The potato cyst nematodes (PCNs)
Globodera rostochiensis
and
Globodera pallida
are internationally recognized quarantine pests. Although not widely distributed in either the United States or Canada, ...both are present and are regulated by the national plant protection organizations (NPPOs) of each country.
G. rostochiensis
was first discovered in New York in the 1940s, and
G. pallida
was first detected in a limited area of Idaho in 2006. In Canada,
G. rostochiensis
and
G. pallida
were first detected in Newfoundland in 1962 and 1977, respectively, and further detections of
G. rostochiensis
occurred in British Columbia and Québec, most recently in 2006. Adherence to a stringent NPPO-agreed-upon phytosanitary program has prevented the spread of PCNs to other potato-growing areas in both countries. The successful research and regulatory PCN programs in both countries rely on a network of state, federal, university, and private industry cooperatorspursuing a common goal of containment, management eradication, and regulation. The regulatory and research efforts of these collaborative groups spanning from the 1940s to the present are highlighted in this review.
Potato cyst nematodes (PCNs; Globodera spp.) cause significant losses in worldwide cultivated potato (Solanum tuberosum) crops. In Colombia, PCN was first reported in 1970 (Baeza 1972), although this ...report lacked a comprehensive species description and diagnosis. After that, G. pallida has been the only PCN species reported affecting potatoes in the main producing regions of Colombia (Evans et al. 1975; Nieto et al. 1983; Vallejo et al. 2021). However, in the survey conducted by Vallejo et al. (2021), a single sample from Chocontá, Cundinamarca in the central region of the country (N 5,22396046668291, W -73,6571338400244) showed molecular characters similar to G. rostochiensis. As correct identification is essential for effective pest management, the location was re-sampled in September 2022. From the soil samples collected, PCN cysts and second-stage juveniles (J2s) were retrieved from soil using Fenwick and centrifugation methods, respectively. Morphometric characters of cysts (n = 53) were consistent with G. rostochiensis, with a length without neck (L) ranging from 451 to 614 μm (X̅ = 546.9 ± 20.3 μm), width (W) from 424 to 658 μm (X̅ = 546.9 ± 25.5 μm) and L/W ratio was 1.00 ± 0.02. Distance from anus to vulva varied from 41 to 109 μm (X̅ =75.67 ± 13.8 μm), Granek's ratio from 2.3 to 5.5 μm (X̅ = 3.89 ± 0.7 μm), and the number of cuticular ridges between the vulva and the anus were 14 to 20 (X̅ = 16.19 ± 1.7). The second-stage juvenile (n = 90) length ranged from 394 to 547 μm (X̅ = 495.62 ± 31.0 μm), the stylet length varied from 18 to 24 μm (X̅ = 21.21 ± 0.9 μm) with rounded knobs. The length of the hyaline tail ranged from 20 - 31 μm (X̅ = 24.09 ± 1.92) and the true tail from 31- 56 μm (X̅ = 48.30 ± 5.71 μm). Molecular analyses confirmed morphological identification. DNA was extracted from cysts and J2s. PCR was performed for the 28S rDNA D2-D3 segment using primers D2A and D3B (Subbotin et al. 2006), and for the mitochondrial COI gene region using primers JB3 and JB5 (Derycke et al. 2005). BLAST analyses of target 28S rDNA D2-D3 sequences (OP293373-OP293380) showed 100% identity of the 658 bp to other sequences on Genbank, including isolates from Turkey, United Kingdom, and Iran (MK311329.1, MG994942.1, KU297659.1, and KU297658.1). Similarly, the target COI region sequences (OP297993-OP298001) were 100% identical to the 407 bp of G. rostochiensis POT01 isolate from Germany, and 99.75% identical to voucher NRM67 from Indonesia, and isolate CD2200 from USA (MF773722.1, MT240262.1, and MN095979.1). Phylogenetic analysis of both gene regions strongly supported G. rostochiensis, with the Colombian sequences clustering with MH399815.1, and KU297654.1 isolates for the COI and 28S regions, respectively (Fig. 1S). In addition, a pathogenicity test was conducted in the greenhouse. For this, ten cysts were inoculated to potato plants of Criolla variety grown in 5 pots of 15 cm diameter with sterile soil and sand (1:1). Noninoculated plants served as controls (three replicates each). After three months, 54 ± 23 cysts/100 g of soil were isolated from inoculated plants (Fig. 2S), resulting in a reproduction factor (R=Pf/Pi) of 4.54 ± 0.86, while no yellow females or cysts were observed on the control plants. To our knowledge, this is the first report of G. rostochiensis in Colombia. This is an important pest that causes serious yield losses of potatoes and is a quarantine nematode in many countries (EPPO 2017). Further studies are necessary to prevent the spread of this PCN species in the main producing potato regions of Colombia.
Plant parasitic nematodes need to overcome the barrier presented by the plant cell wall in order to invade their host. A variety of plant cell wall degrading enzymes are present in endoparasitic ...nematodes including enzymes that degrade cellulose (beta 1,4 endoglucanases) and various pectin components. We describe the cloning and functional analysis of genes encoding GH53 arabinogalactan endo-1,4-beta-galactosidases from three related plant parasitic nematodes Globodera rostochiensis, Globodera pallida and Rotylenchulus reniformis. Phylogenetic and structural analyses strongly indicate that these genes have been acquired by horizontal gene transfer from bacteria. We show that the genes are expressed at invasive stages of the parasites in the secretory gland cells. We also demonstrate that the enzymes from these species are biochemically active, showing the expected hydrolytic enzymatic activity when galactan was used as a substrate. This work further demonstrates the importance of cell wall degradation to the success of the parasitic process and the extensive role that horizontal gene transfer has played in the evolution of plant parasitism by nematodes.
•Some plant-parasitic nematodes, including cyst nematodes and related species, produce GH53 endo β 1,4 galactanases.•The genes encoding these proteins are expressed in the pharyngeal gland cells of these nematodes, and secreted into the host.•These genes are expressed at the early stages of the life cycle, consistent with a role in the host-parasite interaction.•The proteins encoded by these genes specifically metabolise galactan as a substrate.
Adding biochar at the onset of composting has proven to be beneficial for this process, and when added to the soil, this biochar-blended (BB) compost has outperformed biochar on soil quality but had ...a similar effect as the compost. Because soil quality gets more and more attention as an important tool for soil health, pot trials were conducted to evaluate the effect of compost and biochar alone, and biochar-blended (BB) compost on disease suppression. In addition, it was investigated whether the disease suppression was associated with changes in soil quality (chemical, physical and biological soil properties). The two selected bio-assays were Rhizoctoniasolani (basal rot) on lettuce and potato cyst nematodes (PCN) on potato. Both compost and BB compost released mineral N and thus increased lettuce and potato yield but biochar did not. None of the amendments affected the susceptibly of lettuce leaves to basal rot. Compost suppressed PCN while biochar had no effect on PCN reproduction. Moreover, BB compost reduced the suppressing effect of compost. We suggest that the inhibitory effect of biochar blended in compost might be attributed to the fungal biomass which was not increased in the BB compost-amended soil compared to compost-amended soil, and/or the absorbance of suppressive compounds by the high surface area of biochar. Interestingly, all three amendments reduced the water evaporation from the soil surface, which can have important implications for drought stress of plants.
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•Compost suppressed potato cyst nematodes, but biochar and BB compost did not.•None of the amendments affected the susceptibly of lettuce leaves to basal rot.•Compost and BB compost increased lettuce and potato yield, but biochar did not.•Compost and BB compost increased total microbial biomass in soil, biochar did not.•Compost, BB compost, and biochar reduced water evaporation from the soil surface.
Plant-parasitic nematodes engage in prolonged and intimate relationships with their host plants, often involving complex alterations in host cell morphology and function. It is puzzling how nematodes ...can achieve this, seemingly without activating the innate immune system of their hosts. Secretions released by infective juvenile nematodes are thought to be crucial for host invasion, for nematode migration inside plants, and for feeding on host cells. In the past, much of the research focused on the manipulation of developmental pathways in host plants by plant-parasitic nematodes. However, recent findings demonstrate that plant-parasitic nematodes also deliver effectors into the apoplast and cytoplasm of host cells to suppress plant defense responses. In this review, we describe the current insights in the molecular and cellular mechanisms underlying the activation and suppression of host innate immunity by plant-parasitic nematodes along seven critical evolutionary and developmental transitions in plant parasitism.
Summary
Globodera pallida is a major pest of potatoes worldwide. In Japan, aiming at eradication of G. pallida, control measures have been implemented in infested fields. To determine the necessity ...of control measures, the detection of viable G. pallida is required. However, the conventional inoculation test performed in Japan, named the ‘cup test,’ is time-consuming, and conventional PCR methods targeting DNA can detect dead individuals. In this study, we developed an intercalator-based RT-qPCR method for the rapid detection of viable G. pallida. We designed a primer set for the partial cDNA sequence of the Y45F10D.4 gene of G. pallida. This primer set successfully amplified Y45F10D.4 mRNA of all tested G. pallida populations without any cross-reactions with other species. The RT-qPCR method detected RNA corresponding to a minimum of 3.9 G. pallida eggs, and a significant negative correlation was observed between the concentrations of RNA extracted from viable eggs and the Ct values. In addition, no amplification by RT-qPCR was observed in G. pallida treated with 1,3-Dichloropropene, indicating that this method detected viable G. pallida specifically. We then compared the detection sensitivity between the cup test and RT-qPCR method using 24 soil samples, and the results showed that the detection sensitivity of the RT-qPCR method was higher than that of the cup test. The RT-qPCR method enabled the rapid and reliable detection of viable G. pallida.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•Trichoderma harzianum ThzID1-M3 was assessed against Globodera pallida on potato.•Trichoderma harzianum ThzID1-M3 reduced Globodera pallida infection and reproduction in soil.•Trichoderma harzianum ...ThzID1-M3 colonized Globodera pallida juveniles (J2) and cysts.•Trichoderma harzianum ThzID1-M3 proliferated in the rhizoplane and rhizosphere of potato.•Trichoderma harzianum ThzID1-M3 has the potential to monitor the biological control processes of Globodera pallida.
The fungus Trichoderma harzianum strain ThzID1-M3 isolated in the Palouse region of the state of Idaho and transformed to express green fluorescent protein (GFP) was used as a biomarker to study the biological control processes of the potato cyst nematode Globodera pallida. Experiments were conducted to evaluate the effect of T. harzianum ThzID1-M3 on G. pallida infection and reproduction at 45 and 75days after inoculation respectively; and to observe, through microscopy rhizosphere chamber, the colonization of G. pallida second-stage juveniles and potato rhizoplane by T. harzianum ThzID1-M3 10days after inoculation. Significant reduction of G. pallida infection in potato roots was observed when soil was amended with T. harzianum ThzID1-M3. Globodera pallida cysts recovered from soil and G. pallida reproduction rate were significantly reduced by 49% and 60% respectively, when soil was amended with T. harzianum ThzID1-M3 compared to the non-amended soil. Microscopic observations showed that T. harzianum ThzID1-M3 colonized G. pallida second-stage juveniles and cysts, and proliferated in the rhizoplane and rhizosphere of potato. To our knowledge, this is the first report on the study of Trichoderma spp. marked with GFP against a potato cyst nematode. The use of GFP-tagged T. harzianum has the potential to monitor the biological control processes of G. pallida and the tools advanced in this study should facilitate the design of novel strategies to control this economically important nematode pest of potato.
•Automatic morphometric measurements were performed on quarantine nematodes.•Both common and uncommon measurements used in nematology were automaticaly extracted.•Individuals were identified to their ...species to 88% accuracy and populations to 100%.•CNN perfomed well, even if slightly under a custom-made computer vision algorithm.•Automated morphometrics should be an invaluable tool in official analyses framework.
Identification of plant parasitic nematode species is usually achieved following morphobiometric analysis, which requires a certain level of expertise and remains time consuming. Moreover, molecular and morphological discrimination of a number of emergent or cryptic species is sometimes difficult. Finding a way to achieve morphological characterisation quickly and accurately would greatly advance nematology science. Here, we developed a complete method in order to identify the two quarantine nematode species Globodera pallida and Globodera rostochiensis. First, we chose discriminative metrics on the stylet of nematodes that are able to be used by algorithms in order to build an automated process. Second, we used a custom computer vision algorithm (CCVA) and a convolutional neural network (CNN) to measure our metrics of interest. Third, we compared the CCVA and CNN predictions and their discriminative power to distinguish closely related species. Results show accurate identification of G. pallida and G. rostochiensis with the two methods, despite small-scale divergence (one to five µm depending on the metric used). However, the error rate is higher for Globodera mexicana, suggesting that the algorithms are too specific. Nonetheless, these methods represent a promising novel approach to automated morphological identification of nematodes and Globodera species in particular.
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