Showing papers on "Meloidogyne incognita published in 1982"

Phytoalexins and their Role in the Resistance of Plants to Nematodes.

Abstract: Phytoalexins are antibiotic compounds synthesized in an infected plant in response to infection. Nematodes are capable of eliciting phytoalexins in resistant plants. Resistant lima bean (Phaseolus lunatus) infected by Pratylenchus penetrans produces the phytoalexin coumestrol; soybean (Glycine max) infected by Meloidogyne incognita produces glyceollin; cotton (Gossypium hirsuturn) infected by M. incognita produces terpenoid aldehydes.

Genetic Basis of the Epidemiologic effects of Resistance to Meloidogyne incognita in the Tomato Cultivar Small Fry.

Abstract: The genetic nature of resistance and its epidemiologic effects on two Meloidogyne incognita populations were assessed in the F[sub1] hybrid tomato cv. Small Fry. The progeny of a Small Fry × Small Fry cross segregated in a 3:1 resistant:susceptible ratio, indicating the presence of a single, completely dominant resistance gene (LMiR[sub2]) in Small Fry. In a subsequent experiment, infection frequency and the rate of development of primary infection on resistant Small Fry × Small Fry segregates were compared to those on susceptible segregates and the susceptible cultivar Rutgers. Suppression in both infection frequency and rate of development of primary infection was entirely attributable to gene LMiR[sub2]. A single egg-mass population of M. incognita propagated for 12 generations on Small Fry showed an increased ability over the wild type population to parasitize plants containing the LMiR[sub2] gene but failed to completely overcome resistance. The relationship of this phenomenon to the genetics of the Lycopersicon esculentum-M. incognita interaction is discussed. Key words: infection frequency, primary infection, selection, rate of development.

Localization of Cuticular Binding Sites of Concanavalin A on Caenorhabditis elegans and Meloidogyne incognita.

Abstract: Utilizing a Concanavalin A (Con A)-hemocyanin conjugate, the majority of cuticular Con A binding sites were shown to be localized on the head region of Caenorhabclitis elegans and Meloidogyne incognita. Secretions which apparently emanated from the amphids and inner labial papillae did not label.

The Relationship Between Soil Populations of Meloidogyne incognita and Yield Reduction of Soybean in the Coastal Plain.

Abstract: In a replicated field plot experiment, the population density of Meloidogyne incognita was monitored biweekly through the overwintering period (December through April) between soybean crops. The population survived as second-stage juveniles whose numbers remained stable through the winter months and did not decline until February. The yields of plots planted with a M. incognita susceptible cultivar were negatively correlated with the numbers of juveniles recovered at all preplanting sampling dates. In the mid-winter period (December through February), a regression equation describing the relationship predicted a yield reduction (slope) equivalent to 5.36 kg/ha for each juvenile in a 10-cm³ soil sample. In two subsequent field experiments, conducted in different sites and years, mid-winter (November) sampling gave yield reduction predictions of 4.65 and 6.69 kg/ha. Tests of the null hypothesis gave no evidence to indicate that the three slopes differed (P = 0.05). A regression analysis of combined data from the three experiments determined a mid-winter predictive yield reduction of 5.31 kg/ha for each juvenile in the 10-cm³ sample. As the sampling time approached the planting date, there were changes in the predictive yield reductions due to each juvenile in a sample. These are best described by the equation,[gamma] (yield loss) = 54.47 - 0.67X + 0.0023X², where X equals the days remaining between sampling and planting. Soil sampling should be performed during mid-winter (November through January) for the most reliable prediction of soybean yield loss. Key words: root-knot nematode, population dynamics, Glycine max.

Development of Meloidogyne incognita in Stored Potato Tubers.

Abstract: The root-knot nematode Meloidogyne incognita (Kofoid 8: White, 1919) Chitwood, 1949 is the most widely distributed species of the genus Meloidogyne in the world (3,4). The two most important Meloidoffyne species which attack potatoes in the tropics (M. incognita and M. ]avanica) have relatively high temperature requirements for opt imum reproduction. Since potatoes are primarily cultivated in temperate areas of the world, root-knot nematodes are economically important only to specific geographic areas. However, attempts to extend the range of potato culture into tropical climates where Meloidogyne species are prevalent increase the potential for serious damage by this pest. Recent studies revealed that the resistance to M. incognita in roots and tubers are independent of one another (2). Apparently there are two types of infected tuber symptom expression. The most common type is the presence of tuber galling or deformation. In the other type, al though developing and egg-laying females may be within the tubers, surface galling is not expressed at harvest; however, symptoms may develop internally. When these internally infected tubers are stored for 2 months or more the majori ty exhibit external symptoms (2).

Influence of Initial Population Densities of Meloidogyne incognita on Three Chile Cultivars.

Abstract: The effects of Meloidogyne incognita on the Big Jim, Jalapeno, and New Mexico No. 6 chile (Capsicum annuum) cultivars were investigated in microplots for two growing seasons. All three cultivars were susceptible to M. incognita and reacted similarly to different initial populations of this nematode. Severe stunting and yield suppressions occurred at all initial M. incognita densities tested ranging from 385 to 4,230 eggs and larvae/500 cm³ soil. Regression analysis of the microplot data from a sandy loam soil showed yield losses of 31% for the 1978 season and 25% for the 1979 season for the three cultivars for each 10-fold increase in the initial population of M. incognita.

Potential of tissue culture for breeding root-knot nematode resistance into vegetables.

Abstract: Plant protoplast technology is being investigated as a means of transferring root-knot nematode resistance factors from Solanum sisymbriifolium into the susceptible S. melongena. Solanum sisymbriifolium plants regenerated from callus lost resistance to Meloidogyne javanica but retained resistance to M. incognita. Tomato plants cloned from leaf discs of the root-knot nematode resistant 'Patriot' were completely susceptible to M. incognita, while sections of stems and leaves rooted in sand in the absence of growth hormones retained resistance. Changes in resistance persisted for three generations. It is postulated that the exogenous hormonal constituents of the culture medium are modifying the expression of genetic resistance.

Influence of Soil Temperature on Meloidogyne incognita Resistant and Susceptible Cotton, Gossypium hirsutum.

Abstract: The degree of resistance by a cotton plant to Meloidogyne incognita is affected by soil temperature, particularly in moderately resistant cultivars, The total number of nematodes in the resistant and moderately resistant rools at 35 C was equal to, or greater than, the number in susceptible roots at 20, 25, or 30 C A shift in numbers to developing and egg-bearing forms of nematodes in the susceptible cultivar as tentperature increased indicates development was affected by temperature rather than by genetic resistance mechanisms However, the nematode resistant cultivar did not support maturation of nematodes until a soil tempurature of 35 C was attained This indicated that resistance mechanisms are partially repressed at 35 C and differences in nematode development cannot be explained in terms of accumulated heat units The moderately resistant cultivar was significantly more sensitive to the effects of high temperature than was the resistant cultivar

Varietal Response of Tomato to the Interaction of Salinity and Meloidogyne incognita Infection.

Abstract: Response of tomato (Lycopersicon esculentum) cultivars to a range of conductivity levels was tested in the presence and absence of Meloidogyne incognita. The conductivity levels were produced by appropriate adjustment of a 1:1 solution of sodium chloride and calcium chloride. The growth of M. incognita resistant ('Beefmaster' and 'Atkinson') and susceptible ('Hunts 2580' and 'Ronita') tomato plants was inversely related to soil salinity between EC[sube] 0 and 5 mmhos/cm. Nematode inoculation of salt-stressed plants significantly redttced plant height, fresh and dry weight, number of flowers, and fruit weight in most cultivars. In Hunts 2580, flower number and fruit weight increased; apparently flower production shifted from determinate to indeterminate, with negative implications for mechanical harvesting. Nematode reproduction on susceptible varieties also decreased with increase in salinity. Key words: Lycopersicon esculentum, salt stress, root-knot.

Ultrastructural aspects of the hypersensitive reaction in tomato root cells resistant to Meloidogyne incognita

Abstract: Juveniles of the root-knot nematode, Meloidogyne incognita (Kofoid et White) Chitw., enter the roots of resistant or susceptible plants in the same numbers (Reynolds et al., 1970). In the tomato cv. Hawaii cells around the anterior end of root-knot nematodes were killed within 24 hours of invasion of the roots (Riggs and Winstead, 1959). Rapid death of the cells isolates the nematode and injury is thus confined to a few cells (Rohde, 1972). This incompatible host-parasite interaction (hypersensitive reaction) has been reported as a common type of response in resistant plants for a wide variety of pathogens (Riggs and Winstead, 1959; Rohde, 1965; Klement and Goodman, 1967; Loebenstein, 1972; Brown, 1978; Politis and Goodman, 1978; Heath, 1980 and 1981). Ultrastructural changes that occur during the development of a hypersensitive reaction (HR) in tomato cv. Nematex, resistant to M. incognita, have been described by Paulson and Webster (1972). However, the mechanism by which resistant plants starve parasitic nematodes and prevent their development remains unknown. This study was undertaken to obtain additional data on the ultrastructural changes in response to penetration of M. incognita in the roots of tomato cv. Brech, resistant to this nematode. Histochemical tests were also made to investigate the nature of the material occurring between the cell wall and plasmalemma in cells surrounding the necrosis.

Influence of Salt concentration on infectivity and development of Meloidogyne incognita on tomato

Abstract: SUMMARY In greenhouse studies, infectivity and development of M. incognita on tomato was impaired by’increasing soil solution concentrations (ECe 1.5, 2.5, 3.5, 5.0 mmhos/cm) of NaCl, CaCl, or combinations of both salts. In two experiments, reduced infectivity was pronounced on a susceptible cultivar (Hunts) at al1 salt concentrations, while infectivity was reduced primarily at higher Salt concentrations on a moderately resistant host (Beefmaster). Development of entrant juveniles was significantly depressed by both salts on cv. Hunts, but merely delayed on cv. Beefmaster. Impaired infectivity and development resulted in population reduction to 23% and 39% of controls on Beefmaster and Hunts, respectively, six weeks after infection. RESUME Influence de la concentration en sels sur l’infectivite et ’le developpement de Meloidogyne incognita sur tomate

The Effect of Arthrobotrys conoides on Meloidogyne incognita Population Densities in Corn as Influenced by Temperature, Fungus Inoculum Density, and Time of Fungus Introduction in the Soil.

Abstract: In greenhouse experiments, the effect of Arthrobotrys conoides on Meloidogyne incognita population densities as affected by soil temperature, inoculum density, and green alfalfa was determined. The effect on M. incognita population densities was greater at a soil temperature of 25 C than at 18 or 32 C. Nematode control by A. conoides was most effective when the fungus was introduced into the soil 2 wk prior to nematode inoculation and planting of corn. Inoculum density of A. conoides was positively correlated with plant shoot weight (r = 0.81) and negatively correlated with numbers of Meloidogyne juveniles (r = -0.96), eggs (-0.89) and galls per gram of root (-0.91). A. conoides was not isolated from green alfalfa, but was isolated from alfalfa-amended soil to which no fungus had been added.

Population Dynamics of Meloidogyne incognita on Corn Grown in Soil in Fested with Arthrobotrys conoides.

Abstract: Microplot and greenhouse experiments were conducted to evaluate the effects of soil incorporation of the nematophagous fungus Arthrobotrys conoides and green alfalfa mulch on the population dynamics of Meloidogyne incognita on corn. Reproduction of M. incognita and the incidence of root galling were reduced by the addition of A. conoides and/or green alfalfa in all tests. Numbers of juveniles were reduced by as much as 84%, and eggs were fewest in early to mid-season soil samples from microplots. Yields increased in treatments with A. conoides and/or green alfalfa in greenhouse tests and in the microplot tests in 1979. No interaction was found between the fungus and green alfalfa in the reduction of the nematode population. Key words: biological control, population dynamics, ecology, green alfalfa, root-knot nematode, soil amendment, nematophagous fungus, nematode trapping fungus, organic mulch.

Reaction of wild and domesticated Triticum and Aegilops species to root-knot nematodes (Meloidogyne).

Abstract: Twenty-nine accessions of wild wheats and commercial cultivars of Triticum monococcum var. boeoticum, T. urartu, T. timopheevii var. araraticum, T. turgidum var. dicoccoides, durum wheat T. turgidum var. durum, and bread wheat T. aestivum, were hosts for Meloidogyne incognita, M. javanica, and M. naasi, assessed by egg production in glasshouse and field tests. No sources of resistance to Meloidogyne were found in Triticum. Four host races of M. incognita reproduced on durum and bread wheat cultivars. One accession of Aegilops squarrosa from Afghanistan was resistant to four host races of M. incognita and four isolates of M. javanica, but not to M. naasi. Twelve other A. squarrosa accessions from Afghanistan and Iran and related Aegilops spp. were hosts for all Meloidogyne spp. The potential for development of Meloidogyne-resistant wheat cultivars is discussed.

Effect of Diurnal Changes in Soil Temperatures on Resistance to Metoidogyne incognita in Tomato.

Abstract: Thermoper iodism is known to influence the growth of tomato, Lycopersicon esculenturn (10), but its effect on reproduct ion of the root-knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood, infecting tomato has not been reported. T o m a t o genotypes carrying the Mi gene for resistance to root-knot nematodes lose their resistance when exposed to constant high temperature (4,5,6,8). T h e objective of this research was to investigate the effects of h igh/ low (day/ night) temperature on the resistance of Lycopersicon esculenturn Mill. and L. peruvianurn var. dentatum Dun. genotypes to M. incognita. T h e degree of nematode reproduct ion on the host plant, i.e., host efficiency (3,9), was the parameter used for determining host resistance. Two greenhouse experiments were conducted. In the first experiment, selected plant introductions of L. peruvianum var. dentaturn were used: PI 306811, PI 1291492(sib)-5-4, PI 129149-3-1-2, and PI 129149-32-1 (R2). In the second experiment, L. esculenturn selections and commercial cultivars were tested: Floradade, Nematex-22, Floradade × Nematex-22, Patriot-17, Piersol, P! 266376, PI 129149-2(sib)-5.4, and PI 129149-2(sib)-5-I 6 ×43. T e n 12-day-old tomato seedlings of each cultivar or selection were individually transplanted into plastic pots (12 cm d × 16.5 cm deep) containing previously autoclaved sandy soil. T h e pots were placed in a controlled temperature tank and maintained at a constant soil temperature (32.5 C) for the durat ion of the experiment. T e n 12-day-

Effects of Meloidogyne Incognita and Fusarium Oxysporum F. Vasinfectum On Plant Growth and Mineral Content of Cotton, Gossypium Barbadense L

Abstract: The effects of Meloidogyne incognita Race 3 and Fusarium oxysporum f. vasinfectum on wilt expression, nematode infestation, plant growth and mineral content were determined on cotton (Gossypium barbadense L.) cultivar Giza 69. The presence of the nematode enhanced the development and severity of wilt. The disease was observed 10 days earlier in the case of infection with both organisms than with the fungus alone. However, the level of wilt incidence, nematode infestation (root-galls and egg masses) and reduction in plant growth were almost more than 2-fold when the two pathogens were present together. Fungal infection induced a significant reduction in K, Mn, Mg, Zn and Cu; but caused a significant increase in N and Ca. Combined infection with both pathogens resulted in a significant reduction in Fe, K, Mg, Zn and Cu and a significant increase in N and Ca. Nematode infection, however, produced a significant increase in N and Zn and a decrease in Cu and Fe.

Optimum Initial Inoculum Levels for Evaluation of Resistance in Tomato to Meloidogyne spp. at Two Different Soil Temperatures.

Abstract: The effects of Meloidogyne incognita or M. javanica at five initial inoculum levels of 20, 100, 200, 1,000, and 2,000 eggs and infective juveniles per seedling on 'Floradade,' 'Nemarex,' 'Patriot,' and 'PI 129149-2(sib)-5' tomatoes maintained at 25 or 32.5 C were studied. The number of egg masses on roots of the susceptible cultivar Floradade was similar for both species of root-knot nematodes at either 2.5 or 32.5 C soil temperatures. At 25 C, very low numbers of egg masses were produced by both species of root-knot nematodes on Nematex, Patriot, and Lycopersicon peruvianum PI 129149-2(sib)-5. At 32.5 C, the best inoculum level for assessing resistance in these tomato genotypes was 200 eggs and infective juveniles per seedling. With 28 days of incubation, this temperature and inoculum level produced quantitative differences in resistance for both species of Meloidogyne.

Effects of Management Practices on Meloidogyne incognita and Snap Bean Yield.

Abstract: Phenamiphos applied at 6.7 kg ai/ha through a solid set or a center pivot irrigation system with 28 mm of water effectively controlled root-knot nematodes, Meloidogyne incognita, and resulted in greater snap bean growth and yields irrespective of growing season, tillage method, or cover crop system. The percentage yield increases attributed to this method of M. incognita control over nontreated controls were 45% in the spring crop, and 90% and 409% in the fall crops following winter rye and fallow, respectively. Root galling was not affected by tillage systems or cover crop, but disk tillage resulted in over 50% reduction in bean yield compared with yields from the subsoil-bed tillage system. Key words: root-knot nematode, phenamiphos, tillage system, cover crop, nemagation, Phaseolus vulgaris.

Chloroplast Differentiation in Tomato Root Galls Induced by the Root Knot Nematode Meloidogyne incognita.

Abstract: Primary roots of tomato, Lycopersicon esculentum cv. Marglobe, were cultured aseptically on agar containing a standard nutrient formulation with or without kinetin. When secondary roots developed, cultures were inoculated with the root-knot nematode, Meloidogyne incognita. Following inoculation, the cultures were divided into two groups which were incubated either in total darkness or in 16-h light-8-h dark cycles. At 24 h, 1, 2, 3, and 4 wk after incubation, roots from all cultures were processed for transmission electron microscopy. Fine structural observation of the parenchyma tissue in galls from the inoculated cultures indicated that starch containing plastids or amyloplasts, which are usually present and remain undifferentiated in these root cells, developed into chloroplasts. These chloroplasts contained a membrane system indistinguishable from those found in leaves of intact plants. Although plastid development was not affected when uninoculated cultures were incubated in the light, differentiation of the amyloplast was induced when roots were cultured on the medium containing kinetin. These results suggest that plastid differentiation in the inoculated tissue may be influenced by an accumulation of kinetin in the gall, which is induced by the nematode and serves as the nutrient sink for its feeding.

Susceptibility of different developmental stages of the root‐knot nematode, Meloidogyne incognita, to the nematicide oxamyl

Abstract: SUMMARY Oxamyl (6.25 μg ml-1 soil water) was applied to cucumber roots containing Meloidogyne incognita at different stages of nematode development. Oxamyl was more effective in reducing the proportion of juveniles which developed into females when applied soon after infection to second stage juveniles than when applied later (to third and fourth stage juveniles). Early application of oxamyl also significantly reduced the proportion of females with egg masses, whereas late application had no such effect. However, the number of eggs per egg mass and the size of the young adult females was significantly reduced by all oxamyl treatments - the earlier the application the greater the effect. These results support the hypothesis that actively feeding second stage juveniles of Meloidogyne spp. are more susceptible to systemic nematicides than are the non-feeding third and fourth stage juveniles.

Studies on Interaction of Root-Knot Nematode, Meloidogyne Incognita and Tobacco Mosaic Virus in Tomato**

Abstract: Estimation of phosphorus, nitrogen and potassium in shoots and roots of tomato varieties as influenced by virus and nematode infections singly or in different combinations was investigated. The roots in nematode affected as well as in nematode virus combined treatments showed a higher percentage of total N, P and K as compared to shoots. The N, P, K percentage of shoot was higher in cases of healthy plants i.e., virus alone (V) and virus preceding nematode inoculation (V+n) treatments while just the reverse was observed in both, simultaneous inoculated (N+V) and the treatment where nematode preceded virus inoculation (N+v). In the roots of N+V and N+v treatments there was more accumulation of N, P and K.

Research Papers: Susceptibility of Six Soybean Cultivars to Meloidogyne incognita Race 4

Abstract: Bedford, Bragg, Forrest, Hardee Late Selection, Hutton and Jupiter soybeans were tested for their susceptibility to a race 4 population of Meloidogyne incognita from okra in greenhouse studies. Based on gall index and larval population levels, Hutton is highly resistant to this root-knot nematode population, while the remaining cultivars were susceptible. Many well-developed females with eggs were present in the roots of susceptible plants, while few were present in the roots of Hutton. Histological examination of roots of susceptible cultivars showed an average of six thick wall, multinucleated giant cells within parenchyma cells of the vascular tissue. Very few small giant cells were located in the vascular tissue of Hutton around the head of female nematodes.

Effect of Temperature on Survival of Meloidogyne incognita in Flooded and Fallow Muck Soil

Abstract: Infective populations of Meloidogyne incognita (Kofoid & White) Chitwood remained high in muck soil after 4 wks of flooding or fallowing at temperatures of 10, 15, 20, 25, and 30C. After 8 wks, infective populations were still high for temperatures of 10 and 15C but there was a sharp reduction in infectivity at 20C and further reductions at 25 and 30C in both fallowed and flooded soil. After 12 wks, infectivity was only slightly reduced at 10 and 15C but was again greatly reduced at 20C and was very low at 25 and 30C in both fallowed and flooded soil. Infectivity was slightly higher after 8 and 12 wks in soil that had been flooded than in soil that had been fallowed. Growth of cucumbers (Cucumis sativus L.) was greatly enhanced by the reduced infectivity of the nematodes in soil held at the higher temperatures.

Chemically-induced resistance to Rotylenchulus reniformis by ethephon growth regulant and relevant pathometabolites in mango seedlings

Abstract: Plant growth regulators have been reported to induce broad spectrum effects and to modify the physiology of the plant and nematode parasitism (Davide and Triantaphyllou, 1968; Mjuge and Viglierchio, 1976). It was shown in an earlier study that the effects of plant retardants and promotors on the growth of guava and associated Meloidogyne incognita (Kofoid et White) Chitwood populations were largely dosage dependant (Badra et al., 1980). Roots of plants pretreated with supra-optimal doses of daminozide and chlorocholine chloride retardants or ethephon and GA stimulators were less galled than untreated plants or those receiving sub-optimal doses of the chemicals. Present research attempted to trigger resistance to nematode parasitism in a host plant by the application of supraoptimal rates of an ethylene-generator chemical. Metabolic changes, mainly auxin-phenol interactions, were investigated as a possible underlying mechanism in host resistance (Giebel, 1970).

Meloidogyne cruciani n. sp. a Root-knot Nematode from St. Croix (U.S. Virgin Islands) with Observations on Morphology of This and Two Other Species of the Genus.

Abstract: Meloidogyne cruciani n. sp. infecting tomato (Lycopersicon esculentum Mill.) in the U.S. Virgin Islands is described and illustrated. M. cruciani is distinguished from other species of the genus by having punctations around the anus of the female and by the second-stage juveniles possessing tri-lobed esophageal glands which are longer than most other species, with their posterier end at about 46.4% of the body length. The esophageal glands of the immature and adult females are contained in five separate lobes.