Nematode Pests Research Articles

Mitochondrial coding genome analysis of tropical root-knot nematodes (Meloidogyne) supports haplotype based diagnostics and reveals evidence of recent reticulate evolution.

The polyphagous parthenogenetic root-knot nematodes of the genus Meloidogyne are considered to be the most significant nematode pest in sub-tropical and tropical agriculture. Despite the crucial need for correct diagnosis, identification of these pathogens remains problematic. The traditionally used diagnostic strategies, including morphometrics, host-range tests, biochemical and molecular techniques, now appear to be unreliable due to the recently-suggested hybrid origin of root-knot nematodes. In order to determine a suitable barcode region for these pathogens nine quickly-evolving mitochondrial coding genes were screened. Resulting haplotype networks revealed closely related lineages indicating a recent speciation, an anthropogenic-aided distribution through agricultural practices, and evidence for reticulate evolution within M. arenaria. Nonetheless, nucleotide polymorphisms harbor enough variation to distinguish these closely-related lineages. Furthermore, completeness of lineage sorting was verified by screening 80 populations from widespread geographical origins and variable hosts. Importantly, our results indicate that mitochondrial haplotypes are strongly linked and consistent with traditional esterase isozyme patterns, suggesting that different parthenogenetic lineages can be reliably identified using mitochondrial haplotypes. The study indicates that the barcode region Nad5 can reliably identify the major lineages of tropical root-knot nematodes.

Cis- and trans-protopinium, a novel nematicide, for the eco-friendly management of root-knot nematodes

Plant-derived nematicides are being increasingly used while select synthetic nematicides are phased out for environmental concerns. This is the first report on the in vitro nematicidal activity of cis- and trans-protopinium isolated from roots of Fumaria parviflora and its in vivo effect on the southern root-knot nematode Meloidogyne incognita. Cis- and trans-protopinium was isolated from the methanolic fraction FM2.1, and its structure elucidated using 13C and 1H nuclear magnetic resonance (NMR). The NMR spectra were characterized using deuterated dimethyl sulfoxide (DMSO) at temperatures of 25 and 80 °C. In an in vitro study, over 120 h of incubation, the area under cumulative percent hatch inhibition and mortality of cis- and trans-protopinium reached 100% at a concentration of 200 μg mL−1. In the greenhouse and field settings, cis- and trans-protopinium was evaluated against M. incognita on tomato at a concentration of 100, 200, and 300 μg mL−1 for two consecutive seasons, that is, spring and autumn, in 2010. At a concentration of 300 μg mL−1 in the greenhouse and field trials during spring and autumn, cis- and trans-protopinium significantly reduced the nematode galling index, the number of females per gram of root, and the reproduction factor, as well as increased plant height, fresh and dry shoot weights, and root length. Therefore, cis- and trans-protopinium can be used as an effective and safe nematicide against M. incognita on tomato in an organic and sustainable agricultural production system. Phytochemicals have various agricultural applications, especially to control economically important nematode pests.

伴生种植皱叶黑膏桐对美藤果植株生长和结实的影响

2012~2015期间，在云南西双版纳和元江那唐山南亚热带高档油料植物试验基地，我们开展了皱叶黑膏桐与美藤果(Inca Peanut)伴生种植的试验。本项试验的目旨在利用膏桐活体根系释放的挥发性化感物质对实验区土壤有害生物进行实时生物防控，以保证美藤果植株健康地生长、开花和结果，实现美藤果引种开发的优质高产。试验结果表明，采用皱叶黑膏桐伴生种植以后，在美藤果种植试验区内线虫、白蚁和病原微生物的危害已明显低于美藤果单一种植区。与此同时在伴生种植区内，美藤果植株生长速率、分枝数量、开花结果物候，雌花比例、坐果率等指标，也得到了明显提高。 During 2012-2015 years, new Jatropha varieties and Inca peanut planting collocation experiment had been conducted on the south subtropical high-grade oil planting test bases of Xishuangbanna and Yuanjiang. This study aimed at using volatile components released by the living roots of Ja-tropha curcas to prevent or/and control nematode, termites and other soil pests, to guarantee healthy growth, flowering and fruiting of Inca peanut plants, and to realize high yield and good quality of Inca peanut production. Experimental results show that after Inca peanut accompanied planting with wrinkled-leaf jatropha, in the planting test area the nematode and termite’s dangers had been greatly lower than those of Inca peanut monoplanting. At the same time, the indicators such as plant growth rate, number of branches, phenology of flowering and fruiting, the proportion of female flowers, fruit setting rate, have also been significantly improved.

Distribution of Hoplolaimus Species in Soybean Fields in South Carolina and North Carolina.

Hoplolaimus columbus is an important nematode pest of soybean in South Carolina and North Carolina. Tolerant cultivars are available for the management of this plant-parasitic nematode; however, variation in the response of soybean cultivars to H. columbus populations has been observed. This variation may be due to the presence of different species or high genetic diversity of H. columbus populations. The objective of this study was to identify the Hoplolaimus spp. present in fields representing the main soybean-growing regions in South Carolina and North Carolina and to examine the genetic variability of these populations. In South Carolina, the only species found associated with soybean was H. columbus but, in North Carolina, H. stephanus was the dominant species. The two species were never found together. Genetic variability analyses of a mitochondrial and a nuclear marker showed that only one haplotype was shared by the H. columbus populations. H. stephanus showed higher genetic variability, with private haplotypes per sampling location. Knowledge of the distribution and genetic variability of these two Hoplolaimus spp. is valuable to growers to determine potentially damaging infestations of these plant-parasitic nematodes in soybean fields.

A genome-wide association study of a global rice panel reveals resistance in Oryza sativa to root-knot nematodes.

The root-knot nematode Meloidogyne graminicola is one of the most serious nematode pests worldwide and represents a major constraint on rice production. While variation in the susceptibility of Asian rice (Oryza sativa) exists, so far no strong and reliable resistance has been reported. Quantitative trait loci for partial resistance have been reported but no underlying genes have been tagged or cloned. Here, 332 accessions of the Rice Diversity Panel 1 were assessed for gall formation, revealing large variation across all subpopulations of rice and higher susceptibility in temperate japonica accessions. Accessions Khao Pahk Maw and LD 24 appeared to be resistant, which was confirmed in large pot experiments where no galls were observed. Detailed observations on these two accessions revealed no nematodes inside the roots 2 days after inoculation and very few females after 17 days (5 in Khao Pahk Maw and <1 in LD 24, in comparison with >100 in the susceptible controls). These two cultivars appear ideal donors for breeding root-knot nematode resistance. A genome-wide association study revealed 11 quantitative trait loci, two of which are close to epistatic loci detected in the Bala x Azucena population. The discussion highlights a small number of candidate genes worth exploring further, in particular many genes with lectin domains and genes on chromosome 11 with homology to the Hordeum Mla locus.

Greenhouse and field evaluations of commonly occurring weed species for their host suitability to Meloidogyne species

Since weeds serve as hosts for nematode pests, the host status of 20 weed species (commonly occurring in fields of developing farmers) to Meloidogyne incognita and M. javanica, respectively, were investigated. Greenhouse studies showed that seven weed species had Rf values >1 for both nematode species indicating susceptibility, while 13 had Rf values ≤ 1 indicating resistance. Greenhouse results showed that Hibiscus trionum and Amaranthus tricolor were identified as the most susceptible and Chenopodium carinatum and Datura ferox the poorest hosts for M. incognita and M. javanica. For field experiments at Kuruman, Solanum retroflexum was the most susceptible weed to a M. javanica population, while the same was evident for H. trionum at Nelspruit, where a mixed population of M. incognita and M. javanica occurred and at Potchefstroom, where a population of M. incognita was present. Results from this study indicated that certain weed species are highly susceptible to root-knot nematodes and should be removed timely and effectively to prevent population level increases of root-knot nematode pests in the fields of farmers.

Agricultural nematology in East and Southern Africa: problems, management strategies and stakeholder linkages.

By 2050, Africa's population is projected to exceed 2 billion. Africa will have to increase food production more than 50% in the coming 50 years to meet the nutritional requirements of its growing population. Nowhere is the need to increase agricultural productivity more pertinent than in much of Sub-Saharan Africa, where it is currently static or declining. Optimal pest management will be essential, because intensification of any system creates heightened selection pressures for pests. Plant-parasitic nematodes and their damage potential are intertwined with intensified systems and can be an indicator of unsustainable practices. As soil pests, nematodes are commonly overlooked or misdiagnosed, particularly where appropriate expertise and knowledge transfer systems are meager or inadequately funded. Nematode damage to roots results in less efficient root systems that are less able to access nutrients and water, which can produce symptoms typical of water or nutrient deficiency, leading to misdiagnosis of the underlying cause. Damage in subsistence agriculture is exacerbated by growing crops on degraded soils and in areas of low water retention where strong root growth is vital. This review focuses on the current knowledge of economically important nematode pests affecting key crops, nematode control methods and the research and development needs for sustainable management, stakeholder involvement and capacity building in the context of crop security in East and Southern Africa, especially Kenya, Tanzania, Uganda and Zimbabwe.

Nematode pests threatening soybean production in South Africa, with reference to Meloidogyne

The area planted to soybean in South Africa has increased by 54% since the 2009 growing season, mainly as a result of the increasing demand for protein-rich food and fodder sources. Moreover, the introduction of advanced technology, namely the availability of genetically modified herbicide tolerant soybean cultivars also contributed towards increased soybean production. The omnipresence of plant-parasitic nematodes in local agricultural soils, however, poses a threat to the sustainable expansion and production of soybean and other rotation crops. Meloidogyne incognita and M. javanica are the predominant nematode pests in local soybean production areas and those where other grain-, legume- and/or vegetable crops are grown. The lack of registered nematicides for soybean locally, crop production systems that are conducive to nematode pest build-ups as well as the limited availability of genetic host plant resistance to root-knot nematode pests, complicate their management. Research aimed at various aspects related to soybean-nematode research, namely, audits of nematode assemblages associated with the crop, identification of genetic host plant resistance in soybean germplasm to M. incognita and M. javanica, the use of molecular markers that are linked to such genetic resistance traits as well as agronomic performance of pre-released cultivars that can be valuable to producers and the industry are accentuated in this review. Evaluation of synthetically-derived as well as biological-control agents are also discussed as complementary management tactics. It is important that lessons learned through extensive research on soybean-nematode interactions in South Africa be shared with researchers and industries in other countries as they might experience or expect similar problems and/or challenges.

Molecular mechanisms of nematode-nematophagous microbe interactions: basis for biological control of plant-parasitic nematodes.

Plant-parasitic nematodes cause significant damage to a broad range of vegetables and agricultural crops throughout the world. As the natural enemies of nematodes, nematophagous microorganisms offer a promising approach to control the nematode pests. Some of these microorganisms produce traps to capture and kill the worms from the outside. Others act as internal parasites to produce toxins and virulence factors to kill the nematodes from within. Understanding the molecular basis of microbe-nematode interactions provides crucial insights for developing effective biological control agents against plant-parasitic nematodes. Here, we review recent advances in our understanding of the interactions between nematodes and nematophagous microorganisms, with a focus on the molecular mechanisms by which nematophagous microorganisms infect nematodes and on the nematode defense against pathogenic attacks. We conclude by discussing several key areas for future research and development, including potential approaches to apply our recent understandings to develop effective biocontrol strategies.

Field resistance of transgenic plantain to nematodes has potential for future African food security.

Plant parasitic nematodes impose losses of up to 70% on plantains and cooking bananas in Africa. Application of nematicides is inappropriate and resistant cultivars are unavailable. Where grown, demand for plantain is more than for other staple crops. Confined field testing demonstrated that transgenic expression of a biosafe, anti-feedant cysteine proteinase inhibitor and an anti-root invasion, non-lethal synthetic peptide confers resistance to plantain against the key nematode pests Radopholus similis and Helicotylenchus multicinctus. The best peptide transgenic line showed improved agronomic performance relative to non-transgenic controls and provided about 99% nematode resistance at harvest of the mother crop. Its yield was about 186% in comparison with the nematode challenged control non-transgenic plants based on larger bunches and diminished plant toppling in storms, due to less root damage. This is strong evidence for utilizing this resistance to support the future food security of 70 million, mainly poor Africans that depend upon plantain as a staple food.

Potential of intercropping for management of some arthropod and nematode pests of leafy vegetables in Kenya

African leafy vegetables (ALVs) play an important role as income and food security crops in many households in Kenya. However, their potential in alleviating poverty and ensuring household food and nutrition security has not been fully exploited. The objectives of this study were to identify some arthropod and nematode pests that infest ALVs and to evaluate the effectiveness of intercropping of susceptible and resistant plants for the management purposes. Three vegetable types: African nightshade, sunn hemp and spider plant were used in determining the efficacy of an intercrop of susceptible and non-susceptible types in reducing arthropod and nematode pest effect. The treatments in the field experiment consisted of different intercrop designs and a sole crop design as control while data was taken based on five different variables. Crops in the field were infested with arthropod pests and eight different species were enumerated. The same row and hill intercropping designs were the most effective in reducing the effect of arthropod and nematode pests compared to the control plots. Spider plant and African nightshade intercrops recorded the least arthropod pest damage, higher fresh and dry shoot yields and differed significantly (P?0.05) to African nightshade planted as a sole crop. A similar trend was observed when the experiment was repeated with a sunn hemp and African nightshade intercrop. It is concluded from this study that intercropping of different crops can be integrated with other methods to provide an easily adaptable technology to apply for effective management of arthropod and nematode pests with low external inputs.

Assessment of germination and carnivorous activities of a nematode-trapping fungus Arthrobotrys dactyloides in fungistatic and fungicidal soil environment

Carnivorism is the ability of nematode-trapping fungi to trap and digest the nematodes by sophisticated devices called traps. Delivery of nematode-trapping fungi in soil for bio-control of pest nematodes often fails or gives inconsistent results. Possible reasons for failure could be the effect of soil fungistasis on germination of nematode-trapping fungi in soil environment, use of avirulent species and sensitivity of these fungi to fungicidal residues in soil. Exploitation of nematode-trapping fungi for nematode control demands that it be compatible with fungicides applied in soil or crops and proliferate in soil. This investigation represents is one of the first to evaluate the effect of fungicides on the nematode-trapping fungus Arthrobotrys dactyloides. A. dactyloides showed in vitro carnivorous potential against Meloidogyne incognita, Meloidogyne javanica, Meloidogyne graminicola, Helicotylenchus dihystera and Heterodera cajani. Conidia of A. dactyloides exposed to agricultural soils showed poor germination but formed conidial traps, which captured and killed the soil nematodes. Conidial traps, which trapped the nematodes, grew well in all soils after killing and nutrient absorption from nematode body. Soil amended with 20mg aikg−1 of carbendazim and thiram, 30mg aikg−1 of mancozeb, 50mg aikg−1 of captan, and 100mg aikg−1 of carboxin completely checked the conidial trap formation and nematode capturing. 30, 50 and 100mg aikg−1 of metalaxyl adversely affected the conidial trap formation and nematode capturing in soil. Propiconazole inhibited 15.2% conidial trap formation up to 50mg aikg−1 but caused 93.3% inhibition of conidial traps formation and complete inhibition of nematode capturing at 100mg aikg−1. Sulphur, triademefon, and tricyclazole showed least toxic effect on conidial trap formation and nematode capturing activities of A. dactyloides in soil up to 100mg aikg−1.

Anthelmintic drugs and nematicides: studies in Caenorhabditis elegans.

Parasitic nematodes infect many species of animals throughout the phyla, including humans. Moreover, nematodes that parasitise plants are a global problem for agriculture. As such, these nematodes place a major burden on human health, on livestock production, on the welfare of companion animals and on crop production. In the 21st century there are two major challenges posed by the wide-spread prevalence of parasitic nematodes. First, many anthelmintic drugs are losing their effectiveness because nematode strains with resistance are emerging. Second, serious concerns regarding the environmental impact of the nematicides used for crop protection have prompted legislation to remove them from use, leaving agriculture at increased risk from nematode pests. There is clearly a need for a concerted effort to address these challenges. Over the last few decades the free-living nematode Caenorhabditis elegans has provided the opportunity to use molecular genetic techniques for mode of action studies for anthelmintics and nematicides. These approaches continue to be of considerable value. Less fruitful so far, but nonetheless potentially very useful, has been the direct use of C. elegans for anthelmintic and nematicide discovery programmes. Here we provide an introduction to the use of C. elegans as a 'model' parasitic nematode, briefly review the study of nematode control using C. elegans and highlight approaches that have been of particular value with a view to facilitating wider-use of C. elegans as a platform for anthelmintic and nematicide discovery and development.

Report on Workshop on “Biological Control in Potato Production”

Thirty-three scientists from 22 countries, mostly not only from Europe (Austria, Belgium, France, Finland, Germany, Ireland, The Netherlands, Slovenia, Switzerland, the UK) but also from Peru and Kenya, actively participated as experts in the EAPR workshop on biological control in potato production. Each participant rated both his own expertise in potato and in biological control, on a scale from 1 (very low) to 5 (very high). The mean rate of expertise of the panel was 3.60 (medium to high) for potato expertise and 2.89 (medium) for biological control. Additionally, the experts were asked to (i) identify the major research areas in biological control, (ii) choose major targets to focus on plant pathogenic fungi, bacteria, and viruses as well as nematode and insect pests, (iii) specify the major gaps and needs in potato biological control, and finally (iv) provide indications on possible technological locks for innovation in biological control.

Genome sequence of Serratia nematodiphila DSM 21420T, a symbiotic bacterium from entomopathogenic nematode

Serratia nematodiphila DSM 21420T (=CGMCC 1.6853T, DZ0503SBS1T), isolated from the intestine of Heterorhabditidoides chongmingensis, has been known to have symbiotic-pathogenic life cycle, on the multilateral relationships with entomopathogenic nematode and insect pest. In order to better understanding of this rare feature in Serratia species, we present here the genome sequence of S. nematodiphila DSM 21420T with the significance of first genome sequence in this species.

First Report of the Southern Root-Knot Nematode Meloidogyne incognita on the Invasive Weed Araujia sericifera in Italy.

Moth plant, Araujia sericifera, is native to South America and was exported to many other countries as an ornamental plant. However, it is now considered an invasive, perennial, noxious weed in Italy. Because of the ability of this plant to spread rapidly and invade natural ecosystems, A. sericifera has been included on the Alert list by the European and Mediterranean Plant Protection Organization (EPPO). In September 2013, numerous plants of A. sericifera with chlorotic leaves and large root-galls were observed in agricultural fields, gardens, and uncultivated locations in Nocera Inferiore, Salerno Province, Italy. Ten samples were collected from a vegetable farm (40°45'40.8″ N, 14°38'18.4″ E) and nematodes were extracted from soil and root samples using standard procedures (1). Meloidogyne sp. was found in all soil and root samples, with nematode population densities ranging from 420 to 1,270 eggs and J2s/10 cm3 of soil and 84 to 2,200 eggs and J2s/5 g of fresh roots. The morphological identification of the nematode was based on characterization of second-stage juveniles (J2s), males, eggs, and females (2). Measurements of J2s (n = 30) include: mean body length (L) = 403 ± 3.7 μm; L/maximum body width = 27.5 ± 0.3; L/esophageal length = 6.2 ± 0.1; stylet length = 12.8 ± 0.1 μm; L/tail length = 9.5 ± 0.1; tail length = 42.5 ± 0.3 μm. Males (n = 10): L = 1,491 ± 0.04 μm; L/maximum body width = 44.4 ± 0.8; L/esophageal length = 16.1 ± 0.3; stylet length = 22.1 ± 0.7 μm; spicules length = 30.1 ± 0.8 μm. Eggs (n = 30): length = 96.6 ± 1 μm; width = 45.1 ± 0.5 μm; length/width ratio = 2.1. Females (n = 20): L = 909.5 ± 38.4 μm; body width = 588.3 ± 19.3 μm; stylet length = 17.0 ± 0.2 μm. Perineal patterns of females had a high dorsal arch with wavy striae bending toward the lateral lines and the absence of distinct lateral line incisures. All measurements conformed to the description of Meloidogyne incognita (Kofoid & White, 1919) Chitwood 1949. DNA was extracted from five individual adult females from each sample and morphological identification was confirmed by a sequence-characterized amplified region (SCAR)-PCR technique using species-specific primers. The amplified product obtained was 1.2 kb in length, demonstrating proper amplification of the species-specific, length variant SCAR marker (3). Weeds are known to serve as hosts for nematodes in the absence of crop plants and to affect the success of nematode management programs. Meloidogyne spp. have been reported to survive and even thrive on weeds; among them, M. incognita is considered the most economically important agricultural nematode pest worldwide as it causes severe yield losses on many hosts. Thus, the invasive plant A. sericifera can be a potential reservoir for M. incognita in Italy and elsewhere. To our knowledge, this is the first report of M. incognita parasitizing A. sericifera.

Evaluating habitat suitability for the establishment of Monochamus spp. through climate-based niche modeling.

Pine sawyer beetle species of the genus Monochamus are vectors of the nematode pest Bursaphelenchus xylophilus. The introduction of these species into new habitats is a constant threat for those regions where the forestry industry depends on conifers, and especially on species of Pinus. To obtain information about the potential risk of establishment of these insects in Chile, we performed climate-based niche modeling using data for five North American and four Eurasian Monochamus species using a Maxent approach. The most important variables that account for current distribution of these species are total annual precipitation and annual and seasonal average temperatures, with some differences between North American and Eurasian species. Projections of potential geographic distribution in Chile show that all species could occupy at least 37% of the area between 30° and 53°S, where industrial plantations of P. radiata are concentrated. Our results indicated that Chile seems more suitable for Eurasian than for North American species.

An ecofriendly root- knot nematode pest management strategy on sugarbeet 2- Using some amino and organic acids

An ecofriendly root- knot nematode pest management strategy on sugarbeet 2- Using some amino and organic acids

Phenotypic screening of pecan seedling rootstocks in search of nematode resistance

Open-pollinated seedstocks for pecan vary in phenology and composition predictably based on their provenance of origin in ways that impact performance. Open-pollinated rootstocks of pecan (Carya illinoinensis), water hickory (Carya aquatica), and their hybrids (Carya × lecontei) were screened for nematode resistance in outdoor above-ground box-plots. Seedstocks were selected to represent the broad geographic range of species diversity. Seedlings were inoculated with eggs of Meloidogyne partityla, the primary nematode pest of Carya, and were harvested after 1 year. All seedlings, except one, manifested nematode damage at moderate to high levels. Evidence of galling was greatest in seedlings from the southern provenance (Mexico), which rated comparably with seedlings from ‘Elliott’. No sources of resistance to Meloidogyne partityla were observed. The box structure allowed harvest of complete root systems and evaluation of plant composition in greater detail than previously observed. Seedlings from the southern provenance were generally distinguishable from other provenances in timing of seasonal growth, stem diameter and seedling height, which is consistent with previous observations. Root and stem dry weights were greatest in seedlings from the southern provenance, as expected based on size measurements. Percent root water varied significantly as a function of seedstock origin, and was negatively correlated with leaf weight. Leaf weights were positively correlated with dates of growth initiation. Uninfected control plants were not observed in this screening effort, and their absence limits the interpretation of patterns. Implications of these observations, as evidence of regional adaptation, merit further exploration by research.

Nematicidal Effect of Trichoderma harzianum T22 on Meloidogyne incognita (Kofoid & White) Chitwood, Infecting Celosia argentea TLV8

Two screenhouse trials were conducted in the Faculty of Agriculture, University of Ilorin in 2010 and 2011 to investigate the effect of filtrate of Trichoderma harzianum on Meloidogyne incognita infecting Celosia argentea seedlings. The filterate reduced root galling and soil nematode population significantly; 2.78 gall index and 117.8 soil nematode population observed in nematode infected plants were significantly higher than 0.4 gall index and 15.2 soil nematode population in Trichoderma harzianum treated plants. The mean plant height and number of leaves were also significantly higher in the treated pots than in the untreated control. The results of this study suggest that the biopesticidal potential of Trichoderma harzianum could be exploited agriculturally to manage the rootknot nematode pests that limit the production of Celosia argentea. Keywords: Trichoderma harzianum, Celosia argentia, Meloidogyne incognita, Bionematicide, Filtrate