Coker 317 was influenced by a M incognita × P brachyurus interaction Reproduction of both nematodes, although dependent on Pi, was mutually suppressed on Coker 317 P brachyurus reproduced better on Gordon than on Coker 317 but did not affect resistance to M incognita Root systems of Coker 317 were split and inoculated with M incognita or P brachyurus or both to determine the nature of the interaction M incognita suppressed reproduction of P brachyurus either when coinhabiting a half-root system or infecting opposing half-root systems; however, P, brachyurus affected M incognita only if both nematodes infected the same half-root system Key words: Glycine max, antagonism, concomitant infection, population density, root-knot nematode, lesion nematode

Behavioral Responses of Meloidogyne incognita to Small Temperature Changes.

Abstract: Small, rapid temperature changes were generated by incandescent radiation, and be- havioral responses of Meloidogyne incognita juveniles were recorded with high time resolution by computer tracking. Temperature changes away from the preferred temperature resulted in de- creases in the rate of movement and increases in the rate of change of direction, whether the changes were toward warmer or cooler temperatures. These behavioral changes lasted about 30 seconds. Temperature changes toward the preferred temperature caused the response rates to change in the opposite directions, and the behavioral changes persisted for several minutes. These results demonstrate that nematodes can respond to a purely temporal thermal stimulus in a manner con- sistent with efficient indirect orientation or klinokinesis. The rate of temperature change was es- timated to be of the order of 10 -4 C/second, suggesting that the nematodes detected a change of about 0.001 C. dogyne incognita (Kofoid & White) Chitwood can migrate in thermal gradients of less than 0.001 C/cm (J. A. Diez, M. J. Pline, and D. B. Dusenbery, unpubl.). Previous experiments demonstrating isothermal tracking (13) suggest that nematodes are capable of direct orientation to thermal gradients, at least when the gradients are steep. The hypothesis that nematodes may also respond by indirect mechanisms using temporal changes was tested in experi- ments reported here and found to be sup- ported.

Extremely Sensitive Thermotaxis of the Nematode Meloidogyne incognita.

Abstract: Eggs of the root-knot nematode Meloidogyne incognita were acclimated to 23 C. Newly hatched second-stage juveniles migrated toward higher temperatures when placed in shallow thermal gradients averaging 23 C. The threshold gradient for this response was below 0.001 C/cm, with a best estimate of 4 x 10⁻⁴ C/cm. Calculations of physical limitations on thermotaxis indicate that this sensitivity is well within the limits of what is physically possible.

Tillage and multiple cropping systems and population dynamics of phytoparasitic nematodes.

Abstract: The effect of two cropping and tillage systems on the population dynamics of four nematode species was evaluated on a loamy sand. Hairy vetch succeeded by corn or grain sorghum was seeded in split plots randomized within whole plots of no-tillage versus conventional tillage over four growing seasons (1980-83). The vetch-corn cropping system increased the density of Meloidogyne incognita 2.9 x more than the vetch-grain sorghum cropping system. In contrast, the vetch-grain sorghum cropping system increased the density of Criconemella ornata 0.7 x more than the vetch-corn cropping system. Meloidogyne incognita and C. ornata were affected more by these cropping systems than were Pratylenchus brachyurus or Paratrichodorus minor. Multiple cropping systems, vetch varieties, and crop host preference affected nematode population densities, whereas tillage treatments, conventional or no-tillage, had little effect on them.

Pasteuria penetrans, a pathogen of the genus Heterodera, its effect on nematode biology and control.

Abstract: The bacterial pathogen, Pasteuria penetrans, parasitized larvae of Heterodera species and Meloidogyne incognita. Mass multiplication of the bacterial inoculum was done on root-knot nematode infested brinjal plants. The total life cycle of the bacterium was completed in 49 days at 10–17°C. Amongst the methods of application, direct mixing of bacterial spore infested soil was found to be most effective against the nematode population. Maximum reduction in cyst population was obtained when spore infected soil was incubated at 30°C before application.

Response of Cotton to Infection by Hoplolaimus columbus.

Abstract: Three field experiments were established in 1987 to determine the reaction of five cotton cultivars to infection by Hoplolaimus columbus and the efficacy of selected nematicides against this nematode. At two sites in Calhoun County, South Carolina, early season plant growth and subsequent yields were greater in plots treated with aldicarb, fenamiphos, and 1,3-dichloropropene. Hoplolaimus columbus suppressed yields approximately 10% at site 1 and 25% at site 2; however, greater yield suppression at site 2 may have been influenced by low levels of Meloidogyne incognita. At one site in Barnwell County, South Carolina, nematicide treatments did not increase plant growth or yield. At sites 1 and 2 where yield losses occurred, no differences in infection rate or yield among untreated cultivars were observed, nor was any nematicide more effective than another in preventing yield losses. Key words: aldicarb, chemical control, Columbia lance nematode, cotton, fenamiphos, Gossypium hirsutum, Hoplolaimus columbus, MeIoidogyne incognita, nematicide, 1,3-dichloropropene, root-knot nematode.

Effect of Steroidal and Triterpenic Saponins on the Mobility of Juveniles of Meloidogyne Incognita

Abstract: Steroidal saponins, asparanin 1 and asparanin B and triterpenic saponins, albichinin II and sonunin III, were found to possess nematicidal activity affecting larval mobility of Meloidogyne incognita. Their efficacy depended on concentration—time product.

Host Suitability of Grain Sorghum Cultivars to Meloidogyne spp.

Abstract: Grain sorghum cultivars (Funk G-499GBR, Funk G-611, Funk G-522A, Funk G-522DR, Coker 7723, Coker 7675, Coker 7623, Pioneer B815, Pioneer 8222, Pioneer 8272) were evaluated in the greenhouse for resistance to populations of Meloidogyne incognita race 3, M. arenaria race 2, and M. javanica from South Carolina, and M. arenaria race 1 from Georgia. All the sorghum cultivars were poor hosts or nonhosts of Meloidogyne spp. with fewer than 1 or 2 egg masses per root system in all cultivar x nematode combinations. Sorghum (Coker 7723) planted in a field infested with M. incognita race 3 and M. arenaria race 2 was not galled; however, galling and egg masses were observed on tobacco (Coker 319). Populations of second-stage juveniles at harvest were 2,865 and 72/500 cm³ soil for the tobacco and sorghum plots, respectively. Sorghum was a poor host of Meloidogyne spp. and may be useful as a rotation crop to reduce populations of root-knot nematodes.

Meloidogyne incognita and Tomato Response to Thiamine, Ascorbic Acid, L-arginine, and L-glutamic Acid.

Abstract: The influence of solutions of ascorbic acid, thiamine, L-arginine, and L-gtutamic acid on egg hatch, juvenile survival, and development and reproduction of Meloidogyne incognita in susceptible and resistant tomatoes was studied. Maximum inhibition of egg hatch occurred at 2,000, 4,000, and 2,000 ppm for ascorbic acid, L-arginine, and L-glutamic acid, respectively. Larval survival was significantly reduced by concentrations of 2,000 ppm ascorbic acid and 1,000 ppm of L-arginine. Maximum inhibition of egg hatch and mortality of juveniles was achieved at a concentration of 4,000 ppm of ascorbic acid and L-arginine. L-glutamic acid and thiamine had respective moderate and minimal toxic effects. Foliar sprays of ascorbic acid, L-arginine, or L-glutamic acid suppressed the numbers of root galls, females, and egg masses on the susceptible tomato cultivar Tropic. Ascorbic acid and L-arginine had highly significant effects when applied to foliage before inoculation with nematodes. Thiamine had little effect. All sprays suppressed the numbers of root galls and females in roots of the resistant cultivar VFN8 when treatments were applied before inoculation. They were not, however, effective as post-inoculation treatments. Growth of a susceptible cultivar was improved by post-inoculation and pre-inoculation treatments when compared with the control plants which had neither nematode infection nor chemical treatment. No positive growth response to chemical treatment was seen in resistant control plants. Key words: amino acid, Meloidogyne incognita, tomato, vitamin.

Evaluation of Nematicidal Potential in some Plant Species Belonging to Family Compositae

Abstract: The root-knot nematode, Meloidogyne incognita and reniform nematode, Rotylenchulus reniformis caused considerable damage to the growth of eggplant. Chopped shoot parts of some plants of the family compositae effectively contained the multiplication of these nematodes, and the root-knot development, consequently the plant growth improved. These additives also showed their manurial value. There was no sign of phyto-toxicity of any additives used.

Histopathology of Root-knot Nematode (Meloidogyne Incognita) Infection on White Yam (Dioscorea Rotundata) Tubers

Abstract: White yam tissues naturally and artificially infected with root-knot nematodes were fixed, sectioned, and examined with a microscope. Infective second-stage juveniles of Meloidogyne incognita penetrated and moved intercellularly within the tuber. Feeding sites were always in the ground tissue layer where the vascular tissues are distributed in the tubers. Giant cells were always associated with xylem tissue. They were thin walled with dense cytoplasm and multinucleated. The nuclei of the giant cells were only half the size of those found in roots of infected tomato plants. Normal nematode growth and development followed giant cell formation. Females deposited eggs into a gelatinous egg mass within the tuber, and a necrotic ring formed around the female after eggs had been produced. Second-stage juveniles hatched, migrated, and re-infected other areas of the tuber. No males were observed from the tuber.

Influence of Fusarium oxysporum f. sp. glycines on the invasion and development of Meloidogyne incognita on soybean

Abstract: SUMMARY The root-hot nematode, Meloidogyne incognita and the wilt fungus, Fusarium oxysporu?n f. sp. glycines were inoculated simultaneously ont0 growing seedlings of soybean resistant to the fungus. Nematode invasion of roots was not affected but giant cells were invaded by the fungus and destroyed. The overall effect was to reduce the number of females and increase the proportion of males.

Effect of Meloidogyne incognita and M. javanica on Leaf Water Potential and Water Use of Tobacco.

Abstract: Greenhouse lysimeter and field microplot tests were conducted to evaluate the effects of Meloidogyne incognita and M. javanica on plant water relations and growth performance of NC 2326 flue-cured tobacco. In the greenhouse, afternoon leaf water potential values at 8-11 weeks after transplanting were lower by as much as 0.22 MPa in plants infected with either nematode than in the control plants. From 11 to 22 weeks, leaf water potential values were similar in all treatments. Over the course of the 22-week experiment, all infected plants showed similar evapotranspiration patterns, and plants in these treatments used 87-88% of the water utilized by noninfected plants. Biomass production from nematode-infected plants, however, was only about 50% of the biomass of control plants. The field microplot study showed water use patterns similar to those in the lysimeter study.

Effect of Sesame Intercropping Against the Root-Knot Nematode (Meloidogyne Incognita) in Okra1)

Abstract: Intercropping with sesame resulted in decreased penetration of okra roots by Meloidogyne incognita second-stage juveniles (J2) and delayed nematode maturation; it favoured development of M. incognita males and increased yields of okra and chickpea in field tests. The largest effect of intercropping sesame with okra was when they were 15-30 cm apart. In pot tests most J2 penetrated okra roots in sandy loam soil and fewest in clay soil.

Influence of Meloidogyne Incognita On Nodulation and Growth of Pea and Black Bean

Abstract: Meloidogyne incognita invaded aseptic roots of Pisum sativum and Phaseolus vulgaris and developed to adult females in about 19 days. Males were occasionally observed. Juvenile nematodes invaded nodules initiated by Rhizobium; nodules formed also on galls initiated by nematodes. M. incognita suppressed root and nodule growth. However, M. incognita stimulated the initiation of nodules which remained undeveloped. Effective nodules had more nitrogenase activity/g on plants with M. incognita than on those without nematodes. M. incognita increased the leghaemoglobin content of nodules on Pisum and decreased it on Phaseolus. All the effects of the nematode invasion were transient and 7d difference in invasion date altered the degree of effect recorded at different harvest dates.

Nematode population densities and yield of sweet potato and onion as affected by nematicides and time of application.

Abstract: Nematode population densities and yield of sweet potato and onion as affected by nematicides and time of application were determined in a 3-year test. Population densities of Meloidogyne incognita race 1 in untreated plots of sweet potato increased each year, but Helicotylenchus dihystera and Criconemella ornata did not. Ethoprop (6.8 kg a.i./ha) incorporated broadcast in the top 15-cm soil layer each spring before planting sweet potato reduced population densities of nematodes in the soil and increased marketable yield in 1982, but not in 1983 and 1984. When DD, fenamiphos, and aldicarb were applied just before planting either sweet potato or onion, nematode population densities at harvest were lower in treated than in untreated plots. No additional benefits resulted when the nematicides were applied immediately before planting both sweet potato and onion. Correlation coefficients (P = 0.05) between yield of marketable and cracked sweet potato storage roots vs. densities of M. incognita juveniles in the soil at harvest among years ranged from r = -0.33 to r = -0.54 and r = 0.31 to r = 0.54 (P = 0.05), respectively. Temperatures of -6 to -8 C in December 1981 and - 11 to - 13 C in December 1983 killed the onion crops. Correlation coefficients for marketable yield of onion seeded in 1982 and harvested in 1983 vs. densities of M. incognita juveniles and H. dihystera in the soil at harvest were r = -0.42 and r = -0.31 (P = 0.05), respectively. Key words: aldicarb, Allium cepa, chemical control, crop rotation, DD, ethoprop, fenamiphos, Ipomoea batatas, Meloidogyne incognita, root-knot nematode.