Nicole Viaene

Bio: Nicole Viaene is an academic researcher from Ghent University. The author has contributed to research in topics: Heterodera avenae & Pratylenchus penetrans. The author has an hindex of 20, co-authored 92 publications receiving 2482 citations.

First Report of the Cereal Cyst Nematode Heterodera latipons on Wheat in Morocco

Abstract: From May to June 2011, during a survey of the wheat-growing areas in Meknes in the Sais Region of Morocco, several cyst nematode populations were detected. Sampling was performed 1 month before wheat (Triticum durum) harvest, in fields showing patches of stunted plants. Plants were growing poorly, had chlorotic lower leaves, and a reduced numbers of ears. Root systems were short and had a bushy appearance because of increased secondary root production. No cysts were visible on the roots, but were found in the soil. Cysts were collected from soil on 200-μm sieves by the modified Cobb decanting and sieving method (1) and identified by morphology and internal transcribed spacer (ITS)-rDNA sequencing. All isolates were identified as Heterodera avenae except the isolate from Ain Jemâa. From the latter, key morphological features from cysts and second-stage juveniles (J2) were determined. The cysts (n = 10) had the following characteristics: bifenestrate vulval cone, body length without neck 590 μm (551 to 632 μm), body width 393 μm (310 to 490 μm), neck length 75 μm (65 to 90 μm), fenestra length 64 μm (60 to 72 μm) and width 21 μm (18 to 25 μm), underbridge length 96 μm (85 to 115 μm), vulval slit length 8 μm (7 to 9 μm), vulva bridge width 27 μm (24 to 33 μm), and bullae absent. The J2s (n = 10) had the following characteristics: body length 445 μm (412 to 472 μm), body width 19 μm (19 to 21 μm), stylet length 24 μm (23 to 25 μm), four lateral lines, tail length 50 μm (46 to 54 μm), and hyaline terminal tail 28 μm (24 to 31 μm). Values of the morphological characters were within the range of H. latipons reported by Handoo (3). The bifenestrate cysts with a strong underbridge and no bullae and J2 with a tail length greater than 40 μm, a stylet longer than 15 μm, and four incisures in the lateral field were typical for H. latipons. To confirm the identification, molecular observations were made. DNA was extracted from three juveniles from three different cysts separately (4). The ITS-rDNA region was amplified using the primers 5'-CGT AAC AAG GTA GCT GTA G-3' and 5'-TCC TCC GCT AAA TGA TAT G-3' as described by Ferris et al. (2). This resulted in a 1,040-bp DNA fragment. The PCR-products were purified and sequenced (Macrogen, Inc., Seoul, Korea). All sequences obtained (GenBank Accession Nos. per cyst: JQ319035, JQ319036, and JQ319037) were compared with sequences available from the GenBank database ( www.ncbi.nlm.nih.gov ), including several species of Heterodera. This comparison revealed a sequence similarity of 97 to 99% with H. latipons and 89% or lower with any other species of Heterodera. Morphological and molecular identification demonstrated that the population of cyst nematodes from a wheat field in Ain Jemâa, Morocco was H. latipons. In the patches with poor growing plants, 65 cysts per 100 cm3 soil were found. To our knowledge, this detection represents a new record of H. latipons. Since the nematode can cause considerable damage to wheat, one of the main cereals produced in Morocco, care should be taken to prevent the spread to other regions. References: (1) K. R. Barker. Page 19 in: An Advanced Treatise on Meloidogyne. Vol II. Methodology. C. C. Carter and J. N. Sasser, eds. North Carolina State University Graphics, Raleigh, 1985. (2) V. R. Ferris et al. Fundam. Appl. Nematol. 16:177, 1993. (3) Z. A. Handoo. J. Nematol. 34:250, 2002. (4) M. Holterman et al. Mol. Biol. Evol. 23:1792, 2006.

Root-knot nematodes ( Meloidogyne spp.) in Europe

Abstract: In Europe, root-knot nematodes are increasingly important. Out of more than 90 Meloidogyne species currently described, 23 have been found on the continent. In the cooler climates, Meloidogyne hapla , M. naasi , M. chitwoodi and M. fallax are prevalent. Meloidogyne arenaria , M. javanica and M. incognita are the most common species in warmer conditions of southern Europe, but also in glasshouses in northern Europe. Morphological identification of root-knot nematodes is difficult and time consuming; therefore, many research groups have been developing molecular techniques for identification of Meloidogyne species. Meloidogyne chitwoodi and M. fallax are quarantine organisms and subject to regulations, and the highly aggressive M. enterolobii has been added to the EPPO alert list. Differences between temperate and tropical Meloidogyne species and their prevalence in Europe imply the need for different management strategies in south and north Europe. Possible crop rotations for the control of root-knot nematodes are limited due to the wide host range of several important species. The banning of methyl bromide and restrictions on other fumigant pesticides in the EU have increased the application of biofumigation significantly in south Europe. The egg-parasitising fungus Paecilomyces lilacinus is commercialised in Germany and applied as dispersible granules for application in water. Intensive research is conducted on the egg-parasitising fungus Pochonia chlamydosporia , and the obligate parasitic bacterium Pasteuria penetrans. European research has paid much attention to resistance breeding and selection. The Mi gene of tomato is widely used but resistance-breaking populations of M. incognita and M. javanica have been reported in different countries.

Management of Meloidogyne hapla on Lettuce in Organic Soil with Sudangrass as a Cover Crop

Abstract: Host suitability for Meloidogyne hapla of six cover crops was tested in the greenhouse. Sudan-grass cv. Trudan 8 and rye (mixture of cultivars) were nonhosts; oat cv. Porter was a poor host; and phacelia cv. Angelia, oilseed radish cv. Renova, and yellow mustard cv. Martigena were maintenance hosts. When incorporated as a green manure before planting of lettuce cv. Mon-tello, sudangrass was the most effective of the cover crops in reducing egg production of M. hapla. Soil amendment with all parts of sudangrass resulted in lower reproduction of M. hapla on lettuce than soil amendment with only roots of sudangrass. Soil incorporation of 2-month-old (or younger) tissues of sudangrass was more effective in reducing nematode reproduction on subsequent lettuce plants than incorporation of 3-month-old tissues. Sudangrass was grown as a cover crop after lettuce for three growing seasons in field microplots and incorporated as a green manure before the first fall frost. Weight of lettuce heads was significantly higher and reproduction of M. hapla was significantly lower in sudangrass-amended microplots compared with those left fallow between lettuce crops, but results varied with year and nematode infestation level.

Effect of Temperature

Abstract: A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.

Microbial diversity in soil: Selection of microbial populations by plant and soil type and implications for disease suppressiveness

Abstract: An increasing interest has emerged with respect to the importance of microbial diversity in soil habitats The extent of the diversity of microorganisms in soil is seen to be critical to the maintenance of soil health and quality, as a wide range of microorganisms is involved in important soil functions This review focuses on recent data relating how plant type, soil type, and soil management regime affect the microbial diversity of soil and the implication for the soil's disease suppressiveness The two main drivers of soil microbial community structure, ie, plant type and soil type, are thought to exert their function in a complex manner We propose that the fact that in some situations the soil and in others the plant type is the key factor determining soil microbial diversity is related to the complexity of the microbial interactions in soil, including interactions between microorganisms and soil and microorganisms and plants A conceptual framework, based on the relative strengths of the shaping forces exerted by plant and soil versus the ecological behavior of microorganisms, is proposed

Top 10 plant-parasitic nematodes in molecular plant pathology

Abstract: The aim of this review was to undertake a survey of researchers working with plant-parasitic nematodes in order to determine a ‘top 10’ list of these pathogens based on scientific and economic importance. Any such list will not be definitive as economic importance will vary depending on the region of the world in which a researcher is based. However, care was taken to include researchers from as many parts of the world as possible when carrying out the survey. The top 10 list emerging from the survey is composed of: (1) root-knot nematodes (Meloidogyne spp.); (2) cyst nematodes (Heterodera and Globodera spp.); (3) root lesion nematodes (Pratylenchus spp.); (4) the burrowing nematode Radopholus similis; (5) Ditylenchus dipsaci; (6) the pine wilt nematode Bursaphelenchus xylophilus; (7) the reniform nematode Rotylenchulus reniformis; (8) Xiphinema index (the only virus vector nematode to make the list); (9) Nacobbus aberrans; and (10) Aphelenchoides besseyi. The biology of each nematode (or nematode group) is reviewed briefly.

Sustainable development: Meaning, history, principles, pillars, and implications for human action: Literature review

Abstract: Sustainable development (SD) has become a popular catchphrase in contemporary development discourse. However, in spite of its pervasiveness and the massive popularity it has garnered over the years...