Showing papers on "Meloidogyne incognita published in 1981"

Oogenesis and the Chromosomes of the Parthenogenic Root-knot Nematode Meloidogyne incognita.

Abstract: 220 populations of Meloidogyne incognita and related forms from 46 countries reproduced by mitotic parthenogenesis (apomixis). Determination of somatic chromosome numbers from oogonia and oocytes revealed the existence of a predominant, possibly triploid race A with 3n = 40 to 46 and a rare, diploid race B with 2n = 32 to 36 chromosomes. There is no correlation between cytological races and the four recognized host races of this species. The characteristic behavior of prophase I chromosomes of maturing oocytes, which results in a prolonged prophase stage, is a unifying feature of all forms of M. incognita and supports monophyletic evolution, distinct from that of other Meloidogyne species. Extensive chromosomal polymorphism detected among populations can be helpful in elucidating the cytological pathway of evolution of the species.

Effects of Soil Temperature and Planting Date of Wheat on Meloidogyne incognita Reproduction, Soil Populations, and Grain Yield.

Abstract: Wheat cultivars Anza and Produra grown in winter in California were planted in Meloidogyne incognita infested and noninfested sandy loam plots in October (soil temperature 21 C) and November (soil temperature 16 C) of 1979. Meloidogyne incognita penetrated roots of mid-October planted Ataza (427 juveniles/g root), developed into adult females by January, and produced 75 eggs/g root by harvest in April. Penetration and development did not occur in late plantings. Anza seedlings grown in infested soil in pots buried in field soil in early spring were not invaded until soil temperature exceeded 18 C. Meloidogyne incognita juveniles can migrate through soil and penetrate roots at temperatures above 18 C (activity threshold), however development can occur at lower temperatures. Grain yields were not significantly different between nematode infested (3,390 kg/ha) and noninfested (2,988 kg/ha) plots. Winter decline of eggs and juveniles in two late plantings anti in fallow soil were 69, 72, and 77%, respectively, but egg and juvenile decline was only 40% in the early Anza plots that supported nematode reproduction in the spring. Delay of planting date until soil temperature is below 18 C is suggested to maximize the use of wheat in rotation as a nematode pest management cultural tactic for suppressing root-knot nematodes.

Inhibition of development of Meloidogyne incognita by root and foliar applications of oxamyl

Abstract: SUMMARY Oxamyl (2.5 μg cm-3sand) applied to the roots of cucumber seedlings significantly reduced the number of vermiform second stage juveniles of Meloidogyne incognita which developed into swollen forms for at least 30 days. However, when cucumber seedlings containing nematodes were removed from oxamyl-treated sand 10 days after the pesticide was applied and placed in clean sand a large proportion of the juveniles had become swollen after a further 18 days. This suggested the effect of oxamyl on nematode development was reversible. A single foliar application of oxamyl (25–100 μg) in distilled water was also found to significantly reduce development of second stage juveniles to saccate forms However, the use of various adjuvants with a threshold foliar treatment (25 μg oxamyl) failed to significantly improve its activity.

Occurrence of root-knot and cyst nematodes in Pakistan.

Abstract: Little is known about the occurrence of root-knot and cyst nematodes in Pakistan. Brown (1962) reported Meloidogyne incognita on banana and M. javanica on eggplant and sugarcane and Riaz and Khan (1973) found M. hapla on potato. The only records for cyst nematode species are those of Akhtar (1961) for Heterodera schachtii in association with sugarcane and of Brown (1962) for Globodera tabacum (syn. Heterodera tabacum) in tobacco fields. A general survey of crops was therefore carried out in 1978-79 and the following nematodes were identified: Globodera rostochiel1sis (Wall.) Mulvey et Stone on potato; Heterodera avenae Wall. on maize and wheat; H. mani Mathewes on wheat; H. motlti Khan et Husain and H. sacchari Luc et Merny on sugarcane; H. sclzaclztii Schmidt on cauliflower and sugarcane; H. Vigl1i Edward et Misra on cowpea; H. zeae Koshy, Swarup et Sethi on maize and wheat and on citrus and pear; Meloidogyne arenaria (Neal) Chitw. on maize, sugarcane and tomato; M. hapla on soybean, chilli, pyrethrum, ginger, okra, potato, tomato and tobacco; M. incognita (Kofoid et White) Chitw. on banana, hyacinth-bean, eggplant, chilli, cotton, pyrethrum, ginger, maize, okra, papaw, sugarbeet, tomato, tobacco and luffa: M. javanica (Treub) Chitw. on banana, hyacinth-bean, eggplant, okra, papaw, sugarbeet, and luffa. To the best of my knowledge, this is the first report from Pakistan for Globodera rostochiensis, Heterodera avenae, H. mani, H. mothi, H. sacchari, H. vigni, H. zeae and Meloidogyne arenaria.

Dynamics of Concomitant Populations of Hoplolaimus columbus, Scutellonema brachyurum, and Meloidogyne incognita on Cotton.

Abstract: Cotton seedlings grown in a greenhouse and a growth chamber were inoculated with Scutellonema brachyurum, Hoplolaimus columbus, and Meloidogyne incognita, singly and in all possible combinations, at two initial population (Pi) levels (100 and 300/100 cm³) S brachyurum alone was not pathogenic to cotton at these population levels It fed primarily as an ectoparasite but matured and reproduced within the root when it penetrated Populations of S brachyurum increased in the presence of H columbus but were suppressed by M incognita H columbus suppressed dry shoot weights of cotton (P = 005) at a Pi of 300/100 cm³ soil Simultaneous inoculation of H columbus with either M incognita or S brachyurum increased H columbus populations over treatments with H columbus alone, both at 60 and 90 d after inoculation M incognita suppressed cotton shoot weights significantly (P = 005) at both Pi levels Inoculation with S brachyurum increased M incognita populations 60 d after inoculation, while H columbus suppressed populations of M incognita Most larvae of M incognita did not develop to maturity in the presence of H columbus Giant cells aborted and were necrotic 20-25 d after inoculation Since M incognita and H columbus feed on different tissues, the inhibition of M incognita may have resulted from a physiological effect of H columbus on the host

Influence of photoperiod and temperature on migrations of meloidogyne juveniles.

Abstract: Photoperiod influences the migration of M. incognita juveniles toward tomato roots. Approximately 33% migrated vertically 20 cm in 7 days to roots when 12 h dark were alternated with 12 h light. Only 7% migrated when light was constant for 24 h. Vertical migration of M. incognita juveniles was studied at 14, 16, 18, 20, and 22 C. The migration of M. incognita juveniles begins at about 18 C and reaches its maximum at 22 C. The migration of M. hapla and M. incognita juveniles were compared at 14, 18, and 22 C. Juveniles of M. hapla were able to migrate at a lower temperature than those of M. incognita. With M. hapla, there was no significant difference in migration between 18 and 22 C.

The Development and Influence of Meloidogyne incognita and M. javanica on Wheat.

Abstract: The effects of soil temperature and initial inoculum density (Pi) of Meloidogyne incognito and M. javanica on growth of wheat (Triticum aestivum cv. Anza) and nematode reproduction were studied in controlled temperature baths in the glasshouse. Nematode reproduction was directly proportional to temperature between 14 and 30 C for M. incognita and between 18 and 26 C for M. javanica. Reproduction rates (Pf/Pi, where Pf = final number of eggs) for Pi's of 3,000, 9,000, and 30,000 eggs/plant were greatest at each temperature when Pi = 3,000. Maximum M. incognita reproduction rate (Pf/Pi = 51.12) was at 30 C. At 26 C, M. javanica reproduction (Pf/Pi = 14.82, 9.02, and 4.23 for Pi = 3,000, 9,000, and 30,000, respectively) was about half that of M. incognita when Pi = 3,000 or 9,000 but similar when Pi = 30,000. Reproduction of both species was depressed between 14 and 18 C. Shoot and root growth and head numbers were inversely related to soil temperature between 14 and 30 C but were not affected by the Pi of M. incognita when 7 d old seedlings were inoculated. When newly germinated seedlings were inoculated with M. incognita or M. javanica, the Pi did not affect shoot and root fresh weights, shoot/root ratio, and tillering, but it did reduce root dry weight (M. javanica at 26 C) and increase shoot dry weight (M. incognita at 18-22 C). The optimum temperature range is lower for wheat growth than for nematode reproduction. Wheat cv. Anza is a good host for M. incognita and M. javanica, but it is tolerant to both species.

Effect of some indigenous plant materials and oil-cake amended soil on the growth of tomato and root-knot nematode population

Abstract: Applications for both soil organic amendments and dry products of certain indigenous plants which are known to possess nematicidal properties have received attention in the recent years for the control of plant parasitic nematodes. In the present study the efficacy of ten dried plant materials viz., Eclipta alba, Canabis sativa, Chenopodium amaranticolor, Atropa belladonna Amaranthus sp., (whole plant) Calotropis gigantea, Ricinus communis, Datura metch, Mangifera indica and Azadirechta indica (leaves only) and five oil cakes, Carthamus tinctorius, Shorea robusta, Calophyllum inophyllum, Pongamia glabra and Azadirechta indica were tested against root-knot nematode on tomato. Each of the dried plant material and cake was ground to fine power and tests conducted in 10 cm plastic pots. Three dosages were selected after the preliminary trial for each soil amendment. For every dosage, six replications were maintained out of which three were inoculated with 1000 larvae of Meloidogyne incognita per pot while the other three were left uninoculated as checks. Besides, adequate checks were also kept without any amendments. Observations were recorded on plant growth characters, nematode populations (both in roots and in soil) as also of the rhizosphere fungi of each treatment. Among plant materials, Eclipta alba was most effective followed by Azadirechta indica, Datura metch and Amarantus sp. in reducing rootknot galls while Cannabis sativa, Ricinus communis and Calotropis gigantea also showed a high inhibition of nematode population. Length and weight of tomato plants in respense to above materials also significantly increased in comparision to infested control. In case of cakes, Shorea robusta, Pongamia glabra, Azadirechta indica and Carthamus tinctorius reduced galls as well as nematodes in soil while Calophyllum inophyllum did not reduce the gall number but inhibited nematode population. The results thus indicated that all the plant extracts and cakes tested possess nematicidal properties.

Yield Response and Injury Levels of Meloidogyne incognita and M. javanica on the Susceptible Tobacco 'McNair 944'.

Abstract: The effects of Meloidogyne incognita and M javanica on a susceptible tobacco (Nicotiana tabacum L) cv McNair 944 were investigated in field microplots during 1978 and 1979 Three initial inoculum levels-4, 16, and 64 nematode eggs and/or second-stage larvae per 100 cm(3) of soil-were used for each nematode species Data obtained from the experiments included plant yield and the amount of reproduction of the two nematode species At comparative inoculum levels, M javanica was more aggressive than M incognita on tobacco and caused approximately twofold more yield suppression than M incognita The calculated initial population of M incognita, derived from the average for 2 yr, which produced a 7% suppression in plant yield was four eggs and/or second-stage larvae per 100 cm(3) of soil; whereas less than one M javanica egg and/or second-stage larvae per 100 cm(3) of soil was needed to achieve similar suppression Nematode reproduction varied in the 1978 and 1979 tests, but similar trends were observed Early season M javanica populations were greater than those of M incognita, but late season populations of M incognita were twice anti three times those of M javanica

Effect of Crotalaria spectabilis and two nematicides, on numbers of Meloidogyne incognita and Helicotylenchus dihystera.

Abstract: An experiment in an infested field indicated that Crotalaria spectabilis at 17 or 34 plants/m2, Nemagon 20G (granular formulation with 20% dibromochloropropane) at 3, 6, or 9 g/m2, or Basamid (powder formulation with 85 % dazomet at 25, 50 or 75 g/m2, decreased numbers of Meloidogyne incognita juveniles by 90% within 2 months. During the first 2 months after planting, C. spectabilis did not decrease numbers of Helicotylenchus dihystera, whereas Basamid at all three rates and Nemagon at 6 and 9 g/m2 decreased numbers by approximately 90%. Nemagon at 3 g/m2 gave less than 50% control of H. dihystera. Okra (Hibiscus esculentus) grown for 6 months on land previously treated with Basamid or Nemagon doubled numbers of M. incognita compared with untreated land planted with the same crop. No such increase occurred in land planted with C. spectabilis for 2 months followed by okra. Okra had no effect on H. dihystera whereas M. incognita was scarce in soil where C. spectabilis had been grown for 8 months.

The Effect of Meloidogyne incognita and Tissue Wounding on Severity of Seedling Disease of Cotton Caused by Rhizoctonia solani.

Abstract: Scans of slash pine wood chips infested with pine wood nematodes showed coiled aggregates of 5-10 nematodes in the axial resin canals, and 1-2 nematodes folded in the radial resin canals. Observations of the pine wood nematode by SEM showed the head to be offset with six labial lohes. A smaller circle nf six inner lobes surrounded the stonta. A single lahial sensillmn was observed on each of the two subventral and two snbdorsal lobes. The two opposite lobes, without sensilla, bore a pore-like amphid. The female vttlva flap was observed to be a pouch. In addition to Iwo pairs of copulatory papillae previously described for the male, three additional papillae were observed: an additional post-anal pair, and a single papilla anterior to the cloaca. Spicules were fused ventrally. Distal spicule ends terminated in two fused half discs. Caudal alae were angular at the tail terminus, but era'led inward at the corners to appear oval. Lateral lields had four lateral striations.

Applying Nematicides through an Overhead Sprinkler Irrigation System for Control of Nematodes.

Abstract: Phenamiphos, ethoprop, and carbofuran each at 6.7 kg a.i./ha were applied to squash, southern pea, and corn via injection into a sprinkler irrigation system. This method was then compared with a conventional application of phenamiphos and ethoprop granules spread on the soil surface and incorporated into the top 15 cm for control of Macroposthonia ornata and Meloidogyne incognita. Nematode populations in the soil and root-gall indices were lower, and yields greater, in treated than in untreated plots, but there were no significant differences between the methods of application in most comparisons.

Scanning Electron Microscope Study of the Root-knot Nematode (Meloidogyne incognita) on Tomato Root.

Abstract: This study examines the types of structural information that can be gained by utilizing the scanning electron microscope (SEM) and a cryofracture technique to examine the host-parasite interaction. Roots of tomato, Lycopersicon esculentum cv. Marglobe, were cultured aseptically and inoculated with the root-knot nematode, Meloidogyne incognita. Twenty-four hours to four weeks after inoculation, developing galls were removed from the cultures and processed for SEM observation. The cryofracture technique was used to reveal internal structural features within the developing galls. The results illustrate structural details concerning penetration of the roots, differentiation of syncytia, and development of the nematodes beginning with the second-stage larvae and ending with adult egg-laying females.

Herbicide effects in nematode diseases.

Abstract: Herbicide use has provided agriculture with cost effective weed control and cont inued good crop yields, bu t occasional complications and adverse effects have been observed in the field. A recent review (1) discussed the effect of herbicides on plant diseases. Other studies have repor ted on the effects of herbicides on nematode infected crop plants (2,5,6,7,8,9,10,12). Effects ranged from aggravation of crop damage caused by nematode parasitism to reduced damage and lower nematode popula t ion levels. T h e differences appear to refiect the different systems, herb ic ide-crop-p lan t nematode, examined. This repor t extends these observations to include the effects of several herbicides applied by two methods to soybeans (Glycine max L.) and tomato (Lycopersicon esculentum L.) in root-knot nematode (Meloidogyne incognita) infested soil. Stock cultures of M. incognita were maintained on tomato (Lycopersicon esculentum cv. VF 145) in the greenhouse. In one experiment, soybean seeds, cv. Williams, were sown in 10-cm pots containing a mixture of sterilized clay soil and sand (1:1). After germination the seedlings were th inned to one plant per pot. Twentyday-old seedlings were each inoculated with 1,000 freshly hatched M. incognita larvae by pouring the nematode suspension into holes around the base of the plant, pressing the holes closed, and watering. Seven days after inoculation the herbicides EPTC (Sethyl dipropylthiocarbamate), glyphosate (N-[phosphonomethyl] glycine), or oryzalin (3,5-dinitro-N 4, N4-dipropylsulfanilamide) were applied at six concentrations as foliar sprays to runoff. Soil contaminat ion by the herbicides was prevented by a luminum foil covers. Plants were harvested 45 d later; the number of galls and nodules counted; and the shoot weight, shoot height, and pod and leaf number determined.

Identification of the Chromosome Carrying the Factor for Resistance to Meloidogyne incognita in Tobacco.

Abstract: To identify the chromosome carrying the factor for resistance to Meloidogyne incognita in tobacco, crosses were made between resistant tobacco 'NC95' as pollen parent and each of the 12 tobacco monosomics (A-L) representative of the Tomentosae half of the Nicotiana tabacum chromosome complement. Of the F seedlings, 927 plants were grown for observation. From these, 223 plants were selected as possible monosomics on the basis of morphological characteristics. These plants were self-pollinated, and the resulting F plants were inoculated with both M. incognita acrita and M. incognita incognita. Sixteen F populations, derived from the haplo-G monosome, were completely resistant. All of the F populations derived from the other 11 monosomic crosses segregated into a 3:1 (resistant:susceptible) ratio. These results indicate that the factor for resistance to M. incognita is located on the G chromosome of N. tabacum. This is the first report establishing the N. tabacum chromosome that carries the factor for root-knot resistance. The results are consistant with our earlier evidence that M. incognita resistance in tobacco is derived from N. tomentosa, a species in the section Tomentosae of the subgenus Tabacum, genus Nicotiana. The other 12 chromosomes of N. tabacum have affinities with N. sylvestris, section Alatae, subgenus Petunoides, genus Nicotiana.

Infectivity of three Meloidogyne spp on soybean in Nigeria

Abstract: Three soybean cultivars, Jupiter, Williarns and TGM 280-3 were inoculated with Meloidogyne incognita, M. javanica and M. arenaria. Williams was susceptible to the three Meloidogyne species. Jupiter and TGM 280-3 were attacked by M. incognita and M. arenaria, but not by M. javanica. Fresh root and fresh top weights of Williams attacked by nematodes did not differ significantly from those of the control (P = 0.05); fresh root and fresh top weights of Jupiter and TGM 280-3 attacked by nematodes were significantly less than those of the control plants. Williams was more tolerant to Meloidogyne infection than were Jupiter and TGM 280-3.

Foliar Spray Effects of Selected Amino Acids on Sunflower Infected with Meloidogyne incognita.

Abstract: Overman and Woltz (3) indicated that amino acid antimetabolites applied to tile soil suppressed reproduct ion of Paratrichodorus minor (Trichodorus christiei) and root galling caused by Meloidogyne incognita on tomatoes. Eight DL-amino acid antimetabolites similarly decreased the population of Aphelenchoides ritzemabosi on Lucerne, whereas DL-alanine suppressed the populat ion of Heterodera spp. without harming the host plants (5). Evans and Trudgi l l (1) found that DL-methionine was toxic to H. rostochiensis (Globodera rostochiensis) infecting potato plants. Methionine did not act as a contact nematicide; it was presumably ingested in sap extracted from giant cells after being taken up by the host plant. Krishna Prasad and Setty (2) showed that two amino acids used

Effect of Foliar Application of Carbofuran and a Related Compound on Plant-parasitic Nematodes under Greenhouse and Growth Chamber Conditions.

Abstract: Greenhouse and growth chamber studies were made to investigate the downward systemic nematicidal activity of carbofuran and its analog 2,3-dihydro-2,2-dimethyl-7-benzofuranyl [(di-n-butyl)-4-aminosulfenyl] carbamate against Meloidogyne incognita, Tylenchorhynchus claytoni, and Pratylenchus penetrans. Oxamyl was used as standard in tests with T. claytonl. Both carbofuran and its analog reduced all three plant-parasitic species when plant foliage was sprayed with chemical suspension of 1,200, 2,400 or 4,800 ppm. The studies show that fewer chemical applications were required to reduce populations of P. penetrans than to reduce populations of T. claytoni. Oxamyl was somewhat less active than either carbofuran or its analog. Key words: nonfumigants, nematicides, Meloidogyne incognita, Tylenchorhynchus claytoni, Pratylenchus penetrans, systemic nematicides, oxamyl, carbofuran analog.

Effect of individual and concomitant inoculation with Meloidogyne incognita and Rotylenchulus reniformis on the growth of black gram (Vigna mungo)

Abstract: Relationships between the different population densities of Meloidogyne incognita and Rotylenchulus reniformis, individually and concomitantly alongwith growth of black gram (Vigna mungo) were studied under pot culture conditions. Both the species caused significant growth reduction at the level of one infective individual per cc of soil. In concomitant inoculations the extent of growth reduction was relatively less than individual effects. The fresh shoot weight was more sensitive to nematode injury than shoot length.

Influence of Meloidogyne incognita infestation on Rhizobium nodule formation in french bean

Abstract: French bean (Phaseolus vulgaris L.) is an important vegetable crop in India and is very susceptible to root-knot nematodes, Meloidogyne spp. (Singh et al., 1979). Infested plants are stunted, and generally unthrifty and the yellowish foliage suggests they may be deficient in nitrogen. Several workers have reported that root-knot nematodes cause reduced nodulation in leguminous plants; but there is no published information on french bean. The object of the present investigation was to ascertain the extent to which the root-knot nematode, Meloidogne incognita (Kofoid et White) Chitwood interferes with nodulation and growth of this crop.

Influence of Meloidogyne incognita on Fusarium Wilt of Tomato at or below the Minimum Temperature for Wilt Development.

Abstract: 'Bonny Best' tomato plants were grown at 16, 21, or 24 C for 28 d in soil infested with either of two isolates of Fusarium oxysporum f. sp. lycopersici race 1 and Meloidogyne incognita. Significant levels of fusarium wilt occurred at all temperatures including 16 C, which has not been reported previously. One Fusarium isolate resulted in the highest levels of disease incidence at 21 and 24 C in the presence of root-knot nematodes, and at 24 C when the nematodes were not present. At 16 C there was no significant difference in the number of plants infected by the second Fusarium isolate alone or in combination with root knot nematodes, although the presence of nematodes resulted in a significant increase in the percentage of disease occurrence and vessel infection at 21 C.

Beta-Glycosidases from Meloidogyne incognita and M. javanica.

Abstract: B-glycosidases have been implicated in plant pathogenesis by numerous authors (6,8,9,10). B-glucosidase from Pratylenchus penetrans was reported to hydrolyse HCN from a cyanogenic glucoside (amygdalin) during pathogenesis of peach roots (7), and the activity of B-glucosidase from preparasitic larvae of Heterodera rostochiensis has been correlated with the ability to parasitize resistant potato lines (13). Currently, data is not available on the types and amounts of B-glycosidase activity associated with root-knot nematodes. Objectives of this study, therefore, were to determine the types of B-glycosidase activities associated with Meloidogyne incognita (Kofoid and White 1919) Chitwood 1949 and M. javanica (Treub 1895) Chitwood 1949 and to compare these enzyme activities to those associated with host root tissues. Nematode populations were reared on Lycopersicon esculentum Mill. 'Rutgers' under greenhouse conditions (24 + 4 C). Adult females were obtained from root tissue 40 d after inoculation as described by Hussey (2). Preparasitic second-stage larvae were collected as described by Vrain (12). Root tissue consisted of excised root-knot galls from tomato 35 d after inoculat ion of M. javanica and root apices (terminal 2 cm) from uninoculated plants of similar age. Crude homogenates of nematode samples were prepared as described by Hussey et al. (3). Nematodes were surface sterilized with 0.1% chlorhexidine acetate then rinsed three times with cold, sterile 0.01 M PO4 buffer (pH 7.5) containing 0.85 NaCI and 0.001 M MgClv Samples were homogenized

Effect of salinity and temperature on reproduction and egg hatching of Meloidogyne incognita in tomato

Abstract: Temperature is an important factor in determining the geographical distribution of root-knot nematodes (Meloidogyne spp.), perhaps more so than plants or soil (De Guiran and Ritter, 1979; Ferris and Van Gundy, 1979). Salinity is a problem in some marginal agricultural land but has not been investigated on plant parasitic nematode reproduction, egg hatching and invasion of roots. This work examines the effect of salinity (salt type and concentration) on rate of reproduction of Meloidogyne incognita (Kofoid et White) Chitw. under different temperatures; and the effect of salinity on cgg viability, egg hatch and infectivity of juveniles.

Protein patterns in resistant and susceptible tomato varieties inoculated with the root-knot nematode Meloidogyne incognita

Abstract: Proteins and peroxidase activity were determined in healthy and Meloidogyne incognita—inoculated tomato varieties Pusa Ruby, SL-120 and Nematex. Vars. Nematex and SL-120 showed resistant reactions, and var. Pusa Ruby was susceptible to the nematode. Increased protein levels were observed in the diseased tissues of all the three vars., 28 days after inoculation. Quantitative changes in protein concentrations were accompanied with qualitative alterations in protein patterns. The increases in the peroxidase activity in the inoculated plants of all the three vars. were sharp, and more conspicuous in the resistant-reacting vars. The qualitative changes fn peroxidase activity were characterized by (i) formation of new components only after nematode infestation of host tissues (ii) increased or decreased intensity of newly formed isozymes (iii) changed intensity of pre-existing components and (iv) disappearance of some components after the parasitic invasion of host tissues. Contrary to the resistant var., the inoculated susceptible var. failed to restore the shift in enzymic balance, 28 days after inoculation.

Effect of simultaneous inoculations and prior establishment of Heterodera zeae, Meloidogyne incognita and Tylenchorhynchus vulgaris singly and in combination on penetration of H. zeae and M. Incognita into maize roots

Abstract: Three day old seedlings of maize (cv. Ganga-5) were inoculated with 50 larvae of H. zeae or M. incognita, either singly or in combination with 50 individuals each of the species in glass vials (7.5 x 2.5 cm). The experiment comprised of six treatments. Similarly in an another experiment comprising of 12 treatments, 3 day time interval was given to one or two of the species to establish themselves before addition of the inoculum of the 3rd species. The observations on the number of larvae penetrated into root system were recorded at one day interval for 7 days. Penetration continued upto 7 days with the majority penetrating by 4th day. In case of simultaneous inoculations, M. incognita did not seem to interfere with penetration of H. zeae. As against this M. incognita was adversely affected by the presence of H. zeae occurring singly or in combination with T. vulgaris. Even though presence of T. vulgaris in simultaneous inoculations tended to increase penetrations of both the endoparasites to varying degrees, its earlier establishment affected their penetration adversely. In general prior establishment of any of the species, either singly or in combination, significantly reduced the invasiveness of both the other species. Larval penetration of both the nematodes was more whenever these were inoculated earlier.