African Journal of
Biotechnology

  • Abbreviation: Afr. J. Biotechnol.
  • Language: English
  • ISSN: 1684-5315
  • DOI: 10.5897/AJB
  • Start Year: 2002
  • Published Articles: 12487

Full Length Research Paper

Technical review of molecular markers and next-generation sequencing technology to manage plant pathogenic oomycetes

Ramadan Ahmed Arafa
  • Ramadan Ahmed Arafa
  • Plant Pathology Research Institute, Agricultural Research Center, Giza, 12619, Egypt.
  • Google Scholar
Kenta Shirasawa
  • Kenta Shirasawa
  • Kazusa DNA Research Institute, Chiba 292-0818, Japan.
  • Google Scholar


  •  Received: 29 October 2017
  •  Accepted: 15 February 2018
  •  Published: 21 March 2018

 ABSTRACT

To feed the world human population which is expected to reach 10 billion in the next three decades, agricultural sustainability is required for stable food production. However, crops always suffer from many biotic and abiotic stresses. Among them, plant pathogens often cause severe yield losses. Plant pathogenic oomycetes are one of the most destructive plant diseases, which include Phytophthora infestans in potato and tomato, Phytophthora capsici in peppers, Phytophthora sojae in soybean, Phytophthora fragariae var. fragariae in strawberry, Plasmopara viticola in grapevine, and Pseudoperonospora cubensis in cucurbits. Therefore, rapid, robust and sophisticated molecular technologies are required for accurate identification and characterization of the oomycetes, to manage crop diseases resistances. In addition, breeding highly disease resistant varieties is also essential for sustainable agriculture. Molecular marker technology, especially recent advanced next-generation sequencing-based methods, would provide helpful information to monitor the pathogen endemicity and to breed the resistant cultivars through a gene pyramiding strategy. In this review, there was focus on both conventional and novel genotyping techniques for oomycete characterization and resistant gene identification in crops, to discuss future outlook for successful disease management.
 
Key words: Oomycete plant pathogens, vegetable crops, genomics, molecular markers, next-generation sequencing technology.


 INTRODUCTION

The world human population is expected to reach approximately 10 billion by 2050 (UN, 2015). To meet the challenges of poverty and the rising population, food production must be increased by at least 70% over the next three decades. Agricultural sustainability is threatened by a number of limiting factors such as water and nutrient deficiencies, infestations of insects and nematodes, and infections of plant pathogenic viruses, bacteria, fungi and oomycetes. Especially, the plant pathogens are responsible for severe yield losses in a wide range of crops throughout the world. Besides, global trade of crops among countries leads to the rapid spreadof plant pathogenic microorganisms and unprecedented disease outbreaks in hitherto unaffected croplands. Molecular markers can be used for identification and taxonomic classification of species across all domains of life (Vignal et al., 2002; Singh et al., 2013). In modern plant breeding programs, a gene pyramiding strategies based on marker-assisted selection (MAS) can facilitate development of new varieties with desirable traits such as disease resistances.
 
In addition, the molecular techniques help in discovering an array of plant disease resistance genes, which have been used for the management of several serious plant pathogens (Gururani et al., 2012). Furthermore, greater understanding of interactions between pathogens and host plants could facilitate disease outbreak forecasting and predictions of yields. In this decade, genome sequencing technology as well as the molecular marker techniques has been greatly advanced due to great advancements of next-generation sequencing (NGS) methods (Davey et al., 2011). For example, whole-genome sequencing analysis of many microorganisms including plant pathogens has contributed to understanding of pathogenicity, host preferences, secreted effector proteins and fungicide resistances of the pathogens (Grunwald et al., 2016). In this review, genomics of oomycete plant pathogens in important crops are summarized for future breeding, to overcome the disease-derived yield losses.


 ADVANCEMENT OF DNA MARKER TECHNOLOGIES

Traditional morphological and biochemical markers are hampered by their reliance on particular factors, for example, developmental stages and environmental conditions. In contrast, DNA markers provide stable results independent of the factors, hence, DNA analysis is the basis of a range of techniques in basic and applied researches (Collard et al., 2005). Since the 1980s, many types of DNA markers have been developed in accordance with advancement of DNA analysis technologies, for example, restriction fragment length polymorphism (RFLP), random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), simple sequence repeat (SSR), inter-simple sequence repeat (ISSR), sequence characterized amplified region (SCAR), sequence related amplified polymorphism (SRAP) and cleaved amplified polymorphic sequence (CAPS) (Table 1). The DNA markers are used to detect polymorphisms between individuals in populations, determine genetic biodiversity among genotypes, and investigate plant-pathogen interactions (Patwardhan et al., 2014). Due to NGS technology, genome-wide SNP discovery and genotyping have been enabled with high precision and accuracy, high-throughput performance and cost-effectiveness (Yang et al., 2016). This situation has made the classical DNA markers mentioned above (Vos et al., 1995; Jarne and Lagoda, 1996) to suffer from some constraints such as time- and cost-consuming.
 
 
 
In Figure 1, a possible experimental approach for genotyping, SNP discovery, and gene identification with NGS strategies is presented. Even in non-model organisms in which genome sequences are not available (Baxter et al., 2011), NGS-based genome-wide genotyping technology has been widely applied for studies on SNP discovery, genetic variability, QTL mapping, candidate gene detection and genome-wide association study (GWAS) (Fu et al., 2014). NGS-based methods are suitable for genome-wide genotyping across large numbers of individuals, for example, reduced-representation libraries (RRLs) (Altshuler et al., 2000), complexity reduction of polymorphic sequences (CRoPS) (van Orsouw et al., 2007), restriction site-associated DNA sequencing (RAD-seq) (Baird et al., 2008) and genotyping-by-sequencing (GBS) (Elshire et al., 2011). In RRL sequencing technology, which has been originally developed in the human genome project (Altshuler et al., 2000), small genomic regions are sequenced for SNP discovery and genotyping. These techniques have been applied in other organisms including plants and animials (Van Tassell et al., 2008; Wiedmann et al., 2008; Gore et al., 2009; Hyten et al., 2010).
 
 
 
 
On the other hand, CRoPS technology, another reduced-representation method, has mitigated the amounts of sequencing data to identify polymorphism in populations (van Orsouw et al., 2007). In RAD-Seq procedure, genome DNAs are cut with restriction enzymes into short DNA fragments, and sequenced to discover and genotype genome-wide SNPs (Baird et al., 2008). GBS is another approach for genotyping and developing novel molecular markers (Sonah et al., 2013; He et al., 2014). The library preparation is affordable, straightforward, rapid and precise (Elshire et al., 2011; Romay et al., 2013). Furthermore, in the fields of plant pathology and microbiology, through the NGS-based approaches, novel molecular markers associated with resistance genes were broadly identified (Devran et al., 2015). For example, resistance gene enrichment sequencing (RenSeq) is an effective genotyping technique with NGS technologies, in sequence variations of nucleotide binding-site leucine-rich repeat (NB-LRR) genes simultaneously identified (Jupe et al., 2013). Subsequently, the RenSeq approach has been widely applied to identify resistance genes in wheat and potato (Jupe et al., 2013; Steuernagel et al., 2016).


 IDENTIFICATION OF KEY INTERACTIVE GENES BETWEEN PLANTS AND OOMYCETE PATHOGENS

Oomycetes are fungus-like eukaryotic microorganisms, many of which are pathogens to humans, animals and plants. Plant pathogenic oomycetes pose substantial threats to global food security. Among the oomycetes, Phytophthora is one of the largest genera containing almost 117 species (Martin et al., 2012), many of which cause severe disease outbreaks in horticultural, fruit, arable crops, forest trees and ornamental plants. In addition, Plasmopara and Pseudoperonospora also thrive on susceptible hosts and pose substantial risks to agriculture worldwide. To overcome the losses from the diseases, breeding new cultivars with resistance (R) genes to the pathogens is an effective strategy. However, the R-gene-derived resistances sometimes decay because of alterations of the plant pathogenic effector proteins, which suppress plant immunity system and modulate host cell functions (Hogenhout et al., 2009). Therefore, to combat the diseases completely, it there is need to understand molecular mechanisms of disease resistance as well as population dynamics of plant pathogens upon the temporal and spatial levels. The genome sequences of the several oomycete pathogens, sizes of which varied depending on the genera (Figure 2), would be useful for this purpose. In addition, methods to monitor and predict alternations of the effector genes are also essential. Also, genetic and genomic analyses of plant pathogens would lead to new strategies for integrated disease management of high aggressive races, which would breakdown existing resistant varieties. The current status of knowledge on important crops and the corresponding pathogens are summarized as follows.
 
 
 
 
Tomato and potato- Phytophthora infestans
 
 
Late blight of tomato (Solanum lycopersicum) and potato (Solanum tuberosum) are caused by the heterothallic oomycete pathogen, P. infestans (Mont.) de Bary, also known as a pathogen of the Irish potato famine in the 1840s (Aragaki and Uchida, 2001; Abad and Abad, 2003). P. infestans can completely destroy tomato and potato plants within a few days after infection. Unfortunately, pathogenic races of P. infestans have been altered in each season and growing areas (Arafa et al., 2017). Therefore, multiple resistance varieties of tomato and potato have been developed by introgression of R genes from the wild relatives. In tomato, six major and race-specific R genes have been identified from the wild relatives, which are Ph-1, Ph-2, Ph-3, Ph-4, Ph-5.1 and Ph-5.2 (Table 2). Among them, Ph-3 derived from Solanum pimpinellifolium L3708 confers a high level resistance against a broad-spectrum of P. infestans genotypes. On the other hand, in potato, eleven resistance genes (R1R11) were identified from a wild potato relative, S. demissum, and R1, R2, R3, R4 and R10 were broadly used in potato breeding programs (Vleeshouwers et al., 2011). Furthermore, new QTLs for P. infestans resistance have been reported in S. pimpinellifolium, Solanum habrochaites, and Solanum pennellii for tomato, and in Solanum bulbocastanum and Solanum phureja for potato. Moreover, RAD-Seq technology was used to identify SNP markers from a tomato wild relative, S. pimpinellifolium (Chen et al., 2014). Genetic linkage maps were constructed, and a QTL associated with late blight resistance was detected on chromosome 2. Recently, a resistance locus to an Egyptian isolate of P. infestans from S. habrochaites (Arafa et al. 2018) was also identified, in which the established analytic pipeline for ddRAD-Seq was employed (Shirasawa et al., 2016).

 

 
However, most of these resistance genes might be subsequently disrupted by new pathotypes, which have been generated due to the unstableness of the P. infestans genomes caused by movements of transposable elements, mitotic recombinations and dispensable chromosomes (Judelson, 2002). Therefore, rapid detection methods and easy monitoring technologies of late blight would be beneficial for pathogen control to reduce yield losses of crops. For example, mitochondrial DNA (mtDNA) haplotypes detected by the RG57 RFLP marker as well as RAPD and AFLP have been used as DNA makers to examine the population diversity of P. infestans isolates. Subsequently, SSRs and SNPs have been also applied to investigate population structures and to monitor alterations of effector proteins of P. infestans. More recently, NGS-based genotyping methods including reduced representative sequencing techniques and whole-genome shotgun (WGS) approaches are used to characterize P. infestans isolates. A GBS approach has also been applied to detect genetic variability within four clonal lineages (US-8, US-11, US-23 and US-24) of P. infestans, where 3,774, 4,363, 5,070 and 4,353 SNPs were discovered, respectively (Hansen et al., 2016).
 
These findings are considered a clear indication that the GBS method is adequately a useful method for high-resolution analysis of population structure of P. infestans, which would contribute to reduction in epidemiology of late blight globally. Furthermore, whole-genome resequencing strategy has also been used for six genomes of four Phytophthora species (P. infestans, P. ipomoeae, P. mirabilis and P. phaseoli) to detect 746,744 SNPs and to estimate genomic evolutionary rates in the genus, Phytophthora (Raffaele et al., 2010).This study suggested that the evolutionary level among the tested isolates fluctuated based on copy number variations (CNVs), frequency of SNPs and the ratio of non-synonymous to synonymous substitutions. Yoshida et al. (2013) also used the genome sequencing approach to compare between ancient and modern populations of P. infestans, to detect 4.5 million SNPs and follow up the historical trajectory of clonal linages to comprehend the epidemiology of this destructive plant pathogen. They also presented the evolutionary process of P. infestans populations since the occurrence of Irish potato famine.
 
Pepper- Phytophthora capsici
 
P. capsici is a soil-borne plant pathogenic oomycete; this pathogen infects a wide range of host crops. P. capsici is considered as a major limiting factor for crop productions (Lamour and Kamoun, 2009; Roy et al., 2009; Zeng et al., 2009). Especially in pepper (Capsicum annuum), root, stem and foliar blights are caused by P. capsici. In the pepper genome, resistance loci for P. capsici, Phyt-1, Phyt-2 and Phyt-3 as well as Phyto.5.2, have been identified through a QTL mapping research. Recently, a novel resistance gene, PhR10, has been identified using NGS technology with Illumina HiSeq 2500 platform (Xu et al., 2016). This race specific gene can be used for breeding programs for resistant varieties to Phytophthora root rot with a marker-assisted selection. However, P. capsici readily undergoes sexual reproduction to develop new races. The new genotypes adapt to challenging environmental conditions by breakdown of pesticides. Therefore, it is important to assess P. capsici population dynamics and to identify new races rapidly. To date, molecular markers based on RFLP (Forster et al., 1990), mtDNA haplotypes (Martin et al., 2012), RAPDs (Yin et al., 2012), AFLPs (Hulvey et al., 2010), SSRs (del Castillo-Múnera et al., 2013) and SNPs (Gobena et al., 2012) have been available. More recently, Fulcher et al. (2014) applied the GBS approach for genotyping of P. capsici population to discover 368,356 SNPs. GBS has been also used to investigate population structure and genetic dynamics of P. capsici where 23,485 high-quality SNPs tightly linked to temporal dynamics and mating types are identified over the genome of P. capsici (Carlson et al., 2017).
 
Soybean- Phytophthora sojae
 
Root rot in soybean (Glycine max) is caused by P. sojae Kaufm. and Gerd. P. sojae attacks soybean plants at all developmental stages from seedling to harvest across a range of varieties (Malvick and Grunden, 2004; Kato, 2010). Soybean has at least 14 R genes, which have been used to develop P. sojae resistant cultivars (Burnham et al., 2003). Two R genes, Rps8 and Rps3, tightly linked to each other can be used to breed new varieties, conferring durable resistance through the gene pyramiding strategy. QTL analyses have shown new resistance gene loci, Rps1-k (Kasuga et al., 1997; Salimath and Bhattacharyya, 1999) and RpsYu25 (Sun et al., 2011), and novel QTLs indicating partial resistance for Phytophthora root and stem rot (Lee et al., 2013). The partial resistance loci have been also reported on chromosomes 3, 13 and 19 where seven QTLs were detected (Schneider et al., 2016). Therefore, pyramiding many minor genes as well as usage of R genes are efficacious ways to increase the resistance level to P. sojae. On the other hand, an avirulence gene, Avr1a in Phytophthora has been identified in the genome of Ph. sojae. This information would be useful to understand interactions between soybean and P. sojae (MacGregor et al., 2002). A whole genome resequencing analysis has been performed to predict effects of sequence variations on the functions of the avirulence genes, Avr1a and Avr1c (Na et al., 2014). Additionally, this study confirmed that NGS-based methods are workable techniques for breeding programs, and genetic and genomics research could be widely applied in release soybean breeding to increase crop immune system against oomycete pathogens.
 
Strawberry- Phytophthora fragariae var. fragariae
 
P. fragariae Hickman var. fragariae Wilcox & Duncan causes red core disease in Rubus species (Wilcox, 1989) including strawberry (Fragaria x ananassa) (Hickman, 1941), which leads to complete destruction and death of the plants. The genome sequence of P. fragariae is available to understand virulence, aggressiveness and evolution of this destructive pathogen (Gao et al., 2015). In strawberry, two R genes, Rpf1 and Rpf2, have been reported as resistance loci (Haymes et al., 1997; Haymes et al., 2000; GelvonauskienÄ— et al., 2007; Mathey, 2013; Van de Weg, 1997).
 
Grapevine- Plasmopara viticola
 
In grapevine (Vitis vinifera), downy mildew disease is caused by P. viticola (Berk. and Curt.) Berl. and de Toni. This pathogen can infect all the green tissues of grapevine, causing substantial losses in crop productivity and quality (Gessler et al., 2011). An R gene, Rpv3, is responsible for the hypersensitive response against P. viticola in resistant grapevine genotypes (Bellin et al., 2009). Another R gene, Rpv8, a major QTL responsible for P. viticola resistance, has been identified from a grape wild relative, Vitis amurensis Rupr. Pyramiding of two genes, Rpv3 and Rpv12+, in one line was an effective strategy to overcome downy mildew disease (Venuti et al., 2013). However, P. viticola exhibits extensive genetic variability (Gobbin et al., 2006), and several genotypes can be discovered from a single field (Gobbin et al., 2003). Therefore, a high-throughput genotyping is required to gain new insight into the genetic structure of P. viticola population (Stark-Urnau et al., 2000). For example, SNP and SSR markers have been used for the genetic variation study of P. viticola strains (Delmotte et al., 2011). Recently, Yin et al. (2017) employed the whole genome sequencing approach to identify pathogenicity genes and effector proteins that are associated with virulence of P. viticola. Moreover, NGS-based methods clarifies the origin and evolution patterns of P. viticola, which is completely different from Hyaloperonospora arabidopsidis, a pathogen for Arabidopsis downy mildew.
 
Cucurbitaceae- Pseudoperonospora cubensis
 
The family Cucurbitaceae suffers from approximately 45 diseases caused by viruses, bacteria, fungi, and oomycetes (Lebeda et al., 2006). Among them, P. cubensis [(Berk. and Curt.) Rost.] causes downy mildew disease. P. cubensis infects approximately 20 cucurbit genera, including cucumber (Cucumis sativus), watermelon (Citrullus lanatus), pumpkin (Cucurbita maxima), squash (Cucurbita pepo) and melon (Cucumis melo) (Lebeda and Urban, 2007). The GBS technique distinguishes P. cubensis from the relative, Pseudoperonospora humuli (Summers et al., 2015; Lee et al., 2016). Numbers of QTLs for P. cubensis resistance has been identified in cucumber (Pang et al., 2013; Yoshioka et al., 2014), while a resistance locus, ILdm, has been found from a wild relative of cucumber, Cucumis hystrix (Guo et al., 2011).

 


 FUTURE DIRECTION OF BREEDING STRATEGIES FOR PLANT DISEASE RESISTANCE

Plant diseases are one of the main threats to global food security and sustainable agriculture. Identifying and tracking oomycete plant pathogens are critical for breeding programs for disease resistances in a range of crop species. Moreover, identification of resistance genes for crops would be required for effective integrated disease management (Table 3). The plant disease resistances could be classified into two major categories: (i) qualitative or race-specific resistance (vertical resistance) controlled by single resistance genes (major genes or R genes), and (ii) quantitative resistance or field resistance (horizontal resistance) regulated by multiple minor genes (Poland et al., 2009). Therefore, the gene pyramiding strategy has a potential to develop varieties with durable resistance against multiple plant pathogens. To understand molecular mechanisms of plant disease infection, responses of plants, and the interaction from both aspects of pathogens and hosts would be essential to control plant disease and maintain stability of food productions. Advancement of NGS technology enables analyzing genetic variations of pathogens and crops at whole genome level. The information would provide a beneficial knowledge in both evolutionary researches on oomycete pathogens and the interactions between the pathogens and their hosts (Yin et al., 2017). Also, NGS-based genotyping techniques would confer diagnosis methods to monitor new diseases. Unambiguously, NGS technology is expected to provide useful information on adequate plant breeding programs for desirable traits such as resistance genes discovery. The plants are deeply nested with plausible future perspectives to overcome plant disease challenges in different host species. Interactive, integrative and comparative researches on plant pathology, breeding, genetics and genomics would pave way for successful disease management.
 
 


 CONFLICT OF INTERESTS

The authors have not declared any conflict of interests.



 REFERENCES

Abad ZG, Abad JA (2003). Advances in the integration of morphological and molecular characterization in the genus Phytophthora: The case of P. niederhauseria sp. nov. Phytopathology 93:S1.

 

Abbott C, Gilmore S, Lewis C, Chapados J, Peters R, Platt H, Coffey MD, Lévesque CA (2010). Development of a SNP genetic marker system based on variation in microsatellite flanking regions of Phytophthora infestans. Can. J. Plant Pathol. 32(4):440-457.
Crossref

 
 

Altshuler D, Pollara VJ, Cowles CR, Van Etten WJ, Baldwin J, Linton L, Lander ES (2000). An SNP map of the human genome generated by reduced representation shotgun sequencing. Nature 407:513-516.
Crossref

 
 

Arafa RA, Rakha MT, Soliman NEK, Moussa OM, Kamel SM, Shirasawa K (2017). Rapid identification of candidate genes for resistance to tomato late blight disease using next-generation sequencing technologies. Plos One 12:e0189951.
Crossref

 
 

Arafa RA, Soliman NEK, Moussa OM, Kamel SM, Shirasawa K (2018). Characterization of Egyptian Phytophthora infestans population using simple sequence repeat markers. J. Gen. Plant Pathol. 84:104-107.
Crossref

 
 

Aragaki M, Uchida JY (2001). Morphological distinctions between Phytophthora capsici and P. tropicalis sp. nov," Mycologia 93:137-145.
Crossref

 
 

Baird NA, Etter PD, Atwood TS, Currey MC, Shiver AL, Lewis ZA, Selker EU, Cresko WA, Johnson EA (2008). Rapid SNP discovery and genetic mapping using sequenced RAD markers. PLoS One 3:e3376.
Crossref

 
 

Baxter SW, Davey JW, Johnston JS, Shelton AM, Heckel DG, Jiggins CD, Blaxter ML (2011). Linkage mapping and comparative genomics using next-generation RAD sequencing of a non-model organism. PLoS One 6:e19315.
Crossref

 
 

Bellin D, Peressotti E, Merdinoglu D, Wiedemann-Merdinoglu S, Adam-Blondon AF, Cipriani G, Morgante M, Testolin R, Gaspero GD (2009). Resistance to Plasmopara viticola in grapevine 'Bianca' is controlled by a major dominant gene causing localized necrosis at the infection site. Theor. Appl. Genet. 120:163-176.
Crossref

 
 

Brurberg MB, Elameen A, Le VH, Nærstad R, Hermansen A, Lehtinen A, Hannukkala A, Nielsen B, Hansen J, Andersson B, Yuen J (2011). Genetic analysis of Phytophthora infestans populations in the Nordic European countries reveals high genetic variability. Fungal Boil. 115(4): 335-342.
Crossref

 
 

Burnham K, Dorrance A, VanToai T, St. Martin S (2003). Quantitative trait loci for partial resistance to Phytophthora sojae in soybean. Crop Sci. 43:1609-1617.
Crossref

 
 

Carlson MO, Gazave E, Gore MA and Smart CD (2017). Temporal genetic dynamics of an experimental, biparental field population of Phytophthora capsici. Front. Genet. 8:26.
Crossref

 
 

Chen AL, Liu CY, Chen CH, Wang JF, Liao YC, Chang CH, Tsai MH, Hwu KK, Chen KY (2014). Reassessment of QTLs for late blight resistance in the tomato accession L3708 using a restriction site associated DNA (RAD) linkage map and highly aggressive isolates of Phytophthora infestans. PLoS One 9(5):e96417.
Crossref

 
 

Chen CH, Wang TC, Black L, Sheu ZM, Perez F, Deahl K (2009). Phenotypic and genotypic changes in the Phytophthora infestans population in Taiwan-1991 to 2006. ‎J. Phytopathol. 157(4):248-255.
Crossref

 
 

Chunwongse J, Chunwongse C, Black L, Hanson P (2002). Molecular mapping of the Ph-3 gene for late blight resistance in tomato. J. Hortic. Sci. Biotechnol. 77(3):281-286.
Crossref

 
 

Collard B, Jahufer M, Brouwer J, Pang E (2005). An introduction to markers, quantitative trait loci (QTL) mapping and marker-assisted selection for crop improvement: the basic concepts. Euphytica 142:169-196.
Crossref

 
 

Davey JW, Hohenlohe PA, Etter PD, Boone JQ, Catchen JM, Blaxter ML (2011). Genome-wide genetic marker discovery and genotyping using next-generation sequencing, Nat. Rev. Genet. 12:499-510.
Crossref

 
 

del Castillo-Múnera J, Cárdenas M, Pinzón A, Casta-eda A, Bernal AJ, Restrepo S (2013). Developing a taxonomic identification system of Phytophthora species based on microsatellites. Rev. Iberoam. Micol. 30(2):88-95.
Crossref

 
 

Delmotte F, Machefer V, Giresse X, Richard-Cervera S, Latorse M, Beffa R (2011). Characterization of single-nucleotide-polymorphism markers for Plasmopara viticola, the causal agent of grapevine downy mildew. ‎ Appl. Environ. Microbiol. 77(21):7861-7863.
Crossref

 
 

Devran Z, Kahveci E, O¨zkaynak E, Studholme DJ, To¨r M (2015). Development of molecular markers tightly linked to Pvr4 gene in pepper using next-generation sequencing. Mol. Breed. 35:101.
Crossref

 
 

Drenth A, Whisson S, Maclean D, Irwin J, Obst N, Ryley M (1996). The evolution of races of Phytophthora sojae in Australia. Phytopathology 86(2):163-169.
Crossref

 
 

Elshire RJ, Glaubitz JC, Sun Q, Poland JA, Kawamoto K, Buckler ES, Mitchell SE (2011). A robust simple genotyping-by-sequencing (GBS) approach for high diversity species. PLoS One 6:e19379.
Crossref

 
 

Flier WG, Grünwald NJ, Kroon LP, Sturbaum AK, van den Bosch TB, Garay-Serrano E, Lozoya-Salda-a H, Fry WE, Turkensteen LJ (2003). The population structure of Phytophthora infestans from the Toluca Valley of central Mexico suggests genetic differentiation between populations from cultivated potato and wild Solanum spp. Phytopathology 93(4):382-390.
Crossref

 
 

Forster H, Oudemans P, Coffey MD (1990). Mitochondrial and nuclear DNA diversity within six species of Phytophthora. Exp. Mycol. 14(1):18-31.
Crossref

 
 

Fu YB, Cheng B, Peterson GW (2014). Genetic diversity analysis of yellow mustard (Sinapis alba L.) germplasm based on genotyping by sequencing. Genet. Resour. Crop Evol. 61:579-594.
Crossref

 
 

Fulcher M, Carlson M, Smart C (2014). Geneva blight genetics: Genotyping-by-sequencing a bi-parental population of Phytophthora capsici," in Proceedings of the 2014 Summer Scholars Program, Geneva, NY.

 
 

Gao R, Cheng Y, Wang Y, Guo L, Zhang G (2015). Genome sequence of Phytophthora fragariae var. fragariae, a quarantine plant-pathogenic fungus. Genome Announc. 3(2):e00034-15.
Crossref

 
 

GelvonauskienÄ— D, Rugienius R, Šikšnianas T, StanienÄ— G, Sasnauskas A, Stanys V (2007). Screening of apple and strawberry plants carrying fungal disease resistance oligogenes using molecular markers. Zemdirbyste Agric. 94:139-145.

 
 

Gessler C, Pertot I, Perazzolli M (2011). Plasmopara viticola: a review of knowledge on downy mildew of grapevine and effective disease management. Phytopathol. Mediterr. 50:3-44.

 
 

Gobbin D, Pertot I, Gessler C (2003). Identification of microsatellite markers for Plasmopara viticola and establishment of high throughput method for SSR analysis. Eur. J. Plant Pathol. 109:153-64.
Crossref

 
 

Gobbin D, Rumbou A, Linde CC, Gessler C (2006). Population genetic structure of Plasmopara viticola after 125 years of colonization in European vineyards. Mol. Plant Pathol. 7(6): 519-531.
Crossref

 
 

Gobena D, Roig J, Galmarini C, Hulvey J, Lamour K (2012). Genetic diversity of Phytophthora capsici isolates from pepper and pumpkin in Argentina. Mycologia 104(1):102-107.
Crossref

 
 

Gore MA, Chia JM, Elshire RJ, Sun Q, Ersoz ES, Hurwitz BL, Peiffer JA, McMullen MD, Grills GS, Ross-Ibarra J, Ware DH, Buckler ES (2009). A first-generation haplotype map of maize. Science 326:1115-1117.
Crossref

 
 

Grunwald NJ, McDonald BM, Milgroom MG (2016). Population genomics of fungal and oomycete pathogens. Annu. Rev. Phytopathol. 54:323-346.
Crossref

 
 

Guo L, Zhu XQ, Hu CH, Ristaino J B (2010). Genetic structure of Phytophthora infestans populations in China indicates multiple migration events. Phytopathology 100(10):997-1006.
Crossref

 
 

Guo ZZ (2011). Screening of molecular markers for downy mildew resistance introgression line of Cucumis Hystrix-C. Sativus and analysis of programmed cell death. China: Nanjing Agricultural University, Master's thesis

 
 

Gururani MA, Venkatesh J, Upadhyaya CP, Nookaraju A, Pandey SK, Park SW (2012). Plant disease resistance genes: current status and future directions. Physiol. Mol. Plant Pathol.78:51-65.
Crossref

 
 

Hansen ZR, Everts KL, Fry WE, Gevens AJ, GruÈnwald NJ, Gugino BK, Johnson DA, Johnson SB, Judelson HS, Knaus BJ, McGrath MT, Myers KL, Ristaino JB, Roberts PD, Secor GA, Smart CD (2016). Genetic variation within clonal lineages of Phytophthora infestans revealed through genotyping-by-sequencing, and Implications for late blight epidemiology. PLoS One 11:e0165690.
Crossref

 
 

Haymes K, Henken B, Davis T, Van de Weg W (1997). Identification of RAPD markers linked to a Phytophthora fragariae resistance gene (Rpf1) in the cultivated strawberry. Theor. Appl. Genet. 94:1097-1101.
Crossref

 
 

Haymes K, Van de Weg W, Arens P, Maas J, Vosman B, Den Nijs A (2000). Development of SCAR markers linked to a Phytophthora fragariae resistance gene and their assessment in European and North American strawberry genotypes. J. Am. Soc. Hortic. Sci. 125:330-339.

 
 

He J, Zhao X, Laroche A, Lu ZX, Liu H, Li Z (2014). Genotyping-by- sequencing (GBS), an ultimate marker-assisted selection (MAS) tool to accelerate plant breeding. Front. Plant Sci. 5:484.
Crossref

 
 

Hickman C (1941). The red core root disease of the strawberry caused by Phytophthora fragariae n. sp. J. Pomol. Hortic. Sci. 18(2):89-118.
Crossref

 
 

Hogenhout SA, Van der Hoorn RA, Terauchi R, Kamoun S (2009). Emerging concepts in effector biology of plant-associated organisms. Mol. Plant Microbe Interact. 22:115-122.
Crossref

 
 

Hulvey J, Gobena D, Finley L, Lamour K (2010). Co-occurrence and genotypic distribution of Phytophthora species recovered from watersheds and plant nurseries of eastern Tennessee. Mycologia 102(5):1127-1133.
Crossref

 
 

Hyten DL, Cannon SB, Song Q, Weeks N, Fickus EW, Shoemaker RC (2010). High-throughput SNP discovery through deep resequencing of a reduced representation library to anchor and orient scaffolds in the soybean whole genome sequence. BMC Genomics 11:38.
Crossref

 
 

Islam SZ, Babadoost M, Lambert KN, Ndeme A, Fouly HM (2005). Characterization of Phytophthora capsici isolates from processing pumpkin in Illinois. Plant Dis. 89(2):191-197.
Crossref

 
 

Jaimasit P, Prakob W (2011). Characterization of Phytophthora infestans population in potato crops from Chiang mai and Tak provinces. J. Agric. Technol. 7(2): 431-439.

 
 

Jarne P, Lagoda PJ (1996). Microsatellites, from molecules to populations and back. Trends Ecol. Evol. 11:424-9.
Crossref

 
 

Judelson HS (2002). Sequence variation and genomic amplification of a family of Gypsy-like elements in the oomycete genus Phytophthora. Mol. Biol. Evol. 19:1313-1322.
Crossref

 
 

Jupe F, Witek K, Verweij W, Sliwka J, Pritchard L, Etherington GJ, Maclean D, Cock PJ, Leggett RM, Bryan GJ, Cardle L, Hein I, Jones JD (2013). Resistance gene enrichment sequencing (RenSeq) enables reannotation of the NB-LRR gene family from sequenced plant genomes and rapid mapping of resistance loci in segregating populations. Plant J. 76:530-44.
Crossref

 
 

Kasuga T, Salimath SS, Shi J, Gijzen M, Buzzell RI, Bhattacharyya MK (1997). High resolution genetic and physical mapping of molecular markers linked to the Phytophthora resistance gene Rps1-k in soybean. Mol. Plant Microbe Interact. 10:1035-1044.
Crossref

 
 

Kato M (2010). Recent research on Phytophthora root and stem rot of soybean in Japan. Plant Prot. 64:497-500.

 
 

Kole C, Ashrafi H, Lin G, Foolad M (2006). Identification and molecular mapping of a new R gene, Ph-4, conferring resistance to late blight in tomato," Solanaceae Conference, University of Wisconsin, Madison.

 
 

Lamour K, Kamoun S (2009). Oomycete genetics and genomics: diversity, interactions and research tools. John Wiley & Sons.
Crossref

 
 

Lebeda A, Urban J (2007). Temporal changes in pathogenicity and fungicide resistance in Pseudoperonospora cubensis populations. Acta. Hortic. 731: 327-336.
Crossref

 
 

Lebeda A, Widrlechner MP, Urban J (2006). Individual and population aspects of interactions between cucurbits and Pseudoperonospora cubensis: pathotypes and races. Proceedings of Cucurbitaceae, Asheville, North Carolina, USA. pp. 453-467.

 
 

Lee JH, Park MH, Lee S (2016). Identification of Pseudoperonospora cubensis using real-time PCR and high resolution melting (HRM) analysis. J. Gen. Plant Pathol. 82(2):110-115.
Crossref

 
 

Lee S, Mian MR, McHale LK, Wang H, Wijeratne AJ, Sneller CH, Dorrance AE (2013). Novel quantitative trait loci for partial resistance to Phytophthora sojae in soybean PI 398841. Theor. Appl. Genet. 126:1121-1132.
Crossref

 
 

Li P, Cao S, Dai Y, Li X, Xu D, Guo M, Pan YM, Gao ZM (2012). Genetic diversity of Phytophthora capsici (Pythiaceae) isolates in Anhui Province of China based on ISSR-PCR markers. Genet. Mol. Res. 11:4285-4296.
Crossref

 
 

MacGregor T, Bhattacharyya M, Tyler B, Bhat R, Schmitthenner AF, Gijzen M (2002). Genetic and physical mapping of Avr1a in Phytophthora sojae. Genetics 160(3):949-959.

 
 

Malvick D, Grunden E (2004). Traits of soybean-infecting Phytophthora populations from Illinois agricultural fields. Plant Dis. 88:1139-1145.
Crossref

 
 

Martin FN, Abad ZG, Balci Y, Ivors K (2012). Identification and detection of Phytophthora: reviewing our progress, identifying our needs. ‎ Plant Dis. 96(8):1080-1103.
Crossref

 
 

Mathey MM (2013). Phenotyping diverse strawberry (Fragaria spp.) germplasm for aid in marker-assisted breeding, and marker-trait association for red stele (Phytophthora fragariae) resistance marker Rpf1. USA. Oregon State University, Master's thesis P 144.

 
 

Meng X, Shoemaker R, Yang X (1999). Analysis of pathogenicity and genetic variation among Phytophthora sojae isolates using RAPD. Mycol. Res. 103(02):173-178.
Crossref

Merk HL, Ashrafi H, Foolad MR (2012). Selective genotyping to identify late blight resistance genes in an accession of the tomato wild species Solanum pimpinellifolium. Euphytica 187(1):63-75.
Crossref

 

Merk HL, Foolad MR (2012). Parent–offspring correlation estimate of heritability for late blight resistance conferred by an accession of the tomato wild species Solanum pimpinellifolium. Plant Breed. 131(1):203-210.
Crossref

 
 

Mochizuki M, Aoki Y, Suzuki S (2012). Detection and analysis of genetic variations in GOB locus of Plasmopara viticola by DNA sequence analysis. J. Gen. Plant Pathol. 78(3):170-175.
Crossref

 
 

Moreau P, Thoquet P, Olivier J, Laterrot H, Grimsley N (1998). Genetic mapping of Ph-2, a single locus controlling partial resistance to Phytophthora infestans in tomato. Mol. Plant Microb. Interact. 11(4):259-269.
Crossref

 
 

Na R, Yu D, Chapman BP, Zhang Y, Kuflu K, Austin R, Qutob D, Zhao J, Wang Y, Gijzen M (2014). Genome re-sequencing and functional analysis places the Phytophthora sojae avirulence genes Avr1c and Avr1a in a tandem repeat at a single locus. PLoS One 9:e89738.
Crossref

 
 

Naegele R, Quesada-Ocampo LM, Kurjan J, Saude C, Hausbeck MK (2015). Spatiotemporal population structure of Pseudoperonospora cubensis isolates in Michigan and Ontario, Canada. Phytopathology 105(Suppl. 4):S4-99.

 
 

Pang X, Zhou X, Wan H, Chen J (2013). QTL mapping of downy mildew resistance in an introgression line derived from interspecific hybridization between cucumber and Cucumis hystrix. J. Phytopathol. 161:536-543.
Crossref

 
 

Patwardhan A, Ray S, Roy A (2014). Molecular Markers in phylogenetic studies-A review. J. Phylogen. Evolution Biol. 2:131.

 
 

Pei-Qing L, Min-Liang W, Ben-Jin L, Cheng-Zhong L, Qi-Yong W, Qing-He C (2013). Development of expressed sequence tag-drived simple sequence repeat markers and diversity analysis of Phytophthora capsici in China. J. Plant Pathol. 2(3):137-146.

 
 

Peirce LC (1971). Linkage tests with Ph conditioning resistance to race 0, Phytophthora infestans. Tomato Genetics Coop. 21:30.

 
 

Poland JA, Balint-Kurti PJ, Wisser RJ, Pratt RC, Nelson RJ (2009). Shades of gray: the world of quantitative disease resistance. Trends Plant Sci. 14:21-29.
Crossref

 
 

Polat Ä°, Baysal Ö, Mercati F, Kitner M, Cohen Y, Lebeda A, Carimi F (2014). Characterization of Pseudoperonospora cubensis isolates from Europe and Asia using ISSR and SRAP molecular markers. Eur. J. Plant Pathol. 139(3):641-653.
Crossref

 
 

Punja Z, Förster H, Cunningham I, Coffey M (1998). Genotypes of the late blight pathogen (Phytophthora infestans) in British Columbia and other regions of Canada during 1993-1997. Can. J. Plant Pathol. 20(3):274-282.
Crossref

 
 

Raffaele S, Farrer RA, Cano LM, Studholme DJ, MacLean D, Thines M, Jiang RHY, Zody MC, Kunjeti SG, Donofrio NM, Meyers BC, Nusbaum C, Kamoun S (2010). Genome evolution following host jumps in the Irish potato famine pathogen lineage. Science 330(6010):1540-1543.
Crossref

 
 

Romay MC, Millard MJ, Glaubitz JC, Peiffer JA, Swarts KL, Casstevens TM, Elshire RJ, Acharya CB, Mitchell SE, Flint-Garcia SA, McMullen MD, Holland JB, Buckler ES, Gardner CA (2013). Comprehensive genotyping of the USA national maize inbred seed bank. Genome Biol. 14: R55
Crossref

 
 

Rouxel M, Papura D, Nogueira M, Machefer V, Dezette D, Richard-Cervera S, Carrere S, Mestre P, Delmotte F (2012). Microsatellite markers for characterization of native and introduced populations of Plasmopara viticola, the causal agent of grapevine downy mildew. Appl. Environ. Microbiol. 78:6337-6340.
Crossref

 
 

Roy SG, Bhattacharyya S, Mukherjee SK, Khatua DC (2009). Molecular identification of Phytophthora spp. affecting some economically important crops in Eastern India through ITS-RFLP and sequencing of the ITS region. ‎ J. Phytopathol. 157:666-674.
Crossref

 
 

Salimath S, Bhattacharyya M (1999). Generation of a soybean BAC library, and identification of DNA sequences tightly linked to the Rps1-k disease resistance gene. Theor. Appl. Genet. 98:712-720.
Crossref

 
 

Sarris P, Abdelhalim M, Kitner M, Skandalis N, Panopoulos N, Doulis A, Lebeda A (2009). Molecular polymorphisms between populations of Pseudoperonospora cubensis from Greece and the Czech Republic and the phytopathological and phylogenetic implications. Plant Pathol. 58(5):933-943.
Crossref

 
 

Scherer E, Gisi U (2006). Characterization of genotype and mating type in European isolates of Plasmopara viticola. J. Phytopathol. 154:489-495.
Crossref

 
 

Schneider R, Rolling W, Song Q, Cregan P, Dorrance AE, McHale LK (2016). Genome-wide association mapping of partial resistance to Phytophthora sojae in soybean plant introductions from the Republic of Korea. BMC Genomics 17:607.
Crossref

 
 

Shirasawa K, Hirakawa H, Isobe S (2016). Analytical workflow of double-digest restriction site-associated DNA sequencing based on empirical and in silico optimization in tomato. DNA Res. 23:145-153.
Crossref

 
 

Singh A, Gupta VK, Kumar A, Singh, VK, Nayakwadi S (2013). 16S rRNA and Omp31 gene based molecular characterization of field strains of B. melitensis from aborted foetus of goats in India. Sci. World J. 2013:160376.
Crossref

 
 

Sonah H, Bastien M, Iquira E, Tardivel A, Légaré G, Boyle B, Normandeau É, Laroche J, Larose S, Jean M, Belzile F (2013). An improved genotyping by sequencing (GBS) approach offering increased versatility and efficiency of SNP discovery and genotyping. PloS One 8:e54603.
Crossref

 
 

Stark-Urnau M, Seidel M, Kast WK, Gemmrich AR (2000). Studies on the genetic diversity of primary and secondary infections of Plasmopara viticola using RAPD/PCR. Vitis 39:163-166.

 
 

Steuernagel B, Periyannan SK, Hernández-Pinzón I, Witek K, Rouse MN, Yu G, Hatta A, Ayliffe M, Bariana H, Jones J D G, Lagudah E S, Wulff B B H. (2016). Rapid cloning of disease-resistance genes in plants using mutagenesis and sequence capture. Nature Biotechnol. 34:652-5.
Crossref

 
 

Stroud J, Shaw D, Hale M, Steele K (2015). SSR assessment of Phytophthora infestans populations on tomato and potato in British gardens demonstrates high diversity but no evidence for host specialization. Plant Pathol. 65(2):334-341.
Crossref

 
 

Summers CF, Gulliford CM, Carlson CH, Lillis JA, Carlson MO, Cadle-Davidson L, Gent DH, Smart CD (2015). Identification of genetic variation between obligate plant pathogens Pseudoperonospora cubensis and P. humuli using RNA sequencing and genotyping-by-sequencing. PloS One 10:e0143665.
Crossref

 
 

Sun S, Wu X, Zhao J, Wang Y, Tang Q, Yu D, Gai JY, Xing H (2011). Characterization and mapping of RpsYu25, a novel resistance gene to Phytophthora sojae. Plant breed. 130:139-143.
Crossref

 
 

United Nations (UN) (2015). Department of Economic and Social Affairs, Population Division, World Population Prospects: The 2015 Revision, Key Findings and Advance Tables. Working Paper No. ESA/P/WP.241, UN, New York.

 
 

Van de Weg W (1997). Resistance to Phytophthora fragariae var. fragariae in strawberry: the Rpf2 gene. Theor. Appl. Genet. 94:1092-1096.
Crossref

 
 

van Orsouw NJ, Hogers RCJ, Janssen A, Yalcin F, Snoeijers S, Verstege E, Schneiders H, van der Poel H, van Oeveren J, Verstegen H, van Eijk MJT (2007). Complexity reduction of polymorphic sequences (CRoPSTM): A novel approach for large-scale polymorphism discovery in complex genomes. PLoS One 2:e1172.
Crossref

 
 

Van Tassell CP, Smith TP, Matukumalli LK, Taylor JF, Schnabel RD, Lawley CT, Haudenschild CD, Moore SS, Warren WC, Sonstegard TS (2008). SNP discovery and allele frequency estimation by deep sequencing of reduced representation libraries. Nat. Methods 5:247-252.
Crossref

 
 

Venuti S, Copetti D, Foria S, Falginella L, Hoffmann S, Bellin D, Cindrić P, Kozma P, Scalabrin S, Morgante M, Testolin R, Di Gaspero G (2013). Historical introgression of the downy mildew resistance gene Rpv12 from the Asian species Vitis amurensis into grapevine varieties. PloS One 8:e61228.
Crossref

 
 

Vignal A, Milan D, Sancristobal M, Eggen A (2002). A review on SNP and other types of molecular markers and their use in animal genetics. Genet. Sel. Evol. 34:275-305.
Crossref

 
 

Vleeshouwers VG, Raffaele S, Vossen JH, Champouret N, Oliva R, Segretin ME, Rietman H, Cano LM, Lokossou A, Kessel G, Pel MA, Kamoun S (2011). Understanding and exploiting late blight resistance in the age of effectors. Annu. Rev. Phytopathol. 49:507-531.
Crossref

 
 

Vos P, Hogers R, Bleeker M, Reijans M, Van de Lee T, Hornes M, Frijters A, Pot J, Peleman J, Kuiper M, Zabeau M (1995). AFLP: a new technique for DNA fingerprinting. Nucleic Acids Res. 23(21):4407-4414.
Crossref

 
 

Whisson S, Drenth A, Maclean D, Irwin J (1995). Phytophthora sojae avirulence genes, RAPD, and RFLP markers used to construct a detailed genetic linkage map. Mol. Plant Microbe Interact. 8(6):988-995.
Crossref

 
 

Wiedmann RT, Smith TP, Nonneman DJ (2008). SNP discovery in swine by reduced representation and high throughput pyrosequencing. BMC Genetics 9:81.
Crossref

 
 

Wilcox W (1989). Identity, virulence, and isolation frequency of seven Phytophthora spp. causing root rot of raspberry in New York. Phytopathology 79:93-101.
Crossref

 
 

Wu Y, Jiang J, Gui C (2012). Low genetic diversity of Phytophthora infestans population in potato in north China. Afr. J. Biotechnol. 11(90):15636-15642.
Crossref

 
 

Xu X, Chao J, Cheng X, Wang R, Sun B, Wang H, Shaobo Luo, Xiaowan Xu, Tingquan Wu, Ying Li (2016). Mapping of a novel race specific resistance gene to Phytophthora root rot of pepper (Capsicum annuum) using bulked segregant analysis combined with specific length amplified fragment sequencing strategy. PloS One 11:e0151401.
Crossref

 
 

Xuanzhe Z, Shengjun X (2010). Analysis on genotypic differentiation of Phytophthora infestans by using random amplified polymorphic DNA (RAPD). J. Northeast Agric. Univ. 17(2):7-14.

 
 

Yang S, Fresnedo-Ramírez J, Wang M, Cote L, Schweitzer P, Barba P, Takacs EM, Clark M, Luby J, Manns DC, Sacks G, Mansfield AK, Londo J, Fennell A, Gadoury D, Reisch B, Cadle-Davidson L, Sun Q (2016). A next-generation marker genotyping platform (AmpSeq) in heterozygous crops: a case study for marker-assisted selection in grapevine. Hortic. Res. 3:16002.
Crossref

 
 

Yin J, Jackson K, Candole B, Csinos A, Langston D, Ji P (2012). Aggressiveness and diversity of Phytophthora capsici on vegetable crops in Georgia. Ann. Appl. Biol. 160(2):191-200.
Crossref

 
 

Yin L, An Y, Qu J, Li X, Zhang Y, Dry I, Wu H, Lu J (2017). Genome sequence of Plasmopara viticola and insight into the pathogenic mechanism. Sci. Rep. 7:46553.
Crossref

 
 

Yoshida K, Schuenemann VJ, Cano LM, Pais M, Mishra B, Sharma R, Lanz C, Martin FN, Kamoun S, Krause J, Thines M, Weigel D, Burbano HA (2013). The rise and fall of the Phytophthora infestans lineage that triggered the Irish potato famine. eLife 2:e00731

 
 

Yoshioka Y, Sakata Y, Sugiyama M, Fukino N (2014). Identification of quantitative trait loci for downy mildew resistance in cucumber (Cucumis sativus L.). Euphytica 198:265-276.
Crossref

 
 

Zeng HC, Ho HH, Zheng FC (2009). A survey of Phytophthora species on Hainan Island of South China. J. Phytopathol.157(1):33-39.
Crossref

 
 

 




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