Potato Cyst Nematode Globodera Rostochiensis Research Articles

Machine learning ensemble model prediction of northward shift in potato cyst nematodes (Globodera rostochiensis and G. pallida) distribution under climate change conditions

Potato cyst nematodes (PCNs) are a significant threat to potato production, having caused substantial damage in many countries. Predicting the future distribution of PCN species is crucial to implementing effective biosecurity strategies, especially given the impact of climate change on pest species invasion and distribution. Machine learning (ML), specifically ensemble models, has emerged as a powerful tool in predicting species distributions due to its ability to learn and make predictions based on complex data sets. Thus, this research utilised advanced machine learning techniques to predict the distribution of PCN species under climate change conditions, providing the initial element for invasion risk assessment. We first used Global Climate Models to generate homogeneous climate predictors to mitigate the variation among predictors. Then, five machine learning models were employed to build two groups of ensembles, single-algorithm ensembles (ESA) and multi-algorithm ensembles (EMA), and compared their performances. In this research, the EMA did not always perform better than the ESA, and the ESA of Artificial Neural Network gave the highest performance while being cost-effective. Prediction results indicated that the distribution range of PCNs would shift northward with a decrease in tropical zones and an increase in northern latitudes. However, the total area of suitable regions will not change significantly, occupying 16–20% of the total land surface (18% under current conditions). This research alerts policymakers and practitioners to the risk of PCNs’ incursion into new regions. Additionally, this ML process offers the capability to track changes in the distribution of various species and provides scientifically grounded evidence for formulating long-term biosecurity plans for their control.

Europe as a secondary distribution hub in the worldwide invasion of the potato cyst nematode Globodera rostochiensis

The potato cyst nematode Globodera rostochiensis originates from the Andean Mountain region in South America and has unintentionally been introduced to all inhabited continents. Several studies have examined the population genetic structure of this pest in various countries by using microsatellite markers. However, merging microsatellite data produced from different laboratories is challenging and can introduce uncertainty when interpreting the results. To overcome this challenge and to explore invasion routes of this pest, we have genotyped 22 G. rostochiensis populations from all continents. Within populations, the highest genetic diversity was observed in the South American populations, the European populations showed an intermediate level of genetic diversity and the remaining populations were the less diverse. This confirmed pre-existing knowledge such as a first introduction event from South America to Europe, but the less diverse populations could originate either from South America or from Europe. At the continental scale, STRUCTURE genetic clustering output indicated that North America and Asia have experienced at least two introduction events. Comparing different evolutionary scenarios, the Approximate Bayesian Computation analysis showed that Europe served as a secondary distribution centre for the invasion of G. rostochiensis into all other continents (North America, Africa, Asia and Oceania).

Characterisation and mapping of a Globodera pallida resistance derived from the wild potato species Solanum spegazzinii

Key messageA new resistance locus acting against the potato cyst nematode Globodera pallida was mapped to chromosome VI in the diploid wild potato species Solanum spegazzinii CPC 7195.The potato cyst nematodes (PCN) Globodera pallida and Globodera rostochiensis are economically important potato pests in almost all regions where potato is grown. One important management strategy involves deployment through introgression breeding into modern cultivars of new sources of naturally occurring resistance from wild potato species. We describe a new source of resistance to G. pallida from wild potato germplasm. The diploid species Solanum spegazzinii Bitter accession CPC 7195 shows resistance to G. pallida pathotypes Pa1 and Pa2/3. A cross and first backcross of S. spegazzinii with Solanum tuberosum Group Phureja cultivar Mayan Gold were performed, and the level of resistance to G. pallida Pa2/3 was determined in progeny clones. Bulk-segregant analysis (BSA) using generic mapping enrichment sequencing (GenSeq) and genotyping-by-sequencing were performed to identify single-nucleotide polymorphisms (SNPs) that are genetically linked to the resistance, using S. tuberosum Group Phureja clone DM1-3 516 R44 as a reference genome. These SNPs were converted into allele-specific PCR assays, and the resistance was mapped to an interval of roughly 118 kb on chromosome VI. This newly identified resistance, which we call Gpa VIlspg, can be used in future efforts to produce modern cultivars with enhanced and broad-spectrum resistances to the major pests and pathogens of potato.

Detection of Resistance, Susceptibility, Tolerance, and Virulence in Plant-Nematode Interactions: Part I-Sedentary Endoparasitic Nematodes.

The use of nonhost, tolerant, or resistant plants, to manage plant parasitic nematodes (PPNs), is an appealing, economic, and environmentally friendly agronomic practice, which is effective when precise information on the identification of PPN species and their virulence to target host crops is available. This chapter describes suggested protocols to evaluate the reaction of the most important crops and fruit trees to infestation by the most damaging PPN with sedentary endoparasitic habits, with the aim of assessing resistance and tolerance traits, sources of resistance in progenies from breeding programs, the reaction to nematodes of newly released cultivars, and the virulence of the most noxious PPNs. These protocols consist of classical screening techniques not involving biochemical and molecular analyses. PPN species and genera considered in this chapter include (i) the most importantspecies of root-knot nematodes Meloidogyne spp., including alsoM. chitwoodi, M. enterolobii, and M. graminicola, and (ii) the cyst-forming nematodes of the genera Globodera and Heterodera, such as the potato cyst nematodes (PCNs) Globodera rostochiensis and G. pallida, and also Heterodera avenae group, H. ciceri, H. glycines, and H. schachtii. Schemes are given to identify virulence groups for most of these nematodes.

The Globodera rostochiensis Gr29D09 Effector with a Role in Defense Suppression Targets the Potato Hexokinase 1 Protein.

The potato cyst nematode (Globodera rostochiensis) is an obligate root pathogen of potatoes. G. rostochiensis encodes several highly expanded effector gene families, including the Gr4D06 family; however, little is known about the function of this effector family. We cloned four 29D09 genes from G. rostochiensis (named Gr29D09v1/v2/v3/v4) that share high sequence similarity and are homologous to the Hg29D09 and Hg4D06 effector genes from the soybean cyst nematode (Heterodera glycines). Phylogenetic analysis revealed that Gr29D09 genes belong to a subgroup of the Gr4D06 family. We showed that Gr29D09 genes are expressed exclusively within the nematode's dorsal gland cell and are dramatically upregulated in parasitic stages, indicating involvement of Gr29D09 effectors in nematode parasitism. Transgenic potato lines overexpressing Gr29D09 variants showed increased susceptibility to G. rostochiensis. Transient expression assays in Nicotiana benthamiana demonstrated that Gr29D09v3 could suppress reactive oxygen species (ROS) production and defense gene expression induced by flg22 and cell death mediated by immune receptors. These results suggest a critical role of Gr29D09 effectors in defense suppression. The use of affinity purification coupled with nanoliquid chromatography-tandem mass spectrometry identified potato hexokinase 1 (StHXK1) as a candidate target of Gr29D09. The Gr29D09-StHXK1 interaction was further confirmed using in planta protein-protein interaction assays. Plant HXKs have been implicated in defense regulation against pathogen infection. Interestingly, we found that StHXK1 could enhance flg22-induced ROS production, consistent with a positive role of plant HXKs in defense. Altogether, our results suggest that targeting StHXK1 by Gr29D09 effectors may impair the positive function of StHXK1 in plant immunity, thereby aiding nematode parasitism. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Chaetomium globosum KPC3: An Antagonistic Fungus Against the Potato Cyst Nematode, Globodera rostochiensis.

The potato cyst nematode (Globodera rostochiensis) is one of the most economically important pests of potato (Solanum tuberosum L.), causing significant economic losses worldwide. The identification of biocontrol agents for the sustainable management of G. rostochiensis is crucial. In this study, a potential biocontrol agent, Chaetomium globosum KPC3, was identified based on sequence analysis of the DNA internal transcribed spacer (ITS)region, the translation elongation factor 1-alpha (TEF1-α)gene, and the second largest subunit of the RNA polymerase II (RPB2)gene. The pathogenicity test of C. globosum KPC3 against cysts and second-stage juveniles (J2s) revealed that fungusmycelium fully parasitized the cyst after 72h of incubation. The fungus was also capable of parasitizing the eggs inside the cysts. The culture filtrate of C. globosum KPC3 caused 98.75% mortality inJ2s of G. rostochiensis after 72h of incubation. The pot experiments showed that the combined application of C. globosum KPC3 as a tuber treatment at a rate of 1 lit kg-1 of tubers and a soil application at a rate of 500mlkg-1 of farm yard manure (FYM)resulted in significantly lesser reproduction of G. rostochiensis compared to the rest of the treatments. Altogether, C. globosum KPC3 has the potential to be used as a biocontrol agent against G. rostochiensis and can be successfully implemented in integrated pest management programs.

An eggshell-localised annexin plays a key role in the coordination of the life cycle of a plant-parasitic nematode with its host.

Host-specific plant pathogens must coordinate their life cycles with the availability of a host plant. Although this is frequently achieved through a response to specific chemical cues derived from the host plant, little is known about the molecular basis of the response to such cues and how these are used to trigger activation of the life cycle. In host-specific plant-parasitic cyst nematodes, unhatched juvenile nematodes lie dormant in the eggshell until chemical cues from a suitable host plant are detected and the hatching process is initiated. The molecular mechanisms by which hatch is linked to the presence of these chemical cues is unknown. We have identified a novel annexin-like protein that is localised to the eggshell of the potato cyst nematode Globodera rostochiensis. This annexin is unique in having a short peptide insertion that structural modelling predicts is present in one of the calcium-binding sites of this protein. Host-induced gene silencing of the annexin impacts the ability of the nematode to regulate and control permeability of the eggshell. We show that in the presence of the chemicals that induce hatching annexin lipid binding capabilities change, providing the first molecular link between a nematode eggshell protein and host-derived cues. This work demonstrates how a protein from a large family has been recruited to play a critical role in the perception of the presence of a host and provides a new potential route for control of cyst nematodes that impact global food production.

A key virulence effector from cyst nematodes targets host autophagy to promote nematode parasitism.

Autophagy, an intracellular degradation system conserved in eukaryotes, has been increasingly recognized as a key battlefield in plant-pathogen interactions. However, the role of plant autophagy in nematode parasitism is mostly unknown. We report here the identification of a novel and conserved effector, Nematode Manipulator of Autophagy System 1 (NMAS1), from plant-parasitic cyst nematodes (Heterodera and Globodera spp.). We used molecular and genetic analyses to demonstrate that NMAS1 is required for nematode parasitism. The NMAS1 effectors are potent suppressors of reactive oxygen species (ROS) induced by flg22 and cell death mediated by immune receptors in Nicotiana benthamiana, suggesting a key role of NMAS1 effectors in nematode virulence. Arabidopsis atg mutants defective in autophagy showed reduced susceptibility to nematode infection. The NMAS1 effectors contain predicted AuTophaGy-related protein 8 (ATG8)-interacting motif (AIM) sequences. In planta protein-protein interaction assays further demonstrated that NMAS1 effectors specifically interact with host plant ATG8 proteins. Interestingly, mutation in AIM2 of GrNMAS1 from the potato cyst nematode Globodera rostochiensis abolishes its interaction with potato StATG8 proteins and its activity in ROS suppression. Collectively, our results reveal for the first time that cyst nematodes employ a conserved AIM-containing virulence effector capable of targeting a key component of host autophagy to promote disease.

First detection of the potato cyst nematode (Globodera rostochiensis) in a major potato production region of China.

The potato cyst nematodes (PCN) Globodera rostochiensis and Globodera pallida are the very important quarantine nematode pests of potato [Stone 1973]. Both species cause serious potato tuber yield losses. These species are subjected to strict quarantine regulations in many countries (EPPO 2017). G. rostochiensis was detected in Sichuan and Yunnan province, China in 2022 (Jiang et al. 2022). A survey for cyst nematodes in potato fields was conducted in Guizhou Province from 2018 to 2020. A total of 200 samples, including roots and soil, were collected from 40 potato fields in Hezhang (N27 06.145, E104 39.153) and Weining (N26 50.541, E104 09.885) counties in Guizhou Province, China. The Cobb decanting and sieving method was used to isolate cysts and J2s from the soil samples (Southey 1986). The potato roots were stained with acid fusion to observe cyst development. Morphological and molecular analyses indicated that 27 (13.5%) of the samples contained G. rostochiensis. The cyst density ranged between 1-85 cysts per 100 cm3 of soil and a mean density was 15 cysts per 100 cm3 soil. The smoothly rounded cysts were in brown and golden color, and the terminal cone was absent and circumfenestrate. The key morphometrics of cysts (n=20) were 695 ± 26 (685-757) μm in length excluding neck and 690 ± 30 (668 to769) μm in width; the number of cuticular ridges between anus and vulval fenestra was 16.3 ±2.1 (14 to 18); fenestral length was 15.1 ± 2.1 μm (13.18 to 19.27); distance from anus to the edge of fenestra was 61.12 ± 8.9 (49.22 to76.27) μm; and Granek's ratio was 4.54 ± 0.8 (3.97-5.26). The key morphometrics of J2 (n = 20): 468.0 ± 20.1 (427 to - 521) μm in body length, 20.58 ± 0.7 (20.2 to 21.8) μm in stylet length, 43.9 ± 5.6 (40.3 to 53.9) μm in tail length, and 23.1 ± 1.8 (21.77 to 25.32) μm in hyaline region length. The cyst and J2 morphologies were consistent with those of G. rostochiensis (Subbotin et al. 2010, EPPO 2017). Genomic DNA was isolated from cysts (n=20). DNA extraction was performed in a volume of 20 μl containing 3 μl 10× PCR buffer, 3 μl Proteinase K (600 μg μl-1), 14 μl distilled water and a single cyst was added and ground in an ice bath as described by Ou et al. (2008). The internal transcribed spacer (ITS) regions were amplified using the universal primers: rDNA1 (5'-TTGATTACGTCCCTGCCCTTT-3') and rDNA2 (5'-TTTCACTCGCCGTTACTAAGG-3') (Fleming 1998 ), and the 28S rDNA-D2/D3 regions were amplified using the primers: D2A (5´-ACAAGTACCGTGAGGGAAAGTTG-3´) and D3B (5´-TCGGAAGGAACCAGCTACTA-3´) (Subbotin et al. 2006). After the brackets at the beginning and end of the sequences were closed-up, the ITS rDNA sequences (GenBank Accession No. MZ042367 and MZ042368) showed 99.66% - 99.92% identity to G. rostochiensis sequences available in GenBank (FJ212166.1, GQ294513, FJ212164.1 and KJ409617.1). Sequences from the 28S region (GenBank Accession No. MZ057597 and MZ057598) were 99.23% - 99.74% similar to those of G. rostochiensis isolate from Slovakia (KJ409625.1), Italy (KJ409631.1) and United Kingdom (KJ409633.1). We used species specific primers ITS5（5'-GGAAGTAAAAGTCGTAACAAGG-3'）and PITSr3 (5'AGCGCAGACATGCCGCAA-3') to amplify the product (Bulman & Marshall 1997; EPPO 2017). A single 434bp fragment was obtained from Hezhang and Weining populations. A host test for the Hezhang and Weining populations were performed by inoculating 1,000 eggs per plant of varieties Qingshu 9, Huize 2 and Hezuo 88 grown in the pots containing 800 cm3 of sterilized soil (soil: sand ratio was 3:1), and four replications were tested in greenhouse under 16 h light, 22°C in the day and 8 h dark in the night. At 90 days post inoculation, 32.6 ± 7, 31.2 ± 8, and 29.5 ± 8 females and cysts were extracted from the infected roots and soils of the varieties Qingshu 9, Huize 2 and Hezuo 88, respectively. No females and cysts were observed on the control plants. The trial indicated that potato cultivars Qingshu 9, Huize 2 and Hezuo 88 are hosts for the Hezhang and Weining populations of Globodera rostochiensis. To the best of our knowledge, this is the first detection of potato cyst nematode Globodera rostochiensis in Guizhou Province, China.

Sustainable management of the potato cyst nematode, Globodera rostochiensis, with two microbial fermentation products.

Potato cyst nematodes (PCN) cause an overall 9% yield loss of total potato production worldwide. Research on sustainable management of PCN is still under progress. Two microbial fermentation products (MFPs) from Alltech, a proprietary blend formulated with a bacterial fermentation media and a Cu component (MFP5075), and a microbial based product (MFP3048), were evaluated against the PCN Globodera rostochiensis. In laboratory tests, effectiveness of the MFPs was recorded in terms of PCN juveniles (J2) hatching from cysts, J2 mortality and their attraction toward potato roots using pluronic gel. Greenhouse trials were conducted to study the effect of the products on PCN infestation in potato plants and a pilot scale experiment was conducted to study the impact of these MFPs on nematode biodiversity in garden soil. All treatments were performed within a concentration range of 0, 0.5, 1, and 2% (v/v) MFP5075 and 2, 6, 10, and 20 g/10 ml (w/v) MFP3048. The attraction assay, juvenile hatching and the PCN infestation in plants results were compared with those in an untreated control and a commercial nematicide (Nemguard™) treatment. After 24 h of treatment with 0.5 and 1% MFP5075, a 13-fold and 43-fold reduction, respectively, relative to J2 survival was recorded compared to that of untreated control. However, no J2 survived at 2% and above concentration of the MFP5075 treatment. Treatment with MFP3048 was effective in causing mortality of J2 only after 48-h. In the attraction assay, a 20-fold and 8-fold reduction in number of J2 attracted toward potato roots was observed, when treated with MFP5075, compared to the untreated and the Nemguard™ treatment, respectively. Subsequently, 30–35 PCN cysts were treated with both products dissolved in potato root diffusate and the results were recorded in terms of number of J2 hatched in each treatment after 10 days. No J2 hatched in the MFP5075 treatment, whereas mean numbers (±SE) of 243 ± 11.5, 30 ± 2.5, and 1.3 ± 0.6 J2 were noted in the untreated control, MFP3048, and the Nemguard™ treatment, respectively. The treatment with the MFPs compromised the integrity of the unhatched J2, which looked granular, whereas the internal organs of the unhatched J2 could be clearly identified in the untreated control. In plant infestation studies, treatment with MFP3048 and MFP5075 caused 90.6 and 84.9 percent reduction in PCN infestation, respectively, in terms of cysts developed on roots compared to untreated control. Overall, results indicate that the MFPs could potentially provide a promising alternative for sustainable PCN management.

PM 3/68 (2) Testing of potato varieties to assess resistance to Globodera rostochiensis and Globodera pallida

Specific scopeThis Standard describes the testing of potato varieties to assess resistance to the potato cyst nematodes Globodera rostochiensis and Globodera pallida. It should be used to fulfil requirements mentioned in PM 9/26 National regulatory control system for Globodera rostochiensis and Globodera pallida.Specific approval and amendmentFirst approved in 1990–091.Revised and edited as an EPPO Standard in 2006–09.First revision of the EPPO Standard approved in 2021–09. 2Authors and contributors are given in the Acknowledgements section.

Assessment of resistance of potato hybrids from the Russian Potato Research Center’s collection to Globodera rostochiensis

The potato cyst nematodes (PCN) Globodera rostochiensis and Globodera pallida are the most common pests feeding on potato roots. These pests have an aggressive distribution dynamic and bring a lot of damage to yield. The study presents results of comprehensively test new potato genotypes for resistance to the golden potato nematode (Globodera rostochiensis), for its further use in breeding and the creation of economically valuable resistant varieties. Almost half of the samples showed laboratory resistance to golden potato nematode, the rest were susceptible. 26 samples have shown the presence of two molecular markers (N146, N19), indicating the presence of H1 gene. Almost all samples showed a correspondence between laboratory resistance and the presence of H1 gene markers.

Comparative genomics of two inbred lines of the potato cyst nematode Globodera rostochiensis reveals disparate effector family-specific diversification patterns

BackgroundPotato cyst nematodes belong to the most harmful pathogens in potato, and durable management of these parasites largely depends on host-plant resistances. These resistances are pathotype specific. The current Globodera rostochiensis pathotype scheme that defines five pathotypes (Ro1 - Ro5) is both fundamentally and practically of limited value. Hence, resistant potato varieties are used worldwide in a poorly informed manner.ResultsWe generated two novel reference genomes of G. rostochiensis inbred lines derived from a Ro1 and a Ro5 population. These genome sequences comprise 173 and 189 scaffolds respectively, marking a ≈ 24-fold reduction in fragmentation as compared to the current reference genome. We provide copy number variations for 19 effector families. Four dorsal gland effector families were investigated in more detail. SPRYSECs, known to be implicated in plant defence suppression, constitute by far the most diversified family studied herein with 60 and 99 variants in Ro1 and Ro5 distributed over 18 and 26 scaffolds. In contrast, CLEs, effectors involved in feeding site induction, show strong physical clustering. The 10 and 16 variants cluster on respectively 2 and 1 scaffolds. Given that pathotypes are defined by their effectoromes, we pinpoint the disparate nature of the contributing effector families in terms of sequence diversification and loss and gain of variants.ConclusionsTwo novel reference genomes allow for nearly complete inventories of effector diversification and physical organisation within and between pathotypes. Combined with insights we provide on effector family-specific diversification patterns, this constitutes a basis for an effectorome-based virulence scheme for this notorious pathogen.

Rapid and sensitive detection of potato cyst nematode Globodera rostochiensis by loop-mediated isothermal amplification assay.

The online version contains supplementary material available at 10.1007/s13205-021-02830-8.

Genome Resources of Two Pathotypes of the Potato Cyst Nematode Globodera rostochiensis from New York.

The potato cyst nematode Globodera rostochiensis is a regulated pest posing a serious threat to potato production worldwide. Although the endemic pathotype (Ro1) of G. rostochiensis has been confined to New York State for several decades as a result of quarantine regulations and management with resistant potato cultivars, a virulent pathotype, Ro2, has emerged, for which control measures are scarce. The ability to detect Ro2 early in fields is necessary to sustain the success of G. rostochiensis quarantine in the United States. Here, we report the comparative analysis of whole-genome sequences of multiple single-cyst-derived Ro1 and Ro2 lines, propagated from original field populations. The identified discriminant variants are good targets for developing molecular diagnostic tools for differentiating G. rostochiensis pathotypes in New York.

A Protocol for Obtaining PCR-Quality DNA from Formalin Preserved Cysts of Potato Cyst Nematode Globodera rostochiensis

A Protocol for Obtaining PCR-Quality DNA from Formalin Preserved Cysts of Potato Cyst Nematode Globodera rostochiensis

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.

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).

Management of Potato Cyst Nematodes Using Liquid Bioformulations of Pseudomonas fluorescens, Purpureocillium lilacinum and Trichoderma viride

The field efficacy of liquid formulations of Pseudomonas fluorescens, Purpureocillium lilacinum and Trichoderma viride was investigated against natural populations of potato cyst nematodes (PCNs) Globodera rostochiensis and Globodera pallida. Two field experiments were conducted using these biocontrol agents applied as seed treatment (ST) at 1 L t−1 of seed and soil drenching (SD) at 5 L ha−1. Their effect was compared with carbofuran 3 G at 1 kg a.i. ha−1. Results showed that all the tested biocontrol agents were capable to reduce PCN egg density or multiplication rate, root penetration and egg numbers cyst−1 at various levels. The biocontrol efficacy also varied according to their delivery method. P. fluorescens-ST was found causing the highest reduction of egg density (83.1–86.5%), multiplication rate (83.1–86.5%), root penetration (67.1–68.1%) and egg numbers cyst−1 (35.4–36.0%). Similar efficacy was observed in P. lilacinum-SD that reduced egg density by 80.9–85.0%, multiplication rate by 80.7–84.3%, root penetration by 62.0–64.4% and egg numbers cyst−1 by 44.3–49.3%. The potato plants from P. fluorescens-ST and P. lilacinum-SD plots were 31.1–49.5% taller than untreated plants which also resulted in 27.2–32.0% higher tuber yield in P. fluorescens-ST and 25.9–30.2% in P. lilacinum-SD plots. The root colonisation of introduced P. fluorescens was 8.6–13.1 times higher in ST than SD. The trend was vice versa in P. lilacinum that colonised 3.1–3.6 times better in SD method than as ST. Their efficacy was comparable to carbofuran application. It is concluded that P. fluorescens-ST at 1 L t−1 of seed and P. lilacinum-SD at 5 L ha−1 are highly effective for management of PCN under naturally infested field conditions.

QTL for Resistance to Globodera rostochiensis Pathotype Ro2 and G. pallida Pathotype Pa2/3 in Autotetraploid Potato

The golden and white potato cyst nematodes (Globodera rostochiensis and G. pallida, respectively) are devastating quarantine pests of potatoes. The most widely distributed pathotype of the golden nematode, Ro1, is well controlled by the H1 resistance gene. A pathotype that overcomes H1, Ro2, has been detected on several farms in New York State. To map Ro2 resistance gene(s), two autotetraploid parental clones – NY121 (Ro2 resistant) and NY115 (susceptible) – along with 182 F1 offspring were genotyped with 8303 SNP markers, and the resistance of each clone to Ro2 was assessed with a greenhouse pot assay. Analysis with TetraploidSNPMap identified two Ro2 resistance QTL on chromosome 5: one QTL was located at 26 cM and explained 24.4% of the variation for resistance, while the second at 59 cM co-localized with a marker (57R) known to be tightly linked to H1 and explained 23.8% of the residual variation. Subsequent inoculation with G. pallida revealed that the chromosome 5 locus at 26 cM also conferred some resistance against pathotype Pa2/3, explaining 9.2% of the variation. A second QTL that increased susceptibility to Pa2/3 was located at 15 cM on chromosome 10 and explained 6.9% of the variation. The resistance gene(s) at 26 cM on chromosome 5 may correspond to previously described Grp1; a marker diagnostic for this region would be useful for applied potato breeding.