Showing papers on "Meloidogyne incognita published in 1972"

Ultrastructure of the hypersensitive reaction in roots of tomato, Lycopersicon esculentum L., to infection by the root-knot nematode, Meloidogyne incognita

Abstract: The hypersensitive reaction in roots of Lycopersion esculentum L., cv. Nematex, infected by Meloidogyne incognita was studied by light and electron microscopy. An increase in cytoplasmic density characterized by increased numbers of ribosomes, proliferation of endoplasmic reticulum and increased stainability of the cytoplasmic ground substance was the first symptom of the resistance response to the nematode larvae. Concomitant with this change was a disappearance of dense osmiophilic inclusions from the vacuoles of hypersensitive cells. There followed a general loss in distinctness of the cell membranes resulting in the disappearance of mitochondria and Golgi bodies. The fibrillar structure of the nucleoplasm disappeared and numerous electron-dense inclusions appeared in the nucleoplasm. Organized arrays of ribosomes appeared on the outer membrane of the nuclear envelope. The plastid stroma lost its granular texture although large starch grains persisted. Changes in cell structure were restricted to cells close to the nematode, but the products of cell breakdown moved away from this region through intercellular spaces. Giant cell production was generally suppressed by the hypersensitive reaction. Heat-treatment of Nematex roots inhibited the hypersensitive reaction and thus enabled giant cell formation. Treatment of roots with the growth substance kinetin did not inhibit the hypersensitive reaction although it appeared to enhance giant cell formation.

Nature of Sweet Potato Resistance to Meloidogyne incognita and the Effects of Temperature on Parasitism.

Abstract: Penetration, rate of development, and total population of Meloidogyne incognita in roots of susceptible 'Allgold' and resistant 'Nemagold' sweet potatoes increased with temperature 24-32 C. Rate of larval penetration in 'Allgold' was significantly higher than in 'Nemagold' after 48 hr of root exposure at 24, 28, and 32 C. At 24, 28, and 32 C (16 hr) day and 20 C (8 hr) night temperature the life cycle of M. incognita required 42, 32, and 28 days in 'Allgold', and 44, 33, and 31 days in 'Nemagold'; mature females in the first generation were 40, 40, 40, and 10, 22, 20 respectively. The correlation between the length of time roots were allowed to grow in the soil prior to inoculation and number of larvae recovered from the roots after inoculation was positive for 'Allgold' and negative for 'Nemagold'. Therefore, a root exudate repellent to M. incognita larvae is proposed as a hypothetical basis for resistance toM. incognita in sweet potatoes. Key Words: tpomoea batatas, Root observation box.

Disc-Electrophoretic Studies of Soluble Proteins and Enzymes of Meloidogyne incognita and M. arenaria.

Abstract: Soluble-protein and eight enzyme profiles obtained by polyacrylamide-gel electrophoresis were compared between Meloidogyne incognita and M. arenaria. Esterase, malate dehydrogenase, and[alpha]-glycerophosphate dehydrogenase patterns were distinctly characteristic for each species. Peroxidase and[alpha]-glycerophosphate dehydrogenase isoenzyme patterns varied when nematodes were propagated on different host plants. Similar profiles were obtained for two populations within each species. Antigenic proteins of these two species were compared following separation by electrophoresis. Key words: peroxidase, root-knot nematodes, characterization, antigens.

Interactions of Pratylenchus penetrans and Meloidogyne incognita as Coinhabitants in Tomato.

Abstract: Greenhouse experiments on the interactions of Pratylenchus penetrans and Meloidogyne incognita showed that the population densities of both nematode species were depressed whenthey coinhabited tomato roots. Fifty days after inoculation, the population level of a P. penetrans monoculture was about four times higher than when M. incognita was present. Conversely, M. incognita reproduced twice as fast alone as in combination. There were no significant differences in the numbers of P. penetrans when they were inoculated either 10 days prior to or after introduction of M. incognita. Root entry by P. penetrans was significantly inhibited by the presence of M. incognita. Split-root experiments showed that the inhibitory effects of M. incognita upon reproduction of P. penetrans involved factors other than the availability of feeding sites. On the other hand, the inhibitory effects of P. penetrans on M. incognita appeared to be primarily due to the quantity of available roots.

Infection of Seedlings of Alfalfa and Red Clover by Concomitant Populations of Meloidogyne incognita and Pratylenchus penetrans.

Abstract: Invasion of 2-day-old seedlings of 'Buffalo' alfalfa and 'Kenland' red clover by larvae of M. incognita and adults of P. penetrans, during 1-3 day periods of incubation at 24 C, was investigated in 50-mm petri dishes on 1% agar. Penetration by both nematodes increased arithmetically with increased numbers in inocula. P. penetrans invaded alfalfa more readily than red cover, but M. incognita invaded red clover more readily than alfalfa. Both nematodes inhibited root-elongation of alfalfa more than that of red clover. In combinations of 10 and 50 of both nematodes, invasion of both plants by both nematodes was the same as for each nematode alone. Penetration by M. incognita into alfalfa, but not into red clover, was significantly reduced when combinations of 50 M. incognita and 200 P. penetrans were inoculated simultaneously. In the presence of large numbers of entrant P. penetrans in both plants, penetration by M. incognita was highly significantly reduced. Penetration by P. penetrans was unaffected in the reciprocal situations.

Physiological Variation in the Genus Meloidogyne as Determined by Differential Hosts

Abstract: Four species of root-knot nematodes, namely Meloidogyne incognita (Kofoid et White) Chitwood, M. javanica (Treub) Chitwood, M. arenaria (Neal) Chitwood, and M. hapla Chitwood have a wide host-range and are widely distributed throughout the world. For each of the species there are certain non-hosts and these are different for each species, thus making it possible, through the use of differential hosts, to identify the species as well as detect pathogenic variations within a species. A knowledge of the nature and extent of this variation is needed for the development of varieties which possess a broad base for resistance.

Serological Relationship of Meloidogyne incognita and M. arenaria.

Abstract: Eight to ten precipitin bands were formed in a double immunodiffusion system comparing antigens of adult females of Meloidogyne incognita and M. arenaria. Most of the precipitin bands, based on band position and coalescence, were common to both species. Antiserum specific for M. incognita was prepared by cross absorption. Two populations of M. incognita were serologically identical, whereas two populations of M. arenaria differed slightly with respect to one weak precipitin band.

An Interpretation of the Ultrastructural Response of Tomato Roots Susceptible and Resistant to Meloidogyne incognita (Kofoid et White) Chitwood

Abstract: Giant cells, which are nutrient sources for the developing larvae of Meloidogyne incognita (Kofoid et White) Chitwood in susceptible tomato roots, are characterized by proliferation of cytoplasm and organelles, lobing of nuclei and irregularly thickened walls. The hypersensitive response of resistant tomato roots occurs more quickly than does the susceptible response and is characterized initially by intercellular deposits, loss of vacuolar electron-dense deposits, increased electron-density of the cytoplasm and an increase in the number of ribosomes. Eventually there is a loss of membrane-distinctness in the cell. The sequence and type of organelle changes suggest that the oesophageal secretions of the nematode into susceptible cells may de-repress a gene (s) to induce DNA synthesis. Subsequently auxin activity increases ribosomal RNA synthesis so facilitating protein synthesis and water and solute translocation. In a resistant plant the oesophageal secretions may activate a gene that produces a thermolabile enzyme that rapidly releases substances from the vacuoles or lysosomes and so manifests the hypersensitive response. The effect of this enzyme is overcome by exogenous kinetin thus supporting the role of cytokinins in the host response.

Control of the Root-knot Nematode, Meloidogyne incognita, on Mimosa (Albizzia julibrissin) by Chemical Dips

Abstract: Root -kno t nematodes severely attack mimosa (Albizzia ]ulibrissin Durazz.) and increase the incidence of wilt caused by Fusarium oxysporum Schlecht . f. sp. perniciosum (3). Fusarium-resistant clones are propagated from root-cuttings which often are infected by nematodes. Softwood cuttings of sprouts from roots readily take root (2, 5) and are a means of propagation which eliminates nematodes. However, it is often desirable for nu r se rymen to propagate directly from root-cuttings, thus elimination of nematodes from root-cuttings would be of value. The purpose of the present research was to evaluate the effectiveness of nematicides for control of root-knot nematodes and their effect upon growth of mimosa root-cuttings. O-ethyl, S,S-dipropyl phosphorodithioate (Prophos), a mixture of the 2,4-dichlorophenyl e s t e r o f m e t h a n e s u l f o n i c acid and 1,2-dibromo-3-chloropropane (SD 1897), O,O-die thyl O-[(p-methylsulfinyl) phenyl] phosphorothioate (Bay 25141), and ethyl 4 ( m e t h y l t h i o ) m t o l y l i s o p r o p y l phosphoramidate (Bay 68138) were used as dip treatments on mimosa root-cuttings that were moderately infected (1 female/cm) with the root.knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood. Treatments were as follows: (i) control; (ii) Prophos, 500 ppm; (iii) SD 1897 (500 ppm of SD 7~27 plus 1075 ppm DBCP); (iv) Bay 25141, 500 ppm; and (v) Bay 68138, 500 ppm.

Application of the Mojé method for testing the susceptibility of nematodes to chemicals

Abstract: In order to estimate analytically the susceptibility of nematodes of different stages, an immersion test proposed by Moje (1959) was examined. The standard procedure by the present authors is as follows: 1) to immerse nematodes in the solution of a given chemical for 24 hours 2) remove the solution of the chemical (needed two hours) and store the treated nematodes in sterile water for 22 hours and 3) separate mobile nematodes from the immobile by cotton wool filter for 24 hours and calculate mortality of the nematodes. Temperature during experiments is 25°.As a test nematode, the southern root-knot nematode, Meloidogyne incognita (Kofoid & White) was used. Larvae were obtained from egg-masses or infected soils by Baermann funnel technique or sieving plus Baermann method. It is convenient to use about a hundred nematodes for a treatment. Loss of M. incognita larvae during test process is considered to be about ten per cent. From 70 to 90 % of mobile larvae of M. incognita were isolated by the cotton wool filter specially designed, where the coefficient of the variation was less than twenty per cent in most experiments. The rate of separation reached the maximum within 24 hours. An example is given in Table 1.Storing treated nematodes in sterile water leads them to death or recovery from anesthetization. Relation of procedure to remove EDB emulsion and period for maintaining the nematodes treated with EDB in water, to the mortality of M. incognita larvae is shown in Table 2. Mortality due to 24 hours store was near to that for 46 hours.In most experiments, linear correlation was observed between concentrations in logarithm of EDB and mortality in probit at the level of 95 % confidence, except some lower concentrations (Figs. 2 and 3). Results of experiments conducted by the same person in August, September and October with M. incognita larvae from egg-masses on the roots of sweet potato in the same field are shown in Figs. 2 and 3. The figures indicate the reproductivity in a sense of the experiments by the present method. LC-50 of the nematodes from sweet potato to EDB was 86 and 80 ppm in August (from Figs. 2 and 3), 54 ppm in September and 77 ppm in October (Fig. 2). The relation between temperatures during immersion in EDB emulsion and the mortality of M. incognita larvae was also examined (Table 3).

The influence of the root-knot nematode, Meloidogyne incognita, on parsley yields under controlled greenhouse conditions

Abstract: Parsley growing in the coarse-textured soils of the coastal areas of southern California is sometimes severely infected with the root-knot nematode, Meloidogyne incognita. Affected plants at first appear slightly stunted and the older leaves chlorotic. With each cutting of the parsley greenery, the lower leaves die at a higher level on the plant and the yields lessen because the dead foliage cannot be used by parsley processors. Since yellow and/or dead leaves are harvested along with green foliage, they must be sorted out manually, thereby increasing grower and processor costs. Following the second cutting, many plants fail to produce harvestable foliage and frequently die. This article establishes the effects of root-knot upon yields of a highly susceptible parsely variety under controlled conditions of the greenhouse.

Histopathology of Thuja orientalis and Juniperus horizontalis plumosa Infected with Meloidogyne incognita.

Abstract: In an unsuitable host Meloidogyne spp. produced few or no mature females (2, 5, 6, 10). The most common reaction of this relationship is reduced plant growth (9). Although typical root galls are the most noticeable evidence of Meloidogyne infection, variable root symptoms have been reported on some resistant plants. Fassul io t is (8) observed that resistant Cucumis ficifolius and C. metuliferus infected with M. incognita acrita, showed only slight swelling whereas the susceptible C. melo developed extensive galls. Barriga-Olivares (1) reported that five Meloidogyne species attained only a low level of reproduction in two camellia species and that symptoms included typical galls, swelling and root tip necrosis. Nemec and Struble (10) found that coniferous woody ornamental plants were more resistant to M. incognita (Kofoid & White, 1919) Chitwood, 1949, than woody ornamental angiosperms. Typical symptoms on the coniferous species consisted of roots thickened two to three times their normal diameter, and slight galling. In this study the host-parasite relations of M. incognita were examined in roots of two conifers which supported a low level of nematode development and responded with atypical root symptoms (10). Plant species studied were Juniperus horizontalis plumosa Rehd. and Thu/a orientalis L. 'Dwarf Greenspike'. Preparation of inoculum and procedures used to grow and inoculate these plants have been reported (10). Rooted cuttings of both species were grown for 75 days

Effects of Nematodes on the Physiology of Vegetable Crops

Abstract: It is well known that the parasitic activity of root-knot nematodes is considerably influenced by temperatures. This study was done in 1971 to clarify the influence of different temperatures on the level of infestation by Cotton root knot-nematod, Meloidogyne incognita var. acrita and Northern root knot-nematode, M. hapla, and to find out the vegetable crops resistant or tolerant to these nematodes. Results are as follows:1. In order to secure the relationship between the level of nematode-infestation and the soil temperatures, more reliable data were obtained under the conditions of constant temperatures than under those of alternating temperatures. The trend of maximum soil temperatures in a time series, without taking the average of temperature measurements, served as a measure fitting to investigate the level of infestation under the conditions of alternating soil temperatures.2. Increase in the level of festation by M. incognita var. acrita and in the degree of injury to plants was found under the conditions of alternating temperatures having the mean of extremes of 32°C.3. If the amount of infestation by nematodes is observed at the time of visible root-knot formation, the infestations were most severe at a constant temperature condition of 27°C in both nematode species. However a rise in the constant temperature to 32°C remarkably decreased the level of infestation by M. hapla and, contrary to this trend, a full in the constant temperature to 18°C remarkably decreased the level of infestation by M. incognita var. acrita.4. Among the vegetable crops, tested species resistant to both nematodes were sweet pepper, green soybeen, chinese cabbage, and leaf mustard, and species to relativcly resistant to them was taro. Considerable infestation by M. hapla was observed in the root of watermelon var. Otome.