Cereal Cyst Nematode Heterodera Research Articles

Morphological and Biochemical Changes in the Mediterranean Cereal Cyst Nematode (Heterodera latipons) during Diapause.

The cereal cyst nematode (Heterodera latipons) is becoming an economically important species in global cereal production as it is being identified in many new cereal cultivated areas and causes significant losses. Consequently, understanding its biology becomes crucial for researchers in identifying its vulnerabilities and implementing effective control measures. In the current study, different morphological and biochemical changes of H. latipons cysts containing eggs with infective juveniles from a barley field in Jordan were studied during the summer of 2021, at two sample dates. The first, at the harvest of the cereal crop (June 2021), when the infective second-stage juveniles (J2s) were initiating diapause, and the second, before planting the sequent cereal crop (late October 2021), when the J2s were ending diapause. The studied population was characterized morphologically and molecularly, showing 98.4% molecular similarity to both JOD from Jordan and Syrian "300" isolates of H. latipons. The obtained results and observations revealed that there were dramatic changes in all the investigated features of the cysts and eggs they contained. Morphological changes such as cyst color, sub-crystalline layer, and thickness of the rigid eggshell wall were observed. A slight change in the emergence time of J2s from cysts was observed without any difference in the number of emerged J2s. The results of biochemical changes showed that the total contents of carbohydrates, glycogen, trehalose, glycerol, and protein were higher in cysts collected in October when compared to those cysts collected in June. The SDS-PAGE pattern indicated the presence of a protein with the size of ca. 100 kDa in both sampling dates, whereas another protein (ca. 20 kDa) was present only in the cysts of October. Furthermore, the expression of trehalase (tre) gene was detected only in H. latipons collected in October. The outcomes of this study provide new helpful information that elucidates diapause in H. latipons and may be used for the implementation of new management strategies of cyst nematodes.

Review of Integrated Management of Cereal Cyst Nematode Heterodera avenae on Wheat Crop under Centre Pivot Irrigation System

Review of Integrated Management of Cereal Cyst Nematode Heterodera avenae on Wheat Crop under Centre Pivot Irrigation System

Laburnicotides A-F: Acyclic N-Acetyl Oligopeptides from the Nematode-Cyst-Associated Fungus Laburnicola nematophila.

Nematode-associated fungi revealed the potential to produce a broad spectrum of chemical scaffolds. In this study, a mycelial extract of Laburnicola nematophila, a fungal strain derived from the cereal cyst nematode Heterodera filipjevi, was chemically explored and afforded six unprecedentedly reported acylic N-acetyl oligopeptides, laburnicotides A-F (1-6). Structure elucidation of the isolated compounds was established based on comprehensive 1D and 2D NMR spectroscopic analyses together with the acquired HR-ESI-MS spectrometric data. The absolute configuration of amino acid residues in 1-6 was established by performing advanced Marfey's derivatization method. All isolated compounds were assessed for their cytotoxic, antimicrobial, antiviral, and nematicidal activities with no potential activity observed.

Morphological and molecular identification of cyst nematode species (Heterodera spp.) in Algerian cereal fields

Cereal cyst nematodes (Heterodera spp.) are distributed globally and cause severe production losses of small grain cereals. To investigate the occurrence of cereal cyst nematodes in wheat-growing areas of Algeria, a survey was conducted and 27 cereal cyst nematode populations were collected. The populations were initially identified based on their morphological and morphometric characters, followed by molecular methods using speciesspecific primers, complemented by ITS-rDNA sequences. The morphological and morphometric features of second-stage juveniles (J2s) and cysts supported the presence of three Heterodera species: H. avenae, H. filipjevi and H. hordecalis. All morphological values of these distinct populations were very similar to those previously described for these species. Using species-specific primers for H. avenae and H. filipjevi, the specific bands of 109 bp and 646 bp confirmed the morphological identification of both species, respectively. In addition, the internal transcribed spacer (ITS) regions were sequenced to study the diversity of the 27 populations. These sequences were compared with those of Heterodera species available in the GenBank database (www.ncbi.nlm.nih.gov) and re-confirmed the identity of the species. Nineteen sequences of ITS-rDNA were similar (99–100%) to the sequences of H. avenae published in the GenBank, six sequences were similar (99–100%) to H. hordecalis, and two were similar (98–99%) to H. filipjevi. The results of this study are of great value to breeding programs and extension services, where they will contribute to the design of control measures to keep damaging nematodes in check.

Population genetics of the cereal cyst nematode Heterodera avenae reveal geographical segregation and host adaptation

Cereal cyst nematodes (CCNs) lead to major losses in the cereal crop industry worldwide and have been reported in many provinces of China. However, this plant nematode’s distribution and genetic differences are not fully understood. In the present study, 821 soil and host root samples were collected from 16 provinces in 2019–2022 to investigate the distribution of the CCNs. Heterodera avenae was detected in 56.39% of the total samples, primarily in Hubei, Henan, Hebei, Shandong, Shanxi, Gansu, Beijing, Tianjin, Inner Mongolia, Ningxia, Xinjiang, Qinghai, Anhui, Shaanxi, and Jiangsu. H. filipjevi was present in 21 samples, with a detection rate of 2.60%, and it was found mainly in Henan, Anhui, Jiangsu, Shandong, Shanxi, and Qinghai. A phylogenetic analysis of the internal transcribed spacer (ITS) region of the rRNA gene indicated that significant evolutionary and genetic differences existed between the Chinese populations and populations from other countries. Our results indicate that ITS1 can be used as a phylogenetic analysis and genetic target for H. avenae populations. The haplotypes of the ITS1 sequences of H. avenae populations from 14 countries were analyzed, and we speculate that H. avenae originated in a Middle East hotspot, then spread westwards to Europe and the United States and eastwards to China and Australia. Genetic differences between Asian and European populations suggest that the Himalayas and Kunlun Mountains formed a barrier that resulted in the formation of a separate evolutionary group in China. The phylogenetic and haplotype analysis results from different hosts showed significant differences among populations isolated from different hosts, and those isolated from weeds were distinct from those from other hosts, indicating that the rich genetic diversity of H. avenae populations is related to the large number of available hosts. Above all, geographic barriers, time of origin, and host adaptation might explain the current known distribution patterns of Chinese H. avenae populations.

Recombinase Polymerase Amplification Coupled with CRISPR-Cas12a Technology for Rapid and Highly Sensitive Detection of Heterodera avenae and Heterodera filipjevi.

The cereal cyst nematodes Heterodera avenae and Heterodera filipjevi are recognized as cyst nematodes that infect cereal crops and cause severe economic losses worldwide. Rapid, visual detection of cyst nematodes is essential for more effective control of this pest. In this study, recombinase polymerase amplification (RPA) combined with clustered regularly interspaced short palindromic repeats (CRISPR)/Cas12a (formerly known as cpf1) was developed for the rapid detection of H. avenae and H. filipjevi from infested field samples. The RPA reaction was performed at a wide range of temperatures from 35 to 42°C within 15 min. There was no cross-reactivity between H. avenae, H. filipjevi, and the common closely related plant-parasitic nematodes, indicating the high specificity of this assay. The detection limit of RPA-Cas12a was as low as 10-4 single second-stage juvenile (J2), 10-5 single cyst, and 0.001 ng of genomic DNA, which is 10 times greater than that of RPA-lateral flow dipstick (LFD) detection. The RPA-Cas12a assay was able to detect 10-1 single J2 of H. avenae and H. filipjevi in 10 g of soil. In addition, the RPA-LFD assay and RPA-Cas12a assays could both quickly detect H. avenae and H. filipjevi from naturally infested soil, and the entire detection process could be completed within 1 h. These results indicated that the RPA-Cas12a assay developed herein is a simple, rapid, specific, sensitive, and visual method that can be easily adapted for the quick detection of H. avenae and H. filipjevi in infested fields.

Polydomus karssenii gen. nov. sp. nov. is a dark septate endophyte with a bifunctional lifestyle parasitising eggs of plant parasitic cyst nematodes (Heterodera spp.)

In this study fungal strains were investigated, which had been isolated from eggs of the cereal cyst nematode Heterodera filipjevi, and roots of Microthlaspi perfoliatum (Brassicaceae). The morphology, the interaction with nematodes and plants and the phylogenetic relationships of these strains originating from a broad geographic range covering Western Europe to Asia Minor were studied. Phylogenetic analyses using five genomic loci including ITSrDNA, LSUrDNA, SSUrDNA, rpb2 and tef1-α were carried out. The strains were found to represent a distinct phylogenetic lineage most closely related to Equiseticola and Ophiosphaerella, and Polydomus karssenii (Phaeosphaeriaceae, Pleosporales) is introduced here as a new species representing a monotypic genus. The pathogenicity tests against nematode eggs fulfilled Koch’s postulates using in vitro nematode bioassays and showed that the fungus could parasitise its original nematode host H. filipjevi as well as the sugar beet cyst nematode H. schachtii, and colonise cysts and eggs of its hosts by forming highly melanised moniliform hyphae. Light microscopic observations on fungus-root interactions in an axenic system revealed the capacity of the same fungal strain to colonise the roots of wheat and produce melanised hyphae and microsclerotia-like structure typical for dark septate endophytes. Confocal laser scanning microscopy further demonstrated that the fungus colonised the root cells by predominant intercellular growth of hyphae, and frequent formation of appressorium-like as well as penetration peg-like structures through internal cell walls surrounded by callosic papilla-like structures. Different strains of the new fungus produced a nearly identical set of secondary metabolites with various biological activities including nematicidal effects irrespective of their origin from plants or nematodes.

Identification of Genetic Resistance to the Crown and Root Rot Caused by Fusarium culmorum and Cereal Cyst Nematode (Heterodera filipjevi) in the Turkish Cereal Varieties

Soilborne pathogens associated with cereals cause significant yield losses throughout the world. Among soilborne pathogens Heterodera filipjevi and Fusarium culmorum are two main destructive causal agents that attack the roots and crowns of cereals and have been reported as the most prevalent species in Türkiye. A total of 245 Turkish cereal varieties consisting of wheat, oat, triticale and rye which were registered between 1931 to 2013; were tested for their resistance to Fusarium culmorum and Heterodera filipjevi. The varieties were screened under controlled and/or field conditions for two successive growing seasons. The bread wheat ‘Murat-1’ was the most resistant variety for both pathogens. The durum wheats ‘Yelken 2000’ and ‘Yılmaz 98’ were found the most promising varieties for resistance to F. culmorum and H. filipjevi, respectively. The triticale ‘Umranhanim’ ranked moderately resistant at adult plant stage while ‘Presto’ and ‘Melez 2001’ were ranked moderately resistant at seedling stage for Fusarium culmorum. The findings of this study are important for the global wheat breeding programs as those genotypes are still being used in crosses for new genotype development.

Two new root endophyte and nematode cyst parasite species of the widely distributed genus Laburnicola

Fungal root endophytes, including the common form group of dark septate endophytes (DSEs), represent different taxonomic groups with potentially diverse life strategies. During surveys of DSE communities and of nematode cysts colonizing fungi, isolates representing Laburnicola (Didymosphaeriaceae, Pleosporales) lineages were discovered. Here we carried out a comprehensive study of the phylogenetic relationships and taxonomy of fungi collected from plant roots in Hungary, Mongolia, and Kazakhstan and from eggs of the cereal cyst nematode Heterodera filipjevi in Turkey. In addition to the study of the morphology and culture characteristics of the strains, four loci (internal transcribed spacer, partial large and small subunit regions of nuclear ribosomal DNA and partial translation elongation factor 1-alpha) were used to infer the molecular phylogenetic relationships of the strains within Laburnicola. The isolates were found to represent two distinct lineages, which are described here as novel species, Laburnicola nematophila and L. radiciphila. The interaction of the strains with plants and nematodes was examined using in vitro bioassays, which revealed endophytic interactions with the plant roots and parasitic interactions with the nematode eggs. Analyses of similar ITS sequences found in public databases revealed that members of the genus Laburnicola are widely distributed characteristic members of the plant microbiome, and they are reported as parasites of plant parasitic cyst nematodes here for the first time.

Transcriptome-based analysis of resistance mechanisms to Bipolaris sorokiniana, a common wheat root-rot disease.

In common root and crown rot (CRR), Bipolaris sorokiniana (Sace.) is one of the important in wheat, causing considerable yield losses globally. Sources of resistance can provide a feasible and effective method of control for plant disease management. However, knowledge on mechanisms of resistance is scarce. We screened 33 wheat genotypes against B. sorokiniana under greenhouse and field conditions. In addition, real-time quantitative PCR (qPCR) analysis using ten novel candidate gene markers, Cre3, EDS1, LTP5, PGIP, PR-1, PIEP1, TLP, UGT, Stb6 and PFT, was conducted on leaves and roots, along with changes in activity of antioxidant enzymes, peroxidase, catalase, β-1,3-glucanase, and phenolic content for their involvement in disease impact mechanisms. Lowest disease severity was in 'Alvand', followed by 'Baharan' and 'Bam' as resistant genotypes. Quantitative gene expression showed that, although the candidate defence genes were upregulated 1.24- to 3.5-fold in wheat roots and leaves inoculated with B. sorokiniana, they were highly regulated in resistant varieties 'Alvand', 'Mehregan' and 'Bam'. Cre3, a resistance gene to cereal cyst nematode Heterodera filipjevi, was regulated in cultivars resistant to B. sorokiniana. Similar results were obtained for Stb6, a gene resistant to Septoria tritici blotch, EDS1 resistant to powdery mildew, Blumeria graminis, and the genes PR-1 and UGT resistant to leaf rust, Puccinia triticina. Antioxidant enzyme activity also showed the highest increases in resistant genotypes. In conclusion, the T. aestivum-B. sorokiniana interaction in resistant wheat cultivars uses defence-related genes and enzymes that protect wheat towards sustainable development. Further such studies will shed light on simultaneous resistance to other diseases in wheat cultivars.

Molecular diagnosis and direct quantification of cereal cyst nematode (Heterodera filipjevi) from field soil using TaqMan real-time PCR

Heterodera filipjevi continues to be a major threat to wheat production worldwide. Rapid detection and quantification of cyst nematodes are essential for more effective control against this nematode disease. In the present study, a TaqMan-minor groove binder (TaqMan-MGB) probe-based fluorescence quantitative real-time PCR (qPCR) was successfully developed and used for quantifying H. filipjevi from DNA extracts of soil. The primers and probe designed from the obtained RAPD-SCAR marker fragments of H. filipjevi showed high specificity to H. filipjevi using DNA from isolates-confirmed species of 23 Heterodera spp., 1 Globodera spp. and 3 Pratylenchus spp. The qPCR assay is highly sensitive and provides improved H. filipjevi detection sensitivity of as low as 4–3 single second-stage juvenile (J2) DNAs, 10–3 female DNAs, and 0.01 μg μL–1 genomic DNAs. A standard curve relating to the threshold cycle and log values of nematode numbers was generated and validated from artificially infested soils and was used to quantify H. filipjevi in naturally infested field soils. There was a high correlation between the H. filipjevi numbers estimated from 32 naturally infested field soils by both conventional methods and the numbers quantified using the qPCR assay. qPCR potentially provides a useful platform for the efficient detection and quantification of H. filipjevi directly from field soils and to quantify this species directly from DNA extracts of field soils.

Origin and Phylogeography of Chinese Cereal Cyst Nematode Heterodera avenae Revealed by Mitochondrial COI Sequences.

Heterodera avenae, a globally distributed plant-parasitic nematode, is one of the most significant pests on cereal crops. In China, it is widely distributed in cereal-growing areas of 16 provinces and causes serious yield losses. In the present study, a total of 98 populations of H. avenae were collected from major wheat-growing regions in China and six other countries. The mitochondrial COI genes were amplified and analyzed. Forty-one mitochondrial COI haplotypes were identified, suggesting a high genetic diversity and endemism level of H. avenae in China. Phylogenetic analysis showed that H. avenae populations in China were divided into four clades. Significant evolutionary and genetic differences were found between Chinese (except Hubei) and foreign populations. Hap1, the most widely distributed haplotype, was considered to be a separate evolutionary origin in China. The gene flow of H. avenae from the northwestern region to the north China region and Huang-Huai-Hai region was significant, so as the direction between north China and Huang-Huai-Hai region. We speculate that water flowing from the Yellow River and mechanical harvesters promoted gene exchange among these groups. A distance-based redundancy analysis showed that genetic distances observed among H. avenae populations were explained foremost not only by geographic distance but also by temperature and precipitation. This study provides theoretical support for the origin and spread of H. avenae populations in China and elsewhere in the world.

Phylogeography of Chinese cereal cyst nematodes sheds lights on their origin and dispersal.

Reconstructing the dispersal routes of pathogens can help identify the key drivers of their evolution and provides a basis for disease control. The cereal cyst nematode Heterodera avenae is one of the major nematode pests on cereals that can cause 10%–90% crop yield losses worldwide. Through extensive sampling on wheat and grasses, the Chinese population of H. avenae is widely identified in virtually all wheat growing regions in China, with H1 being the predominant haplotype. The monoculture of wheat in north China might have been the key driver for the prevalence of H1 population, which should date no earlier than the Han Dynasty (202 BCE–220 CE). Molecular phylogenetic and biogeographic analyses of Chinese H. avenae suggest a Pleistocene northwest China origin and an ancestral host of grasses. We assume that the prosperity of Heterodera in this region is a result of their preference for cooler climate and various grass hosts, which only appeared after the uplift of Qinghai‐Tibetan Plateau and aridification of Inner Asia. Nematode samples from the current and historical floodplains show a significant role of the Yellow River in the distribution of Chinese H. avenae. Whereas mechanical harvesters that operate on an inter‐provincial basis suggest the importance in the transmission of this species in eastern China in recent times. This study highlights the role of environmental change, river dynamics, and anthropogenic factors in the origin and long‐distance dissemination of pathogens.

Interactions among cereal cyst nematode Heterodera filipjevi, dryland crown rot Fusarium culmorum, and drought on grain yield components and disease severity in bread wheat

The cereal cyst nematode (CCN) Heterodera and crown rot caused by Fusarium species limit cereal production and yield potential. Losses increase when CCN and crown rot occur together, especially under water stress conditions. The objective of this study was to investigate the interactions among Heterodera filipjevi, Fusarium culmorum, and drought on a set of wheat germplasm with differing levels of resistance/tolerance to CCN, crown rot and drought. Plant emergence was significantly reduced (56% seedling death) when seeds were planted in a water stress environment where F. culmorum and H. filipjevi were present. Crown rot was more severe under water stress compared with Fusarium inoculation alone. The number of cysts fell significantly when H. filipjevi was co-inoculated with F. culmorum, revealing an antagonistic interaction between the nematode and fungus. The highest number of cysts was found on the susceptible accession ‘Seri’ under water stress conditions. Water stress caused a significant reduction in plant height, while F. culmorum inoculation did not, unless combined with water stress. Yield components were significantly reduced by each of the single stresses and losses were greater when plants were exposed to double or triple stresses. Water stress and F. culmorum inoculation caused a significant reduction in spike weight and seeds per spike. The chlorophyll content of wheat leaves was negatively affected by water stress and inoculation by both nematode and fungus. In conclusion, water stress exacerbates the damage caused by CCN and crown rot, and planting drought-resistant varieties would be an ideal solution to reduce losses.

The hatching of cereal cyst nematode (Heterodera avenae) in response to different inorganic ions

Cereal cyst nematode is a major pest of small grain cereals, which causes huge yield losses to crops in China and other parts of the world. In this study, the effects of five inorganic ion concentrations on egg hatching of Heterodera avenae were studied. Results revealed that ZnCl2 and FeCl3 promoted hatching of induced and natural diapausing eggs. The cumulative hatching rates of eggs were 49 % and 13 % at 30 mM ZnCl2 and 10 mM FeCl3, respectively, which were higher than those of other treatments. The hatching ability promoted by ZnCl2 is greater than by FeCl3. Diapause induced eggs in ZnCl2 continued to hatch after 10 days; however, those in FeCl3 mainly hatched in the first two weeks. ZnCl2 had obvious stimulating effects on the hatching of natural diapause and non–diapause free eggs at 15 and 30 mM concentrations. FeCl3 promoted the hatching of natural diapause eggs; howevr, it inhibited hatching of non–diapause free eggs. Conversely, different concentrations of inorganic ions did not have any stimulatory effect on white female eggs. In the nematode life cycle, hatching is the critical stage because juveniles may be infected. The results of this study provide useful information the use of new fertilizers (including promoted hatching inorganic ions) applied before planting for controlling nematode diseases caused by H. avenae.

Wheat Root Protection From Cereal Cyst Nematode (Heterodera avenae) by Fluopyram Seed Treatment.

Cereal cyst nematode (Heterodera avenae), an important plant-parasitic nematode causing yield losses of wheat, has been found in many provinces in China. It is urgent to develop an effective method of protecting wheat from H. avenae damage. Because of its novel mode of action, fluopyram has been registered for controlling root-knot nematodes on cucumber and tomato in China. However, the bioactivity of fluopyram against H. avenae and whether this seed treatment can effectively control H. avenae on wheat remains unknown. In this study, a bioactivity assay revealed that fluopyram increased the mortality of H. avenae second-stage juveniles (J2), with lethal concentrations (LC) required to kill 50% (LC50) and 90% (LC90) of 0.92 mg⋅liter-1 and 2.92 mg⋅liter-1, respectively. Hatching tests showed that the H. avenae egg hatching percent was reduced by 35.2 to 69.2% with fluopyram at rates of 1.6 to 6.4 mg⋅liter-1, and that the egg hatching period was delayed by 3 to 9 days compared with the control. During pot and field trials, fluopyram seed treatment significantly reduced the H. avenae population density and increased wheat yield by 3.0 to 13.7%. Therefore, fluopyram seed treatment is an effective approach for the management of H. avenae on wheat in China.

Resistance Response of Drought and Heat Tolerant Spring Wheat Lines against the Cereal Cyst Nematode Heterodera filipjevi

Wheat (Triticum aestivum L.) is extremely affected by several abiotic and biotic stresses. Drought and/or heat alongside the parasitism of cereal cyst nematodes of the Heterodera genera can have a combined destructive impact on wheat. Solely, the cereal cyst nematode species Heterodera filipjevi can cause wheat yield losses of up to 50%. Several control measures have been implemented, yet, the most economical and convenient control strategy is the use of resistant hosts. Therefore, the main aim of this study was to evaluate the resistant response of 257 spring wheat lines obtained from CIMMYT to Heterodera filipjevi that might contain novel sources of resistance and be added as genetic resources for future breeding programs. Also, provide a base for future research to understand the relationship between nematode resistances and drought and heat tolerance. The results indicated that 11 lines (4%) and 36 lines (14%) were resistant and moderately resistant, respectively. High frequency of susceptible and highly susceptible lines and low frequency of resistant lines within this set were also recorded. The linear regression analysis between the number of cysts formed and the resistance response grouping showed a strong, positive, linear correlation. Log-linear regression analysis showed that there is a weak positive correlation between the yield of heat tolerant wheat lines and their resistance to the cyst nematodes as these lines showed tolerance, while there was a weak negative correlation of formed cyst nematodes on the yield of drought tolerant lines. This study was able to add new genetic sources of resistance to Heterodera filipjevi for upcoming breeding programs.

Diversity of Mycobiota Associated with the Cereal Cyst Nematode Heterodera filipjevi Originating from Some Localities of the Pannonian Plain in Serbia.

Simple SummaryHeterodera filipjevi, the cereal cyst nematode, is one of the most globally recognized and economically important nematodes on wheat. As some other cyst nematodes that are plant root parasites, the cysts of H. filipjevi survive in soil for years and shelter a large number of microbes. The aims of this study were to investigate the diversity of mycobiota associated with the cereal cyst nematode H. filipjevi, to infer phylogenetic relationships of the found mycobiota, and to explore the ecological connection between fungi and the field history, including the potential of fungi in bioremediation and the production of novel bioactive compounds. The study showed that the fungal species associated with the H. filipjevi cysts belong to diverse phyla, including Ascomycota, Basidiomycota, and Mucoromycota. The members of Ascomycota (Fusarium avenaceum, Sarocladium kiliense, Setophoma terrestris) are plant parasites, indicating that crops were host plants for fungal infection of recent origin. The members of Basidiomycota (Bjerkandera adusta, Cerrena unicolor, Trametes hirsuta, etc.) are wood-decay fungi, the presence of which in agricultural soil indicates that forests were the preceding plants.Cereals, particularly wheat, are staple food of the people from the Balkans, dating back to the Neolithic age. In Serbia, cereals are predominantly grown in its northern part between 44° and 45.5° N of the Pannonian Plain. One of the most economically important nematodes on wheat is the cereal cyst nematode, Heterodera filipjevi. Cysts of H. filipjevi survive in soil for years and shelter a large number of microorganisms. The aims of this study were to investigate the diversity of mycobiota associated with the cereal cyst nematode H. filipjevi, to infer phylogenetic relationships of the found mycobiota, and to explore the ecological connection between fungi and the field history, including the potential of fungi in bioremediation and the production of novel bioactive compounds. Cysts were isolated from soil samples with a Spears apparatus and collected on a 150-µm sieve. The cysts were placed on potato dextrose agar, and maintained for two weeks at 27°C. Following fungal isolation and colony growing, the fungal DNA was extracted, the ITS region was amplified, and PCR products were sequenced. The study showed that the isolated fungal species belong to diverse phyla, including Ascomycota, Basidiomycota, and Mucoromycota. Ascomycota is represented by the families Clavicipitaceae, Sarocladiaceae, Nectriaceae, and Phaeosphaeriaceae. Basidiomycota is represented by the families Cerrenaceae, Polyporaceae, Phanerochaetaceae, and Meruliaceae, and the order Cantharellales. The family Mortierellaceae represents Mucoromycota. The members of Ascomycota and Basidiomycota both depict the field history. Ascomycota indicate the fungal infection is of recent origin, while Basidiomycota point toward the preceding host plants, enabling the plant field colonization history to be traced chronologically.

Effects of temperature and duration of storage on the hatching behaviour ofHeteroderalatipons (Nematoda: Heteroderidae)

Mediterranean cereal cyst nematode (CCN) Heterodera latipons is considered as one of the main CCN that causes significant economic losses in the production of intolerant cereal crops in Turkey. Accordingly, this study aimed at evaluating the effect of different storing temperatures and durations on the emergence of second-stage juveniles (J2s) of the nematode populations obtained from the eastern Mediterranean (Adana and Hatay) and south-eastern (Gaziantep and Kilis) regions of Turkey. The obtained results revealed a variation in the J2s hatching profiles of the regional nematode populations. The eastern-Mediterranean and the south-eastern populations hatched at between 5 and 20 °C; however, considerable divergences in the J2 hatching were noticed. The highest emergence of J2s for the populations occurred at 10 °C, whereas the lowest level was observed at 5 °C. To simulate the preplanting soil temperatures in Turkey, the cysts were stored at 5 °C and 20 °C, before incubation at 10 and 15 °C, to stimulate hatching of the J2s. The highest cumulative hatching was obtained at a constant temperature of 10 °C, while the lowest cumulative hatching occurred at 5 °C. Moreover, storing cysts at 5 °C, before incubation at 10 and 15 °C, significantly stimulated hatching of the populations of H. latipons when compared to the control. However, storing the cysts at 20 °C, before incubation at 10 °C, substantially stimulated the emergence of J2s relative to the control. The obtained results about the hatching behaviour of H. latipons may help in the development of effective control strategies for this nematode in Turkey.

Three-dimensional imaging reveals that positions of cyst nematode feeding sites relative to xylem vessels differ between susceptible and resistant wheat.

Resistance conferred by the Cre8 locus of wheat prevents cereal cyst nematode feeding sites from reaching and invading root metaxylem vessels. Cyst nematodes develop syncytial feeding sites within plant roots. The success of these sites is affected by host plant resistance. In wheat (Triticum aestivumL.), 'Cre' loci affect resistance against the cereal cyst nematode (CCN)Heterodera avenae. To investigate how one of these loci (Cre8, on chromosome 6B) confers resistance, CCN-infected root tissue from susceptible (-Cre8) and resistant (+Cre8) wheat plants was examined using confocal microscopy and laser ablation tomography. Confocal analysis of transverse sections showed that feeding sites in the roots of -Cre8 plants were always adjacent to metaxylem vessels, contained many intricate 'web-like' cell walls, and sometimes 'invaded' metaxylem vessels. In contrast, feeding sites in the roots of +Cre8plants were usually not directly adjacent to metaxylem vessels, had few inner cell walls and did not 'invade' metaxylem vessels. Models based on data from laser ablation tomography confirmed these observations. Confocal analysis of longitudinal sections revealed that CCN-induced xylem modification that had previously been reported for susceptible (-Cre8) wheat plants is less extreme in resistant (+Cre8) plants. Application of a lignin-specific stain revealed that secondary thickening around xylem vessels in CCN-infected roots was greater in +Cre8plants than in -Cre8plants. Collectively, these results indicate thatCre8resistance in wheat acts by preventing cyst nematode feeding sites from reaching and invading root metaxylem vessels.