Cereal Cyst Nematode Heterodera Avenae Research Articles

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.

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.

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.

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.

Optimization of the Fermentation Media and Parameters for the Bio-control Potential of Trichoderma longibrachiatum T6 Against Nematodes.

The cereal cyst nematode Heterodera avenae is one of the important soil-borne pathogens of cereal crops and causes high yield losses worldwide. Trichoderma spp. formulations are applied as commercial bio-control agents against soil-borne plant pathogens such as H. avenae. However, the relationship between Trichoderma longibrachiatum fermentation parameters and its bio-control potential against H. avenae has not been exclusively established. In the present study, the effect of 10 different fermentation media and conditions on the nematicidal activity of T. longibrachiatum T6 (T6) was evaluated with a single-factor method and a Plackett–Burman design, and the interaction between different fermentation parameters was investigated by a Box–Behnken design. The variables for enhancing the nematicidal activity of T6 culture filtrates were explored and optimized using response surface methodology (RSM). The Minor Medium (MM) plus wheat bran-2 medium was found to be the most effective fermentation medium for T6 culture filtrates against the second stage juveniles (J2s) of H. avenae. The maximum mortality of the J2s was obtained using the T6 culture filtrates under the following fermentation conditions: initial pH 6, 28°C culture temperature, 180 rpm rotating speed, 60 ml of fermentation media, 7 days of incubation time, and 1 ml of inoculation volumes. Among these parameters, the initial pH, inoculation volume, and incubation day were identified as the most significant parameters and critical independent variables for enhancing the nematicidal activity of the T6 culture filtrates. After further optimizations based on statistical predictions, the highest nematicidal activity (92.42%) was obtained with the T6 culture filtrates fermented under an initial pH of 6.06, an inoculation volume of 1.62 ml, and an incubation time of 7.15 days. The nematicidal activity was increased approximately by as high as 1.07% compared with that before optimization. Bio-control efficacy of T6 culture filtrates was 83.88% at the 70th day after wheat seeds sowing in greenhouse experiments. The results from the validation experiments agreed with the model predictions. Our study has improved the bio-control potential of Trichoderma spp. against the plant-parasitic nematodes H. avenae and provided a cost-efficient bio-resource in the future development of novel bio-control agents.

Signatures of adaptation to a monocot host in the plant‐parasitic cyst nematode Heterodera sacchari

Interactions between plant-parasitic nematodes and their hosts are mediated by effectors, i.e. secreted proteins that manipulate the plant to the benefit of the pathogen. To understand the role of effectors in host adaptation in nematodes, we analysed the transcriptome of Heterodera sacchari, a cyst nematode parasite of rice (Oryza sativa) and sugarcane (Saccharum officinarum). A multi-gene phylogenetic analysis showed that H.sacchari and the cereal cyst nematode Heterodera avenae share a common evolutionary origin and that they evolved to parasitise monocot plants from a common dicot-parasitic ancestor. We compared the effector repertoires of H.sacchari with those of the dicot parasites Heteroderaglycines and Globodera rostochiensis to understand the consequences of this transition. While, in general, effector repertoires are similar between the species, comparing effectors and non-effectors of H.sacchari and G.rostochiensis shows that effectors have accumulated more mutations than non-effectors. Although most effectors show conserved spatiotemporal expression profiles and likely function, some H.sacchari effectors are adapted to monocots. This is exemplified by the plant-peptide hormone mimics, the CLAVATA3/EMBRYO SURROUNDING REGION-like (CLE) effectors. Peptide hormones encoded by H.sacchari CLE effectors are more similar to those from rice than those from other plants, or those from other plant-parasitic nematodes. We experimentally validated the functional significance of these observations by demonstrating that CLE peptides encoded by H.sacchari induce a short root phenotype in rice, whereas those from a related dicot parasite do not. These data provide a functional example of effector evolution that co-occurred with the transition from a dicot-parasitic to a monocot-parasitic lifestyle.

Effects of Heterodera avenae on the absorption and translocation of N, P, K, and Zn from the soil in wheat

Cereal cyst nematode (CCN) (Heterodera avenae) is a major root parasite of wheat throughout the world. A pot experiment was conducted in screen house in CCS Haryana Agricultural University, Hisar during 2016–2017 for studying the nutrient uptake by wheat plants infected with H. avenae. Urea, single super phosphate (SSP), Muriate of potash (MOP), and zinc sulfate (Zn SO4) were applied singly and in combinations, and compared with a control without fertilizers. H. avenae reduced the uptake of nutrients (nitrogen (N), phosphorous (P), potassium (K), and Zn) as compared to uninfested soil. Improved nutrients uptake was found in the treatment where all nutrients were applied in soil. Lesser uptake was recorded in the treatment where no nutrient was applied in soil. In the soil, more nutrients were recorded in infested soil as compared to uninfested soil and, nutrients were also more in soil in the treatments where individual nutrients were applied than their combined application.

Genetic Background of the Resistance against Parasitic Nematodes in Wheat

The state of the art in research on the genes responsible for the resistance of soft wheat Triticum aestivum L. against cereal cyst nematode Heterodera avenae and root lesion nematode Pratylenchus neglectus and the use of these genes in plant breeding programs are described. Most genes responsible for the resistance to these plant pathogens are listed and their chromosomal localization and resistance specificity are described. The sources of resistance genes widely used to control the cereal cyst nematode are presented. The alternative methods for transferring nematode resistance genes into wheat are outlined.

СОЗДАНИЕ НЕМАТОДОУСТОЙЧИВЫХ СОРТОВ И ГИБРИДОВ СЕЛЬСКОХОЗЯЙСТВЕННЫХ КУЛЬТУР

This review article provides examples of the possibilities of plant breeding for resistance to phytoparasitic nematodes. In many countries resistant to nematodes varieties are included in the integrated system of protection of agricultural crops. Potato breeding should be aimed at developing varieties resistant to Golden and Pale potato cyst nematodes Globodera rostochinensis and G. pallida, as well as to potato rot nematode Ditylenhus destructor. Actual is breeding varieties and hybrids of sugar and table beet, resistant to the cyst nematode Heterodera schachtii. For cereals crops represent danger cereal cyst nematode Heterodera (Bidera) avenae. Breeding varieties resistant to this phytohelminthes is an important task of breeding cereals. Important is the selection of tomatoes, cucumbers, beans, alfalfa, rice, fruit and other crops resistant to meloidoginosis caused by species of Meloidogyne spp. To different races stem nematode D. dipsaci bred varieties of forage herbs: alfalfa, white, meadow clover, oats. The use of methods of biotechnology, genetic, cellular engineering, molecular methods in breeding opens up new opportunities for the purposeful creation of resistant varieties.

RNAi-Based Biocontrol of Wheat Nematodes Using Natural Poly-Component Biostimulants.

With the growing global demands on sustainable food production, one of the biggest challenges to agriculture is associated with crop losses due to parasitic nematodes. While chemical pesticides have been quite successful in crop protection and mitigation of damage from parasites, their potential harm to humans and environment, as well as the emergence of nematode resistance, have necessitated the development of viable alternatives to chemical pesticides. One of the most promising and targeted approaches to biocontrol of parasitic nematodes in crops is that of RNA interference (RNAi). In this study we explore the possibility of using biostimulants obtained from metabolites of soil streptomycetes to protect wheat (Triticum aestivum L.) against the cereal cyst nematode Heterodera avenae by means of inducing RNAi in wheat plants. Theoretical models of uptake of organic compounds by plants, and within-plant RNAi dynamics, have provided us with useful insights regarding the choice of routes for delivery of RNAi-inducing biostimulants into plants. We then conducted in planta experiments with several streptomycete-derived biostimulants, which have demonstrated the efficiency of these biostimulants at improving plant growth and development, as well as in providing resistance against the cereal cyst nematode. Using dot blot hybridization we demonstrate that biostimulants trigger a significant increase of the production in plant cells of si/miRNA complementary with plant and nematode mRNA. Wheat germ cell-free experiments show that these si/miRNAs are indeed very effective at silencing the translation of nematode mRNA having complementary sequences, thus reducing the level of nematode infestation and improving plant resistance to nematodes. Thus, we conclude that natural biostimulants produced from metabolites of soil streptomycetes provide an effective tool for biocontrol of wheat nematode.

Transcriptional profiling of wheat (Triticum aestivum L.) during a compatible interaction with the cereal cyst nematode Heterodera avenae

Cereal cyst nematode (CCN, Heterodera avenae) presents severe challenges to wheat (Triticum aestivum L.) production worldwide. An investigation of the interaction between wheat and CCN can greatly improve our understanding of how nematodes alter wheat root metabolic pathways for their development and could contribute to new control strategies against CCN. In this study, we conducted transcriptome analyses of wheat cv. Wen 19 (Wen19) by using RNA-Seq during the compatible interaction with CCN at 1, 3 and 8 days past inoculation (dpi). In total, 71,569 transcripts were identified, and 10,929 of them were examined as differentially expressed genes (DEGs) in response to CCN infection. Based on the functional annotation and orthologous findings, the protein phosphorylation, oxidation-reduction process, regulation of transcription, metabolic process, transport, and response process as well as many other pathways previously reported were enriched at the transcriptional level. Plant cell wall hydrolysis and modifying proteins, auxin biosynthesis, signalling and transporter genes were up-regulated by CCN infection to facilitate penetration, migration and syncytium establishment. Genes responding to wounding and jasmonic acid stimuli were enriched at 1 dpi. We found 16 NBS-LRR genes, 12 of which were down-regulated, indicating the repression of resistance. The expression of genes encoding antioxidant enzymes, glutathione S-transferases and UDP-glucosyltransferase was significantly up-regulated during CCN infection, indicating that they may play key roles in the compatible interaction of wheat with CCN. Taken together, the results obtained from the transcriptome analyses indicate that the genes involved in oxidation-reduction processes, induction and suppression of resistance, metabolism, transport and syncytium establishment may be involved in the compatible interaction of Wen 19 with CCN. This study provides new insights into the responses of wheat to CCN infection. These insights could facilitate the elucidation of the potential mechanisms of wheat responses to CCN.

RNAi-mediated Resistance against Plant Parasitic Nematodes of Wheat Plants Obtained in Vitro Using Bioregulators of Microbiological Origin

Background:Plant parasitic nematodes are dangerous pests that damage various agricultural crops and decrease their productivity.Objective:The resistance of new lines of wheat (Triticum aestivum L.) plants obtained under in vitro conditions on MS media containing microbial bioregulators to plant parasitic nematodes was studied under in vitro and greenhouse conditions.Methods:Here we conducted physiological and molecular-genetic studies of resistance of wheat plants to nematodes.Results:In vitro experiments showed that wheat plants grown on MS media with microbial bioregulators had 20-37 % of infestation with cereal cyst nematode Heterodera avenae, significantly lower when compared with 73 % of infestation of the control plants grown without bioregulators. Bioregulators increased morphometric parameters of the wheat plants obtained under in vitro conditions on MS media and further grown under greenhouse conditions on the natural invasive background: stem height increased 13.6-37.5 %, flag leaf length 18.0-19.3 %, ear length 6.8-24.6 %, and ear weight 27.0- 54.5 %, when compared with control wheat plants. The difference in the degree of hybridizated molecules mRNA and si/miRNA from control and experimental wheat plants increased: 15-39 % in plants grown under in vitro conditions on the invasive background created by H. avenae and 33-56 % in seeds of plants grown under greenhouse conditions on the natural invasive background. The silencing activity of si/miRNA from wheat plants grown on MS media with bioregulators increased: 20-51 % in plants grown under in vitro conditions on the invasive background created by H. avenae or 38-64 % in plants grown under greenhouse conditions on the natural invasive background.Conclusion:Our studies confirm the RNAi-mediated resistance to plant nematodes of wheat plants obtained on media with microbial bioregulators and grown under in vitro and greenhouse conditions.

Fine mapping of Rha2 in barley reveals candidate genes for resistance against cereal cyst nematode

Key messageThe cereal cyst nematode resistance locus Rha2 was mapped to a 978 kbp region on the long arm of barley chromosome 2H. Three candidate genes are discussed.The cereal cyst nematode (CCN) Heterodera avenae is a soil-borne obligate parasite that can cause severe damage to cereals. This research involved fine mapping of Rha2, a CCN resistance locus on chromosome 2H of barley. Rha2 was previously mapped relative to restriction fragment length polymorphisms (RFLPs) in two mapping populations. Anchoring of flanking RFLP clone sequences to the barley genome assembly defined an interval of 5077 kbp. Genotyping-by-sequencing of resistant and susceptible materials led to the discovery of potentially useful single nucleotide polymorphisms (SNPs). Assays were designed for these SNPs and applied to mapping populations. This narrowed the region of interest to 3966 kbp. Further fine mapping was pursued by crossing and backcrossing the resistant cultivar Sloop SA to its susceptible ancestor Sloop. Evaluation of F2 progeny confirmed that the resistance segregates as a single dominant gene. Genotyping of 9003 BC2F2 progeny identified recombinants. Evaluation of recombinant BC2F3 progeny narrowed the region of interest to 978 kbp. Two of the SNPs within this region proved to be diagnostic of CCN resistance across a wide range of barley germplasm. Fluorescence-based and gel-based assays were developed for these SNPs for use in marker-assisted selection. Within the candidate region of the reference genome, there are nine high-confidence predicted genes. Three of these, one that encodes RAR1 (a cysteine- and histidine-rich domain-containing protein), one that is predicted to encode an acetylglutamate kinase and one that is predicted to encode a tonoplast intrinsic protein, are discussed as candidate genes for CCN resistance.

Investigation of resistance to Pratylenchus penetrans and P. thornei in international wheat lines and its durability when inoculated together with the cereal cyst nematode Heterodera avenae, using qPCR for nematode quantification

The root lesion nematodes Pratylenchus penetrans and P. thornei cause high yield losses in rain-fed wheat fields in Morocco, as well as worldwide. Growing resistant varieties is one of the most effective methods for controlling nematodes. Therefore, a collection of 14 lines of spring wheat and 11 lines of winter wheat (Triticum aestivum and T. durum), provided by CIMMYT, were screened for resistance to P. penetrans and P. thornei in tubes (15 × 20 × 120 mm3) under greenhouse conditions. The resistance level was evaluated based on the numbers of nematodes extracted from roots and soil 9 weeks after infestation. Three lines (L9, L12 and L13) were found moderately resistant (reproduction factor < 1) to P. thornei and one of these (L9) was also moderately resistant to P. penetrans. To investigate the durability of this resistance, we co-inoculated juveniles of Heterodera avenae, a cereal cyst nematode widely present in Moroccan wheat fields, and assessed the reproduction of both lesion nematodes on the three lines. Our results showed that the lines L9, L12, L13 remained moderately resistant in the presence of H. avenae. Moreover, the numbers of Pratylenchus spp. were generally lower when plants were co-inoculated with H. avenae. The number of P. penetrans or P. thornei were determined visually using a microscope and with a qPCR assay. The counts with qPCR were even lower than microscopic counts. These findings on resistance are promising but the field performance of these lines against root lesion nematode attacks should be evaluated.

Transcriptional responses of wheat and the cereal cyst nematode Heterodera avenae during their early contact stage

Cereal cyst nematode (Heterodera avenae) is attracted to and aggregated around wheat roots to initiate infection, but this interaction between wheat and the nematode is not fully understood. The transcriptional responses of both wheat and H. avenae were examined during their early contact stage by mRNA sequencing analysis; certain numbers of the differentially expressed genes (DEGs) were validated using quantitative real-time PCR. The immobile host wheat root only had 93 DEGs (27 up-regulated and 66 down-regulated), while the mobile plant parasitic nematode reacted much more actively with 879 DEGs (867 up-regulated and 12 down-regulated). Among them, a number of wheat DEGs (mostly down-regulated) were involved in biotic stress pathways, while several putative effector genes were up-regulated in the nematode DEGs. One putative chitinase-like effector gene of H. avenae was able to suppress BAX-triggered programmed cell death in Nicotiana benthamiana. Results of these experiments demonstrated that nematode responded more actively than wheat during the contact stage of parasitism. The parasite’s responses mainly involved up-regulation of genes including at least one anti-plant-defence effector gene, whereas the host responses mainly involved down-regulation of certain defence-related genes.

Development and characterization of EST-derived SSR markers in the cereal cyst nematode Heterodera avenae

The cereal cyst nematode Heterodera avenae is a pathogen of cereal crops and causes high yield losses worldwide. In this study, a collection of 37,348 expressed sequence tags (ESTs) of H. avenae was mined for EST-based simple sequence repeat (SSR) markers, which resulted in the identification of 5604 SSRs. A total of 210 pairs of SSR primers were further developed and used for validation of the amplification rate and assessment of the polymorphism. Eight SSR markers were finally identified and analyzed using 96 individual cysts of H. avenae sampled from three provinces in China. These loci were found to be moderately polymorphic with 3–8 alleles per locus. The observed and expected heterozygosity across the three populations ranged from 0.000 to 0.594 and from 0.000 to 0.731, respectively. The polymorphism information content (PIC) was medium and ranged from 0.080 to 0.562, with a mean of 0.409. The F ST ranged from 0.1034 to 0.1550, indicating moderate genetic differentiation among the three H. avenae populations. These EST-SSR markers can be used to study population genetic diversity and the dispersal route of H. avenae in China.

English

English

Biochemical changes of the cereal cyst nematode, Heterodera avenae, at low temperatures

Cereal cyst nematode (Heterodera avenae) diapause is induced by high temperatures and is broken by low temperatures. In this study, metabolic responses were monitored in diapause and non-diapause H. avenae during exposure to 4°C for 10 weeks. The results showed that there was no difference in total carbohydrate content. The content of glycogen and glycerol at 0 week was relatively high but decreased with increased storage time at 4°C. The content of trehalose of the nematode at 10 weeks was significant lower than that at 5 weeks at 4°C. Protein content increased significantly after incubation for 5 and 10 weeks. Esterase and trehalase activity increased with the increasing period at 4°C and showed a significant difference between treatments for esterase activity but there was no significant difference between 5 and 10 weeks for trehalase activity. The SDS-PAGE pattern indicated that a 15.5 kDa protein was absent at 10 weeks and present at 0 and 5 weeks. Esterase isoenzyme patterns of H. avenae showed that at 10 weeks there were four bands: EST 0.21, EST 0.24, EST 0.30 and EST 0.34 (Rf values). EST 0.24 was the common band in the three treatments. Biochemical tests were conducted to correlate with hatching experiments using the same treatments. 2-DE patterns of H. avenae showed that diapause and non-diapause nematodes had 409 and 412 protein spots, respectively, and 19 protein spots were unique: 11 distinct proteins in non-diapause and eight distinct proteins in diapause. This information could be helpful in understanding the diapause mechanism of the cereal cyst nematode.

Influence of temperature and storage conditions on the hatching behavior of cereal cyst nematodes (Heterodera avenae Wollenweber) from Egypt

The cereal cyst nematode Heterodera avenae has been reported in wheat fields in Egypt; however no information is available on the hatch of second-stage juveniles (J2) from such populations of H. avenae. The aim of this study was to subject five Egyptian populations of H. avenae that were obtained from different regions in the Ismailia Province to different temperatures and storage durations to determine the effects on J2 emergence. The Egyptian populations of H. avenae were compared to a population originating from a different climatic zone in Germany (Grafenreuth, Bavaria). Results showed that the J2 hatching pattern of the Egyptian H. avenae populations did not differ from each other. Although the Egyptian and the German populations of H. avenae hatched primarily between 5 and 20 °C, significant differences in J2 hatching have been observed among them. Highest emergence of J2 of the Egyptian populations was observed between 10 and 15 °C, whereas the highest level of J2 emergence of the German population was between 5 and 10 °C. Storing cysts to 5 °C before incubation at 10 °C stimulated the hatch of the German population of H. avenae significantly compared to the control. Whereas, storing cysts at 20 °C, before incubation at 10 °C, significantly stimulated J2 hatching of the Egyptian populations compared to the control. The J2 hatching behavior of the Egyptian populations of H. avenae was in agreement with reports for Mediterranean ecotypes which have winter activity, while the hatching pattern of the German population was similar to those of the Northern ecotypes with spring activity.