Showing papers in "Nematologica in 1971"
TL;DR: Pot experiments indicated that top growth in some species of plants was stimulated by low numbers of larvae of Meloidogyne javanica, and in such plants, root weight increased as numbers of nematodes increased.
Abstract: Pot experiments indicated that top growth in some species of plants was stimulated by low numbers of larvae of Meloidogyne javanica (Treub). In such plants, root weight increased as numbers of nematodes increased. In a second group of plants, weights of tops were not influenced by nematode density and in a third group of plants, weights of tops decreased linearly with increasing nematode numbers, The differences in the responses of plants to infection by M, javanica is considered to be the result of the interaction between inhibitory and stimulatory processes in the plant. Plants in which top growth remains constant up to a particular nematode density, the tolerance level, are considered to be just one example of a series of possible relationships between the stimulatory and inhibitory processes. Studies on the relationship between numbers of Helicotylenchus dthystera (Cobb) and the growth of turf and between Trichodorus porosus (Allen) and the growth of pine seedlings are discussed in relation to the usefulness of the concept of tolerance level in field ecology.
58 citations
TL;DR: Hatching of eggs of Heterodera avenae was similar to that in water, and was not influenced by the presence of host roots, but more eggs hatched in unsterile than in sterilized soil, and damage to crops in the field in southern Australia is discussed.
Abstract: Hatching of eggs of Heterodera avenae can be divided into two phases: the first, thought to be a period of larval development, has an optimum of about 10°; the second, of relatively short duration, and concerned with eclosion, has an optimum about 20°. These optima are independent of the temperature at which the other phase is undergone. Both phases occur over the range 5° to 20° and rate of hatching at constant temperature is the resultant of the different times taken to complete each phase. Alternating temperatures failed to hasten phase 1 development. Cumulative hatch with time at 10° followed a symmetrical sigmoid curve, the flex point of which coincided with 50% of "total" hatch between 8 and 9 weeks when maximum numbers of eggs would have completed their phase 1 development; of the times when eggs were moved from 10° to 20°, the greatest hatching response was obtained after 7 weeks at 10° as this time was closest to the flex point. Some eggs were induced into dormancy by warmth following a period of cold; the proportion induced was influenced by time at the low temperature and magnitude of the temperature rise, but induction of this dormancy could be prevented by alternating temperatures daily or 4-daily. Hatching in soil at field capacity was similar to that in water, and was not influenced by the presence of host roots, but more eggs hatched in unsterile than in sterilized soil. The significance of these results to activity of H. avenae and damage to crops in the field in southern Australia is discussed.
41 citations
TL;DR: Results suggest that the ability to osmoregulate and the permeability of the body wall are altered during senescence, which is probably associated with deterioration of the hypodermis organelles.
Abstract: Caenorhabditis briggsae was used as a model to study aging of a metazoan under gnotobiotic conditions. At higher temperatures nematodes were shorter-lived and had a shorter generation time. Nematodes moved more slowly as they aged. Physiologic aging was marked by a decreased ability to withstand osmotic stress, a possible increase in the body's internal solute concentration, and increased sensitivity to formaldehyde. These results suggest that the ability to osmoregulate and the permeability of the body wall are altered during senescence. The interchordal hypodermis, as well as the chordal hypodermis, contained fairly abundant structures having biosynthetic activity. During aging mitochondria of the hypodermis degenerated, some areas of the thin hypodermal band thickened and lysosome-like bodies formed in the interchordal hypodermis. Changes in osmoregulatory and excretory mechanisms are probably associated with deterioration of the hypodermis organelles.
41 citations
TL;DR: The potato variety 'Multa' was more tolerant to attack by Heterodera rostochiensis than several other varieties in two field experiments, and the relation between nematode density and plant weight, as found in the experiments, could be explained without having recourse to this hypothesis.
Abstract: The potato variety 'Multa' was more tolerant to attack by Heterodera rostochiensis than several other varieties in two field experiments. The results of a pot experiment with the varieties 'Multa' and 'Libertas' suggest that attack by this nematode reduces plant weight in two ways: at medium to high densities there is a reduction of the rate of growth of the roots associated with necrosis of root tips caused by the penetration of second stage larvae and at lower densities because of the development of giant cells. At high nematode densities the first cause of damage checked the growth of the plants almost entirely in the first weeks after planting and also kept tuber yield low. The second type of damage only resulted in a small reduction of the yield. In both varieties, when grown at a low nitrogen fertilizer level, haulms were considerably longer and also a little heavier finally at high than at low nematode densities. This suggests growth stimulation. However, the relation between nematode density and plant weight, as found in the experiments, could be explained without having recourse to this hypothesis, by assuming that the invasion necrosis retarded the development of the plants and delayed the moment tuber formation began but did not influence the growth of the tubers. The development of the plants was thereby shifted partly to a period with longer days and higher temperatures resulting in taller plants. Tolerance limits were 1.5 eggs per g of soil for 'Libertas' at low nitrogen fertilizer level and 6 eggs per g of soil for 'Multa' at the same fertilizer level. Minimum yields of 'Libertas' and 'Multa' were 10% and 30% of the maximum yields respectively.
37 citations
TL;DR: Two new species of nematode, discovered from the cadavers of Tipula paludosa larvae collected from the field in British Columbia, were discovered and cultured successfully on Galleria mellonella L. larvae in the laboratory.
Abstract: Two new species of nematode, described herein as Panagrolaimus tipulae and Rhabditis (Rhabditella) tipulae, were discovered from the cadavers of Tipula paludosa larvae collected from the field in British Columbia. They were cultured successfully on Galleria mellonella L. larvae in the laboratory. Tests on G. mellonella and T. paludosa larvae show that these nematodes are normally saprophytic in the soil. They feed on and multiply in the insect only after it is debilitated or dead.
33 citations
TL;DR: Rate of hatching of new-season's eggs of H. avenae in South Australia changed only to a small extent over summer when soil temperatures were high, but in each of two years a sharp increase in the rate coincided with the onset of low soil temperatures in late autumn-winter.
Abstract: Rate of hatching of new-season's eggs of H. avenae in South Australia changed only to a small extent over summer when soil temperatures were high (> 20°C), but in each of two years a sharp increase in the rate coincided with the onset of low soil temperatures in late autumn-winter. Low temperature was not essential for hatching but in the laboratory broke dormancy more rapidly. High soil moisture tensions (pF4) inhibited eclosion but permitted changes which enabled eggs to hatch. These changes were associated with the egg and not the cyst wall. A type of dormancy which suppressed hatch was induced in a proportion of encysted eggs when they were moved to 20° following 8 weeks at 7°. Eggs entered a similar type of dormancy in the field in spring. There was no evidence of an inherent seasonal cycle of hatching. The significance of these changes in relation to activity and survival of the nematode and damage to cereal crops under local conditions is discussed.
29 citations
TL;DR: Histopathogenesis of galls induced by Meloidogyne naasi in wheat roots was studied, revealing a complete degeneration of cell contents in many giant cells but their thick walls remained intact.
Abstract: Large numbers of Meloidogyne naasi larvae penetrated root tips of 'Wintok' oats within the first 24 hours and first sign of incipient giant cell formation was visible 4 days after inoculation. Three independent responses were observed: a) Necrosis of inner cortical and endodermal cells in contact with the nematode lip region and failure of larvae to enter the stele; b) Necrosis of cells around the incipient giant cells, finally resulting in degeneration of giant cells and larvae; c) Uninterrupted giant cell development, which is indistinguishable from that in a susceptible host. These responses indicate that 'Wintok' oats are only partially resistant to M. naasi.
28 citations
TL;DR: It is suggested that the relatively large sand grains in the Fox soil provided pore sizes and moisture characteristics more suitable for nematode movement.
Abstract: The movement and survival of Pratylenchus penetrans were studied in three soils, Fox loamy sand, Jeddo loam, and Vineland silt loam that had marked differences in particle-size distribution, moisture retention, aeration, and pore size. Nematodes on paper disks were placed on the surface of soil cores that had been packed to two bulk densities and equilibrated at eight moisture regimes. After seven days the cores were partitioned, the nematodes extracted and counted. At low bulk density, a percentage of 4th and adult stages moved 4 cm in Fox between 10 and 3000 cm H2Ο moisture tension and in Jeddo and Vineland between 30 and 300 H2Ο; a percentage of 2nd and 3rd stages moved 4 cm in Fox between 10 and 100 cm H2Ο moisture tension and in Jeddo and Vineland at 30 and 100 cm H2Ο. However all stages moved only an average of 2.0 cm in Fox at 10 cm H2Ο moisture tension and in Jeddo and Vineland at 100 cm H2Ο. At high bulk density, a smaller percentage of all stages moved 4 cm only in Fox at 30 and 100 cm H2Ο moisture tension and in Jeddo at 100 cm H2Ο. Moreover 4th and adult stages moved only an average of 1.0 cm in Fox, 1.3 cm in Jeddo and 0.5 cm in Vineland at 100 cm H2Ο moisture tension in each soil; 2nd and 3rd stages moved an average of 1.0 cm in Fox and 0.5 cm in Jeddo at 100 cm H2Ο in both soils. In Vineland 2nd and 3rd stages did not move. Eight to 12 percent of the soil volume was occupied by air when movement of all stages peaked in each soil. It is suggested that the relatively large sand grains in the Fox soil provided pore sizes and moisture characteristics more suitable for nematode movement.
25 citations
TL;DR: Between the vulva and the tail of round-cyst nematodes, Heterodera s.
Abstract: Between the vulva and the tail of round-cyst nematodes, Heterodera s.g. Globodera, is a distinct area of transversely ridged cuticle containing the anus. Differences in the size of this area divide the group into two and differences in the number of ridges and the type of branching subdivide each group. The vulva is a shallow pit on the walls of which are two crescentic papillated areas. Their size and the form of the papillae on them are characters that, together with the differences in the terminal area, may be used to distinguish species and pathotypes. The morphological differences between H. rostochiensis pathotypes A, B and E (British notation) are as great as those between described species. The group has probably diversified because populations are isolated and inbred.
24 citations
TL;DR: Two new species of cyst nematode occurring on grasses in Northern Ireland are described and illustrated, having bifenestrate bullate cysts, belong to the avenae species-group.
Abstract: Two new species of cyst nematode occurring on grasses in Northern Ireland are described and illustrated. Both, having bifenestrate bullate cysts, belong to the avenae species-group. H. mani n. sp. infests Lolium, Dactylis and Festuca species. It differs from H. avenae Woll., 1924 in that the larvae have deeply concave stylet-knobs and four lines in the lateral field; the more rounded females have shorter stylet-knobs; the males have smaller heads and longer spicules and the cysts are more rounded and possess a distinct underbridge. H. iri n. sp. parasitizes Agrostis sp. and differs from both H. avenae and H. mani in that the larvae possess exceptionally long tails (true-tail and clear-tail averaging 94 μ and 62 μ respectively) ; the cysts are more spheroidal, much lighter in colour, have a thin matt-white subcrystalline layer and a strong underbridge. Unlike H. avenae neither new species attacks cereals.
24 citations
TL;DR: Differences in numbers of nematodes between three selected areas were correlated with differences of nitrogen (N), potassium (K) and soluble salts in the soil solution, and not with soil type.
Abstract: Fifty-one genera of nematodes were found in three types of soil in southern Manitoba. Butlerius spp., Leptonchus spp., and Pseudhalenchus spp. were newly recorded in Canada. Helicotylenchus spp., Tylenchorhynchus spp. Tylenchus spp., Mesorhabditis spp., Panagrolaimus spp., and Eudorylaimus spp. were most numerous. Clay soils harbored more nematodes than sand. Differences in numbers of nematodes between three selected areas were correlated with differences of nitrogen (N), potassium (K) and soluble salts in the soil solution, and not with soil type. In pot experiments, nematode populations at the same initial density in clay and sand under grass were exposed to different levels of N, phosphorus (P) and K. After approximately 12 weeks, numbers of nematodes were greater in clay than in sand, but the difference may have been due to greater plant growth in clay. Nematode numbers decreased as N content in clay increased, whereas numbers increased with addition of N to sand. Numbers of dorylaimids were similar in clay and sand. Tylenchids were more numerous in clay than in sand, and decreased as N concentrations were increased in clay. In sand, tylenchids increased in number with higher N levels. Numbers of non-stylet bearing (NSB) nematodes were similar in clay and sand. Increased N levels produced no change in NSB populations in clay, but were correlated with larger populations in sand. Nematode biomass was greater in clay than in sand, and decreased steadily in both soils as N increased.
TL;DR: The life cycle of P. penetrans on Cryptomeria seedlings was studied at each of five temperatures by following the reproduction of a solitary female inoculated per seedling root and the development of its offspring.
Abstract: The life cycle of P. penetrans on Cryptomeria seedlings was studied at each of five temperatures, 15°, 20°, 24°, 30°, and 33°C by following the reproduction of a solitary female inoculated per seedling root and the development of its offspring. The life cycle was completed in 86 days at 15°, in 42-44 days at 20°, in 35 days at 24°, and in 30-31 days at 30°. At 33°, the development was inhibited. The incubation period of eggs was 25 days at 15°, 14-16 days at 20°, 8-10 days at 24°, and 9-10 days at 30°. The nematode produced nearly the same number of offspring within a generation period at each temperature of 15°, 20°, and 24°. At 30°, however, reproduction was slightly suppressed. At 24°, females of P. penetrans laid an average of 1.1 eggs each day for about 35 days. The maximum number of eggs laid by a female was 68. Males were necessary for reproduction in this species.
TL;DR: The results indicate that it is very difficult to predict population densities much in advance of the tobacco crop and that density determinations should, therefore, be made in the fall or spring rye crop prior to tobacco planting.
Abstract: Seasonal changes in soil and root population densities of Pratylenchus penetrans (Cobb), and changes in soil moisture and temperature, were studied at weekly intervals for 28½ months under a rye-tobacco rotation in Ontario, Canada In general, population densities tended to be low in the summer and high in the fall, but the seasonal changes were not consistent from year to year The results indicate that it is very difficult to predict population densities much in advance of the tobacco crop and that density determinations should, therefore, be made in the fall or spring rye crop prior to tobacco planting Winter mortality of P penetrans in both soil and roots ranged from 40-65% Fall and winter fallow in place of the normal rye cover crop reduced the number of P penetrans and increased the growth of the ensuing tobacco at mid season
TL;DR: The sedentary female cyst-nematodes feed similarly to aphids and probably excrete a copious sugary waste, which the fungus converts to inert fatty acid thereby preventing local pollution of the rhizosphere, and may also act as a barrier to potential pathogens and predators.
Abstract: The sub-crystalline layer from lemon-shaped females of plant parasitic cyst-nematodes belonging to the genus Heterodera was examined by the scanning electron microscope, X-ray diffraction, X-ray fluorescence spectrometry and mass spectrometry. In H. mani the inner zone of the layer, closely adpressed to the female cuticle and replicating the cuticle pattern, consisted almost entirely of n-tetracosanoic acid. The outer thicker zone consisted of a mixture of the acid and its calcium salt. In H. avenae, the layer had up to 25% hexacosanoic acid in addition; another species, H. trifolii had three aliphatic acids, do-, tetra-, and hexa-cosanoic acids. The outer layer, either from intrinsic shrinkage caused by calcium salts forming or from increasing pressure as the female grows, fractures into pyramidal blocks presenting an irregular polygonal appearance. The fatty acid seems to be produced by an unidentified fungus that metabolises products excreted by the nematode. The sedentary female cyst-nematodes feed similarly to aphids and probably excrete a copious sugary waste, which the fungus converts to inert fatty acid thereby preventing local pollution of the rhizosphere. The layer of acid and its calcium salt may also act as a barrier to potential pathogens and predators. The relationship between the nematode and fungus seems to be symbiotic.
TL;DR: The effect of methyl-2-chloro-9-hydroxyfluorene-(9)-carboxylate (morphactin), a plant antimitotic agent, was studied on tomato seedlings infected with Meloidogyne javazzica and suppressed giant cell formation and consequently reduced the rate of nematode development.
Abstract: The effect of methyl-2-chloro-9-hydroxyfluorene-(9)-carboxylate (morphactin), a plant antimitotic agent, was studied on tomato seedlings infected with Meloidogyne javazzica. Morphactin suppressed giant cell formation and consequently reduced the rate of nematode development. Sex reversal occurred, and the percentage of males in the population increased up to 60%. The activity of morphactin was most conspicuous during the early stages of gall formation. Gall parenchymal tissue differentiated to vascular cells, resulting in abnormal distorted female adults, and the host plant exhibited distorted apices, retarded growth and strong epinasty. The substance did not significantly suppress the population of the saprozoic nematode, Panagrellus redivivus.
TL;DR: It was concluded that N has a direct inhibitory effect on SCN, and simultaneous inoculations of nodulating and nonnodulating lines of soybean with R and SCN (minus N), as compared to SCN alone, reduced the number of cysts developing.
Abstract: Greenhouse experiments were conducted to determine the effects of source and concentration of nitrogen (N) as well as inoculation of soybean with Rhizobium japonicum (R) on the activity of Heterodera glycines (SCN). The application of NaNO3 or NH4NO3 at 56 to 896 ppm N to soil or silica sand reduced nematode hatch, penetration and "cyst" development of SCN on soybean. Inhibitory effects were positively correlated with concentration of N. Concentrations of > 112 ppm N also reduced numbers of eggs per cyst. High concentrations of NaCl also resulted in slight inhibition of nematode penetration of host roots as compared to demineralized water. Since most N concentrations used (56-225 ppm) were below those necessary to give an osmotic inhibitory effect on nematode activity and since R also interfered with nematode development, it was concluded that N has a direct inhibitory effect on SCN. Simultaneous inoculations of nodulating (Nod) and nonnodulating (Nonnod) isogenic lines of soybean with R and SCN (minus N), as compared to SCN alone, reduced the number of cysts developing especially on the Nod line.
TL;DR: It is suggested, as a working hypothesis, that the nominal species, Ditylenchus dipsaci, gene pool be considered as "wild type" polyphagous with race deviations as part of the gene continuum in the fashion illustrated by the schematic representation.
Abstract: A garlic isolate of Ditylenchus dipsaci has been found to be polyphagous. Under aseptic conditions this isolate has reproduced on a wide range of plant host tissues many of which are the key hosts reported for the biological races of the stem and bulb nematode. In addition the garlic isolate reproduced on two of nineteen fungus cultures tested. It is clear from the literature reports of many workers that different populations of D. dipsaci can vary in host ranges from very narrow to very broad. It is suggested, as a working hypothesis, that the nominal species, Ditylenchus dipsaci, gene pool be considered as "wild type" polyphagous with race deviations as part of the gene continuum in the fashion illustrated by the schematic representation.
TL;DR: Der Saugvorgang von Trichodorus similis an Epidermiszellen and Wurzelhaaren von Brassica rapa var wurde in speziellen Beobachtungskammern bei sehr starker Vergroserung beobachtet.
Abstract: Der Saugvorgang von Trichodorus similis an Epidermiszellen und Wurzelhaaren von Brassica rapa var. silvestris wurde in speziellen Beobachtungskammern bei sehr starker Vergroserung beobachtet. Ein kompletter Saugvorgang dauert nur wenige Minuten. Er setzt sich aus funf Phasen zusammen. Wahrend der Speichelabgabe, der langsten Phase, sammelt sich an der Einstichstelle Cytoplasma an. Dieses wird bei der Nahrungsaufnahme innerhalb kurzer Zeit aufgesaugt. Der Mundstachel wird kontinuierlich vor- und zuruckgezogen, sehr schnell beim Anstechen, langsamer bei der Speichelabgabe und wieder schneller bei der Nahrungsaufnahme. In der Mundhohle bildet sich ein Saugrohr, das in der Einstichstelle fest verankert bleibt. Das Zusammenwirken von Pharynx- und Osophagusmuskulatur wurde mit Hilfe der Filmtechnik analysiert. Die Funktion der Pharynxwandung als zusatzliche Pumpvorrichtung wird diskutiert.
TL;DR: Electron microscope studies on the female genital tube of A. blastophihorus show that the ovary, oviduct, uterus, vagina and post-vulval sac are morphologically distinct.
Abstract: Electron microscope studies on the female genital tube of A. blastophihorus show that the ovary, oviduct, uterus, vagina and post-vulval sac are morphologically distinct. The functions of the different parts of the genital tube in egg production are discussed and the constrictor and dilator vulvae muscles described.
TL;DR: Tylenchorhynchus dissitus Colbran and Tylenchoides bursifer Loof are transferred to Paratrophurus Arias whose diagnosis is emended.
Abstract: Histotylenchus gen. n. is proposed for H. histoides sp. n. (Type) from soil around roots of Napier grass in Malawi, H. historicus (Jairajpuri & Baqri) comb. n. and H. baoulensis (Netscher & Germani) comb. n. Telotylenchoides gen. n. is proposed for T. housei (Raski et al.) comb. n. (Type) and T. lobatus (Loof & Yassin) comb. n. T. lobatus is briefly described from specimens collected around roots of Citrus nobilis and Ipomoea batatas in Central Sudan. Tylenchorhynchus dissitus Colbran and Tylenchorhynchus bursifer Loof are transferred to Paratrophurus Arias whose diagnosis is emended.
TL;DR: The glandular part of the esophagus of tylenchids in which it is said to overlap the intestine differs from that of species having a glandular bulb in one or more of the following respects: ventral shift of the Esophageal lumen, lateral shift of this lumen to a position between the dorsal and one subventral gland, forward displacement of theEsophago-intestinal junction and elongation of the subvental glands or of the dorsal gland.
Abstract: The glandular part of the esophagus of tylenchids in which it is said to overlap the intestine differs from that of species having a glandular bulb in one or more of the following respects: ventral shift of the esophageal lumen to a position between the subventral glands, lateral shift of this lumen to a position between the dorsal and one subventral gland, forward displacement of the esophago-intestinal junction and elongation of the subventral glands or of the dorsal gland. The ventral shift of the esophageal lumen occurs, for example, in Rotylenchus, Hoplolaimus, Radopholus and Nacobbus; the lateral shift together with elongation of the subventral glands, in Pratylenchus, Helicotylenchus, Heterodera and Meloidogyne; the lateral shift together with elongation of the dorsal gland, in Telotylenchus, Trichotylenchus, Morulaimus, Belonolaimus and Aphasmatylenchus. The latter genera are closely related to certain genera with a glandular bulb.
TL;DR: Experimental results demonstrated the necessity of controlling pH in emergence experiments and suggested that inorganic ions applied as fertilizers may influence the inoculum potential of the soybean cyst nematode.
Abstract: Experiments were conducted to determine effects of pH and inorganic ions on emergence of the soybean cyst nematode, Heterodera glycines. Emergence from "cysts" without egg masses was greatest at pH 3.5 but was depressed at pH 5.5. Hatching from egg masses was insensitive to pH. The influence of inorganic ions on emergence was determined in a factorial experiment in which the cations NH4+, Ca++, and Mg++ were used in combination with each of the anions NO3-, SO4=, and Cl-. Compounds containing NH4+ or NO3- inhibited emergence as compared to phthalate buffer control, whereas CaSO4 was stimulatory. Experimental results demonstrated the necessity of controlling pH in emergence experiments and suggested that inorganic ions applied as fertilizers may influence the inoculum potential of the soybean cyst nematode.
TL;DR: P. penetrans kann in lufttrockenem Boden unter Gewachshausbedingungen mindestens 11 Monate in so hohen Zahlen uberdauern, das nach erneuter Bewasserung immer noch empfindliche Pflanzen geschadigt werden konnen.
Abstract: Trichodorus-Arten sind empfindlicher gegen Austrocknung des Bodens als Pratylenchus penetrans und Rotylenchus robustus. Geringe Bodenfeuchtigkeit wirkt sich oft erst bei langerem Andauern dezimierend auf die Populationen einiger Nematodenarten aus. Aus ursprunglich ausgetrocknetem, spater gleichmasig bewassertem Boden lassen sich mehr Nematoden als aus trockenen Vergleichsproben isolieren. Das Uberdauern in ausgetrocknetem Boden wird durch die Art der fruheren Wirtspflanzen beeinflust. Beim Isolieren von P. penetrans und R. robustus ergeben sich Unterschiede zwischen Tieren aus feuchtem und trockenem Boden. Aus trockenem Boden wandert ein groserer Teil der Population verzogert durch die Nematodenfilter. P. penetrans kann in lufttrockenem Boden unter Gewachshausbedingungen mindestens 11 Monate in so hohen Zahlen uberdauern, das nach erneuter Bewasserung immer noch empfindliche Pflanzen geschadigt werden konnen. Mit den ublichen Isolierungsverfahren ohne entsprechende Vorbehandlung des Bodens werden diese Tiere aber nicht oder unzureichend erfast. Die Trockenheitstoleranz zwischen P. penetrans im Boden und in den Wurzeln ist verschieden. Einige Entwicklungsstadien von R. robustus werden durch Trockenheit besonders stark betroffen.
TL;DR: The localization of the active peroxidase, tyrosinase and β-glucosidase in roots of potatoes both susceptible and resistant to Heterodera rostochiensis and invaded with larvae of this nematode was tested.
Abstract: The localization of the active peroxidase, tyrosinase and β-glucosidase in roots of potatoes both susceptible and resistant to Heterodera rostochiensis and invaded with larvae of this nematode was tested. In the necrotic cells in roots of resistant potato a high activity of all the three above mentioned enzymes was observed. Giant cells formed in roots of susceptible potato contained an active tyrosinase, but did not show the presence of active peroxidase and β-glucosidase. β-glucosidase was seen only in the cells lying close to the nematodes. The role of the enzymes tested in resistant - susceptible reactions of the potato to H. rostochiensis is discussed.
TL;DR: Although methionine affected populations of H. rostochiensis in field plots, even large amounts did not control it adequately and the D and L forms were equally toxic to the nematodes which became less sensitive as they aged.
Abstract: Of several racemic mixtures of amino acids tested, the most toxic to H. rostochiensis and the least toxic to potato plants growing in pots was DL methionine. The D and L forms were equally toxic to the nematodes which became less sensitive as they aged. Methionine did not act directly by contact with the nematode: it had first to be taken up by the host plant and was presumably ingested in sap extracted from giant cells. Although methionine affected populations of H. rostochiensis in field plots, even large amounts did not control it adequately.
TL;DR: It is suggested that heat and cold formalin, which caused least change, should be the standard methods of killing and fixing larvae to be measured.
Abstract: Some commonly used methods of processing larvae of Heterodera rostochiensis for microscopical examination cause changes in body and stylet size, greater than the difference between pathotypes. It is suggested that heat and cold formalin, which caused least change, should be the standard methods of killing and fixing larvae to be measured.
TL;DR: Biometrical and morphological characteristics of the holotype and paratypes of Xiphinema mediterraneum are presented together with those of other Italian populations and of the juvenile stages and males.
Abstract: Studies were carried out to clarify and stabilize the taxonomical position of Xiphinema mediterraneum Martelli & Lamberti, 1967. Biometrical and morphological characteristics of the holotype and paratypes are presented together with those of other Italian populations and .of the juvenile stages and males. The type locality is indicated.
TL;DR: The validity of Aphelenchus radicicolus, as distinct from A. avenae Bastian, 1865, is discussed and Seinura aurangabadensis n.
Abstract: The validity of Aphelenchus radicicolus, as distinct from A. avenae Bastian, 1865, is discussed. Seinura aurangabadensis n. sp. has a spear without basal knobs, measuring 19-20.5 μ in length ; excretory pore just behind the metacorpus and anterior to the nerve ring; vulva at 73-75.5% and postvulval uterine branch absent. S. paratenuicaudata Geraert, 1962 is reported. S. indica n. sp. has a spear without basal knobs; cuticle transversely striated, with striae about 1.2 μ apart; lateral fields with five incisures; excretory pore posterior to nerve ring; vulva at 69-70%; postvulval uterine branch slightly less than vulval body width long and the tail shorter than the vulva-anus distance, with filiform terminus. Aphelenchoides goldeni n. sp. has a spear without basal knobs and the tail about seven anal body widths long with three mucronate projections at the tip. It differs from A. andrassyi Husain & Khan, 1967 in having two incisures in the lateral field and a longer spear (14-15 μ).