Globodera Rostochiensis Research Articles

Does solanoeclepin A act as a host-searching cue for <i>Globodera rostochiensis</i>?

Does solanoeclepin A act as a host-searching cue for <i>Globodera rostochiensis</i>?

Bacterial Microbiota Isolated from Cysts of Globodera rostochiensis (Nematoda: Heteroderidae).

The potato cyst nematode (PCN) Globodera rostochiensis is a plant parasite of potato classified into a group of quarantine organisms causing high economic losses worldwide. Due to the long persistence of the parasite in soil, cysts harbor numerous bacteria whose presence can lead to cyst death and population decline. The cysts of G. rostochiensis found in two potato fields were used as a source of bacteria. The universal procedure was applied to extract DNA from bacteria which was then sequenced with 16S primers. The aims of the study were to identify bacterial microbiota associated with the PCN populations and to infer their phylogenetic relationships based on the maximum likelihood and Bayesian phylogeny of the 16S sequences. In addition, the impact of the most significant climate and edaphic factors on bacterial diversity were evaluated. Regarding the higher taxonomy, our results indicate that the prevalent bacterial classes were Bacilli, Actinobacteria and Alphaproteobacteria. Phylogenetic analyses clustered Brevibacterium frigoritolerans within the family Bacillaceae, confirming its recent reclassification. Long-term climate factors, such as air temperature, insolation hours, humidity and precipitation, as well as the content of soil organic matter, affected the bacterial diversity. The ability of cyst nematodes to persist in soil for a long time qualifies them as a significant natural source to explore the soil bacterial microbiota.

EFFECT OF CYST NEMATODE (GLOBODERA ROSTOCHIENSIS) ISOLATE DDH1 ON GENE EXPRESSION IN SYSTEMIC LEAVES OF POTATO PLANT

Globodera rostochiensis (Cyst nematode-DDH1) is a major pathogen of potato, this type of nematode was recently reported in Egypt in 2017 as a serious plant pathogen especially in Alexandria and El-Behera governorates. This study aimed to identify this species (G. rostochiensis) on the molecular level in addition to examine the plant-cyst nematode interaction. The results of ITS-PCR showed two bands with molecular sizes 238 bp and 370 bp. The small band is identified as internal band for the large one. The sequence analysis was conducted on 238 bp amplicon and the results obtained confirm that the obtained DNA sequence belong cyst nematodes (G. rostochiensis) with similarity 77%. The constructed phylogenetic tree based on the DNA nucleotide sequence showed close relationship with a Japanese G. rostochiensis (AB207271). The functional transcriptome of the infected and non-infected potato plants was analyzed using Differential Display- PCR technique and about 57 up regulated and 22 down regulated genes. Seven genes (2 downregulated and 5 upregulated) were chosen at random and sequenced. The nucleotide sequences observed that the two down regulated genes were; Chitinase domain containing protein 1 and N-like putative resistance protein. Whereas, the five up regulated genes were; Glucan endo 1,3 beta glucosidase A precursor, STS 14 protein gene, Phytoalexin deficient 4-1 protein gene, PEN1 gene and Linoleate 13S lipoxigenase 2-1, chloroplastic like, respectively. We can concluded that the regulation changes occurred for some pathogen related genes in systemiclly acquired immunity of infected potato plant compared with control were the main observation. Moreover, the cyst nematode could be able to suppressd some of plant defense system genes and inducing another in the same time.

Distribution, DNA barcoding and genetic diversity of potato cyst nematodes in Indonesia

Global trading of plant materials, in combination with agricultural practices, may facilitate the spreading of cyst nematodes to so far non-infected areas. Recently Potato Cyst Nematode (PCN) was recognized to be present in Indonesia and both diversity and distribution require further study. Assessment of PCN populations was done by collecting soil samples, determination of morphological characteristics in combination with ITS rDNA and COI mtDNA sequencing. Thirty-seven soil samples were collected from potato fields in the Indonesia archipelago. The results showed the presence of Globodera rostochiensis in 22 out of 37 sampling fields, namely North Sumatra (6 fields), Central Java (12 fields), East Java (3 fields), and -for the first time- in Sulawesi (North Sulawesi) (1 field). The highest observed density was found in Banjarnegara (Central Java), i.e., 872 cysts 100 ml soil−1. Globodera pallida was not recovered. Both ITS and COI characterisation of Indonesian PCN (G. rostochiensis) revealed the virtual absence of sequence variation as compared to most PCN from the rest of the world; the COI sequences were identical to the most common and mostly distributed haplotype around the world. Microsatellite genotyping indicated a higher genetic diversity for populations from East Java than for populations from North Sumatra, suggesting that cysts at the origin of populations in North Sumatra were coming from populations in East Java. These data on species identification, population density, genetic diversity, and distribution of potato cyst nematode over the Indonesian archipelago constitute the very basis for the design of environmentally-sound and effective PCN control strategies.

Identification, distribution and genetic diversity of Globodera rostochiensis (Wollenweber, 1923) Skarbilovich, 1959 (Tylenchida: Heteroderidae) populations in Turkey

The golden nematode, Globodera rostochiensis (Wollenweber, 1923) Skarbilovich, 1959 (Tylenchida: Heteroderidae) is one of the most economically important pests of potato in the world. Tests for this nematode are routinely performed for outbreaks and densities in potato growing areas. The morphological and molecular analyses for precise determination of the nematode are employed to establish appropriate management strategies. This study showed that 96% of soil samples obtained from Bozdağ and Ödemiş Districts of İzmir Province, during 2017 and 2018 potato growing seasons, were positive for G. rostochiensis . The mean number of cysts ranged from 0.01 to 3.70 cysts g-1 soil in the fields examined. The examination of the morphological and morphometric features of the second-stage juveniles and cysts of the G. rostochiensis revealed slight differences among the populations obtained from Bozdağ and Ödemis. To assess the accuracy of the identification, partial sequences of ribosomal DNA for all populations were amplified, sequenced, and deposited in GenBank. The comparisons of the sequences with those of corresponding G. rostochiensis populations available in GenBank showed 99.89-100% nucleotide similarity. The results of this study will help to better understand the physiology, ecology and biology of the nematode to quarantine this pest more effectively.

Diversity of Nematode Microbial Antagonists from Algeria Shows Occurrence of Nematotoxic Trichoderma spp.

Fungi and bacteria associated to phytoparasitic nematodes Globodera rostochiensis and Meloidogyne spp. in Algeria were identified and characterized. Trichoderma spp. showed the highest prevalence in the cysts of G. rostochiensis. A number of isolates were identified through PCR amplification and the sequencing of the internal transcribed spacer (ITS)1-2 and Rpb2 gene regions. The most represented species were T. harzianum and T. afroharzianum. The latter and T. hirsutum were reported for the first time in Algeria. Fusarium spp., including F. oxysporum and F. solani, comprised a second group of fungi found in cysts. Taxa associated to females of Meloidogyne spp. included T. harzianum, Fusarium spp. and other hyphomycetes. To assess the efficacy of Trichoderma spp., two assays were carried out in vitro with the culture filtrates of two T. afroharzianum and T. harzianum isolates, to check their toxicity versus the second stage juveniles of M. incognita. After 24–48 h exposure, a mortality significantly higher than the control was observed for both filtrates at 1% dilutions. The TRI genes involved in the production of trichothecenes were also amplified with the PCR from some Trichoderma spp. isolates and sequenced, supporting a putative role in nematode toxicity. Bacteria isolated from the cysts of G. rostochiensis included Brucella, Rhizobium, Stenotrophomonas and Bacillus spp., identified through 16S rRNA gene sequencing. The potential of the microbial isolates identified and their mechanisms of action are discussed, as part of a sustainable nematode management strategy.

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.

Resistance to causal agents of late blight and golden potato nematode of the modern cultivars of seed potatoes and their phytosanitary status in various agroclimatic zones of the European part of Russia

Активная экспансия зарубежных сортов картофеля на территорию Российской Федерации привела к смене доминирующих видов патогенов этой культуры и появлению новых патотипов возбудителей вредоносных болезней. Целью работы была оценка устойчивости к возбудителям фитофтороза и глободероза современного сортимента картофеля и определение поражаемости возделываемых сортов картофеля грибными и оомицетными болезнями в различных агроклиматических зонах России. Проведена оценка устойчивости 41 сорта зарубежной селекции, разрешенного к использованию на территории РФ, к патотипу Ro1 Globodera rostochiensis и к изоляту VZR17 Phytophthora infestans, включающего гены вирулентности 1.2.3.4.5.6.7.8.9.10.11. Устойчивыми к золотистой картофельной нематоде оказались 38 сортов. У 96.6 % изученных нематодоустойчивых сортов выявлен маркер гена Н1 устойчивости к патотипу Ro1 G. rostochiensis, восприимчивые сорта этим маркером не обладали. Абсолютной устойчивостью к возбудителю фитофтороза отличались сорта Alouette и Sarpo Mira (балл 9); высоким уровнем устойчивости (баллы 6 и 7) характеризовались сорта Evolution, Red Fantasy и Ricarda. Сорта Baltic Rose, Damaris, Desiree, Gala, Labella, Laperla, Mia, Sanibel, Zekura, Queen Anne, Red Lady и 7 for 7 были отнесены к восприимчивым, хотя в характеристиках оригинаторов указана средняя устойчивость к фитофторозу. Фитопатологическая экспертиза проведена для 92 образцов 39 сортов семенного картофеля из четырех федеральных округов РФ: Приволжского, Северо-Западного, Центрального и Северо-Кавказского. Наибольшее распространение на всех сортах получили ризоктониоз, сухая фузариозная гниль и серебристая парша. Стопроцентное поражение клубней серебристой паршой отмечено в различных регионах на сортах элитных репродукций Red Scarlett, Evolution, Labella, Colombo, Gala, Невский. Широко распространен антракноз картофеля; сильнее всего были поражены клубни элитной и второй репродукции сорта Red Scarlett – от 50.0 до 71.4 % в Центральном федеральном округе.

Chitinase activity of biocontrol fungi cultured from the golden potato cyst nematode, Globodera rostochiensis

Chitinase activity of biocontrol fungi cultured from the golden potato cyst nematode, Globodera rostochiensis

The collection of potato varieties as a reserve of source material for breeding for high yield, earliness, and resistance to diseases and pests

Background. Information is provided about the results obtained by screening the VIR collection of improved potato varieties for main commercial traits: earliness, high yield, high starch content, and resistance to late blight (Phytophthora infestans (Mont.) de Bary), viruses, and pests, such as cyst nematode (Globodera rostochiensis Woll. (Ro1)), and Colorado beetle (Leptinotarsa decemlineata Say).Materials and methods. Potato accessions representing domestic and foreign varieties from the VIR collection served as the material for this research. The screening was performed according to the techniques developed at the Potato Genetic Resources Department of VIR.Results and conclusion. Potato varieties with valuable commercial traits were identified as breeding sources promising for earliness: ‘Bashkirskiy’ (k-25338), ‘Charoit’ (k-25221), ‘Colleen’ (k-25224), ‘Lagun’ (k-25294), etc.; for high yield: ‘Ametist’ (k-25336), ‘Banba’ (k-25222), ‘Bastion’ (k-25198), ‘Nur-Alem’ (k-25253), ‘Senim’ (k-25306), etc.; for high starch content: ‘Charaўnik’ (k-25139), ‘Darnitsa’ (k-25179), ‘Lad’ (k-25180), ‘Maksimum’ (k-25136), etc.; for resistance to late blight: local variety (Georgia) (k-25298, k-25326), ‘Sunkar’ (k-25258), ‘Udovitskiy’ (k-25260), ‘Vektor’ (k-25200), ‘Zvezdochka’ (k-25209); for resistance to viruses: ‘Azart’ (k-25196), Gala (k-25270), ‘Nadezhda’ (k-25213), Utro (k-25219), ‘Volat’ (k-25263), etc. Varieties combining resistance to gold potato cyst nematode with other valuable commercial traits were selected. Varieties with relative resistance to Colorado potato beetle were isolated under favorable conditions for the pest’s development. As a result of the research, new source material was identified, with a potential to improve major commercial traits of potato: earliness, high yield, high starch content, resistance to late blight, viruses, and pests (cyst nematode and Colorado beetle).

Prevalence and Spread of Potato Cyst Nematodes, <I>Globodera</I> spp. in Northern Hilly Areas of India

Potato cyst nematodes (PCNs), Globodera rostochiensis (Woll.) and G. pallida (Stone), are globally important pests of potato prevalent in the Nilgiri area of South India. PCNs were first intercepted from North India at Shimla, Himachal Pradesh (HP) in 2010. Subsequent surveys in the hilly areas of North India have revealed the occurrence of PCNs in several districts of HP, Uttarakhand and Jammu & Kashmir, despite domestic quarantine against this nematode. High populations of PCN were mainly encountered in the Potato Seed Multiplication Farms that supply seed potato to farmers. Here, a hypothesis on the dissemination of PCNs within India is proposed.

Mediation of Potato-Potato Cyst Nematode, G. rostochiensis Interaction by Specific Root Exudate Compounds.

Potato (Solanum tuberosum) is a widely consumed staple food crop worldwide whose production is threatened by potato cyst nematodes (PCN). To infect a host, PCN eggs first need to be stimulated to hatch by chemical components in the host root exudates, yet it remains unknown how most root exudate components influence PCN behavior. Here, we evaluated the influence of eight compounds identified by LC-QqQ-MS in the root exudate of potato on the hatching response of the PCN, Globodera rostochiensis at varying doses. The eight compounds included the amino acids tyrosine, tryptophan and phenylalanine; phytohormones zeatin and methyl dihydrojasmonate; steroidal glycoalkaloids α-solanine and α-chaconine and the steroidal alkaloid solanidine. We additionally tested two other Solanaceae steroidal alkaloids, solasodine and tomatidine, previously identified in the root exudates of tomato, an alternative host for PCN. In dose-response assays with the individual compounds, the known PCN hatching factors α-chaconine and α-solanine stimulated the highest number of eggs to hatch, ∼47 and ∼42%, respectively, whereas the steroidal alkaloids (aglycones), solanidine and solasodine and potato root exudate (PRE) were intermediate, 28% each and 21%, respectively, with tomatidine eliciting the lowest hatching response 13%. However, ∼60% of the hatched juveniles failed to emerge from the cyst, which was compound- and concentration-dependent. The amino acids, phytohormones and the negative control (1% DMSO in water), however, were generally non-stimulatory. The use of steroidal glycoalkaloids and their aglycones in the suicidal hatching of PCN offers promise as an environmentally sustainable approach to manage this pest.

Identification of Interspecific Potato Hybrids with Combined Resistance to Late Blight (Phytophthora Infestans) and Nematode (Globodera Rostochiensis)

Abstract Late blight (agent Phytophthora infestans) and potato cyst nematode (PCN) caused by Globodera rostochiensis are economically important pathogens, which may significantly reduce potato yields. In this study interspecific potato hybrids were used as a source of resistance for combined resistance to economically important potato pathogens: late blight and cyst nematode. The aim of our study was to identify hybrid progenies with combined resistance to both pathogens and to verify the applicability of several molecular markers associated with resistance to G. rostochiensis pathotype Ro1 to identify resistant plants. Ninety-two clones of eleven original interspecific potato hybrids obtained in crosses with the cultivated S. tuberosum group tuberosum, S. tuberosum group Andigena, S. tuberosum group Phureja and wild S. guerreroense, S. microdontum, S. kurtzianum, S. neoantipoviczii and S. tarijense potato species were screened in bioassays and by molecular markers. PCN resistant or moderately resistant clones were found among the progenies of nine hybrids. Results were highly correlated with resistance status detected by molecular markers linked to the H1 (marker 57R) and Gro1-4 (marker Gro1) genes. Marker CP113 (linked to the H1 gene) was not polymorphic and failed to detect resistance status. Combination of foliar late blight resistance and resistance to PCN was identified in hybrids obtained in crosses with plants of species S. microdontum, S. tarijense and S. phureja and in the hybrid between S. guerreroense and Black’s P. infestans race differential carrying gene R-5.

EVALUATION OF RESISTANCE OF POTATO VARIETIES OF FOREIGN SELECTION TO GLOBODERA

Under the vegetation experiment, two susceptible potato varieties (Sineglazka, Udacha) and 11 varieties of foreign selection were grown in the soil infected with golden potato nematode (Globodera rostochiensis) (more than 4 thousand eggs and larvae of Globodera rostochiensis per a 800 cubic cm vessel). On the 70th day after the emergence of seed potatoes on the surface of the ball of soil, 53 white and yellow Globodera rostochiensis females were found on the roots of the susceptible Sineglazka variety, and 17 females were found on the ball of soil of the standard Udacha variety, which may be explained by weak development of the root system due to rotten tubers. As a result of foreign potato varieties evaluated for resistance to Globodera rostochiensis, it was found that all tested potato varieties Riviera, Excellence, Bellarosa, Rocco, Arizona, Evolution, Impala, Picasso, Arrow, Veneta and Coletta were resistant to the Vladimir population of the golden potato nematode Globodera rostochiensis of the pathotype Ro1. One to three Globodera rostochiensis females were found on the roots of varieties Excellence, Bellarosa, Rocco, Arizona, Impala, Veneta and Coletta. Six females of Globodera rostochiensis were identified in the Arrow variety. Females were not found on the roots of varieties Riviera, Evolution and Picasso.

Potato Cyst Nematodes: A New Threat to Potato Production in East Africa.

Potato cyst nematodes (PCN), such as Globodera rostochiensis and Globodera pallida, are quarantine restricted pests of potato causing major yield and financial losses to farmers. G. rostochiensis was first reported from Kenya’s key potato growing area in 2015. We sought to determine the diversity, prevalence and distribution of PCN species across the country by conducting a country-wide survey between 2016 and 2018, which included a more focused, follow-up assessment in three key potato growing counties. A total of 1,348 soil samples were collected from 20 potato growing counties. Information regarding local potato farming practices, potato cultivar use, their diversity and availability was also recorded. PCN cysts were obtained from 968 samples (71.8%) in all the counties surveyed, with Nyandarua County recording the highest PCN field-incidence at 47.6%. The majority of PCN populations, 99.9%, were identified as G. rostochiensis, while G. pallida was recovered from just one field, in a mixed population with G. rostochiensis. Inconsistencies in PCR amplification efficiency was observed for G. rostochiensis using the recommended EPPO primers, compared with ITS primers AB28/TW81, indicating that this protocol cannot be entirely relied upon to effectively detect PCN. Egg density in Nyandarua County varied between 30.6 and 158.5 viable eggs/g soil, with an average egg viability of 78.9 ± 2.8% (min = 11.6%, max = 99.9%). The PCN-susceptible potato cultivar named Shangi was the most preferred and used by 65% of farmers due to its shorter dormancy and cooking time, while imported cultivars (Destiny, Jelly, Manitou, and Markies) with resistance to G. rostochiensis were used by 7.5% of farmers due to unavailability and/or limited access to seeds. Thus, most farmers preferred using their own farm-saved seeds as opposed to purchasing certified seeds. Establishing the distribution and prevalence of PCN and elucidating the local farming practices that could promote the spread of PCN is a necessary precursor to the implementation of any containment or management strategy in the country and ultimately across the region.

Solanum gourlayi\u2014a Source of Cyst Nematode Resistance in Potato Breeding

The potato cyst nematodes (PCN) Globodera rostochiensis and G. pallida are among the most important pests causing significant yield loss in potato production. Cultivating resistant cultivars of potato is the most effective and environmentally safe method for protecting potato crops against nematodes. However, widespread cultivation of cultivars resistant to G. rostochiensis can affect the reproduction of G. pallida. Therefore, breeding for resistance to nematodes remains among the major aims of potato breeding programmes. Many wild Solanum species could be valuable sources of nematode resistance. This study examined the resistance to G. pallida identified in two accessions of the wild species Solanum gourlayi. Both accessions demonstrated resistance to pathotypes Pa2 and Pa3, but show asymmetric distribution of resistance among the progeny clones. The presented distributions of resistance scores indicate quantitative nature of resistance to G. pallida. Furthermore, this resistance is specific to each pathotype and may be controlled by different genes. We also conclude that there is a need for independent evaluation of resistance for both pathotypes of G. pallida (Pa2 and Pa3).

THE STUDYING OF DYNAMICS OF THE DISTRIBUTION OF GOLDEN POTATO NEMATODES IN UKRAINE AND SEPARATE FACTORS ITS REGULATION

In recent years, the main sowing areas of potatoes have moved from collective farms to the private sector, which makes it difficult to detect nematodes and establish their level of harmfulness in different regions of Ukraine. The cultivation of potatoes in monoculture for many years, the unpredictability of the existing seed system of regular maintenance of individual farms with healthy planting material, the lack of knowledge about the protection of plants against nematodes, contribute to the spread of globoderosis in new territories. Research strategy to protect the potato crop from nematodes should be aimed at a low-energy and environmentally friendly system based on the use of nematodes, the correct application of crop rotation crops, the introduction of organic and mineral fertilizers, the quality of planting material, since chemical hazards protect the environment. The outstanding issues in terms of regulating the abundance of golden potato nematodes remain the factors of the agrochemical properties of soils and their relationship with the pest size, aspects of the use of different potato precursors in terms of influencing the prevalence of the nematode, and estimating the monitoring status of its comparative numbers. The article summarizes the results of quarantine monitoring of the distribution of the golden potato nematode (Globodera rostochiensis Woll) in Ukraine and by region. A comparison of the pest prevalence rate over ten years of quarantine monitoring has been conducted and conclusions have been made regarding their success at the regional level. The phenological development of the pest is specified taking into account the climatological features of the Vinnitsa region. A review of the features of biology and the pest development cycle is made on the basis of which briefly described signs of potato damage in the field. On the basis of field studies, the effectiveness of the control of the potato nematode was evaluated by introducing crop rotation and selecting the appropriate alternation of different plants. The effectiveness of the use of potato varieties resistant to the nematode was assessed, and the level of their productivity against an infectious background was determined in comparison with the variety unstable to the pest. Conclusions have been made in the main areas of restricting the spread of the potato nematode in the private sector of potato cultivation in permanent crops. Key words: golden potato nematode, yield, varieties, crop rotation, prevalence.

Integrated management of Globodera rostochiensis: a novel biocontrol agent, crop rotation and fallow

A major problem for potato production worldwide is Globodera rostochiensis. Field control of this nematode is difficult because of the high reproductive rate of this genus and its resistance to biotic and abiotic factors. Biological control of nematodes is an increasingly popular strategy because it is effective and has low environmental impact. In this study, the potential of the nematophagous fungus Metarhizium carneum to mitigate the G. rostochiensis population in the presence of a susceptible potato host without previous management and during two crop cycles was evaluated, which included cultivation of the non-host faba bean followed by a susceptible potato crop. The effect of M. carneum application to the soil allowing the field to remain fallow for 2 years was also evaluated. Although M. carneum reduced the G. rostochiensis population by 33% during one potato crop cycle, the yield did not increase. With the application of M. carneum and a faba bean/potato rotation, the nematode population in the soil was reduced by 81%, with a significant increase in yield. Likewise, the use of the fungal biological control agent and the fallow period resulted in an 87% reduction in the nematode population after 2 years. Additionally, Rhizoctonia solani damage in tubers to which M. carneum was applied was lower than that in non-treated tubers in both experiments. The reduction in the population density of G. rostochiensis without the application of the biological control agent, including in the crop rotation and fallow treatments, was very low in both experiments. The combination of two management strategies, such as the use of biological control and crop rotation or a fallow period, may be a viable approach for the integrated management of G. rostochiensis in areas where high densities of this nematode occur.

Activity of Saponins from Medicago Species against Phytoparasitic Nematodes.

Content of bioactive saponins of Medicago species suggests that they may also exert, as previously demonstrated on M. sativa, nematicidal properties exploitable for the formulation of new products for sustainable phytoparasitic nematode management. This study was addressed to highlight the bioactivity of saponins from five different Medicago species still poorly known for their biological efficacy, i.e., M. heyniana, M. hybrida, M. lupulina, M. murex and M. truncatula, against the plant parasitic nematodes Meloidogyne incognita, Xiphinema index and Globodera rostochiensis. The bioactivity of the extracts from the five Medicago species was assessed by in vitro assays on the juveniles (J2) and eggs of M. incognita and G. rostochiensis and the adult females of X. index. The suppressiveness to M. incognita of soil treatments with the Medicago plant biomasses was also investigated in a tomato experiment. The nematicidal activity of the five Medicago species was reported and discussed in relation to their phytochemical profile.

Identification and prevalence of potato cyst nematodes and root-knot nematodes in the potato production areas of İzmir Province, Turkey

Globodera spp. and Meloidogyne spp. were identified using morphological and molecular methods. Also, the distribution and population densities of these nematodes were determined in potato cultivation areas of İzmir (Turkey) in 2015. Two hundred and twenty-three soil samples were collected during the survey and 32 samples were found to be infested with Globodera spp. and 41 samples with Meloidogyne spp. The identification of nematodes was made morphologically using perennial patterns of cyst/female individuals and morphometrics of second stage juveniles. Also, species specific primers were used for molecular identification. Only Globodera rostochiensis (Wollenweber, 1923) Skarbilovich, 1959 (Tylenchida: Heteroderidae) were found in the samples that contained cyst nematodes. Also, the root-knot nematodes, Meloidogyne chitwoodi Golden, O'Bannon, Santo & Finley, 1980, Meloidogyne hapla (Chitwood, 1949), Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949, and Meloidogyne javanica (Treub, 1885) Chitwood, 1949 (Tylenchida: Meloidogynidae) were found. The prevalence rates of Meloidogyne species were determined as 2.4, 12.2, 61.0 and 24.4%, respectively. In terms of the number of individuals in soil, all G. rostochiensis (10 eggs/g soil) and M. chitwoodi (1 juvenile/250 cm 3 soil) population levels were detected above the economic damage thresholds for potato production. Also, two populations of M. incognita (0.5-2 juvenile/250 cm 3 soil) were found above the specified threshold levels.