Showing papers in "Nematologica in 1977"
TL;DR: Following joint tests in the Netherlands, Germany and the United Kingdom a new scheme is proposed for naming pathotypes of potato cyst-nematodes, with several of the pathotypes recognised in the British, Dutch and German National Schemes are the same.
Abstract: Following joint tests in the Netherlands, Germany and the United Kingdom a new scheme is proposed for naming pathotypes of potato cyst-nematodes. Pathotypes of Globodera ( = Heterodera) rostochiensis and G. pallida are designated separately using a simple nomenclature Ro1 to Ron for G. rostochiensis and Pa1 to Pan for G. pallida. Currently seven clones are used to differentiate five pathotypes of G. rostochiensis and three of G. pallida. Several of the pathotypes recognised in the British, Dutch and German National Schemes are the same. Results of pathotyping tests may show considerable variation; adequate replication and standardisation of method are essential. With an internationally used scheme it is highly desirable that new pathotypes or differential clones are added only after testing at Institutes in several countries.
248 citations
TL;DR: The life history of an Entomophthora-like fungus, which kills females and causes the breakdown of the cuticle preventing cyst formation, is described and a method is described for estimating the number of diseased eggs in females and cysts.
Abstract: Most populations of the cereal cyst-nematode are parasitised by fungi killing females and eggs. The life history of an Entomophthora-like fungus, which kills females and causes the breakdown of the cuticle preventing cyst formation, is described. This fungus attacks other cyst-nematodes but not Globodera rostochiensis. A method is described for estimating the number of diseased eggs in females and cysts. Verticillium chlamydosporium was the most frequently observed egg parasite; it killed 50% of the eggs in females on barley roots in July in a field trial. Tarichium auxiliare and Cylindrocarpon destructans were found more frequently in soils where the nematode failed to multiply than in those where it increased but were not considered important as few females were infected. Similar numbers of new females were produced in soils where populations multiply or decline but in decline soils many failed to form cysts and few healthy eggs were produced.
128 citations
TL;DR: This review primarily covers literature on the hatching of cyst-nematodes that has appeared since 1971 and the effects of temperature, moisture, aeration and seasonal effects especially in relation to diapause.
Abstract: This review primarily covers literature on the hatching of cyst-nematodes that has appeared since 1971. The section on physical factors which influence hatching includes the effects of temperature, moisture, aeration and seasonal effects especially in relation to diapause. Research dealing with chemical stimulation and inhibition of hatching is also reviewed and the mechanism of hatching is discussed with particular reference to Globodera rostochiensis.
96 citations
TL;DR: Living nematodes induced trap formation in Arthrobotrys oligospora more rapidly than did additions of morphogenetic peptides, and ammonia was shown by gas chromatography to be excreted in nematode suspensions in amounts that could affect trap formation.
Abstract: Living nematodes induced trap formation in Arthrobotrys oligospora more rapidly than did additions of morphogenetic peptides. In nematode-induced morphogenesis, excreted substances as peptides and amino acids were only partly responsible for the effect. Additional effects were due to volatile substances from nematodes or to direct contact between living nematodes and the hyphae. Ammonia was shown by gas chromatography to be excreted in nematode suspensions in amounts that could affect trap formation. It is proposed that living nematodes act primarily through another mechanism than peptide-induced morphogenesis.
93 citations
TL;DR: The infective stage juveniles of Heterorhabditis bacteriophora Poinar carry a specific bacterium in the lumen of their pharynx and intestine that is released by the infective-stage juveniles after they reach the hemolymph of susceptible insects.
Abstract: The infective stage juveniles of Heterorhabditis bacteriophora Poinar (Heterorhabditidae: Rhabditida) carry a specific bacterium in the lumen of their pharynx and intestine. The bacterial cells are large, motile, peritrichously flagellated, gram negative, non-sporeforming rods. They are released by the infective-stage juveniles after they reach the hemolymph of susceptible insects. Additional cultural and biological characteristics of the specific bacterium are presented.
82 citations
TL;DR: Since there are different systems for classifying races, none of which fitted the findings, a new scheme was developed and under this scheme British and Dutch races as well as Andean populations of the potato cyst nematode can be identified.
Abstract: Fifty six populations of the potato cyst nematode collected from Northern Bolivia to Southern Colombia were tested on the European host differentials as well as on six additional clones derived from Solanum vernei and S. spegazzinii in order to determine their potential as differentials for the Andean nematode populations. Although S. vernei (VT n ) 2 62.33.3 was an inefficient host for 32 populations, all differential plants were efficient hosts for most Andean potato cyst nematode populations; thus the expression of variability was limited when British and Dutch differential plants were used. Since there are different systems for classifying races, none of which fitted our findings, a new scheme was developed. Under this scheme British and Dutch races as well as Andean populations of the potato cyst nematode can be identified.
62 citations
TL;DR: Bridging and grafting experiments indicate that a factor emanating from this nematode-plant interaction is translocated considerable distances to the upper foliage across a resistant scion.
Abstract: Root-knot nematodes (Meloidogyne incognita) often occur together with the wilt fungus (Fusarium oxysporum f. lycopersici) on tomato in a plant disease complex. An interaction between the plant and the nematode may transform a genetically resistant host plant into one that is susceptible to the wilt-fungus and which subsequently develops wilt symptoms. Bridging and grafting experiments indicate that a factor emanating from this nematode-plant interaction is translocated considerable distances to the upper foliage across a resistant scion. Disease indices based on chlorosis of the foliage and on propagule counts from stem exudates showed primarily distal rather than proximal translocation of the factor.
43 citations
TL;DR: The fine structure of the esophagus, including procorpus, metacorpus, isthmus, gland lobe, and esophago-intestinal junction is compared in males of Heterodera glycines and Meloidogyne incognita.
Abstract: The fine structure of the esophagus, including procorpus, metacorpus, isthmus, gland lobe, and esophago-intestinal junction is compared in males of Heterodera glycines and Meloidogyne incognita Although the anterior portion of the esophagus is similar, striking differences are observed posterior to the metacorpus In both species the esophageal lumen is lined with cuticle consisting of four layers The lumen is round in the procorpus, and triradiate from the metacorpus valve (pump chamber) through the isthmus In M incognita the lumen terminates as a network of membranes between esophago-intestinal cells These cells are excluded from the anterior portion of the glandular isthmus at about 10 μm posterior of the metacorpus valve In H glycines the lumen extends the length of the isthmus, and terminates in similar membranes near the level of the dorsal gland nucleus In M incognita, the intestine extends anteriorly from the esophago-intestinal cells and forms a distinct intestinal caecum The gland lobe of H glycines consists of a dorsal gland with a process which terminates anteriorly in the procorpus, and two indistinctly separated subventral glands with processes which terminate in the subventral sectors of the metacorpus The gland lobe of M incognita consists solely of two subventral glands, one of which is longer, and posteriorly is composed of a distinct cortex, medulla and core Each gland has a subventral process, which terminates anteriorly in the metacorpus Although a vestige of a dorsal gland process is present in the anterior part of the procorpus, a dorsal gland was not observed in males of M incognita The esophagus of both species is innervated by nerve processes which originate from ganglia associated with the nerve ring as well as from perikaryons within the metacorpus Muscular elements are limited to radial muscles in the metacorpus, and sheath muscles near the junction of metacorpus with isthmus
27 citations
TL;DR: As nematode density was increased, roots of NC 95 were not damaged significantly, and higher nicotine content in infected roots resulted in higher nicotine levels in the leaves because nicotine translocation apparently was not restricted.
Abstract: Seedlings of Meloidogyne incognita resistant (NC 95) and susceptible (McNair 30) tobacco cultivars were grown in 15 cm clay pots containing steamed soil infested with 0, 4, 16, and 64 eggs of M. incognita per 1.5 cc soil. Dry root weight of NC 95 and McNair 30 decreased from 22 g to 15 g and from 24 g to 0.8 g, respectively, as nematode density was increased from 0 to 64 eggs per 1.5 cc soil. Sixteen amino acids, including precursors for nicotine, and nicotine increased significantly in roots of NC 95 and McNair 30 as nematode density was increased. Nicotine content increased 77% and 56% in roots of NC 95 and McNair 30 respectively as the initial nematode density was increased from 0 to 64 eggs per 1.5 cc soil. Leaf-nicotine content increased from 0.9% to 1.5% in NC 95, and decreased from 0.8% to 0.7% in McNair 30 as nematode density was increased from 0 to 64 eggs per 1.5 cc soil. As nematode density was increased, roots of NC 95 were not damaged significantly, and higher nicotine content in infected roots resulted in higher nicotine levels in the leaves because nicotine translocation apparently was not restricted. In McNair 30 severe root damage by increased nematode density probably decreased nicotine movement to vegetative organs.
26 citations
TL;DR: The results suggest that the major metabolic block in the pathway of sterol biosynthesis occurs between the step of farnesol and squalene, which supports significant population growth in all four nematodes.
Abstract: The quantitative sterol requirements were studied in C. briggsae, C. elegans (Be), C. elegans (Br), and T. aceti. It was shown that all four nematodes had similar minimal sterol requirements (0.1-2.0 μg/ml) and toxicity appeared in T. aceti at 50 μg/ml. Cholesterol and five precursors were tested for population growth. We found that acetic acid, DLmevalonic acid lactone, and farnesol did not support population growth; while squalene, lanosterol, and cholesterol supported significant population growth in all four nematodes. Our results suggest that the major metabolic block in the pathway of sterol biosynthesis occurs between the step of farnesol and squalene.
26 citations
TL;DR: Von 24 quantitativ erfasten Merkmalen an Larven II von funfzehn in Westeuropa haufigen Arten der Heteroderinae erwiesen sich vierzehn als brauchbar fur die Unterscheidung der Arten.
Abstract: Von 24 quantitativ erfasten Merkmalen an Larven II von funfzehn in Westeuropa haufigen Arten der Heteroderinae erwiesen sich vierzehn als brauchbar fur die Unterscheidung der Arten. Es wurden zwei Bestimmungsschlussel fur die funfzehn untersuchten Arten aufgestellt, von denen der eine nur auf Larvenmerkmalen, der andere auf Larven- und Zystenmerkmalen beruht.
TL;DR: Changes in the taxonomy of cyst-nematodes in the past decade and the contributions and usefulness of some new techniques are reviewed and the problems of distinguishing sibling species and the way in which they may have evolved are discussed.
Abstract: Changes in the taxonomy of cyst-nematodes in the past decade and the contributions and usefulness of some new techniques are reviewed The problems of distinguishing sibling species and the way in which they may have evolved are discussed The occurrence of pathotypes within Globodera and Heterodera is reviewed and a revised classification of the Heteroderoidea presented Nacobbodera Golden & Jensen is synonymised with Meloinema Choi & Geraert
TL;DR: Fossil nematodes occur in amber found in the La Quinta Formation of the southern Mexican state of Chiapas and are thought to represent males in the family Diplogasteridae and a third species which is considered microbivorous (free-living) is described.
Abstract: Fossil nematodes occur in amber found in the La Quinta Formation (Late Oligocene) of the southern Mexican state of Chiapas. This amber is around 25 million years old and was deposited in marine sediments during the late Oligocene epoch. Breeding populations of a member of Aphelenchoididae are described as Oligaphelenchoides atrebora n. gen., n. sp. Two specimens which appear to represent males in the family Diplogasteridae are described as Oligodiplogaster antiqua n. gen., n. sp. A third species which is considered microbivorous (free-living) is described as robustus n. sp. in the fossil genus Vetus Taylor.
TL;DR: The increases in growth and components of yield of Halberd were associated with reduction in the density of the nematode following the growth of the resistant cultivar and the number of nematodes tended to decrease in and on roots of AUS 10894.
Abstract: Resistance to a South Australian population of H. avenae was shown in five cultivars of barley: Athinais, Morocco, Nile, Orge-Martin 839 and CI 8147. With wheat grown under field conditions, similar numbers of larvae invaded seedlings of a susceptible (Halberd) and a resistant (AUS 10894) cultivar. The number of nematodes in, and the number of galls developed on roots of Halberd increased during the growing season, but the number of nematodes tended to decrease in, and the number of galls remained the same on, roots of AUS 10894. In the season after AUS 10894 had been grown, the length of flag leaf and number of fertile spikelets and grains per spikelet were increased on Halberd but grain weight was not affected. The increases in growth and components of yield of Halberd were associated with reduction in the density of the nematode following the growth of the resistant cultivar. Halberd, grown after a season of fallow or medic, grew and yielded better than following a season of AUS 10894.
TL;DR: The nematode is present in a small area around the town of Samaru, northern Nigeria and can affect the commercial value of confectionery groundnuts, but have not been shown to diminish yield.
Abstract: Aphelenchoides arachidis Bos was found in northern Nigeria as a facultative endoparasite of groundnuts (Arachis hypogaea L.). It occurs within the tissues of the pods, testas, roots and hypocotyls, but not within the cotyledons, embryos or other parts of the plant. Many nematodes within testas caused discolouration and were associated with shrivelled and small seeds. The nematode is present in a small area around the town of Samaru, northern Nigeria. The nematodes can affect the commercial value of confectionery groundnuts, but have not been shown to diminish yield. A simplified hot water treatment of seeds successfully controlled the nematodes, and other methods of cultural control can be used.
TL;DR: The infective spores of the fungus that developed on attacked females were more important than the resting spores from the previous year in determining the proportion of females that became infected.
Abstract: A simple method of observing the development of females of the cereal cyst-nematode on cereal roots is described. Females became infected by an Entomophthora-like fungus within 2 to 25 days after rupturing the root cortex, and resting spores were produced approximately 4 days later. All infected females eventually disintegrated and disappeared: time-lapse film indicated that other nematodes and enchytraeid worms were responsible. When formalin was applied to soil at 2988 1/ha females were not attacked by the fungus but completed their development and produced cysts. The infective spores of the fungus that developed on attacked females were more important than the resting spores from the previous year in determining the proportion of females that became infected.
TL;DR: TheSpicules of Aphelenchoides blastophthorus are thorn-shaped, with a large dorsal and a smaller ventral limb, and a flattened base embedded in the tail tissues, and the relationship between the morphology of spicules and accessory sensory structures and mating behaviour is discussed.
Abstract: The spicules of Aphelenchoides blastophthorus are thorn-shaped, with a large dorsal and a smaller ventral limb, and a flattened base embedded in the tail tissues. When retracted, the spicule tips are not exposed through the cloacal opening as they are in some other genera. The large spicular nerve runs along the dorsal limb. Within the nerve a single dendritic process is differentiated and this passes to the outer edge of the dorsal limb, running just beneath the surface towards the tip, where there is a single pore. The spicules do not form an enclosed tube; the ventral limbs abut but the dorsal limbs gape open when extended. Two innervated cuticular processes from the wall of the cloacal sac are exposed when the spicule tips are protruded. These are probably mechanoreceptors. Three pairs of caudal papillae, in adanal, mid-tail and terminal positions, are probably chemosensory as the sensilla open to the exterior through a pore. The relationship between the morphology of spicules and accessory sensory structures and mating behaviour is discussed.
TL;DR: The tolerance of carrot to attack by Rotylenchus uniformis (Thorne) was about the same at 12° and at 17° to 22° and increased with increase of the age of the plants, so that tolerance limits (T), estimated by fitting curves according to the equation y = m + (1 - m) z P-T, increased to the threefold value between 4 to 5 weeks after sowing and the end of the experiments.
Abstract: The tolerance of carrot to attack by Rotylenchus uniformis (Thorne) was about the same at 12° and at 17° to 22°. It increased with increase of the age of the plants, so that tolerance limits (T), estimated by fitting curves according to the equation y = m + (1 - m) z P-T (eq. (1)) to the data increased to the threefold value between 4 to 5 weeks after sowing and the end of the experiments (6 to 9 weeks later). Observations on the increase of leaf length suggested that nematode attack reduced the rate of growth of the plants only during a limited period which was probably longer with higher nematode density. Models based on this assumption and on a retardation of the growth of the plants by nematode attack were developed. The observations on growth and ultimate weights of the plants including those in experiments by Seinhorst & Kuniyasu (1969) were in good accordance with these models. Increase in root density during the development of the plants is considered the cause of the increase in tolerance. Because it is faster at low than at higher nematode densities it causes a deviation from proportionality at low nematode density, of the relation between nematode density and reduction of plant weight, which is expressed in eq. (1) by the use of the term z P-T.
TL;DR: Electrophoretic protein patterns of females of round-cyst nematodes vary with the host plant on which they are cultured, rendering the method unreliable for the characterisation of species on the basis of protein separation.
Abstract: Electrophoretic protein patterns of females of round-cyst nematodes vary with the host plant on which they are cultured. This and other difficulties render the method unreliable for the characterisation of species on the basis of protein separation. Patterns obtained from newly hatched 2nd stage larvae, which have not fed and are free from host-plant proteins, form a more useful criterion for distinguishing species.
TL;DR: Studies on the mechanism of resistance of tomato varieties to the root-knot nematode, Meloidogyne incognita, indicate that proteins containing hydroxyproline are present in the mitochondria of tomato roots and that the hydroxyProline concentration increases in resistant varieties when these are invaded by the nematodes.
Abstract: Studies on the mechanism of resistance of tomato varieties to the root-knot nematode, Meloidogyne incognita (Kofoid & White), indicate that proteins containing hydroxyproline are present in the mitochondria of tomato roots and that the hydroxyproline concentration increases in resistant varieties when these are invaded by the nematode. It is suggested that the difference between nematode resistant and susceptible plants is the capability of developing cyanide-insensitive respiration following the nematode attack.
TL;DR: Histochemical investigations showed that Romanoinermis culicivorax accumulates storage products, primarily in the trophosome, from the fourth day of parasitic development onwards.
Abstract: Histochemical investigations showed that Romanoinermis culicivorax accumulates storage products, primarily in the trophosome, from the fourth day of parasitic development onwards. Lipids constitute the predominant storage metabolite, glycogen the next most abundant, and proteins quantitatively only a minor storage product. Analytical studies showed that sterols (free and bound forms) constitute the greatest proportion of trophosomal lipids with triacylglycerol and phospholipids also present. Twelve proteins, one glycoprotein but no lipoprotein fractions were identified from the trophosome.
TL;DR: Howardula busseyi n.
Abstract: Howardula busseyi n. sp. is illustrated and described. It is an obligate parasite of the mushroom phorid fly Megaselia halterata. Female H. husseyi lay eggs in the haemocoel of phorid pupae and adults. First stage larvae moult soon after hatching. Second stage larvae invade the host's ovaries, pass into the oviducts and are liberated into mushroom compost during fly oviposition. In the compost further larval moults occur: female larvae moult twice to reach the fourth stage (when they are inseminated), while developing males moult three times to become adults. Adult males die after inseminating pre-adult females which are then infective. The latter penetrate young phorid maggots, undergo a final moult and develop into flaccid microvilli-covered adults.
TL;DR: Data on distribution of 37 cyst nematodes of the genera Heterodera, Globodera and Punctodera known in the U.S.R. are reviewed including short descriptions, diagnoses and comments on 21 species erected in this country.
Abstract: Data on distribution of 37 cyst nematodes of the genera Heterodera, Globodera and Punctodera known in the U.S.S.R. are reviewed including short descriptions, diagnoses and comments on 21 species erected in this country. Heterodera paratri f olii is synonymized with H. trifolii and Globodera pseudorostochiensis with G. rostochiensis. Although a distinct biological species, Globodera millefolii should be regarded as a species inquirenda until it is redescribed. Heterodera mirabile is considered as genus et species inquirenda and H. aquatica as a species inquirenda. The generic diagnosis of Globodera is emended.
TL;DR: The genus Clarkus jairajpuri, 1970 is subdivided into Clarkus (sensu stricto) represented by the type species, C. papillatus having a non-denticulate ventral ridge in the buccal cavity opposite dorsal tooth, and Coomansus n.
Abstract: The genus Clarkus jairajpuri, 1970 is subdivided into Clarkus (sensu stricto) represented by the type species, C. papillatus having a non-denticulate ventral ridge in the buccal cavity opposite dorsal tooth, and Coomansus n. gen. represented by C. parvus which is devoid of such a ridge. Two new species, viz., Clarkus elongatus and Coomansus indicus are described from India.
TL;DR: The morphology of walls of syncytia induced by Nacobbus aberrans in tomato roots has been examined by scanning electron microscopy after digesting out the cytoplasm from the cells.
Abstract: The morphology of walls of syncytia induced by Nacobbus aberrans in tomato roots has been examined by scanning electron microscopy after digesting out the cytoplasm from the cells. A clear boundary exists between the gall cells which surround the syncytium and the transformed cells. Syncytial cells are interconnected by perforations through their walls; these perforations are numerous and are frequently round or oval in shape. Wall ingrowths are absent. The structure of these syncytia is compared with those induced by other endoparasites.
TL;DR: Feeding mechanisms in Xiphinema index were observed, filmed and later analysed with the aid of cine film evaluation facilities and emphasis was placed on the events of a complete feeding cycle which is composed of distinct phases.
Abstract: Feeding mechanisms in Xiphinema index were observed, filmed and later analysed with the aid of cine film evaluation facilities. All the studies were made with X. index feeding on root tips of Ficus carica seedlings on agar culture in special observation chambers. Emphasis was placed on the events of a complete feeding cycle which is composed of distinct phases. Feeding sites are explored by lip contact only. The odontophore rotates during cell wall perforation by the odontostyle, but rotation is absent when the odontostyle is thrust rapidly through the contents of perforated cells. The odontostyle is usually inserted three to four cells deep before X. index starts feeding. Feeding behaviour after odontostyle protraction is characterized by a short phase (average 18s) with a definite sequence of events such as basal bulb elongation, depletion of gland ducts, shortening of the bulb and subsequent initiation of ingestion. Ingestion of food is achieved by the rapid pumping action of the basal bulb and is typically intermittent. Periods of continuous bulb pulsation alternate with short periods of pumping quiescence during which the bulb shortens and the gland ducts narrow from back to front, forcing fluids through them and also through the short duct that opens into the oesophageal lumen. It is possible that X. index releases salivary fluids into perforated cells during the short phase of prolonged bulb elongation just after odontostyle penetration and probably also during the brief ingestion pauses.
TL;DR: Several methods of assessing their variability are described, including hierarchical analyses of variance and canonical variate analyses, and a simple method of determining the minimum number of observations required to differentiate between given populations is described.
Abstract: A hundred and thirty one populations of potato cyst-nematodes from South America and sixteen populations from elsewhere were examined and several methods of assessing their variability are described, including hierarchical analyses of variance and canonical variate analyses. A simple method of determining the minimum number of observations of a given character required to differentiate between given populations is also described. Some effects of changes of environment on nematode morphology are reported and standard procedures for comparative morphological studies are recommended. Populations collected in South America north of 15.6° S were Globodera pallida except for one or two populations which seemed to be mixtures of G. pallida and G. rostocbiensis and two populations of G. rostocbiensis in Venezuela which may have been introduced from Europe.
TL;DR: A continuing supply of food was found to be necessary for maximum egg production by Heterodera avenae and there were no differences in egg contents of females from a very early maturing host and from one which remained vegetative throughout the nematode life cycle.
Abstract: A continuing supply of food was found to be necessary for maximum egg production by Heterodera avenae. In glasshouse experiments a minimum of 28 days on the host was necessary before egg production; females allowed to feed longer produced more eggs and formed larger cysts than starved females. On intact root systems of defoliated plants some egg production was possible; young females on detached root pieces or freed from roots had sufficient food reserves for limited egg production. Changes in host physiology associated with anthesis did not affect fecundity, and there were no differences in egg contents of females from a very early maturing host and from one which remained vegetative throughout the nematode life cycle.