Showing papers in "Nematologica in 1974"
206 citations
TL;DR: Soil sampling experiments were conducted on 0.01 hectare plots of Fox loamy sand in areas of low, medium, or high population densities of Pratylenchus penetrans (Cobb).
Abstract: Soil sampling experiments were conducted on 0.01 hectare (ha) plots of Fox loamy sand in areas of low, medium, or high population densities of Pratylenchus penetrans (Cobb). Nematode count data from 1, 20, and 40 core samples were statistically analysed to find normalizing transformations and to compare the efficiency of different sampling schemes. Although negative binomial distributions fitted the observed frequency distributions, normalizing transformations of the form log (x + c), that stabilized variance for all population densities, were obtained empirically. It was estimated that at least seven hours of field sampling and laboratory analysis are required to obtain an estimate of mean population density of a plot within 20 % of the true mean with 95 % confidence. An estimate of nematode population density in a 0.01 ha plot based on a subsample from one 20 or 40 core sample is shown to have very low precision.
68 citations
TL;DR: Five new species of Deladenus parasitizing siricid woodwasps from world wide sources are described in detail and their differences from other species of the genus are given.
Abstract: Five new species of Deladenus parasitizing siricid woodwasps from world wide sources are described in detail and their differences from other species of the genus are given. A key to the seven species of Deladenus known to parasitize siricids is included. The biology of these nematodes involves two life cycles associated with profound functional dimorphism of adult female nematodes and of spermatozoa. One cycle is parasitic with a sphaerulariid form of female reproducing ovoviviparously within the haemocoel of various siricids and the other is free living involving a neotylenchid form of female that reproduces oviparously while feeding on the symbiotic fungus within coniferous timber. Parasitism by three of the five new species of nematode results in sterilization of their female hosts; another species does not sterilize its only known host, while the other varies in its effect depending on host species.
41 citations
TL;DR: The results do not support the hypothesis that creation of metabolic sinks in the roots, caused by the formation of syncytia and galls, have a major influence on top growth and indicate that inhibition of upward translocation of water and nutrients may be more important.
Abstract: With an inoculum of 250 larvae, photosynthetic rate was less than in uninfected control plants but as inoculum level increased there was a rise and then a marked fall in photosynthesis. It is suggested that the complex nature of this relationship is due to the influence of several factors on photosynthesis. 14C-glucose incorporation into the roots was initially constant and only fell at the highest inoculum level (2,000 nematodes/plant). There was a marked decrease in 14CO2 incorporation with an inoculum of 250 nematodes compared with uninfected controls and a further decrease with 1,000 nematodes. Inoculation with 2,000 nematodes did not reduce 14CO2 incorporation further. The results do not support the hypothesis that creation of metabolic sinks in the roots, caused by the formation of syncytia and galls, have a major influence on top growth. The photosynthesis data indicate that inhibition of upward translocation of water and nutrients may be more important.
40 citations
TL;DR: Meldola Blue and Nile Blue A were generally superior to and more dependable than Phloxine B, New Blue R and, in some respects better than Chrysoidin as stains for distinguishing dead from living nematode regardless of whether the dead nematodes had been killed by lethal amounts of heat, cold, dryness or by certain nematicides.
Abstract: Meldola Blue and Nile Blue A were generally superior to and more dependable than Phloxine B, New Blue R and, in some respects better than Chrysoidin as stains for distinguishing dead from living nematodes regardless of whether the dead nematodes had been killed by lethal amounts of heat, cold, dryness or by certain nematicides. These stains were effective on specimens of Dorylaim us, Helicotylenchus, Mononchus, Panagrolaimus, Pratylenchus, Rhabditis, Tylenchorhynchus and Xiphinema species.
39 citations
TL;DR: The low populations maintained under continuous cropping with these cereals suggested that a rapid selection of a resistance-breaking biotype is unlikely to result from the continued use of inefficient hosts.
Abstract: Microplots containing soil, naturally infested with the cereal cyst nematode (Heterodera avenae) were left fallow or sown to one of nine cereal cultivars or grass species for five consecutive years. Wild oat (Avena fatua) was the most efficient host and, after three plantings, the nematode reached a potential increase ceiling of 42.2 eggs/g soil. Of the cereal cultivars tested, wheat (cv. Olympic) and barley (cv. Prior) were the most efficient hosts and levels of approximately 40 eggs/g were reached after five plantings. Barley grass (Hordeum leporinum) was less efficient than Wimmera ryegrass (Lolium rigidum) which maintained a ceiling population of about 10 eggs/g. Under fallow, populations declined to 0.5 eggs/g after 4 years. The most inefficient cereal hosts were the oat, cv. Avon, and cereal rye, cv. South Australian. The low populations maintained under continuous cropping with these cereals suggested that a rapid selection of a resistance-breaking biotype is unlikely to result from the continued use of inefficient hosts. Growth and yield of a subsequent wheat crop on all plots reflected the relative levels of nematode populations. At the low levels of infestation, grain yields were more than double those on heavily infested plots.
37 citations
29 citations
TL;DR: Extracts of ginger, garlic and chilli pepper showed strong nematicidal action by killing Meloidogyne incognita and other species of soil nematodes in 40 min, and served as a manure in reducing Meloidsogyne infestation of ladies' finger.
Abstract: Extracts of ginger, garlic and chilli pepper showed strong nematicidal action by killing Meloidogyne incognita and other species of soil nematodes in 40 min. Ladies' finger plants inoculated with M. incognita and then treated with the aqueous extracts of these plant materials showed marked increase in growth and decreased root galling. The population of M. incognita was considerably reduced in the pots treated with the plant extracts. The garlic extract was highly phytocidal but most effective in reducing Meloidogyne infestation of ladies' finger. Ginger showed mild phytotoxicity and capsicum none. Besides their nematicidal activity the plant extracts served as a manure.
29 citations
28 citations
TL;DR: The existence of variability in the cereal cyst nematode, Heterodera avenae Woll.
Abstract: The existence of variability in the cereal cyst nematode, Heterodera avenae Woll. in India is confirmed. Tentatively five biotypes have been identified using an assortment of cereals and grasses; the distribution of the biotypes in the light soils of Rajasthan and Haryana is plotted. These biotypes do not appear to be identical to those in Denmark, The Netherlands, Britain, Germany and Australia. They have been designated as 1, 2, 3, 4 and 5 of which biotype 3 is the most common in India. The possibilities of the existence of more biotypes is also indicated.
24 citations
TL;DR: Heterodera hordecalis n.sp.
Abstract: Heterodera hordecalis n.sp. occurs commonly in light soils in southern Sweden, where cereals (especially barley and rye) and grasses are hosts. The cysts resemble those of H. latipons but are generally paler in colour and the cyst wall is more transparent. The vulval cone is usually more pointed and the bridge is on average narrower than in H. latipons. The length of the vulval slit is 17-25 μm, compared with 6-9 μm in H. latipons.
TL;DR: It is suggested that a decrease of PRO/HYPRO ratio after nematode infection may inhibit cell hypertrophy and so increase the resistance of the plant to H. rostochiensis.
Abstract: Both protein proline and hydroxyproline in roots of hosts and non-hosts of H. rostochiensis were examined. The ratios of proline to hydroxyproline (PRO/HYPRO) were 1.59-2.11 and 2.20-2.54 in uninfected susceptible and resistant potato varieties, respectively. After infection, the ratio increased to 2.30-2.36 in susceptible plants, but it decreased to 0.93-1.22 in resistant ones. It is suggested that a decrease of PRO/HYPRO ratio after nematode infection may inhibit cell hypertrophy and so increase the resistance of the plant to H. rostochiensis.
TL;DR: The fine structure of the anterior body region of Aporcelaimellus is described, and it is concluded that the stomodeal cuticle, and epidermis are continuous.
Abstract: The fine structure of the anterior body region of Aporcelaimellus is described. The body wall ultrastructure is similar to that of Longidoridae and the feeding apparatus is comparable, but more primitive. The structure of the guiding apparatus and anterior oesophagus is given in detail, with the protractor system and two sets of retractors. The nervous system is outlined, with special attention to papillae and body pores. It is concluded that the stomodeal cuticle, and epidermis are continuous. The structure of the stomodaeum can be described more appropriately by Inglis' (1966) terminology than by the usual rhabditoid one. The nature of the "hydrostatic tissue" is discussed.
TL;DR: Host specificity tests indicated that at least some of the hybrid populations combined the host range characteristics of the parental races, and no resistance-breaking features were observed among the hybrid nematodes.
Abstract: Hybridization was attempted with ten stem nematode races in 44 different combinations and a total of nearly 900 single crossings, using Melilotus dentatus seedlings as the "bridging host" and occasionally callus tissue and potato tubers. Fertile hybrid populations were obtained in most combinations, but there was a consistent failure in some cases where one combination was successful but the reciprocal one with the same two races failed, producing only eggs which did not hatch. This happened most notably where the lucerne, red clover and white clover races were involved. The significance of these observations is discussed with reference to host specialization and reproductive isolation that approaches the sibling species concept. Host specificity tests indicated that at least some of the hybrid populations combined the host range characteristics of the parental races. No resistance-breaking features were observed among the hybrid nematodes.
TL;DR: A test tube method is described for the mono-axenic culture of wheat seedlings on mineral agar medium containing larvae hatched from individual cysts, which may be useful for various nematological investigations and for selection in backcross breeding programmes.
Abstract: Tests for resistance to Australian Heterodera avenae confirmed a high resistance to cyst development in two introduced wheats, AUS. 10894 and AUS. 11577 (cv. Loros). A test tube method is described for the mono-axenic culture of wheat seedlings on mineral agar medium containing larvae hatched from individual cysts. In ten such cultures with susceptible Summit wheat, cyst counts per plant ranged from 27 to 44; on average over 50 % of the hatched larvae became sexually mature. In 100 similar cultures with the two resistant wheats, many developed no females and a maximum of nine white cysts was found, although large numbers of males developed. The results agreed with those from pot tests using natural soil infestation, but since test tube cultures facilitated total recovery of all eggs and nematodes from each cyst, the percentage of sexually mature males and females could also be determined. The percentages of males and females on susceptible roots were variable, but averaged 1.33 males to 1 female, whereas resistant wheats produced over 20 males to 1 female. No difference was found in the overall reaction of AUS. 10894 and AUS. 11577 to H. avenae sampled from seventeen locations. The method may be useful for various nematological investigations and for selection in backcross breeding programmes.
TL;DR: Reduction in crop yield after three consecutive cropping seasons coincided with an increase in nematode populations both within and around maize roots and in soils around weeds.
Abstract: Populations of Pratylenchus brachyurus increased significantly under maize and were most abundant during the rainy season from June through October. Populations reached their peak in soil around maize in June (299-435/100 g); in roots of maize in July (10,333-11,213/100 g); and in soils around weeds in October (3-4/100 g). Populations were low but detectable in soils at the peak of the dry season (December-January) and multiplied rapidly on maize from March to July. Populations under weeds were significantly lower than those under maize throughout the experiment and those within maize roots were also significantly higher than in soils under maize. Reduction in crop yield after three consecutive cropping seasons coincided with an increase in nematode populations both within and around maize roots.
TL;DR: A study was made of oxygen consumption in all six developmental stages, eggs, juveniles 1-4 and adults, of the microbivorous nematode Panagrolaimus rigidus, using the Cartesian diver method, indicating that the respiration intensity is proportional to the surface area of the body of those nematodes examined.
Abstract: A study was made of oxygen consumption in all six developmental stages, eggs, juveniles 1-4 and adults, of the microbivorous nematode Panagrolaimus rigidus (Schneider). The Cartesian diver method was used. The exponent of regression for the relationship between respiration and weight was 0.64, indicating that the respiration intensity is proportional to the surface area of the body of those nematodes examined. Eggs had a Respiratory Rate seven times lower than juveniles just after hatching. The results are presented as Respiratory Rate and also as Metabolic Rate. The respiration equation calculated by the authors R = (2.02 ± 1.28).W0.64±0.12, could be used to estimate the energy budget of a real population of P. rigidus or as an estimation of the cost of maintenance of various size-age groups of the species similar, ecologically, to P. rigidus. A comparison is also given of regressions for the relation between respiration and weight in other species or whole groups of nematodes, known in the literature. The regression for P. rigidus is similar to the general results for a larger number of nematodes.
TL;DR: Die Schwankungen in der Populationsdichte von Pratylenchus thornei in Erdbeerkleewurzeln und im Boden an acht Stellen im Umkreis von 30 km um Adelaide stehen in enger Beziehung zur Boden-textur (% Lehm).
Abstract: Die Schwankungen in der Populationsdichte von Pratylenchus thornei in Erdbeerkleewurzeln und im Boden an acht Stellen im Umkreis von 30 km um Adelaide stehen in enger Beziehung zur Boden-textur (% Lehm). Andere Bodenfaktoren haben offensichtlich einen geringeren Einflus auf die Anzahl der Nematoden. Die Populationen von P. thornei erreichten ihr Maximum auf Lehmboden im Sommer und auf Sandboden im Winter. Die Hochstwerte waren in den Lehmboden groser als in den Sandboden.
TL;DR: These ideas give a new slant to host parasite relationships of plant parasitic nematodes and suggest new and possibly more fruitful lines of research than those at present being prosecuted.
Abstract: Progress in attempts to establish that a gene for gene relationship exists between potato cyst-nematodes and potatoes bearing genes for resistance is reviewed. An antibody/antigen relationship may exist between host cell contents and nematode saliva. It seems that all pathotypes of Heterodera rostochiensis and H. pallida are able to induce syncytial transfer cells in potato plants whatever their constitution but whether they can do so depends on a compatible response to nematode saliva. The induction system for transfer cells and the host cell/nematode saliva system appear to be separate entities. These ideas give a new slant to host parasite relationships of plant parasitic nematodes and suggest new and possibly more fruitful lines of research than those at present being prosecuted.
TL;DR: The feeding behaviour and length of individual feeds on perennial ryegrass roots varied with the different species of both Tylenchorhynchus and Merlinius, with feeding by T. maximus resulting in decreased growth of main roots but an increase in lateral root growth.
Abstract: The feeding behaviour and length of individual feeds on perennial ryegrass roots varied with the different species of both Tylenchorhynchus and Merlinius. T. dubius, T. lamelliferus and T. maximus fed in the manner of browsing ectoparasites initially on epidermal cells along the root but T. maximus also fed in marked aggregations on root tips causing mechanical breakdown of epidermal, cortical and undifferentiated cells of the vascular cylinder resulting in cessation of root growth. Aggregation on root tips also occurred with T. lamelliferus to a lesser extent. No aggregation was observed with any of the Merlinius species. M. brevidens and M. nothus exhibited a simple, browsing feeding behaviour with short feeds on both root hairs and epidermal cells, whereas M. icarus and M. macrurus fed, either as sedentary ectoparasites remaining for many hours or days feeding continuously at the one site, or as migratory semi-endoparasites with their heads embedded in the outer cortical cells of roots. Neither M. icarus nor T. maximus caused reduction in total shoot or root growth in soil. Feeding by T. maximus on root tips of ryegrass seedlings resulted in decreased growth of main roots but an increase in lateral root growth.
TL;DR: Experiments conducted in enclosed glass vials indicated that the survival of Aphelenchoides besseyi Christie is inversely related to the extent and rate of dehydration, and Larvae and adults of the nematode were found equally capable of withstanding desiccation.
Abstract: Experiments conducted in enclosed glass vials whose relative humidities were held constant with glycerol solutions, indicated that the survival of Aphelenchoides besseyi Christie is inversely related to the extent and rate of dehydration. Though gravimetric determinations detected no difference in the extents and rates of desiccation, the nematodes in larger aggregates were found to survive better than those in the smaller ones. Dry weights of the adult nematodes decreased significantly with the age of culture two weeks after nematode inoculation, apparently due to the exhaustion of the host mycelia, Aureobasidium pullulans. The starvation adversely affected the ability of the nematode to survive dehydration. Larvae and adults of the nematode were found equally capable of withstanding desiccation.
TL;DR: The cephalic sensory system of Rotylenchus robustus (De Man) consists of eighteen branches of six nerve trunks, their arrangement corresponding to De Coninck's (1942) scheme of labial symmetry.
Abstract: The cephalic sensory system of Rotylenchus robustus (De Man) consists of eighteen branches of six nerve trunks, their arrangement corresponding to De Coninck's (1942) scheme of labial symmetry. The internal labial nerves each have two ciliary terminals; they are connected with the vestibule by pores. The lateral external labial nerves, having one ciliary process, are short; the other external labial nerves shift position with the respective cephalic nerves. The amphidial nerve contains eleven ciliary processes, seven of which are enclosed within the amphidial ampulla. No papillar projections are present; the external labial and cephalic nerves have blind endings in the cuticle. The reduction of the lateral external labial nerve is thought to be correlated with the relative size of the amphid and the reduction of the lateral sectors. A comparison is made with the cephalic sensory system of Macrotrophurus arbusticola, Ditylenchus dipsaci and Radopholus similis.
TL;DR: Seinura demani was reared on five species of bacterial feeding nematodes and 3 fungus feeding species, under culture conditions prey were recognised on contact; there was no evidence of an ability to track victims.
Abstract: Seinura demani was reared on five species of bacterial feeding nematodes and 3 fungus feeding species. Under culture conditions prey were recognised on contact; there was no evidence of an ability to track victims. S. demani is a bisexual species, its life-history includes one juvenile stage within the egg, two post-hatch juvenile stages, and the adult. Development of all stages are described and measurements given. In cultures incubated at 20°C, the generation time is 41/2-5 days. Male S. demani are attracted to pre-adult moulting females and are retained in their immediate vicinity until the moult is completed. Mating behaviour and copulation are described. Descriptions of behaviour are based on observation, not on experiments, and should therefore be considered as items for further research. Conclusions drawn from the observations are tentative at this stage.
TL;DR: The adult stages of Parasitaphelenchus oldhaini are described and illustrated for the first time and its life cycle and biology are discussed, together with an assessment of its effect on the host bark beetles Scolytus scolytus and S. multistriatus.
Abstract: The adult stages of Parasitaphelenchus oldhaini are described and illustrated for the first time The life cycle and biology of the parasite are discussed, together with an assessment of its effect on the host bark beetles Scolytus scolytus and S multistriatus The J3 is the infective and moults to the J4 inside the beetle larvae The J4 is found in the haemocoel of the beetle larvae, pupae and adults and for a short time in the gut and frass The other stages are all found in the frass Adult nematodes feed on fungal hyphae
TL;DR: Observations on the effect of aldicarb and phorate on adult female Aphelenchus avenae in vitro indicated that there was no mortality over a 24-hour period, and effects were reversible if treated nematodes were allowed to recover in water for 24 hours.
Abstract: Observations on the effect of aldicarb and phorate on adult female Aphelenchus avenae in vitro indicated that there was no mortality over a 24-hour period. In solutions of 25 ppm aldicarb or 23 ppm phorate, abnormal stylet and median bulb activity, the adoption of coiled postures and a gradual decrease in the rate of dispersal was observed. These effects, however, were reversible if treated nematodes were allowed to recover in water for 24 hours.
TL;DR: Results may explain the apparent absence of the cereal cyst nematode in regions which do not experience a cold, wet winter or hot, dry summer and the probable spread of H.H. avenae by wind-blown cysts.
Abstract: Laboratory experiments, under controlled conditions of temperature and relative humidity, showed that eggs within cysts of Heterodera avenae are able to survive in a state of cryptobiosis for at least 5.5 years when stored at either 75 % R.H. and 5°C, or at 40 % R.H. and 15°. The results suggest that storage at 40 % R.H. and 5° could be even more favourable to survival. Discrepancies with European observations on the effects of desiccation on H. avenae are explained by differences in experimental technique and in the age and condition of the cysts used. In a saturated atmosphere, survival was poor; at 21°, eggs decomposed rapidly; at 15° larval emergence was less than 1 % after one year of storage, and after 2 years at 5°, viability as judged by chrysoidin staining, had declined more rapidly than in cysts stored dry. The latter treatment, however, appeared to induce dormancy or a hatching periodicity so that, when hatched at 15°, there was no larval emergence for a period of 24 weeks. Hatching then recommenced and finally resulted in the emergence of about 10% of the initial egg content. Results may explain the apparent absence of the cereal cyst nematode in regions which do not experience a cold, wet winter or hot, dry summer and the probable spread of H. avenae by wind-blown cysts.
TL;DR: The somatic setae of Chromadorina bioculata and Enoplus communis have been examined with the electron microscope and their structure is in agreement with their function as mechanoreceptors.
Abstract: The somatic setae of Chromadorina bioculata and Enoplus communis have been examined with the electron microscope. Their structure is in agreement with their function as mechanoreceptors. The cuticular elements of the setae are weakened at their base and they appear to pivot in a cuticular depression. The sensory element is a modified cilium, which takes the form of a typical (9 + n) microtubular organisation at the base of the setae. These cilia connect with nerves which proceed into the lateral cords. The wider possibility of mechanical deformation of the cuticle being transmitted to the setae is discussed.