Phenotypic and DNA Marker-Assisted Characterization of Russian Potato Cultivars for Resistance to Potato Cyst Nematodes

Potato is one of the most important food crops in the world and also in the Russian Federation. Among harmful organisms reducing potato yield potential, the potato cyst nematodes (PCN) are considered to be ones of the most damaging pests. Information on PCN resistant cultivars is important for potato breeding and production. Russian potato cultivars are characterized in the state-bio-test program for resistance to only one PCN species Globodera rostochiensis and one pathotype Ro1 which is reported to be present in the country. This study aimed to find domestic cultivars with multiple resistances to different PCN species and different pathotypes using phenotyping coupled with molecular marker analysis due to the risk of the occasional introduction of new pests. The phenotypic response was determined by the inoculation of plants with pathotypes Ro5 of G. rostochiensis and Pa3 of G. pallida. The obtained results were supplemented by the state-bio-test data on resistance to Ro1 of G. rostochiensis. Nine of 26 Russian cultivars were resistant both to Ro5 and Ro1 pathotypes and two cultivars possess multiple resistances to both PCN species. Most tested molecular markers associated with the Gpa2, GpaVvrn, GpaVsspl, Grp1 loci showed discrepancies with phenotyping. However, a predictive haplotype and epistatic effect were detected.

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.

Occurrence and molecular characterization of cyst nematode species (Globodera spp.) associated with potato crops in Colombia

Potato cyst nematodes (PCN) from the genus Globodera spp. cause major losses in the potato (Solanum tuberosum) industry worldwide. Despite their importance, at present little is known about the status of this plant pathogen in cultivated potatoes in Colombia. In this study, a total of 589 samples collected from 75 geographic localities in nine potato producing regions of Colombia (Cundinamarca, Boyacá, Antioquia, Nariño, Santander, Norte de Santander, Tolima, Caldas and Cauca) were assayed for the presence of potato cyst nematodes. Fifty-seven percent of samples tested positive for PCN. Based on phylogenetic analysis of the internal transcribed spacer region (ITS1-5.8S-ITS2) of the rRNA gene and D2-D3 expansion segments of the 28S rRNA gene, all populations but one were identified as Globodera pallida. Sequences of G. pallida from Colombia formed a monophyletic group closely related to Peruvian populations, with the lowest average number of nucleotide substitutions per site (Dxy = 0.002) and net nucleotide substitutions per site (Da = 0.001), when compared to G. pallida populations from Europe, South and North America. A single sample formed a well-supported subclade along with G. rostochiensis and G. tabacum from Japan, USA and Argentina. To our knowledge this is the first comprehensive survey of Globodera populations from Colombia that includes genetic data. Our findings on species diversity and phylogenetic relationships of Globodera populations from Colombia may help elucidate the status and distribution of Globodera species, and lead to the development of accurate management strategies for the potato cyst nematodes.

Resisting Potato Cyst Nematodes With Resistance

Potato cyst nematodes (PCN) are economically important pests with a worldwide distribution in all temperate regions where potatoes are grown. Because above ground symptoms are non-specific, and detection of cysts in the soil is determined by the intensity of sampling, infestations are frequently spread before they are recognised. PCN cysts are resilient and persistent; their cargo of eggs can remain viable for over two decades, and thus once introduced PCN are very difficult to eradicate. Various control methods have been proposed, with resistant varieties being a key environmentally friendly and effective component of an integrated management programme. Wild and landrace relatives of cultivated potato have provided a source of PCN resistance genes that have been used in breeding programmes with varying levels of success. Producing a PCN resistant variety requires concerted effort over many years before it reaches what can be the biggest hurdle—commercial acceptance. Recent advances in potato genomics have provided tools to rapidly map resistance genes and to develop molecular markers to aid selection during breeding. This review will focus on the translation of these opportunities into durably PCN resistant varieties.

Effect of steroidal glycoalkaloids on hatch and reproduction of the potato cyst nematode Globodera pallida

Steroidal glycoalkaloids (SGAs) are phytoanticipins found in solanaceous crops that act as the first line of chemical defense against pathogen attacks. Solanum sisymbriifolium, a trap crop for potato cyst nematodes, has been shown to effectively reduce populations of Globodera pallida. Solanum sisymbriifolium contains α- solamargine and other solasodine type glycoalkaloids that may contribute to plant defenses. The current study evaluated the influence of solanaceous SGAs on G. pallida hatch, development, and reproduction. Exposure to α- solamargine and α- solamarine reduced G. pallida hatch by 65 % and 87 % respectively. Exposure of G. pallida cysts with the glycoalkaloids α- solamargine and solasodine significantly reduced infection in susceptible potato Russet Burbank by 98 and 94 % compared to the control. Exposure of cysts to either solasodine or solamargine significantly reduced reproduction of G. pallida on Russet Burbank by 99 % compared to the control. The study demonstrated the deleterious effect of SGAs on G. pallida hatch, infection, and reproduction.

Integrative Morphometric and Molecular Approach to Update the Impact and Distribution of Potato Cyst Nematodes Globodera rostochiensis and Globodera pallida (Tylenchida: Heteroderidae) in Algeria

Morphological and molecular studies were conducted to characterize the specific identity of 36 isolates of potato cyst nematodes (PCNs) recovered from soil samples collected in several potato producing areas of Algeria. Morphometric data revealed that 44% of isolates contained Globodera pallida alone, 28% contained Globodera rostochiensis alone and 28% mixtures of the two species. Morphometric values of cysts and second-stage juveniles were generally distributed with slight differences in the expected ranges for both Globodera species. Inter- and intraspecific morphometric variability in nematode isolates was noted. Molecular analysis using conventional multiplex PCR with species-specific primers and TaqMan real-time PCR confirmed the morphological identification. In addition, the distribution of both potato cyst nematode species throughout various parts of the country was investigated. In the central areas, the isolates of G. pallida alone dominate, whereas isolates of G. rostochiensis alone are more frequent in the southern areas. In the eastern regions, mixed isolates are more representative. Most isolates examined in the western areas are mixtures of the two species or G. rostochiensis alone. Comparatively, G. pallida remains the most widely distributed species in its geographic range. This study confirms the presence of two PCN species, G. pallida and G. rostochiensis, in Algeria and provides additional information on their biogeographic distribution.

Taxonomy, Morphological and Molecular Identification of the Potato Cyst Nematodes, Globodera pallida and G. rostochiensis

The scope of this paper is limited to the taxonomy, detection, and reliable morphological and molecular identification of the potato cyst nematodes (PCN) Globodera pallida and G. rostochiensis. It describes the nomenclature, hosts, life cycle, pathotypes, and symptoms of the two species. It also provides detailed instructions for soil sampling and extraction of cysts from soil. The primary focus of the paper is the presentation of accurate and effective methods to identify the two principal PCN species.

The need for new approaches for management of potato cyst nematodes: the view from the Rhineland-Palatinate.

Potato is an important crop throughout Europe and especially in Germany where potatoes are grown on over 250,000 hectares. The production of potato worldwide is negatively affected by the presence of the golden and the white potato cyst nematodes (PCN) Globodera rostochiensis and G. pallida. The two species originated in South America. PCN is present with restricted distribution in all counties in Germany where potato is produced and these infestations are strictly regulated. Both species are present and often in mixed populations. Potato yield and overall production is negatively impacted by both species of PCN from planting to harvest, but there are differences in importance within the country and on crop type. This chapter discusses the economic importance, host range, distribution, symptoms of damage, biology and life cycle, integrated nematode management (including the use of nematicides, resistant cultivars and rotation), and interactions with other nematodes and pathogens, of PCN. Results are also summarized of field trials conducted between 2010 and 2017 to compare the efficacy of resistant cultivars and nematicide Nemathorin 10G with the alternative control techniques biofumigation and sowing of Solanum sisymbriifolium that has PCN suppressive activity.

Will the Globodera pallida epidemic signal the end of the seed potato industry in Scotland?

Among pests and diseases of potatoes, British potato growers consider potato cyst nematodes (PCN: Globodera pallida and G. rostochiensis) to cause the most damage. By feeding on the roots, PCN stunt plant growth, adversely affecting yields, tuber size and skin finish. Yield losses depend on the population level of the PCN in the soil, the soil type and the tolerance of the potato cultivar to the nematode damage. The increase in G. pallida has been most marked in the county of Angus, traditionally the part of Scotland most intensively cultivated with potatoes. The incidence of G. pallida in Angus is estimated as 9% of the area used for potato production, accounting for 68% of the total area of G. pallida infested land in Scotland. This chapter discusses the economic importance, host range, distribution, symptoms of damage, biology and life cycle, recommended integrated nematode management, and management optimization of PCN in Scotland. Future research requirements are also mentioned.