Nematode Pests Research Articles

Bacterial shield for seeds

Agribusiness giant Syngenta will pay up to $113 million to acquire Pasteuria Bioscience, a small biotech with a novel natural process to control nematode pests in plants. Under the terms of the agreement, the Baselbased Syngenta giant will acquire Pasteuria for $86 million, with additional deferred payments of up to $27 million. The deal is expected to close in the fourth quarter this year. The 21-employee company has worked out of the University of Florida Sid Martin Biotechnology Incubator in Alachua since 2003, and began an exclusive partnership with Syngenta in 2011. Its products are based on the cultivation of Pasteuria, a naturally occurring genus of soil bacteria. The organisms are lethal parasites of nematodes with spores that attach and infect the nematode body, reducing its reproductive rate and killing it. Pasteuria’s antinematode properties have been known for many years, but few researchers have been able to grow the bacteria in the laboratory. “It’s a very difficult organism to work with,” says Charles Opperman, a nematologist at North Carolina State University in Raleigh. Most groups have only been able to culture Pasteuria on its host, which limits production of the bacteria. Pasteuria Bioscience came up with a proprietary way to grow the bacteria outside its host and in large quantities. “No one else has been able to culture Pasteuria in vitro like they have,” says Opperman. With chemical controls for nematodes being restricted or pulled off the market in recent years, for fear of environmental damage, the company’s biological product should arrive at a good time. Syngenta expects to launch the first product, a seed treatment against cyst nematodes on soybeans, in the US in 2014, says Paul Minehart, a spokesperson for Syngenta. Emily Waltz in brief

Trapping Activity of Nematode-Trapping Fungus Arthrobotrys dactyloides on the Presence of Sawdust, Microorganisms, and Nematodes

Once biological control agents of nematodes are introduced into soil, they must function in a very complex and dynamicenvironment. In soil, both nematodes and their antagonists are influenced by other biotic and abiotic factors. However,our knowledge of the effects of these factors in soil is limited. Hence, instead of focusing on the role of individualorganisms in controlling nematode pests, this research aimed to determine the effects of sawdust, microorganisms,and nematodes on trapping activity of Arthrobotrys dactyloides. Experiments were conducted with “standardslide test” and “soil microcosm” using soil amended with various concentrations or without sawdust, with thepresence or the absence of microorganisms, and with the presence or the absence of nematodes (Caenorhabditiselegans and/or Meloidogyne javanica). The experiments were carried out with completely randomized design anddata were analyzed with analysis of variance followed by Tukey’s Honestly Significant Different test. Resultsshowed that sawdust did not have direct effect on ring formation and trapping activity of A. dactyloides. However,sawdust did have effect on microorganisms and C. elegans which then these two factors stimulated ring formationand trapping activity of A. dactyloides.

Molecular characterization of cereal cyst nematodes from the South Anatolian Region in Turkey using ITS-rDNA sequences

Summary The Heterodera avenae group includes 12 species feeding on roots of cereals. Three species, Heterodera avenae Wollenweber, 1924, Heterodera filipjevi (Madzhidov, 1981) Stelter, 1984 and Heterodera latipons Franklin, 1969 are among the most economically important cyst nematode pests of cereals cultivated in different parts of Turkey. In this study, forty seven cereal cyst nematode isolates collected from cereal growing areas of the South

Cloning arginine kinase gene and its RNAi in Bursaphelenchus xylophilus causing pine wilt disease

Since Bursaphelenchus xylophilus causes serious losses in pine forestry, new ways of controlling this nematode damage are urgently needed. Arginine kinase (AK) is a phosphotransferase, which plays a critical role in cellular energy metabolism in invertebrates. It is only present in invertebrates and may be a suitable chemotherapeutic target in the control of this pest. RNA interference (RNAi) technology has been developed in biological science in recent decades as a powerful tool to silence the target gene function in the post-translational status. In this study, one AK gene, BxAK1 (GeneBank accession No. EU853862) was firstly cloned, and then its functions were identified by RNAi technology. Results show that the full-length cDNA of the BxAK1 gene contains 1206 base pairs and an 1086 bp open reading frame encoding 361 amino acids. The length of the BxAK1 genomic coding region contains 2430 bp consisting of four introns of 421, 117, 475, and 268 bp respectively, and five exons of 57, 207, 309, 360, and 215 bp respectively. A dsRNA targeting BxAK1 was constructed and tested for its RNAi effect on B. xylophilus by soaking bioassays. RNAi not only significantly increased the mortality of B. xylophilus, but also greatly reduced its fecundity and fertility. These results suggest that RNAi targeting BxAK1 may be an effective approach for controlling nematode pests.

Interactions of Selected Potato Cultivars and Populations of Meloidogyne hapla Adapted to the Midwest U.S. Soils

ABSTRACTMeloidogyne hapla Chitwood is among the most serious nematode pests in temperate vegetable crops grown in rotation with potato (Solanum tuberosum L.), a crop with known resistance to potato cyst. While the types of agronomic trait improvements, crops, and pests are limited by resources, preserving improved crops in a rotation system requires understanding their performance against nontarget pests such as M. hapla. In greenhouse experiments, the interactions of four populations of M. hapla (Mh 1, Mh 2, Mh 3, and Mh 4) and six potato cultivars and lines, including ‘Boulder’ and ‘Missaukee’ with the H1 gene, were tested. The potato cultivars showed a 12 to 33% degree of suitability to the populations of M. hapla when compared with tomato (Solanum lycopersicum L. [syn. Lycopersicon esculentum Mill.), the host in which the populations were cultured, indicating that buildup of the populations of M. hapla potentially may be a problem. However, the responses varied by M. hapla population and potato cultivar interactions, suggesting that the management challenges will be site specific. Of the four M. hapla populations, Mh 3, an isolate from sandy soil under extended methyl bromide and other pesticide application, was the most pathogenic. The study provides critical data for developing agro‐biologically integrated approaches to managing nematode parasitic variability.

Macrocyclic Lactone Anthelmintics: Spectrum of Activity and Mechanism of Action

Macrocyclic lactones (MLs), exemplified by the prototype of the class, ivermectin (IVM), are mainstays of programs for the control of nematode and arthropod parasites and pests. Since their introduction 30 years ago, research has revealed that they act on a family of ligand-gated chloride channels gated by glutamate, which is largely restricted to animals in the phyla Nematoda and Arthropoda. Studies on IVM in model organisms have contributed greatly to our understanding of ML pharmacology, but our understanding of the basis for differences among species and among MLs in potency and spectrum remains far from complete.

EPPO Workshop on Meloidogyne chitwoodi and Meloidogyne fallax (2011‐03‐08): importance for potato production and experience of management in EPPO countries

Prior to the meeting of the Panel on Phytosanitary Measures for Potato in 2011, a one-day workshop on Meloidogyne chitwoodi and Meloidogyne fallax was held. Several additional experts, including nematologists, attended the workshop. The objectives were to review current knowledge on these Meloidogyne nematode pests; to share experiences of dealing with outbreaks; and to consider what further work, if any, should be undertaken by EPPO. There were four presentations by experts followed by discussions of several key issues. The conclusions of the workshop are presented. Meloidogyne nematodes are extremely polyphagous, difficult to detect and difficult to eradicate. In view of the regulatory status of both M. chitwoodi and M. fallax, there is a need for more systematic surveillance of these nematodes in the EPPO region to investigate their distribution and the feasibility of phytosanitary measures for the longer term. The participants at the EPPO workshop concluded that, based on current knowledge, M. chitwoodi and M. fallax do not pose a major threat for potato production. However, to promote awareness and surveillance, a national regulatory control system is needed to assist countries in taking action in case these nematodes are found. The experiences shared during this workshop will be used to develop a National Regulatory Control System for M. chitwoodi and M. fallax (EPPO PM 9 Standard). Mr Niere (Julius Kuhn-Institut, DE) gave a general introduction to Meloidogyne nematodes with emphasis on M. chitwoodi and M. fallax. Root-knot nematodes are the most important group of plant parasitic nematodes. In 1949, the first five species were described by B. Chitwood; by 2009, nearly 100 species had been described. The decreasing use of nematicides, coupled with more intensive host cropping systems, may explain why these nematodes have become a more prominent problem for growers. Meloidogyne nematodes are extremely polyphagous and damaging and have a worldwide distribution. The origin of these nematodes is not known. The species that have traditionally been recognized as major pests are M. incognita, M. arenaria, M. javanica and M. hapla. New species are emerging, however, including M. enterolobii, M. paranaenis, M. fallax, M. chitwoodi and M. minor, which also pose a major threat. Meloidogyne species are especially damaging in tropical regions for numerous vegetable crops, and can cause complete loss of harvest. Root-knot nematodes damage root systems and can induce the formation of galls, thereby weakening root systems, but rarely cause plant death. Necrotic lesions can also occur in the cortex. In

Rice root-knot nematode (Meloidogyne graminicola) infestation in rice

Rice (Oryza sativa) is an important staple food crop for majority of human population in the world in general and in Asia in particular. However, among various pests and diseases which constitute important constraints in the successful crop production, plant parasitic nematodes play an important role and account for yield losses to the extent of 90%. The major nematode pests associated with rice are Ditylenchus angustus, Aphelenchoides besseyi, Hirschmanniella spp., Heterodera oryzicola and Meloidogyne graminicola. However, rice root-knot nematode (M. graminicola) happens to be the most important pest and is prevalent in major rice producing countries of the world. In India, the distribution of M. graminicola in rice growing areas of different states has been documented in nematode distribution atlas prepared by All India Coordinated Research Project (Nematodes) and published by Directorate of Information and Publications of Agriculture, Indian Council of Agricultural Research, New Delhi, India during 2010. M. graminicola affected rice plants show stunting and chlorosis due to the characteristic terminal swellings/galls on the roots which ultimately result in severe reduction in growth and yield. Number of eco-friendly management technologies against M. graminicola have been developed and demonstrated, including the use of bioagents for minimising the losses due to rice root-knot nematode. This review is focused on collating information to understand the current scenario of rice root-knot nematodes with greater emphasis on its ecological requirements, damage symptoms, biology, morphology, host range and management strategies.

Evaluation of Nematode Pests and Fungal Diseases of Ceratotheca Sesamoides in Ilorin

Field and Laboratory experiments were conducted to find out the incidence of diseases caused by nematode pests and fungal pathogens associated with two cultivars (tall and short) of black sesame, Ceratotheca sesamoides (L) Endl. Two cultivars of C. sesamoides were planted at random on the field in a completely randomized block design. Rate of fungal infection significantly differed in the two varieties and the tall cultivar had higher rate of infection. The nematode genera found associated with the plant in were Meloidogyne, Pratylenchus, Helicotylenchus, Trichodorus, Hemicricomoides, and Scutellonema while fungal pathogens were Septoria, Fusarium, and Penicillium. Although not significantly different, there was appreciable difference in the nematode population of the soil at planting, one and two months after planting. The nematode counts in and around the root did not significantly differ.

Discovery of Potato Rot Nematode, Ditylenchus destructor, Infesting Garlic in Ontario, Canada.

Potato rot nematode, Ditylenchus destructor Thorne, 1945, is a serious nematode pest in a number of root and tube crops, primarily in potatoes, and is an internationally quarantined pest (2). In garlic, it was only reported in Japan (3). In 2011, a survey was conducted for the stem and bulb nematode, Ditylenchus dipsaci (Kühn) Filipjev in Ontario, Canada. PCR analysis revealed that a population of Ditylenchus from one garlic (Allium sativum) bulb sample in a 0.81-ha field (2-acre) in the Ottawa area had a significantly longer ITS1 (approximately 100 bp) than that of D. dipsaci. Subsequent morphology and DNA sequencing concluded that the population was Ditylenchus destructor, a quarantine species in Canada. Twenty females and twenty males were fixed and permanently mounted for morphological studies. The main diagnostic characters matched the description of D. destructor by Thorne (4). The female stylets had strong knobs, 11.1 ± 0.9 (10 to 12) μm long, lateral fields with six distinct lines in the middle section of the body, excretory pore 4.7 ± 1.3 (3 to 6) μm posterior to the hemizonid, esophageal base bulb overlaps dorsally with the intestine, post-vulval uterine sac extends up to two-thirds of the vulva-anus distance, and tail terminus finely rounded. A total of 20 nematode individuals were used for the molecular studies. They had 5-bp differences with the ITS1 (GenBank Accession No. EF208210; 650 bp) sequence of an isolate from Sihong County, China. The sequence of the partial 18S gene (GenBank Accession No. AY593912; 864 bp) was identical to the sequence of an isolate of D. destructor in the Netherlands. The detection of stem and bulb nematode was also confirmed from the field. Infested garlic plants were stunted and the basal bulbs became dark and somewhat rotten. Prior to this finding in Canada, D. destructor was only reported in a few isolated locations in the province of Prince Edward Island (PEI) in 1946 (1). The nematodes in PEI were effectively controlled. Another suspected case in British Columbia was not confirmed since the infested field had been known to be infested with D. dipsaci. To our knowledge, this is the first report of D. destructor on the mainland of Canada. The infested field has been subjected to strict quarantine measures to prevent the spread of the pest. Reference: (1) A. D. Baker et al. Sci. Agric. 26:138, 1946. (2) EPPO. No. 123. Data Sheets on Quarantined Organisms. Bulletin OEPP/EPPO Bull. 8, 1978. (3) T. Fujimura et al. Jpn. J. Nematol. 8:22, 1989. (4) G. Thorne. Proc. Helminthol. Soc. Wash. 12:27, 1945.

EFFECT OF STRAWBERRY AND BARLEY DEFENCE PROTEINS ON NEMATODE PESTS

ISHS XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Berries: From Genomics to Sustainable Production, Quality and Health EFFECT OF STRAWBERRY AND BARLEY DEFENCE PROTEINS ON NEMATODE PESTS

Characteristics and Antagonistic Potential of Pseudomonas spp. against Pratylenchus loosi

The tea root lesion nematode, Pratylenchus loosi, has been shown internationally serious nematode pest causing yield losses in tea plantations. The purpose of this study is that, with regard to biological control as one of the main section nematodes and sustainable agriculture, integrated management systems, allowing application and Pseudomonas fluorescens in the rhizosphere of tea root lesion nematode control to check. To evaluate these potentiality more than forty bacterial strains were collected from rhizosphere of tea plants and screened for their antagonistic activities towards adult and juvenile Pratylenchus loosi for population density reduction under in vitro condition. Eight selected isolates with nematicidal activity were characterized and identified. All belonged to the genus Pseudomonas. Seven strains were identified as Pseudomonas fluorescens and one as P. aeruginosa. Death percentage of juveniles ranged from 63.10% to 95.24% for P. fluorescens (Rh-36) and P. fluorescens (Rh-19), respectively.

A field study on the host status of different crops for Meloidogyne minor and its damage potential on potatoes

For several years, a new species of root-knot nematode, Meloidogyne minor, has been reported from parts of The Netherlands, Belgium, UK and Ireland. So far, this species causes most problems on golf courses but has also been reported from a potato field in Zeijerveld (The Netherlands) where it caused strong growth reduction on potato plants, but no damage to potato tubers. As The Netherlands is a potato-producing country, field experiments were set up to evaluate the potential risks this species poses. We tested the host status of some common crops for M. minor under field conditions and, more importantly, also tested its potential to harm potato production in terms of quantity as well as quality. In a 2-year field experiment (2007-2009), the host status of potato (cv. Bartina), rye, annual ryegrass, sugar beet, and maize was tested in the first growing season. Afterwards, these plots were used to evaluate the damage potential of M. minor on two commonly cultivated potato cultivars (cvs Astérix and Markies). In general, only potato seemed to be a good host for this nematode species with a Pf∕Pi-ratio about 1.5. Reproduction was observed mostly on roots but also on tubers, which increases the spread of M. minor by seed potatoes. However, there was no reduction in potato production, neither in yield nor in tuber quality. No significant reproduction could be observed on the other plants (Pf∕Pi values close to zero). From these results one might conclude that this nematode will not become a major threat to European agriculture. However, care has to be taken as within additional glasshouse experiments potato tubers were susceptible for damage caused by M. minor. Thus, further studies on the general biology and ecology of M. minor are needed to make a better risk assessment on this new nematode pest.

Enhanced tolerance of Mentha arvensis against Meloidogyne incognita (Kofoid and White) Chitwood through mutualistic endophytes and PGPRs

The use of herbs in pharmaceutical preparation is ever increasing, and the demand for pesticides free material by the concern industries is on the rise. Consequently the need to grow disease-free plants using non-chemical fertilizers and pesticides is the need of the hour. Mentha arvensis cv. kosi is highly infested with Meloidogyne incognita (Kofoid and White) Chitwood, and severe oil yield loss occurs due to this nematode pest. Employing ecofriendly ways of nematode management, the mutualistic endophytes (Trichoderma harzianum strain Thu, Glomus intraradices) and plant growth promoting rhizobacteria (Bacillus megaterium and Pseudomonas fluorescens) were assessed individually and in combination on plant biomass, oil yield of menthol mint (M. arvensis cv. kosi), reproduction potential and population development of root knot nematode, M. incognita under glasshouse conditions. These microbes enhanced the plant biomass and percent oil yield both with and without M. incognita inoculation. Dual application of mutualistic fungal endophytes and Plant Growth Promoting Rhizobacteria (PGPRs) may be a wise option for enhancing the oil yield and tolerance of menthol mint against M. incognita infection.

Purpureocillium, a new genus for the medically important Paecilomyces lilacinus

Paecilomyces lilacinus was described more than a century ago and is a commonly occurring fungus in soil. However, in the last decade this fungus has been increasingly found as the causal agent of infections in man and other vertebrates. Most cases of disease are described from patients with compromised immune systems or intraocular lens implants. In this study, we compared clinical isolates with strains isolated from soil, insects and nematodes using 18S rRNA gene, internal transcribed spacer (ITS) and partial translation elongation factor 1-α (TEF) sequences. Our data show that P. lilacinus is not related to Paecilomyces, represented by the well-known thermophilic and often pathogenic Paecilomyces variotii. The new genus name Purpureocillium is proposed for P. lilacinus and the new combination Purpureocillium lilacinum is made here. Furthermore, the examined Purpureocillium lilacinum isolated grouped in two clades based on ITS and partial TEF sequences. The ITS and TEF sequences of the Purpureocillium lilacinum isolates used for biocontrol of nematode pests are identical to those causing infections in (immunocompromised) humans. The use of high concentrations of Purpureocillium lilacinum spores for biocontrol poses a health risk in immunocompromised humans and more research is needed to determine the pathogenicity factors of Purpureocillium lilacinum.

Effect of methomyl and oxamyl soil applications on early control of nematodes and insects

Methomyl is a widely used carbamate insecticide that has traditionally been applied as a foliar spray. More recently, methomyl has been labeled as a soil application via drip chemigation. Not much is known about the insecticidal and nematicidal potential of soil-applied methomyl. Methomyl soil applications were evaluated for their potential to control soil nematodes and foliar insect pests in a series of lab and greenhouse tests. Methomyl showed rapid knockdown of Meloidogyne incognita (Kof. & White) Chitwood in aqueous assays, with EC50 and EC90 values that were similar to oxamyl and averaged 4.9 and 15.2 mg L(−1). In the greenhouse, soil applications of methomyl ranging from 0.56 to 4.0 kg ha(−1) provided significant M. incognita control similar to oxamyl during early growth (up to 25 days after planting) of pea and bean. Higher application rates and split applications improved nematode control, but also increased the risk of phytotoxicity. Methomyl soil applications were highly effective on several insects including Myzus persicae (Sulzer), Aphis gossypii (Glover), Frankliniella occidentalis Perg. and Spodoptera exigua (Hübner). Methomyl was about 5–9-fold more potent on M. persicae and A. gossypii when applied via soil drench as opposed to foliar spray. Potency on Bemisia tabaci Genn., S. exigua and Trichoplusia ni Hübner was about the same with the two application methods. Methomyl soil applications showed good potential for early control of various insect and nematode pests. Further testing is required to verify activity under field conditions.

Population development of beet cyst nematodes and their damage potential to sugar beets under different temperature regimes

Heterodera schachtii, the white beet cyst nematode, is considered as one of the most important nematode pests on sugar beet and is present in most sugar-beet growing areas. The yellow beet cyst nematode, Heterodera betae, is less prevalent but has also been found damaging beet crops. However, knowledge about the damage potential and population dynamics of the yellow beet cyst nematode is limited. The amount of damage inflicted by nematodes is dependent on different factors. An important factor influencing the sugar beet yield decline by beet cyst nematodes is the soil temperature. Relationships between soil temperature, H. schachtii population densities and sugar beet yields have been reported previously. Until present, most studies have been conducted under constant temperatures. Since several studies have demonstrated that the population dynamics of many species are sensitive to small differences in temperature (1-4°C), we subjected in our pot experiment sugar beet plants (cultivar Monza) to 2 gradually increasing temperature regimes in separate climate chambers. Temperatures in the two climate chambers were increased from 8°C to 22°C and 12°C to 26°C, respectively. Results on the influence of soil temperature on the Heterodera schachtii and Heterodera betae population densities and sugar beet growth parameters are presented

Population development of beet cyst nematodes and their damage potential to sugar beets under different temperature regimes

AbstractHeterodera schachtii, the white beet cyst nematode, is considered as one of the most important nematode pests on sugar beet and is present in most sugar-beet growing areas. The yellow beet cyst nematode, Heterodera betae, is less prevalent but has also been found damaging beet crops. However, knowledge about the damage potential and population dynamics of the yellow beet cyst nematode is limited. The amount of damage inflicted by nematodes is dependent on different factors. An important factor influencing the sugar beet yield decline by beet cyst nematodes is the soil temperature. Relationships between soil temperature, H. schachtii population densities and sugar beet yields have been reported previously. Until present, most studies have been conducted under constant temperatures. Since several studies have demonstrated that the population dynamics of many species are sensitive to small differences in temperature (1-4°C), we subjected in our pot experiment sugar beet plants (cultivar Monza) to 2 gradually increasing temperature regimes in separate climate chambers. Temperatures in the two climate chambers were increased from 8°C to 22°C and 12°C to 26°C, respectively. Results on the influence of soil temperature on the Heterodera schachtii and Heterodera betae population densities and sugar beet growth parameters are presented

Development of Species-Specific PCR Primers and Sensitive Detection of the Tylenchulus semipenetrans in China

Tylenchulus semipenetrans is the most economically important and widespread nematode pest of citrus in China. rDNA-ITS of 14 populations of T. semipenetrans which were collected from different citrus groves or Chinese fir ( Cunninghamia lanceolata) plantations in China were amplified and sequenced. The species-specific primers were designed for the first time to diagnosis T. semipenetrans based on the sequences of rDNA-ITS regions of geographic population above. The primers were sensitive to amplify the expected band size (297 bp) from DNA template of a single second-stage juvenile (J2) or different life stages of T. semipenetrans. No specific band was amplified from 15 non-target nematode species which were commonly found in citrus groves. Specificity and reliability of the primers were validated by further PCR amplification of 16 extra populations of T. semipenetrans collected from 4 provinces of China. The primers successfully detected a single J2 of T. semipenetrans within a whole nematode community comprising a large numbers of non-target nematode. The developed diagnostic technique can be used for accurate identification of T. semipenetrans and also as a decision tool for nematode management for citrus or Chinese fir in China.

Overexpression of a cuticle-degrading protease Ver112 increases the nematicidal activity of Paecilomyces lilacinus

Due to their ability to degrade the proteins in nematode cuticle, serine proteases play an important role in the pathogenicity of nematophagous fungi against nematodes. The serine protease Ver112 was identified from the nematophagous fungus Lecanicillium psalliotae capable of degrading the nematode cuticle and killing nematodes effectively. In this study, the gene ver112 was introduced into the commercial biocontrol fungal agent Paecilomyces lilacinus by the restriction enzyme-mediated integration transformation. Compared to the wild strain, the transformant P. lilacinus 112 showed significantly greater protease activity, with nematicidal activities increased by 79% and 96% to Panagrellus redivivus and Caenorhabditis elegans at the second day, respectively. The crude protein extract isolated from the culture filtrate of P. lilacinus 112 also showed 20-25% higher nematicidal activity than that of the wild-type strain. Reverse transcription PCR results showed that the expression of gene ver112 in P. lilacinus 112 was correlated to protease activity of the culture filtrate. Our results demonstrated the first successful transfer of a virulence gene from one nematophagous fungus to another nematophagous fungus, and improved the pathogenicity of the recipient fungus against pest nematodes.