Belowground Chemical Interactions: An Insight Into Host-Specific Behavior of Globodera spp. Hatched in Root Exudates From Potato and Its Wild Relative, Solanum sisymbriifolium

Understanding belowground chemical interactions between plant roots and plant-parasitic nematodes is immensely important for sustainable crop production and soilborne pest management. Due to metabolic diversity and ever-changing dynamics of root exudate composition, the impact of only certain molecules, such as nematode hatching factors, repellents, and attractants, has been examined in detail. Root exudates are a rich source of biologically active compounds, which plants use to shape their ecological interactions. However, the impact of these compounds on nematode parasitic behavior is poorly understood. In this study, we specifically address this knowledge gap in two cyst nematodes, Globodera pallida, a potato cyst nematode and the newly described species, Globodera ellingtonae. Globodera pallida is a devastating pest of potato (Solanum tuberosum) worldwide, whereas potato is a host for G. ellingtonae, but its pathogenicity remains to be determined. We compared the behavior of juveniles (J2s) hatched in response to root exudates from a susceptible potato cv. Desirée, a resistant potato cv. Innovator, and an immune trap crop Solanum sisymbriifolium (litchi tomato – a wild potato relative). Root secretions from S. sisymbriifolium greatly reduced the infection rate on a susceptible host for both Globodera spp. Juvenile motility was also significantly influenced in a host-dependent manner. However, reproduction on a susceptible host from juveniles hatched in S. sisymbriifolium root exudates was not affected, nor was the number of encysted eggs from progeny cysts. Transcriptome analysis by using RNA-sequencing (RNA-seq) revealed the molecular basis of root exudate-mediated modulation of nematode behavior. Differentially expressed genes are grouped into two major categories: genes showing characteristics of effectors and genes involved in stress responses and xenobiotic metabolism. To our knowledge, this is the first study that shows genome-wide root exudate-specific transcriptional changes in hatched preparasitic juveniles of plant-parasitic nematodes. This research provides a better understanding of the correlation between exudates from different plants and their impact on nematode behavior prior to the root invasion and supports the hypothesis that root exudates play an important role in plant-nematode interactions.

Improving a pest management tool for scenario analysis of economic populations of Globodera pallida

Summary Globodera pallida is the most damaging pest of potato in the UK. This work underpins enhancement of a well-established, web-based scenario analysis tool for its management by recommending additions and modifications of its required inputs and a change in the basis of yield loss estimates. The required annual decline rate of the dormant egg population is determined at the individual field sample level to help define the required rotation length by comparing the viable egg content of recovered cysts to that of newly formed cysts for the same projected area. The mean annual decline was 20.4 ± 1.4% but ranged from 4.0 to 39.7% annum−1 at the field level. Further changes were based on meta-analysis of previous field trials. Spring rainfall in the region where a field is located and cultivar tolerance influence yield loss. Tolerance has proved difficult to define for many UK potato cultivars in field trials but uncertainty can be avoided without detriment by replacing it with determinacy integers. They are already determined to support optimisation of nitrogen application rates. Multiple linear regression estimates that loss caused by pre-plant populations of up to 20 viable eggs (g soil)−1 varies from ca 0.2 to 2.0% (viable egg)−1 (g soil)−1 depending on cultivar determinacy and spring rainfall. Reliability of the outcomes from scenario analysis requires validation in field trials with population densities over which planting is advisable.

Globodera pallida. [Distribution map].

A new distribution map is provided for Globodera pallida (Stone) Behrens. Chromadorea: Tylenchida: Heteroderidae. Hosts: Solanaceae, especially potato (Solanum tuberosum), tomato (S. lycopersicum) and aubergine (S. melongena). Information is given on the geographical distribution in Africa (Algeria, Kenya, Morocco, Tunisia), Asia (India, Himachal Pradesh, Jammu and Kashmir, Kerala, Tamil Nadu, Uttarakhand, Indonesia, Java, Japan, Hokkaido, Pakistan, Turkey), Europe (Austria, Belgium, Bosnia and Herzegovina, Bulgaria, Croatia, Cyprus, Czechia, Denmark, Estonia, Faroe Islands, Finland, France, Germany, Greece, Crete, Hungary, Iceland, Ireland, Italy, Sicily, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Mainland, Madeira, Romania, Serbia, Slovakia, Slovenia, Spain, Balearic Islands, Canary Islands, Sweden, Switzerland, Ukraine, United Kingdom, England, Northern Ireland, Scotland, Wales), North America (Canada, Newfoundland and Labrador, Costa Rica, Panama, United States, Idaho), Oceania (New Zealand), South America (Argentina, Bolivia, Chile, Colombia, Ecuador, Falkland Islands, Peru, Venezuela).

Comparative genomics among three cyst nematode species reveals distinct evolutionary histories among effector families and an irregular distribution of effector-associated promoter motifs

Potato cyst nematodes (PCNs), an umbrella term used for two species, Globodera pallida and G. rostochiensis, belong worldwide to the most harmful pathogens of potato. Pathotype-specific host plant resistances are an essential handle for PCN control. However, the poor delineation of G. pallida pathotypes hampers the efficient use of available host plant resistances. Long-read sequencing technology allowed us to generate a new reference genome of G. pallida population D383 and, as compared to the current reference, the new genome assembly is 42 times less fragmented. For comparison of diversification patterns of six effector families between G. pallida and G. rostochiensis, an additional reference genome was generated for an outgroup, the beet cyst nematode Heterodera schachtii (IRS population). Large evolutionary contrasts in effector family topologies were observed. While VAPs diversified before the split between the three cyst nematode species, the families GLAND5 and GLAND13 only expanded in PCN after their separation from the genus Heterodera. Although DNA motifs in the promoter regions thought to be involved in the orchestration of effector expression (DOG boxes) were present in all three cyst nematode species, their presence is not a necessity for dorsal gland-produced effectors. Notably, DOG box dosage was only loosely correlated with expression level of individual effector variants. Comparison of the G. pallida genome with those of two other cyst nematodes underlined the fundamental differences in evolutionary history between effector families. Re-sequencing of PCN populations with deviant virulence characteristics will allow for the linking of these characteristics with the composition of the effector repertoire as well as for the mapping of PCN diversification patterns resulting from extreme anthropogenic range expansion.

UPLC-MS/MS analysis and biological activity of the potato cyst nematode hatching stimulant, solanoeclepin A, in the root exudate of Solanum spp.

Main conclusion Solanoeclepin A is a hatching stimulant for potato cyst nematode in very low (pM) concentrations. We report a highly sensitive method for the analysis of SolA in plant root exudates using UHPLC-MS/MS and show that there is considerable natural variation in SolA production in Solanum spp. corresponding with their hatching inducing activity. Abstract Potato cyst nematode (PCN) is a plant root sedentary endoparasite, specialized in the infection of solanaceous species such as potato (Solanum tuberosum) and tomato (Solanum lycopersicum). Earlier reports (Mulder et al. in Hatching agent for the potato cyst nematode, Patent application No. PCT/NL92/00126, 1996; Schenk et al. in Croat Chem Acta 72:593–606, 1999) showed that solanoeclepin A (SolA), a triterpenoid metabolite that was isolated from the root exudate of potato, induces the hatching of PCN. Its low concentration in potato root exudate has hindered progress in fully understanding its hatching inducing activity and exploitation in the control of PCN. To further investigate the role of SolA in hatching of PCN, the establishment of a highly sensitive analytical method is a prerequisite. Here we present the efficient single-step extraction and UHPLC-MS/MS based analysis for rapid determination of SolA in sub-nanomolar concentrations in tomato root exudate. This method was used to analyze SolA production in different tomato cultivars and related solanaceous species, including the trap crop Solanum sisymbriifolium. Hatching assays with PCN, Globodera pallida, with root exudates of tomato genotypes revealed a significant positive correlation between SolA concentration and hatching activity. Our results demonstrate that there is natural variation in SolA production within solanaceous species and that this has an effect on PCN hatching. The analytical method we have developed can potentially be used to support breeding for crop genotypes that induce less hatching and may therefore display reduced infection by PCN.

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.

The impact of management strategies on the development and status of potato cyst nematode populations in Switzerland: An overview from 1958 to present

Globodera rostochiensis and Globodera pallida are some of the most successful and highly specialized plant-parasitic nematodes, and appear among the most regulated quarantine pests globally. In Switzerland, they have been monitored by annual surveys since their first detection in Swiss soil, in 1958. The dataset created was reviewed to give an overview of the development and actual status of PCN in Switzerland. Positive fields represent 0.2% of all the samples analyzed, and currently their distribution is limited to central-west and western Switzerland, suggesting that new introduction of PCN and the spread of the initial introduced PCN populations did not occur. In this way, the integrated management used in Switzerland appears to be effective. However, the increasing availability of potato varieties with resistance to G. rostochiensis and the limited availability of varieties with resistance to G. pallida, together with other biotic and abiotic factors promoted changes in the dominance of either species. Consequently, an extended monitoring program would be of interest to Swiss farmers, to avoid favoring virulent traits that could be present within Swiss Globodera populations.

Assessment and Validation of Globodera pallida as a Novel In Vivo Model for Studying Alzheimer’s Disease

Background: Whole transgenic or non-transgenic organism model systems allow the screening of pharmacological compounds for protective actions in Alzheimer’s disease (AD). Aim: In this study, a plant parasitic nematode, Globodera pallida, which assimilates intact peptides from the external environment, was investigated as a new potential non-transgenic model system of AD. Methods: Fresh second-stage juveniles of G. pallida were used to measure their chemosensory, perform immunocytochemistry on their neurological structures, evaluate their survival rate, measure reactive oxygen species, and determine total oxidized glutathione to reduced glutathione ratio (GSSG/GSH) levels, before and after treatment with 100 µM of various amyloid beta (Aβ) peptides (1–40, 1–42, 17–42, 17–40, 1–28, or 1–16). Wild-type N2 C. elegans (strain N2) was cultured on Nematode Growth Medium and directly used, as control, for chemosensory assays. Results: We demonstrated that: (i) G. pallida (unlike Caenorhabditis elegans) assimilates amyloid-β (Aβ) peptides which co-localise with its neurological structures; (ii) pre-treatment with various Aβ isoforms (1–40, 1–42, 17–42, 17–40, 1–28, or 1–16) impairs G. pallida’s chemotaxis to differing extents; (iii) Aβ peptides reduced survival, increased the production of ROS, and increased GSSG/GSH levels in this model; (iv) this unique model can distinguish differences between different treatment concentrations, durations, and modalities, displaying good sensitivity; (v) clinically approved neuroprotective agents were effective in protecting G. pallida from Aβ (1–42) exposure. Taken together, the data indicate that G. pallida is an interesting in vivo model with strong potential for discovery of novel bioactive compounds with anti-AD activity.