Evaluation of PCR, IEF and ELISA techniques for the detection and identification of potato cyst nematodes from field soil samples in England and Wales

First report of morphological and molecular characterization of Moroccan populations of Globodera pallida

Potato cyst nematodes (PCNs) are the most important potato pest causing major crop losses across the world with a quarantine status in many countries. In Morocco, several potato crops are infected with PCNs and the monitoring of potato production as well as the control of import and export of potato seeds are currently carried out by morphological methods. The present work was aimed to use molecular and morphometric methods for identifying and differentiating PCN species in Morocco for the first time. The morphological identification of PCN species from collected soil samples were carried out using the shape of the cysts, the length of the stylet, the number of cuticular ridges, and the Granek’s ratio. The J2 had a slightly shorter body length, the number of cuticular ridges was 9 and the Granek’s ratio averaged 2.2. The morphobiometric analysis revealed proximity of the Moroccan population to G. pallida species. PCNs sampled from contaminated fields were analyzed molecularly using PCR. DNA amplification was performed using the multiplex PCR method and PCR-RFLP from the ITS region of the total genomic DNA compared to multiplex PCR-specific DNA sequences. All confirmed the presence G. pallida in all samples of the Moroccan PCN populations.

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.

PCR detection of potato cyst nematode

Potato cyst nematode (PCN) is responsible for losses in potato production totalling millions of euros every year in the EC. It is important for growers to know which species is present in their land as this determines its subsequent use. The two species Globodera pallida and Globodera rostochiensis can be differentiated using an allele-specific PCR.

Advances in molecular-based diagnostics in meeting crop biosecurity and phytosanitary issues

Awareness of crop biosecurity and phytosanitation has been heightened since 9/11 and the unresolved anthrax releases in October 2001. Crops are highly vulnerable to accidental or deliberate introductions of crop pathogens from outside U.S. borders. Strategic thinking about protection against deliberate or accidental release of a plant pathogen is an urgent priority. Rapid detection will be the key to success. This review summarizes recent progress in the development of rapid real-time PCR protocols and evaluates their effectiveness in a proposed nationwide network of diagnostic laboratories that will facilitate rapid diagnostics and improved communication.

Determination of relative proportions of Globodera species in mixed populations of potato cyst nematodes using PCR product melting peak analysis

Summary Using a novel approach based on melting peak analysis of PCR products, we have developed a semi-quantitative assay to measure the relative proportions of Globodera pallida and Globodera rostochiensis in a sample of potato cyst nematodes (PCN). The method depends on a competitive multiplex PCR where the products of each species can be separated by their distinct melting temperatures (T(m)). The melting curves of the products are measured by continual fluorescence monitoring in the presence of the intercalating dye SYBR Green I whilst gradually increasing the temperature. Varying the proportion of cysts of each PCN species gave rise to melting curves with different peak heights, which reflected the relative amounts of each DNA in the sample. By calculating the ratio of the melting peak heights at the Tm of each product and comparing it with standards run under the same conditions, it was possible to estimate the proportion of each product in the mixture. Sensitivity was such that 2% of G. pallida cysts in a mixture could be detected. All results predicted by the analysis were confirmed by agarose gel electrophoresis of the PCR products. The method is rapid, reproducible and following DNA extraction, up to 25 samples can be analysed in an hour.