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Summary: The mechanism of root-knot nematode (RKN) resistance in black oat 'Terara' and its stability under high temperatures were examined. To investigate the suppressive mechanism, we observed root invasion and development of RKN in 'Terara'. Juveniles of Meloidogyne incognita , M. arenaria and M. javanica successfully invaded roots of 'Terara' 3 days after inoculation (DAI), whereas juveniles of M. hapla were hardly observed in black oat roots. The total number of M. incognita and the ratio of successfully developing juveniles were significantly lower in roots of 'Terara' than a susceptible cultivar from 7 DAI. A number of M. incognita developed to sausage-shaped juveniles in 'Terara'; however, juveniles beyond that stage were seldom observed. Histological observation of feeding sites suggested the poor development of giant cells was involved in this arrested development. Juveniles of M. arenaria and M. javanica also only developed to the sausage-shaped stage at 21 DAI. These observations indicated that 'Terara' and resistant common oat cultivars suppressed RKN in a similar way. The effect of high temperature on resistance was evaluated using 'Terara' cultivated at 30°C throughout the experiment and at 32°C for the initial 5 DAI. The number of egg masses of M. incognita under the 32°C treatment was slightly higher than the 25°C control. However, it was still suppressed to 4.9% of the susceptible cultivar. [ABSTRACT FROM AUTHOR]

Summary: The effects of temperature and absence of a host plant on the population dynamics of the sheath nematode, Hemicycliophora conida , were studied under glasshouse conditions. Regarding temperature, population dynamics of H. conida on tomato 'Moneymaker' were monitored weekly over a period of 12 weeks. In the first experiment, with an average temperature of 21.4°C, population growth of H. conida continuously increased over time from an initial density of 106 nematodes (100 ml soil)−1 to a final density of 820 nematodes (100 ml soil)−1, resulting in a reproduction rate of 7.7. The time required to complete one generation was 6.5 weeks or 598 temperature degree days at 8°C base temperature (TDD8). A second experiment showed that the development of H. conida on tomato was faster at 22.1°C than at 19.0°C. At 22.1°C, one generation was completed after 6 weeks (= 588 TDD8) compared to 8 weeks (=634 TDD8) at 19.0°C. The higher temperature also resulted in a higher reproduction rate (93 at 22.1°C vs 7.8 at 19.0°C). In the absence of a host plant, the population density of H. conida decreased over time. However, this natural decline was less pronounced than for the root-knot nematode Meloidogyne hapla. In the first experiment, the population density of H. conida decreased within 18 weeks by 89.5%, while M. hapla was already no longer detectable 12 weeks after inoculation. In the second experiment, H. conida decreased by 98.2% within 16 weeks compared to 99.98% for M. hapla. [ABSTRACT FROM AUTHOR]

Keywords: Cyclopia maculata; herbal tea; Meloidogyne hapla; Meloidogyne javanica; plant-parasitic nematode EN Cyclopia maculata herbal tea Meloidogyne hapla Meloidogyne javanica plant-parasitic nematode 591 593 3 07/03/20 20200501 NES 200501 Root-knot nematode (RKN) I Meloidogyne i species are one of the most important plant-parasitic nematodes causing severe damage to agricultural crops worldwide. Significant yield losses often result from the feeding activities of the nematodes on plant roots, which in many cases disrupt the vascular system of the roots and may lead to plant death. Cyclopia maculata, herbal tea, Meloidogyne hapla, Meloidogyne javanica, plant-parasitic nematode. [Extracted from the article]

The suppressive effect of a black oat, Avena strigosa, breeding line KH1a on Meloidogyne spp. was examined in pot tests and on Meloidogyne incognita in pot and field tests. In pot tests, roots of black oats were examined 42-46 days after inoculation of 500 second-stage juveniles. There were significantly fewer egg masses on the roots of KH1a than on 12 black oat cultivars examined. KH1a was a poor host for four isolates of M. incognita, two isolates of M. arenaria and one isolate of M. javanica, and a non-host for one isolate of M. hapla. The effect of autumn and spring cropping of KH1a on soil nematode density was examined in M. incognitainfested fields. Nematode density after autumn cropping of KH1a was significantly lower than that after susceptible black oat, resulting in significantly lower Pf/Pi in KH1a (0.10 and 0.13) than in susceptible black oat (0.42 and 0.74). Damage indices of the succeeding crop, sweet potato, were significantly lower in KH1a plots than in susceptible black oat plots. In spring cropping, there were significantly fewer soil nematodes in KH1a plots than in susceptible black oat plots 3 weeks after cultivation. In both autumn and spring cropping, there was no significant difference in soil nematode density between KH1a and bare fallow. These results suggested that KH1a is a good alternative to current susceptible cultivars for the management of M. incognita. [ABSTRACT FROM AUTHOR]

An economical method for extracting nematode DNA from 100 g of soil was developed to facilitate nematode detection and quantification, and tested using the Northern root-knot nematode, Meloidogyne hapla. The method utilised enzymatic laundry detergent lysis, Fe3O4 super paramagnetic iron oxide nanoparticle (SPION) capture, and polyvinylpolypyrrolidone (PVPP) purification. Resultant DNA from this SPION capture method was approximately 100-fold less but of similar quality to DNA obtained from a standard phenol procedure and a commercial DNA extraction kit. An addition of 10 mg of nanoparticles to the extraction lysate was identified to maximise DNA yield while minimising co-capture of contaminants. The detection limit of the SPION capture method was approximately 100 nematodes (100 g soil)-1. The SPION capture method extracted nematode DNA from mineral soils but requires further optimisation for extraction from high organic matter (i.e., 'muck') soils. The benefits of this method compared to alternative techniques are discussed. [ABSTRACT FROM AUTHOR]

Here we report the genome sequence of the lesion nematode, Pratylenchus coffeae, a significant pest of banana and other staple crops in tropical and sub-tropical regions worldwide. Initial analysis of the 19.67 Mb genome reveals 6712 protein encoding genes, the smallest number found in a metazoan, although sufficient to make a nematode. Significantly, no developmental or physiological pathways are obviously missing when compared to the model free-living nematode Caenorhabditis elegans, which possesses approximately 21 000 genes. The highly streamlined P. coffeae genome may reveal a remarkable functional plasticity in nematode genomes and may also indicate evolutionary routes to increased specialisation in other nematode genera. In addition, the P. coffeae genome may begin to reveal the core set of genes necessary to make a multicellular animal. Nematodes exhibit striking diversity in the niches they occupy, and the sequence of P. coffeae is a tool to begin to unravel the mechanisms that enable the extraordinary success of this phylum as both free-living and parasitic forms. Unlike the sedentary endoparasitic root-knot nematodes (Meloidogyne spp.), P. coffeae is a root-lesion nematode that does not establish a feeding site within the root. Because the P. coffeae nematode genome encodes fewer than half the number of genes found in the genomes of root-knot nematodes, comparative analysis to determine genes P. coffeae does not carry may help to define development of more sophisticated forms of nematode-plant interactions. The P. coffeae genome sequence may help to define timelines related to evolution of parasitism amongst nematodes. The genome of P. coffeae is a significant new tool to understand not only nematode evolution but animal biology in general. [ABSTRACT FROM AUTHOR]

Oilseed radish is resistant to the beet cyst nematode (Heterodera schachtii Schmidt), interrupting the life cycle of this sedentary pathogen by blocking feeding cell development in the root. A complete set of nine disomic rape-radish chromosome additions, a to i, derived from a susceptible rapeseed parent as recipient and a resistant radish as chromosome donor, was assayed for nematode resistance. The addition line d exhibited the resistance level of the radish parent, confirming previous results that radish chromosome d carries a dominant gene, Hs1Rph, for nematode resistance. It was investigated if Hs1Rph is effective against a further important sedentary parasite, the northern root-knot nematode Meloidogyne hapla. The set of chromosome addition lines and the parents, rape and radish, were inoculated with second-stage juveniles (J2) of M. hapla and the plant reaction was evaluated by counting the number of egg masses per root system. By contrast to the situation in H. schachtii, the radish parent as well as addition line d showed no resistance against M. hapla and was even more susceptible than rape. It was concluded that the resistance gene Hs1Rph, which inhibits syncytium development of H. schachtii, is ineffective against M. hapla, a nematode inducing giant cell formation. Most added radish chromosomes significantly changed the number of egg masses in the recipient rape towards higher susceptibility. Two chromosomes enhanced the egg mass number beyond that of the chromosome donor radish. However, one radish chromosome decreased the egg mass production in the corresponding addition line below that in rape. This wide range of effects of the individual radish chromosomes in the rape background indicates a quantitative inheritance of host suitability to M. hapla and a complex interaction between the pathogen and radish. [ABSTRACT FROM AUTHOR]

Pluronic F-127 is a stable, non-toxic, copolymer that forms a gel at room temperature and a liquid at 15°C when the concentration is 20-30%. Root-knot nematode (Meloidogyne spp.) second-stage juveniles can move freely through the gel and display attraction toward roots of tomato, Medicago truncatula, common bean and Arabidopsis. The excellent clarity of the gel allows examination of behavioural changes in the nematode as it reaches and infects its host. Attraction assays showed that Meloidogyne javanica and M. incognita move to roots much more rapidly than does M. hapla. Nematodes form aggregates when in contact with root tips suggesting that the presence of a signal from the nematode or from the root is involved in the attraction. Nematodes suspended in Pluronic gel without roots aggregate into balls after 1 to 2 days. A coverslip placed on the gel accelerates and serves as a focus for the aggregation, suggesting that lower oxygen, or perhaps a volatile attractant, is involved in this behaviour. These observations demonstrate that Pluronic gel is a useful medium for dissecting attraction of root-knot nematodes to their hosts and for studying additional aspects of their behaviour. [ABSTRACT FROM AUTHOR]

Differences in amplified fragment length polymorphisms (AFLP) between isolates and between mono-female lines of facultative automictic Meloidogyne hapla race A and obligate apomictic M. incognita were determined to test the hypothesis that inverted meiosis occurs. DNA of the parthenogenetic nematode lines were extracted from juveniles, which had been propagated for two generations, allowing males in M. hapla lines to be formed and fertilisation to take place. Based on AFLP analysis, the genetic distance between mono-female lines of M. incognita appeared to be almost nil. By contrast, the genetic distance between isolates and between mono-female lines after seven generations of parthenogenesis of M. hapla was larger. The genetic distance between two mono-female lines of M. hapla, after one generation of parthenogenesis and originating from one line with six generations of parthenogenesis, was larger than the distance between M. incognita lines and the smallest distance between M. hapla lines. The numbers of DNA fragments appeared to be equally variable between lines within a single M. hapla isolate as between various isolates of M. hapla. This maintenance of genetic variation in M. hapla is likely to be caused by the combination of post-reduction in an inverted meiosis, due to chromosomes with diffuse centromeres, and the fusion of the haploid products of the second meiotic division. [ABSTRACT FROM AUTHOR]

Aqueous extracts of the tree Quillaja saponaria Molina, containing triterpenoid saponins, polyphenols, salts and sugars, were tested against the most important plant-parasitic nematodes present in Chile: Xiphinema index, X. americanum s.l., Meloidogyne hapla, M. ethiopica, Pratylenchus thornei, Tylenchorhynchus sp., Criconemoides xenoplax and Helicotylenchus sp. Three different products were tested in the laboratory: i) QL 1000® (whole extract containing saponin and non-saponin fractions); ii) QL ULTRA® (saponin fraction); and iii) QL NS® (non-saponin fraction). The results showed that QL 1000® had important nematicidal effects at economically attractive doses (e.g., 100 ppm). When used separately, QL ULTRA® and QL NS® had minimum nematicidal effects. However, the combined use of both products gave similar results to QL 1000®, suggesting a synergy between the saponin and non-saponin fractions. Based on this, QL 1000® was tested in commercial vineyards and table grapes in the Central region of Chile. The use of 30 l ha-1 showed a similar control and fruit yields to synthetic chemical nematicides. [ABSTRACT FROM AUTHOR]

The development from growing plants in field soil to soil-less culture systems has not resulted in the elimination of problems caused by plant-parasitic nematodes. Species of Meloidogyne and Radopholus have been reported to occur in soil-less culture systems, such as flower crops. The reasons for initial nematode infestation are numerous but the primary reason is likely to be infested plant material. Since nematodes are not expected in soil-less systems, they are often overlooked. However, extension specialists report an increasing occurrence of plant-parasitic nematodes in soil-less culture systems and nematodes seem to be more prevalent than is often thought likely. In an attempt to increase the awareness of the prevalence of plant-parasitic nematodes in soil-less culture systems, this short paper summarises incidences of nematode detections and reviews methods for their detection and strategies for their control. [ABSTRACT FROM AUTHOR]

Clonal white clover growing in pots was inoculated with Heterodera trifolii, Meloidogyne hapla, Meloidogyne trifoliophila, Pratylenchus sp., or Xiphinema diversicaudatum, pulse-labelled with [sup 14]C and after 15 days the distribution of [sup 14]C in compartments of the soil: plant: nematode system determined. Nematode inoculation had no effect on shoot, root and soil microbial biomasses, but the nematode treatments significantly affected the distribution of [sup 14]C in these compartments. The greatest translocation of [sup 14]C to the soil was in pots with X. diversicaudatum, M. hapla or M. trifoliophila. The percentage of [sup 14]C in the microbial biomass varied significantly, being highest with X. diversicaudatum and Pratylenchus sp., and lowest in control pots. Nematodes of all species from the soil consistently had lower specific activity than those from roots. It has now been demonstrated for a range of nematodes and soils that nematode infection increases translocation of photosynthate to soil microbial biomass. As the soil microbial biomass plays a critical role in the availability of plant nutrients it appears that low infections of plant-parasitic nematodes may lead to greater availability of plant nutrients. Anstieg der Verlagerung von [sup 14]C-Kohlenstoff in die mikrobielle Biomasse, wenn funf Arten pflanzenschadigender Nematoden Wurzeln von Weissklee befallen - In Topfen gehaltene Weisskleeklone wurden mit Heterodera trifolii, Meloidogyne hapla, Meloidogyne trifoliophila, Pratylenchus sp. oder Xiphinema diversicaudatum infiziert. Die Nematoden waren mit [sup 14]C markiert, und nach 15 Tagen wurde die Verteilung des [sup 14]C in Abschnitten des Systems Boden: Pflanze: Nematode bestimmt. Nematodenbefall hatte zwar keine Wirkung auf die Biomassen von Spross, Wurzel und Mikroben, doch beeinflusste die Behandlung mit Nematoden signifikant die Verteilung von [sup 14]C in diesen Abschnitten. Die grosste Verlagerung von [sup 14]C in den Boden fand in den Topfen mit X. diversicaudatum, M. hapla oder M. trifoliophila statt. Der Anteil von [sup 14]C in der mikrobiellen Biomasse variierte stark. Er war am hochsten in Topfen mit X. diversicaudatum und Pratylenchus sp. und am gerigsten in den Kontrolltopfen. Bei allen Arten hatten die Nematoden aus dem Boden durchweg eine geringere spezifische Aktivitat als die aus den Wurzeln. Es wurde jetzt fur eine Reihe von Nematoden und Boden gezeigt, dass Nematodenbefall die Verlagerung von Photosyntheseprodukten in die mikrobielle Biomasse des Bodens steigert. Da die mikrobielle Biomasse im Boden eine kritische Rolle bei der Verfugbarkeit von Pflanzennahrstoffen spielt, scheint es, dass geringer Befall durch pflanzenschadigende Nematoden zu einer grosseren Verfugbarkeit von Pflanzennahrstoffen fuhren kann. [ABSTRACT FROM AUTHOR]