Ditylenchus Dipsaci Research Articles

Observations on predation of Rhizoglyphus robini (Acari: Acaridae) on the alfalfa stem nematode, Ditylenchus dipsaci (Nematoda)

The alfalfa stem nematode, Ditylenchus dipsaci (Kuhn) causes substantial damage to alfalfa crops in Iran every year. Rhizoglyphus robini Claparede is a polyphagous pest of bulbs, corms and tubers, but can be beneficial in some situations. This study examined the effect of R . robini as a predator of D . dipsaci in greenhouse conditions. Pot experiments showed that R . robini caused high mortality of D . dipsaci . The effect of R . robini density on mortality of D . dipsaci was mathematically modeled using the response surface methodology (RSM). These observations suggest that R . robini may contribute to regulate populations of this nematode.

A myo-inositol-1-phosphate synthase gene, IbMIPS1, enhances salt and drought tolerance and stem nematode resistance in transgenic sweet potato.

Myo-inositol-1-phosphate synthase (MIPS) is a key rate limiting enzyme in myo-inositol biosynthesis. The MIPS gene has been shown to improve tolerance to abiotic stresses in several plant species. However, its role in resistance to biotic stresses has not been reported. In this study, we found that expression of the sweet potato IbMIPS1 gene was induced by NaCl, polyethylene glycol (PEG), abscisic acid (ABA) and stem nematodes. Its overexpression significantly enhanced stem nematode resistance as well as salt and drought tolerance in transgenic sweet potato under field conditions. Transcriptome and real-time quantitative PCR analyses showed that overexpression of IbMIPS1 up-regulated the genes involved in inositol biosynthesis, phosphatidylinositol (PI) and ABA signalling pathways, stress responses, photosynthesis and ROS-scavenging system under salt, drought and stem nematode stresses. Inositol, inositol-1,4,5-trisphosphate (IP3 ), phosphatidic acid (PA), Ca(2+) , ABA, K(+) , proline and trehalose content was significantly increased, whereas malonaldehyde (MDA), Na(+) and H2 O2 content was significantly decreased in the transgenic plants under salt and drought stresses. After stem nematode infection, the significant increase of inositol, IP3 , PA, Ca(2+) , ABA, callose and lignin content and significant reduction of MDA content were found, and a rapid increase of H2 O2 levels was observed, peaked at 1 to 2days and thereafter declined in the transgenic plants. This study indicates that the IbMIPS1 gene has the potential to be used to improve the resistance to biotic and abiotic stresses in plants.

Diagnostics of stem and bulb nematodes, Ditylenchus weischeri and D. dipsaci (Nematoda: Anguinidae), using PCR with species-specific primers

The stem and bulb nematodes of the Ditylenchus dipsaci (Kühn) Filipjev species complex are obligate endoparasites of various agricultural plants, causing stunting and swelling and resulting in significant economic losses. Recently, a new closely related Ditylenchus species, D. weischeri Chizhov, Borisov and Subbotin, a parasite of the cosmopolitan herbaceous perennial weed, Cirsium arvense (L.) Scop., was described. Many countries impose quarantine restrictions for the presence of D. dipsaci in imported plant and soil materials. In the current study, we developed PCR with species-specific primers for the rapid and reliable separation of D. weischeri and D. dipsaci using gel electrophoresis and melting curve analysis. Species-specific primer sets were designed based on the nucleotide sequence of the heat shock protein (hsp90) gene for both nematode species. The PCR protocol was verified using samples of D. weischeri, D. dipsaci and the closely related species, D. gigas, which parasitizes broadbean (Vicia faba L.). The species-specific primer sets were able to detect D. weischeri and D. dipsaci from samples containing mixtures of Ditylenchus species. The PCR species-specific protocol should allow for more rapid identification of Ditylenchus species recovered from plant materials than previously possible.

A new stem nematode, Ditylenchus oncogenus n. sp. (Nematoda: Tylenchida), parasitizing sowthistle from Adriatic coast dunes in southern Italy

Morphological and molecular analyses of a stem nematode causing a severe disease on infected sowthistle (Sonchus bulbosus) plants, involving the formation of gall-like structures on infected leaves and stems, have led to the description of a new species named Ditylenchus oncogenus n. sp. Morphologically, the new species is characterized by a medium to large body size (all adults more than 1 mm in length); a delicate stylet (9.0-11.0 μm long) with minute, rounded knobs; a long post-vulval uterine sac (c. 65% of the vulva-anus distance); six incisures at the lateral fields and characteristic D. destructor-pattern of spicules (with pronounced ventral tumulus and anteriorly pointed, less sclerotized, cuticle parts present within the lamina). The results of molecular analysis of rRNA gene sequences, including the D2-D3 expansion regions of 28S rRNA, internal transcribed spacer (ITS) rRNA, partial 18S rRNA gene, the protein-coding mitochondrial gene, cytochrome oxidase c subunit I (COI), and the heat-shock protein 90 (hsp90) gene, support the new species status. The results of a host-suitability test indicated that the new species does not parasitize potato (Solanum tuberosum) tubers and broad bean (Vicia faba) seedlings. Histopathological observations on naturally infected sowthistle tissues revealed that D. oncogenus n. sp. causes floral stem neoplasia and midrib leaf gall formation on the type, and to date only known, host. The galls were characterized by extensive hyperplasia, where several necrotic cells in the neoplasic area were directly damaged by feeding of the nematode, whereas a number of adjacent cells showed typical cytological changes, such as granulated cytoplasm with hypertrophied nuclei and nucleoli.

Efficacy of Some Organic Amendments for the Control of Stem and Bulb Nematode, Ditylenchus dipsaci (Kühn) Filipjev on Garlic (Allium sativum)

A greenhouse experiment was conducted to evaluate effect of some soilamendments, i.e; fresh chopped leaves or dry leaves powder of Datura stramonium,Peganum harmala or Tagetes minuta, poultry and sheep manure in controlling thestem and bulb nematode, Ditylenchus dipsaci on garlic (Allium sativum) ascompared to the nematicide, Vydate® (Oxamyl). All applied treatments significantly(P≤ 0.05) reduced final population of D. dipsaci except in treatment of sheepmanure at lowest dosage rate, which significantly increased the population incomparison to that of the check. Efficacy of the treatments differed according to thetype of organic soil amendment, dosage rate and type of application. Dry leavespowder of Peganum harmala was the most effective in reducing nematode counts insoil and garlic bulbs at the different rates, followed by fresh chopped leaves ofDatura stramonium and T. minuta while, the lowest % reduction in such nematodeparameters was recorded in case of soil amended with sheep manure followed bydry leaves powder of Datura stramonium. As for plant growth criteria the resultsreveal that most tested materials improved plant growth criteria of shoot, root andbulb compared to the untreated controls.

First Report of Bloat Nematode (Ditylenchus dipsaci) Infecting Garlic in Ohio.

First Report of Bloat Nematode (<i>Ditylenchus dipsaci</i>) Infecting Garlic in Ohio.

Effect of Ditylenchus dipsaci Kühn, 1857 (Tylenchida: Anguinidae) on onionyield in Karaman Province, Turkey

This study was conducted to investigate the effect of the stem and bulb nematode Ditylenchus dipsaci Kühn (Tylenchida: Anguinidae) on yield parameters of some onion varieties in Karaman Province, Turkey. Experiments were established in a naturally infested onion field during two consecutive years (2012-2013). Nematode population development was followed at the beginning and end of the experiment. The reproduction rate was also calculated. Onion yield and the representative average diameter and length of the onion cultivar bulbs were determined. Yield parameters of six onion varieties were compared on nematicide-treated and untreated control plots in the experiments. Nematode populations significantly decreased in the nematicide-treated plots at the beginning of the experiment during both growing seasons. The average population density of D. dipsaci was 104 individuals/100 g dry soil in the first year and 68 individuals/100 g dry soil in the second year of the experiment. The initial and final nematode populations were significantly positively correlated with Betapanko, Pan88, and Local variety1 cultivars, whereas they were negatively correlated with the Valenciana cultivar during the first year. This suggests that Betapanko, Pan88, and Local variety1 were susceptible to D. dipsaci, whereas the Valenciana cultivar could have some resistance. The overall reproduction rate of D. dipsaci was negatively correlated with initial population density and was primarily <1, which presumably represented a downward trend in nematode reproduction due to environmental conditions at the end of the experiment in September. Betapanko and Pan88 were susceptible varieties, and stem and bulb nematode caused yield losses of up to 12.93% and 15.33%, respectively; these varieties were considered intolerant. The yield of Local variety1 was positively related with initial nematode population density and it was categorized as tolerant to D. dipsaci.

Ultrastructure of sperm development in the genus Ditylenchus (Nematoda: Anguinidae)

Spermatogenesis in Ditylenchus arachis and D. dipsaci was studied using transmission electron microscopy. Spermatogenesis includes the formation of complexes of fibrous bodies (FB) and membranous organelles (MO) in the spermatocytes, which dissociate in separated MO and FB in the spermatids. Immature spermatozoa are unpolarised cells with separate FB and MO. Mature spermatozoa are arranged in chains. Ditylenchus dipsaci is unique in having MO that have already fused with the outer membrane in immature spermatozoa and have mature spermatozoa in the male testis, proving that not only insemination plays a role in spermiogenesis. Contrary to what has been described before, spermatogenesis in Ditylenchus, and other early diverging Tylenchomorpha, follow the typical ‘rhabditid’ pattern, while the absence of MO within Tylenchomorpha appears to be an apomorphic trait for the molecular defined clade of tylenchids that exclusively parasitise higher plants. This confirms the value of traits related to spermatogenesis in nematode phylogeny.

Plant-Parasitic Nematodes Associated with Garlic in Yemen

A survey was undertaken to determine the frequency and abundance ofplant-parasitic nematodes associated with garlic (Allium sativum L.) in major garlicproduction governorates in Yemen. Twenty nematode genera were found inassociation with garlic in Sana'a, Ibb and Hadramout governorates of whichAntarctenchus, Aphelenchoides, Aphelenchus, Basiria, Boleodorus, Ditylenchus,Helicotylenchus, Heterodera, Hoplolaimus, Meloidogyne, Microposthonia,Nothanguina, Pratylenchus, Rotylenchulus, Rotylenchus, Scutellonema,Tetylenchus, Tylenchorhynchus, Tylenchus and Zygotylenchus. All nematodegenera except Aphelenchus, Helicotylenchus, Meloidogyne and Tylenchorhynchushave been reported for the first time on garlic in Yemen. The most prevalent plantnematode genera associated with garlic cultivars in all surveyed districts wereAphelenchus, Ditylenchus, Pratylenchus, Tylenchorhynchus and Tylenchus. Thelargest number of nematode genera was recorded in Sana'a governorate (19genera) compared to Ibb (14 genera) and Hadramout (12 genera). Antarctenchus,Hoplolaimus, Microposthonia, Nothanguina, Scutellonema and Zygotylenchusgenera were only found in Sana'a governorate, while Heterodera was recorded onlyin Ibb governorate. The most serious pests on garlic, stem and bulb nematode(Ditylenchus) exhibited the highest average population density of 4214nematodes/250gm soil with frequency of occurrence 49%. Therefore, effects ofnematode damage on growth, vigor and yield of garlic need further investigation.

Effect of initial population densities of Ditylenchus destructor and D. dipsaci on potato tuber damage and nematode reproduction

Glasshouse experiments were conducted to evaluate the effect of initial population densities () of Ditylenchus destructor and D. dipsaci on potato tuber damage and nematode reproduction. Ditylenchus destructor did not influence tuber numbers but influenced tuber weight at high levels. Ditylenchus dipsaci influenced tuber numbers and weights at a level of 14.29 (g growing medium)−1. Tolerance limit estimates according to the Seinhorst model were very low indicating both nematode species have a major impact on potato tuber weight. External and internal tuber rot caused by both species increased with levels. Ditylenchus destructor caused more tuber rot than D. dipsaci at all levels. Reproduction rates of D. destructor were higher at all levels studied compared to D. dipsaci. The equilibrium density of 1.3 and 0.6 for D. destructor and D. dipsaci, respectively, was observed at level of 14.29 (g growing medium)−1.

Resistance and tolerance of potato varieties to potato rot nematode (Ditylenchus destructor) and stem nematode (Ditylenchus dipsaci)

Ditylenchus destructor and Ditylenchus dipsaci are economically important plant-parasitic nematodes, affecting potato production mostly in temperate climates. Management through crop rotation is not feasible because of their wide host range. These nematodes are listed as quarantine pests in many countries. Limited information exists on the resistance and tolerance of currently cultivated potatoes to D. destructor and D. dipsaci. Two greenhouse experiments were conducted to screen 25 potato varieties for resistance to and tolerance for D. destructor and D. dipsaci infections. Reproduction factor (RF) and relative susceptibility (RS) were used to evaluate resistance, while potato tuber damage and tuber weight reduction was used to evaluate tolerance. Based on the RF, 16 varieties were evaluated as susceptible (S) while 5 varieties were evaluated as resistant (R) to D. destructor; varieties ‘Innovator’, ‘Aveka’ and ‘Spunta’ were resistant to D. dipsaci based on RF. ‘Desiree’ was observed to be highly susceptible to D. destructor and D. dipsaci in both experiments and was used as the standard susceptible control variety for the calculation of RS. A scale of 1–9 was used to classify RS of the potato varieties to D. destructor and D. dipsaci, where 9 indicated the highest level of resistance. All classes of resistance to D. destructor and D. dipsaci were observed in the potato varieties tested in the experiments. Six varieties had significantly lower RS to D. dipsaci than the standard susceptible control variety. Tolerant to highly sensitive potato varieties to both nematodes were also observed. RS and external potato tuber damage were identified as suitable methods for resistance and tolerance determination, respectively. This study provides essential information on the status of resistance and tolerance in potato varieties against D. destructor and D. dipsaci but needs to be confirmed under field conditions.

Stem nematode counteracts plant resistance of aphids in alfalfa, Medicago sativa.

Plants are exploited by a diverse community of insect herbivores and phytopathogens that interact indirectly through plant-mediated interactions. Generally, plants are thought to respond to insects and pathogens through different defensive signaling pathways. As plants are selected for resistance to one phytophagous organism type (insect vs. pathogen) in managed systems, it is not clear how this selection may affect community interactions. This study examined the effect of nematode-resistant varieties on aphid (Acyrthosiphon pisum) suppression, and then determined how infection by the stem nematode, Ditylenchus dipsaci, mediated ecological effects on aphids and on plant defense proteins. Four alfalfa (Medicago sativa) varieties were selected with resistance to nematodes only (+,−), aphids only (−,+), nematodes and aphids (+,+), and susceptibility to nematodes and aphids (−,−). Field and greenhouse experiments were conducted to isolate the effect of nematode infection and aphid abundance on each variety. We found that varieties resistant to nematode, regardless of aphid resistance, had the lowest aphid counts, suggesting possible cross-resistance. Aphid abundance, however, increased when plants were exposed to nematodes. Resistant varieties were associated with elevated saponins but these compounds were not affected by insect or pathogen feeding. Concentrations of peroxidases and trypsin inhibitors, however, were increased in nematode resistant varieties when exposed to nematodes and aphids, respectively. The patterns of plant defense were variable, and a combination of resistance traits and changes in nutrient availability may drive positive interactions between nematodes and aphids aboveground.

First Report of Bloat Nematode (Ditylenchus dipsaci) Infecting Garlic in Ohio.

Bloat nematode, Ditylenchus dipsaci (Kühn) Filipjev (also known as stem and bulb nematode), is a key pest of garlic (Allium sativum) globally (1) as heavy infestations can lead to complete crop loss. Although not a major crop in Ohio, garlic is grown in diversified vegetable production systems. In July 2013, diseased garlic bulbs were received from a grower in Lorain County, OH, from a field with wide symptom distribution. Bulbs were discolored, exhibited splitting, and had basal plate damage including reduced roots. Nematodes were extracted for examination by placing bulb slices in water. Recovered nematodes had morphological characteristics of D. dipsaci, including a short stylet with prominent knobs, a distinct median esophageal bulb, a basal bulb slightly overlapping the intestine, a conical and pointed tail, and males with distinct bursa (1). To confirm the identity of the nematode, further morphological and molecular studies were performed. Nematode images were captured on a DM IRB inverted microscope (Leica Microsystems, Wetzlar, Germany) using a Retiga 2000 camera (Q Imaging, Surrey, Canada). Images were analyzed using Image J (NIH). For females (n = 16), means and ranges were: L = 1,080.1 (972.2 to 1,229.5) μm, a = 36.6 (33.5 to 41.9), b = 6.2 (5.3 to 6.8), c = 11.1 (9.1 to 12.8), and stylet 10.1 (8.9 to 11.2) μm. For males (n = 6), L = 1,589.2 (1,494 to 1,702.7) μm, a = 43.0 (40.7 to 46.0), b = 6.9 (6.4 to 7.3), c = 11.7 (9.2 to 13), with stylet 10.8 (10 to 12.2) μm and spicules 25.2 (23.8 to 26.8) μm. The measurements were highly similar to those of D. dipsaci (1). DNA was extracted from 50 to 100 nematodes using a PowerSoil DNA Isolation Kit (Mo-Bio Laboratories, Inc., Carlsbad, CA) as well as from individual females, and partial ITS sequences were amplified using primer set TW81/AB28 (3). The partial ITS sequences shared 99 to 100% sequence identity with GenBank accessions of D. dipsaci from garlic (DQ452956, JX123258). Expansion segments D2-D3 were sequenced following amplification of DNA from individual females using primer set D2A/D3B (4) and shared 99% sequence identity with D. dipsaci from garlic (FJ707362, JX123259). In this case, the grower noted bloat nematode symptoms following the introduction of new planting material into the field. Therefore, the availability of bloat nematode-free planting material or treated bulbs (2) is essential for preventing introduction of this pathogen. Once established, management options are limited as this nematode is difficult to eliminate. With this first report of D. dipsaci on garlic in Ohio, we have identified a new pest that can greatly reduce garlic yields in this state.

Banning of methyl bromide for seed treatment: could Ditylenchus dipsaci again become a major threat to alfalfa production in Europe?

In Europe, the stem and bulb nematode Ditylenchus dipsaci has been listed as a quarantine pest by EPPO: without any control, it may cause complete failure of alfalfa crops. Movement of nematodes associated with seeds is considered to be the highest-risk pathway for the spread of this pest. Since the 2010 official withdrawal of methyl bromide in Europe, and in the absence of any alternative chemical, fumigation of contaminated seed batches is no longer possible, which makes the production of nematode-free alfalfa seeds difficult to achieve and leads to unmarketable seed batches. Thermotherapy is being considered as a realistic alternative strategy, but its efficiency still remains to be validated. The combination of the currently available methods (i.e. use of resistant cultivars, seed production according to a certification scheme, mechanical sieving, seed batch inspection) could significantly reduce the likelihood of seed contamination. However, it does not guarantee a total eradication of the nematode. Although it is already widely distributed all over Europe, reclassification of D. dipsaci as a regulated non-quarantine pest to reduce the possibility of further introductions and the rate of spread of this pest appears to be a risky strategy because of the lack of up-to-date documented data to evaluate damage thresholds and determine acceptable tolerance levels.

Exploitation of FTA Cartridges for the Sampling, Long-Term Storage, and DNA-Based Analyses of Plant-Parasitic Nematodes

The use of DNA-based analyses in molecular plant nematology research has dramatically increased over recent decades. Therefore, the development and adaptation of simple, robust, and cost-effective DNA purification procedures are required to address these contemporary challenges. The solid-phase-based approach developed by Flinders Technology Associates (FTA) has been shown to be a powerful technology for the preparation of DNA from different biological materials, including blood, saliva, plant tissues, and various human and plant microbial pathogens. In this work, we demonstrate, for the first time, that this FTA-based technology is a valuable, low-cost, and time-saving approach for the sampling, long-term archiving, and molecular analysis of plant-parasitic nematodes. Despite the complex structure and anatomical organization of the multicellular bodies of nematodes, we report the successful and reliable DNA-based analysis of nematode high-copy and low-copy genes using the FTA technology. This was achieved by applying nematodes to the FTA cards either in the form of a suspension of individuals, as intact or pestle-crushed nematodes, or by the direct mechanical printing of nematode-infested plant tissues. We further demonstrate that the FTA method is also suitable for the so-called "one-nematode-assay", in which the target DNA is typically analyzed from a single individual nematode. More surprisingly, a time-course experiment showed that nematode DNA can be detected specifically in the FTA-captured samples many years after initial sampling occurs. Collectively, our data clearly demonstrate the applicability and the robustness of this FTA-based approach for molecular research and diagnostics concerning phytonematodes; this research includes economically important species such as the stem nematode (Ditylenchus dipsaci), the sugar beet nematode (Heterodera schachtii), and the Northern root-knot nematode (Meloidogyne hapla).

Nematicidal activity of fluensulfone against some migratory nematodes under laboratory conditions

The fluoroalkenyl fluensulfone, known to have strong nematicidal activity against Meloidogyne spp. (root-knot nematodes), was evaluated in vitro and in soil against the migratory nematodes Bursaphelenchus xylophilus, Aphelenchoides besseyi, Aphelenchoides fragariae, Ditylenchus dipsaci, Pratylenchus penetrans, Pratylenchus thornei and Xiphinema index. B. xylophilus and D. dipsaci were not immobilised by 48 h in vitro exposure to up to 16 mg L(-1) of fluensulfone. A. besseyi and A. fragariae were affected by 8 mg L(-1) , the highest concentration used for these nematodes. More than 60% of P. penetrans and P. thornei were immobilised by 4 mg L(-1) of fluensulfone; however, exposure of P. penetrans to the compound prior to inoculation did not affect their root penetration ability. The immobilisation rate of X. index was increased by 48 h exposure to even 1.0 mg L(-1) of fluensulfone. Incorporation of over 2 mg L(-1) of fluensulfone into the soil reduced populations of P. penetrans and P. thornei before and after planting lettuce and chickpea respectively. The efficacy of fluensulfone against the tested nematodes was the same or higher than that of fenamiphos in most cases. A. besseyi, A. fragariae, B. xylophilus and D. dipsaci were tolerant to fluensulfone and fenamiphos. P. penetrans, P. thornei and X. index were affected by fluensulfone, but nematicidal activity was much lower than that reported for root-knot nematodes.

Identification of QTLs for Starch Content in Sweetpotato (Ipomoea batatas (L.) Lam.)

Sweetpotato (Ipomoea batatas (L.) Lam.) breeding is challenging due to its genetic complexity. In the present study, interval mapping (IM) and multiple quantitative trait locus (QTL) model (MQM) analysis were used to identify QTLs for starch content with a mapping population consisting of 202 F1 individuals of a cross between Xushu 18, a cultivar susceptible to stem nematodes, with high yield and moderate starch, and Xu 781, which is resistant to stem nematodes, has low yield and high starch content. Six QTLs for starch content were mapped on six linkage groups of the Xu 781 map, explaining 9.1–38.8% of the variation. Especially, one of them, DMFN_4, accounted for 38.8% of starch content variation, which is the QTL that explains the highest phenotypic variation detected to date in sweetpotato. All of the six QTLs had a positive effect on the variation of the starch content, which indicated the inheritance derived from the parent Xu 781. Two QTLs for starch content were detected on two linkage groups of the Xushu 18 map, explaining 14.3 and 16.1% of the variation, respectively. They had a negative effect on the variation, indicating the inheritance derived from Xu 781. Seven of eight QTLs were co-localized with a single marker. This is the first report on the development of QTLs co-localized with a single marker in sweetpotato. These QTLs and their co-localized markers may be used in marker-assisted breeding for the starch content of sweetpotato.

A new stem nematode associated with peanut pod rot in China: morphological and molecular characterization of Ditylenchus arachis n. sp. (Nematoda: Anguinidae)

Surveys conducted in peanut production areas of China revealed peanut pod rot in several fields in Shandong and Hebei Provinces, China. A large quantity of an unknown stem nematode was isolated from the hulls and seeds of peanuts, herein described as Ditylenchus arachis n. sp. The new species is characterized by a combination of the following features: lateral lip sectors distinctly projected, stylet delicate, 8·4–10 μm in length, six lines in the lateral field, tail elongate–conoid, bursa covering about 68–86% of tail length. Pathogenicity tests showed that D. arachis n. sp. could infect peanut (Arachis hypogaea), but not sweet potato (Ipomoea batatas) or potato (Solanum tuberosum). Morphologically, D. arachis n. sp. appears closest to D. africanus, D. myceliophagus and D. destructor, but can be differentiated based upon a combination of morphological characteristics, host preference and molecular sequence data. The results of the phylogenetic analysis, based on 18S rDNA, the D2–D3 expansion region of 28S rDNA, and the ITS1–5·8S–ITS2 region, confirmed its status as a new species. A sister relationship with D. destructor was appointed, rather than with its ecologically very similar congener D. africanus.

Impact of New Natural Biostimulants on Increasing Synthesis in Plant Cells of Small Regulatory si/miRNA With High Anti-Nematodic Activity

Plant endoparasitic cyst nematode Heterodera schachtii Schmidt, gallic nematode Meloidogyne incognita and stem nematode Ditylenchus destructor damage various agricultural crops. The application of ecologically safe natural biostimulants with bioprotective properties is a newer approach for increasing plant resistance to parasitic nematodes. The molecular-genetic analysis of biostimulants action on plant genome is necessary for creation of new effective bioregulators for plant protection against phytopathogenic organisms. In our field and greenhouse experiments, we investigated the influence of new natural biostimulants Avercom and its derivatives on plant protection against nematodes Meloidogyne incognita and Ditylenchus destructor. Considerable increase of resistance to nematodes and productivity of cucumber and potato were observed for plants treated by biostimulant Avercom and its derivatives. Impact of biostimulants Radostim-super and Avercom on increase of resistance of sugar beet and cucumber sprouts to nematodes Heterodera schachtii and Meloidogyne incognita was studied in the laboratory conditions. Comparative analysis of morpho-physiological signs of control and experimental plants showed that plants treated by Radostim-super and Avercom were more viable and resistant to these nematodes as compared to control sprouts. In the molecular-genetic experiments, we studied the impact of these biostimulants on inducing synthesis of small regulatory si/miRNA, which plays key role in plant immune protection. Using method Dot-blot hybridization we studied degree of homology between si/miRNA with mRNA populations, isolated from plants untreated and treated with new natural biostimulants. We found considerable difference in the degree of homology (6-28%) between populations of mRNA and si/miRNA from nematode-infected plants that were either untreated or treated with biostimulants. We have also investigated silencing of translation of mRNA activity of si/miRNA in the wheat embryo cell-free system of protein synthesis. In these experiments, we found high inhibitory activity (38-65%) of si/miRNA from plants treated by biostimulants as compared to low inhibitory activity (15-20%) of si/miRNA from untreated plants. Obtained differences in the degree of homology between populations of mRNA and si/miRNA from untreated and treated with biostimulants plants, which were infected by nematode, and also the high inhibitory activity of si/miRNA from plants treated by biostimulants confirm that these biostimulants induce synthesis of anti-nematodic si/miRNA in plants, resulting in considerable increase of their resistance to these phytopathogens.

A Comparative and Phylogenetic Study of the Ditylenchus dipsaci, Ditylenchus destructor and Ditylenchus gigas Populations Occurring in Poland

AbstractThe genus Ditylenchus contains more than 80 recognized nematode species with a very wide host range. The most serious species are Ditylenchus dipsaci and Ditylenchus destructor. Populations of D. dipsaci species complex were collected from Allium cepa, Cichorium endivia and Phlox paniculata in Poland. The Ditylenchus gigas population was collected from Vicia faba minor, and populations of D. destructor, from Solanum tuberosum spp. tuberosum. Analyses of the rDNA sequences spanning both ITS1 and ITS2 fragment regions were carried out on the collected populations. The obtained DNA sequences were compared with those DNA sequences deposited in GenBank of populations isolated in other countries. Phylogenetic analysis was performed using the data obtained from the DNA sequence comparisons. The results indicated that there is no clear distinction between European and non‐European populations within D. dipsaci. The results also showed no clear distinction between populations isolated from different host plant species, including populations found in Poland. The populations of D. destructor described here constitute a common group together with American and Chinese populations belonging to the haplotype C of the D. destructor species. On the other hand, the D. gigas population was localized separately from those populations that have been described up until now, from Europe and Africa. This is also the first report on the occurrence of D. gigas in Poland.