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36-554: Attempts to find resistance to the potato cyst nematode Globodera rostochiensis in wild potatoes began in 1941, when Conrad Ellenby started testing over 60 species held in the Commonwealth Potato Collection, finding that few were resistant or suitable to breed with cultivated potatoes. In a letter to Nature in 1952, Ellenby reported that by 1948 he had found four types that were resistant and could be crossed with contemporary varieties. All four were

72-486: A broad term that indicates a gene that encodes any determinant of the specificity of the interaction with the host. Thus, this term can encompass some conserved microbial signatures, also called pathogen or microbe associated molecular patterns (PAMPs or MAMPs), and pathogen effectors (e.g. bacterial type III effectors and oomycete effectors) as well as any genes that control variation in the activity of those molecules. Intracellular recognition of an avirulence gene product

108-506: A feeding tube has been established, a syncytium begins to form through the breakdown of multiple cell walls adjacent to each other. J2 nematodes continue to feed until they grow into third-stage juveniles (J3), then fourth-stage juveniles (J4), and finally reach the adult stage. The shape of the J3 females begins to appear more like a sac as the female grows into a J4 nematode. At the J4 stage, the body of

144-495: A pathogen keeping a protein that only serves to have it recognised by the plant, it is believed that the products of Avr genes play an important role in virulence in genetically susceptible hosts. Example: AvrPto is a small triple-helix protein that, like several other effectors, is targeted to the plasma membrane by N-myristoylation. AvrPto is an inhibitor of PRR kinase domains. PRRs signal plants to induce immunity when PAMPs are detected. The ability to target receptor kinases

180-411: A so-called gene-for-gene relationship. Potato cyst nematode Potato root nematodes or potato cyst nematodes ( PCN ) are 1-mm long roundworms belonging to the genus Globodera , which comprises around 12 species. They live on the roots of plants of the family Solanaceae , such as potatoes and tomatoes . PCN cause growth retardation and, at very high population densities, damage to

216-463: A specific R gene product are resistant towards a pathogen that produces the corresponding Avr gene product. Gene-for-gene relationships are a widespread and very important aspect of plant disease resistance . Another example can be seen with Lactuca serriola versus Bremia lactucae . Clayton Oscar Person was the first scientist to study plant pathosystem ratios rather than genetics ratios in host-parasite systems. In doing so, he discovered

252-467: A substance secreted by the roots of host plants otherwise known as root exudates. The nematodes hatch when they grow into a second-stage juvenile (J2). At this stage, the J2 nematodes find host cells to feed off of. The potato cyst nematodes are endoparasites meaning they go completely into the root to feed. Access to the root cells is gained through piercing through the cell wall using the nematode’s stylet. After

288-499: Is also crucial in keeping track of the prevalence of the nematodes. Controlling the quantity of the nematodes allows the prevention of an epidemic. Lastly, resistance to potato cyst nematode has been found in Solanum acaule . The downside is that Solanum acaule is a wild potato species containing high glycoalkaloid content making it toxic for consumers. The use of trap crops such as Solanum sisymbriifolium as been shown to reduce

324-564: Is hyperphosphorylated by the Avr proteins. Another high profile study that supports the guard hypothesis shows that the RPS5 pair uses PBS1, a protein kinase as a guardee against AvrPphB. Yeast two-hybrid studies of the tomato Pto/Prf/AvrPto interaction showed that the Avirulence protein, AvrPto, interacted directly with Pto despite Pto not having an LRR. This makes Pto the guardee protein, which

360-498: Is required for the virulence function of AvrPto in plants. However, Pto is a resistant gene that can detect AvrPto and induce immunity as well. AvrPto is an ancient effector that is conserved in many P. syringae strains, whereas Pto R gene is only found in a few wild tomato species. This suggests recent evolution of the Pto R gene and the pressure to evolve to target AvrPto, turning a virulence effector to an avirulence effector. Unlike

396-530: Is there direct interaction between the R gene product and the Avr gene product. For example, both FLS2 and XA21 interact with the microbial peptides. In contrast, for the NBS-LRR class of R genes, direct interaction has not been shown for most of the R/avr pairs. This lack of evidence for a direct interaction led to the formation of the guard hypothesis for the NBS-LRR class of R genes. This model proposes that

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432-438: The nematodes from field to field can be reduced by cleaning equipment of possibly infested soil before changing location and by using only certified PCN-free seed tubers. If possible, ask for seed potatoes grown on fields which were declared free of the potato cyst nematode. Pesticides can be used, but they will not get a field free of nematodes. They will increase yields and are only profitable at high population densities, when

468-593: The MAMP or PAMP class of avr genes that are recognized by the host PRRs, the targets of bacterial effector avr proteins appear to be proteins involved in plant innate immunity signaling, as homologues of Avr genes in animal pathogens have been shown to do this. For example, the AvrBs3 family of proteins possess DNA binding domains, nuclear localisation signals and acidic activation domains and are believed to function by altering host cell transcription. In only some cases

504-546: The PRRs contain extracellular, juxtamembrane, transmembrane and intracellular non-RD kinase domains. Within the NBS-LRR class of R genes are two subclasses: The protein products encoded by this class of resistance gene are located within the plant cell cytoplasm . The PRR class of R genes includes the rice XA21 resistance gene that recognizes the ax21 peptide and the Arabidopsis FLS2 peptide that recognizes

540-520: The R proteins interact, or guard, a protein known as the guardee which is the target of the Avr protein. When it detects interference with the guardee protein, it activates resistance. Several experiments support this hypothesis, e.g. the Rpm1 gene in Arabidopsis thaliana is able to respond to two completely unrelated avirulence factors from Pseudomonas syringae . The guardee protein is RIN4, which

576-458: The bacterial disease common scab , which causes corky lesions to form on the skin. Common scab is controlled by irrigating crops just as the potatoes begin to form, requiring "perfect timing and perfect irrigation". Maris Piper was one of the first varieties with resistance to G. rostochiensis , with the H1 gene giving complete resistance to UK strains. The widespread growth of Maris Piper led to

612-455: The closely related G. pallida (to which Maris Piper has no resistance) becoming the main potato cyst nematode in the UK. When nematodes feed on the roots, the H1 gene results in the potato roots dying, preventing the nematodes from feeding and making it likely they die or turn into males. H1 is thought to encode a protein that specifically detects the product of one nematode gene during feeding,

648-471: The density of PCN in soil by up to 80%, reducing the need for pesticide application Potato cyst nematodes have the ability to cause a large scale devastation in crops due to the massive amounts of nematode embryos in each cyst. Many continents across the world such as Australia, North America, Asia, Europe, and Africa have had many epidemics of potato cyst nematodes that continue to persist year after year. Potato cyst nematodes are important economically due to

684-547: The differential interaction that is common to all gene-for-gene relationships and that is now known as the Person differential interaction. There are several different classes of R genes. The major classes are the NBS-LRR genes and the cell surface pattern recognition receptors (PRR). The protein products of the NBS-LRR R genes contain a nucleotide binding site (NBS) and a leucine rich repeat (LRR). The protein products of

720-547: The fact that they can substantially reduce crop yields. Globodera pallida are able to cause 80% yield loss in a potato field if left untreated. On a more global scale, the Australian potato industry is worth about AUD$ 500 million yearly which equates to $ 340 million U.S. dollars. Gene-for-gene The gene-for-gene relationship is a concept in plant pathology that plants and their diseases each have single genes that interact with each other during an infection. It

756-412: The female nematode lies outside of the root while the head remains inside the cell. During this stage, the male nematodes become motile again and are then able to fertilize the female nematodes leading to embryos developing inside the female body. Once the female is fertilized, the female dies and leaves a protective cyst containing 200-500 eggs. Once the cysts detach from the original hosts, they remain in

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792-526: The financial profit of the extra yield will surpass the cost of the pesticide application. Crop rotation with at least 6 years between planting of a susceptible crop is an effective means to reduce nematode population densities to below damage threshold. However, the best way to manage potato cyst nematodes is the use of (partial) resistant potato varieties. During the last 10 years a number of varieties have been developed which can keep both potato cyst nematode species below damage and detection threshold, without

828-415: The flg22 peptide from flagellin. There are other classes of R genes, such as the extracellular LRR class of R genes; examples include rice Xa21D for resistance against Xanthomonas and the cf genes of tomato that confer resistance against Cladosporium fulvum . The Pseudomonas tomato resistance gene (Pto) belongs to a class of its own. It encodes a Ser/Thr kinase but has no LRR. It requires

864-577: The greatest variation amongst resistance genes occurs in the LRR domain. LRR swapping experiments between resistance genes in flax rust resulted in the specificity of the resistance gene for the avirulence gene changing. Most resistance genes are autosomal dominant but there are some, most notably the mlo gene in barley , in which monogenic resistance is conferred by recessive alleles . mlo protects barley against nearly all pathovars of powdery mildew . The term "avirulence gene" remains useful as

900-456: The presence of a linked NBS-LRR gene, prf , for activity. R gene specificity (recognising certain Avr gene products) is believed to be conferred by the leucine rich repeats. LRRs are multiple, serial repeats of a motif of roughly 24 amino acids in length, with leucines or other hydrophobic residues at regular intervals. Some may also contain regularly spaced prolines and arginines . LRRs are involved in protein-protein interactions, and

936-566: The root system will occur. The female individuals swell up and appear as cysts on the surface of the roots, each containing up to 400 eggs. In temperate zones only one generation per year will occur. In the Mediterranean countries sometimes a second generation is reported. Cysts can then also be found on the skin of the tubers. Each year without host a certain fraction of the eggs will hatch (spontaneous hatch). The eggs can survive for up to 20 years inside these cysts. The speed of spread of

972-481: The roots and early senescence of plants. The nematode is not indigenous to Europe but originates from the Andes. Fields are free from PCN until an introduction occurs, after which the typical patches, or hotspots, occur on the farmland. These patches can become full field infestations when unchecked. Yield reductions can average up to 60% at high population densities. The eggs hatch in the presence of Solanoeclepine A ,

1008-588: The soil until they find another suitable host beginning the cycle again. Cyst nematodes are monocyclic because they have one life cycle per season. Potato cyst nematodes can be detected by their patchy distribution in the field. The specific distribution is caused by the limited spread of these nematodes. Most potato cyst nematodes don’t migrate very far across a field because of their feeding patterns. Both susceptible and resistant potato varieties will suffer from growth retardation at low and medium populations densities. At very high population densities mechanical damage of

1044-598: The species Solanum tuberosum andigena , and one of these, CPC 1673, was the source of nematode resistance in Maris Piper. Although resistant to PCN, the wild potato produced very small tubers in the UK climate. Led by H. W. Howard , workers at the Plant Breeding Institute in Cambridge crossed the wild potato with contemporary varieties to produce a high-yielding, resistant variety. CPC 1673

1080-507: The use of pesticides. Other methods of pest control include nematicides such as fosthiazate (Nemathorin), aldicarb (Temik), oxamyl (Vydate) and fluopyram which are applied to the soil. The level of toxicity is important to consider when applying and depends on the manufacturer and the specific instructions of application. The use of certified disease free seed will also assure that potato cyst nematodes are not present due to planting infected tubers. Soil testing for potato cyst nematodes

1116-459: The variety is also suitable for processing into frozen or dehydrated products. It has been recommended by chefs Heston Blumenthal and Tom Kerridge for making triple cooked chips . In his book Perfection , Blumenthal stated they were "in a league of their own" for making roast potatoes and he also considers them the best variety for mashed potatoes . Maris Piper is one of the most susceptible potato varieties to being eaten by slugs, and also

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1152-420: Was backcrossed , crossed with Ulster Knight , and then crossed with a cross of Arran Cairn and Herald . Arran Cairn was bred by Donald Mackelvie , the leading Scottish potato breeder in the early 20th century, and Ulster Knight was bred by John Clarke , an eminent potato breeder from Antrim . The final cross was made in 1956, but it took another ten years for the variety to be tested and multiplied before it

1188-432: Was first demonstrated by Gopalan et al 1996. They found that artificial expression of Pseudomonas syringae ' s avrB in the host Arabidopsis produced cell death when combined with expression of the host R gene , RPM1 . This proved recognition was occurring intracellularly and not on the surface. There is no common structure between avirulence gene products. Because there would be no evolutionary advantage to

1224-406: Was proposed by Harold Henry Flor who was working with rust ( Melampsora lini ) of flax ( Linum usitatissimum ). Flor showed that the inheritance of both resistance in the host and parasite ability to cause disease is controlled by pairs of matching genes. One is a plant gene called the resistance ( R ) gene . The other is a parasite gene called the avirulence ( Avr ) gene. Plants producing

1260-802: Was recommended by the National Institute of Agricultural Botany in 1966. The PBI and Howard were awarded the Queen's Award for Technology in 1982 for breeding Maris Piper. The first part of the variety's name came from Maris Lane in Trumpington where the Plant Breeding Institute was located. By convention, the breeder got to choose the second name, with Piper chosen arbitrarily by Howard's son, although earlier, he had proposed calling it Maris Pard. It should not be confused with Maris Peer, another variety of potato. The variety

1296-510: Was the most popular in the UK by 1980, accounting for 24 % of the British potato crop in 1982, 20 % in 2005 and 16 % in 2014. It became popular due to both its resistance to nematodes and its pleasing taste for consumers. Maris Piper has a fluffy texture and is considered an "all-rounder" potato. It is widely used to make chips (French fries) due to it having high dry matter and low reducing sugars . As well as being sold fresh,

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