Assessing new SSR markers for utility and informativeness in genetic studies of brown rust fungi on wheat,triticale, and rye

The aim of the present study was to validate new simple-sequence repeat (SSR) markers and use them to assess genetic variability among 24 isolates of Puccinia triticina collected from wheat (Pt-wheat) and triticale (Pt-triticale), and 15 isolates of P. recondita f. sp. secalis (Prs) collected from rye. The Pt and Prs isolates were tested for virulence on a set of 35 Thatcher wheat near-isogenic lines, eight rye lines with known resistance genes, and 53 triticale cultivars with uncharacterized leaf rust resistance. Molecular genotypes were determined using a newly developed set of 34 SSR microsatellite primer pairs. All SSR markers tested on Pt isolates successfully amplified fragments of appropriate size. When tested on the Prs isolates, 21 out of the 34 Pt SSRs amplified expected fragments. Sixteen of these 21 SSRs were polymorphic, providing for the first time microsatellite markers to study genetic variation in Prs. Based on virulence data, variation among Prs isolates was low, probably due to the small number of rye differential lines available. Much higher variation for virulence was observed within the collection of Pt isolates from wheat and triticale, and two separate groups were established with mixed host origin. Substantial genetic variation was detected among the isolates studied with the SSR markers, assuming two different models of SSR evolution (infinite alleles model and stepwise mutation model). The newly developed set of SSR markers proved their effectiveness in detecting genetic variation and should be useful in further population genetics investigations of the two pathogens.     

Virulence and Molecular Diversity within Colletotrichum lindemuthianum Isolates from Andean and Mesoamerican bean Varieties and Regions

Virulence on a standard set of 12 common bean differential varieties, DNA sequence of repetitive-elements (Rep-PCR) and random amplified microsatellites (RAMS) were used to assess the genetic variability of 200 Colletotrichum lindemuthianum isolates collected from Andean and Mesoamerican bean varieties and regions. High levels of pathotypic (90 pathotypes) and genetic diversity (0.97) were identified among 200 isolates, revealing that C. lindemuthianum is a highly diverse pathogen. Although a significant number of pathotypes were common to Andean and Mesoamerican regions, many more were only found in the Mesoamerican region. Cluster analysis of virulence and molecular data did not separate isolates into groups that were structured with common bean gene pools. No genetic differentiation (G _ST=0.03) was apparent between Andean and Mesoamerican isolates of C. lindemuthianum. The diversity exhibited by C. lindemuthianum does not appear to cluster according to common bean gene pools, and the high diversity found in the Mesoamerican region seems to indicate that C. lindemuthianum originated and was disseminated from this region. Due to the high genetic variation exhibited by C. lindemuthianum, stacking major resistance genes appears to be the best option for developing cultivars with durable anthracnose resistance.     

Analysis of sources of oxolinic acid-resistant field strains of <Emphasis Type="Italic">Burkholderia glumae</Emphasis> based on rep-PCR analysis and nucleotide sequences of <Emphasis Type="Italic">gyrB</Emphasis> and <Emphasis Type="Italic">rpoD</Emphasis>

Repetitive sequence-based polymerase chain reaction (rep-PCR) analysis using BOX and ERIC as primers showed a highly divergent phylogeny among field strains of Burkholderia glumae. To elucidate the sources of oxolinic acid (OA) resistance in field strains of B. glumae isolated from rice seedlings cultivated in Mie, Toyama, and Iwate prefectures, Japan, the amino acid at position 83 of GyrA (GyrA83), which is involved in OA resistance, and the DNA patterns from the rep-PCR and the partial nucleotide sequences of gyrB and rpoD from various strains were analyzed. The ten Mie strains, in which GyrA83 was isoleucine (Ile), were divided into two groups based on the band patterns in rep-PCR analysis, although the nucleotide sequences of gyrB and rpoD were identical among the strains. Based on the band patterns in the rep-PCR analysis and the gyrB and rpoD sequences, two highly OA-resistant Toyama strains, Pg-13 and Pg-14, for which GyrA83 was serine (Ser) and Ile, respectively, were in the same lineage. This suggests that the bacteria might acquire OA resistance faster than phylogenic diversity as determined with the repetitive sequences BOX and ERIC and with gyrB and rpoD. Furthermore, three Iwate strains (H95, H101, and H104), isolated from seedlings of different cultivars grown in different years and having Ile at GyrA83, are probably in the same lineage, suggesting that OA-resistant bacteria might be transferred among different cultivars.     

Bacterial blight of rice and its control in Nepal

Research on Xanthomonas oryzae pv. oryzae, the bacterial blight of rice pathogen, was initiated at the Institute of Agriculture and Animal Science (IAAS) with the main objective of assessing the population structure of X. o. pv. oryzae through the use of both conventional and molecular markers in combination with virulence typing. A high DNA polymorphism was detected in the pathogen populations using different DNA probes and rep-PCR primers. Most strains were avirulent to cultivars containing the bacterial blight resistance gene Xa-21, which suggested the strategy that targets gene deployment is feasible in Nepal.     

Genetic differentiation of the wheat leaf rust fungus Puccinia triticina in Europe

The objective of this study was to determine whether genetically differentiated groups of Puccinia triticina are present in Europe. In total, 133 isolates of P. triticina collected from western Europe, central Europe and Turkey were tested for virulence on 20 lines of wheat with single leaf rust resistance genes, and for molecular genotypes with 23 simple sequence repeat (SSR) markers. After removal of isolates with identical virulence and SSR genotype within countries, 121 isolates were retained for further analysis. Isolates were grouped based on SSR genotypes using a Bayesian approach and a genetic distance method. Both methods optimally placed the isolates into eight European (EU) groups of P. triticina SSR genotypes. Seven of the groups had virulence characteristics of isolates collected from common hexaploid wheat, and one of the groups had virulence characteristics of isolates from tetraploid durum wheat. There was a significant correlation between the SSR genotypes and virulence phenotypes of the isolates. All EU groups had observed values of heterozygosity greater than expected and significant fixation values, which indicated the clonal reproduction of urediniospores in the overall population. Linkage disequilibria for SSR genotypes were high across the entire population and within countries. The overall values of R_ST and F_ST were lower when isolates were grouped by country, which indicated the migration of isolates within Europe. The European population of P. triticina had higher levels of genetic differentiation compared to other continental populations.     

Molecular diversity in <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> isolates from common bean fields in Brazil

The common bean (Phaseolus vulgaris L.) is widely cultivated in Brazil and is known as a very important crop for families in this country. Fusarium wilt severely harms common beans and has become a big issue for this crop. In order to assist the breeding programs that target resistance to this disease, the evaluation of genetic diversity of the pathogen and its molecular characterization are crucial. Thus, the present goal was to identify Fusarium isolates obtained from several places in Brazil using molecular tools; select molecular markers for these isolates; and analyze their diversity. All of isolates were molecularly identified as Fusarium oxysporum f. sp. phaseoli (Fop). By using seven selected SSR markers, the results of diversity obtained by the dendrogram and the Bayesian analysis formed four groups where a large diversity of this fungus was found within each state. However, the groups were more homogenous according to the collection source and the pathogenicity test. More specifically, group 2 was composed of the most virulent strains and originated from Minas Gerais State – UFV, and group 3 was mostly composed by isolates from Goias state. Group I was also more diverse in terms of location and virulence. The overall results indicated a positive correlation between Fusarium diversity and its virulence to common bean. Furthermore, the use of these markers was effective in molecular identification and in detecting polymorphism within F. oxysporum f. sp. phaseoli.     

DNA fingerprinting of Pyricularia grisea by rep-PCR using a single primer based on the terminal inverted repeat from either of the transposable elements Pot2 and MGR586

We investigated the use of single primers complementary to sequences in the terminal inverted repeat (TIR) of either Pot2 or MGR586, transposable elements found in Pyricularia grisea, for DNA fingerprinting by repetitive-element-based polymerase chain reaction (rep-PCR). Under standard amplification conditions, rep-PCR with each single primer generated distinct fingerprint patterns among rice-infecting P. grisea isolates collected in Japan. With the Pot2-TIR primer, bands ranging in size from 0.2 to 8 kb and in number from 8 to 13 per isolate were amplified. Although fewer bands were amplified with the MGR586-TIR primer, this molecular technique should be more reliable to identify and classify P. grisea isolates by combining the data of fingerprint patterns from each TIR primer. In a cluster analysis based on DNA fingerprints from this rep-PCR with the Pot2-TIR primer, 10 reference isolates and 12 field isolates from Saga Prefecture in 2002 were separated into six clonal lineages. We also demonstrated that the 12 field isolates belonged to one clonal lineage. Thus, this rep-PCR method using the single primer Pot2-TIR will be useful for the analysis of the population structure of rice blast pathogens.     

中国小麦条锈病菌CYR32和CYR33的毒性及基因型多样性

为明确我国小麦条锈病菌当前主要流行生理小种CYR32和CYR33的毒性及基因型特征,从全国11个省(区)随机选取29个CYR32菌株和39个CYR33菌株,利用近等基因系及辅助鉴别寄主对其进行毒性鉴定,利用SSR分子标记技术对其进行基因型分析,并对其进行聚类分析。结果显示,CYR32和CYR33菌系各有17种毒性表型,而且在抗病基因Yr2、Yr17、Yr27、Yr32、Yr43、Yr Sp、Yr Exp2、Yr28、Yr V23上都发生了毒性分化,CYR32和CYR33菌系的多样性指数分别为0.089、0.097;CYR32和CYR33菌系的香农信息指数均值分别为0.44和0.45;当相似性系数为0.93时,CYR32和CYR33菌系分别被聚为5个和8个毒性类群;当相似性系数为0.84时,CYR32和CYR33菌系分别被聚为10个和16个基因型类群。表明在中国鉴别寄主上具有相同毒性谱特征的CYR32和CYR33菌系在近等基因和SSR分子标记中发生了不同程度的毒性和基因型分化。     

Pathogenicity and population structure analysis of Pyricularia oryzae in different districts of Jiangsu province,China

Rice blast caused by Pyricularia oryzae is one of the most destructive rice diseases worldwide. In this study, 224 isolates were isolated from neck blast samples from nine districts in Jiangsu. We analysed the resistance frequency of 24 resistance (R) genes using 32 monogenic rice lines from the International Rice Research Institute (IRRI), including Pii, Pik-h, Pi5, Piz-5, and Piz, which exhibit high resistance frequencies. PAC (pathogenicity association coefficients) and VAC (virulence association coefficients) analyses identified three combinations of R genes, Piz/Pii, Piz/Piz-5, and Piz/Pi5, as being suitable for use in Jiangsu. Mating-type analysis of P. oryzae isolates indicated that sexual reproduction occurred less frequently in northern Jiangsu than in other areas, which may affect genetic diversity and dissemination. Pot2-TIR analysis indicated that the genetic diversity of P. oryzae in Xuzhou was mainly due to the insertion of transposable elements, while that of Nanjing was due to both the insertion of transposable elements and sexual recombination. Therefore, some R genes or gene combinations were suitable for resistance breeding in Jiangsu, and repetitive-PCR (rep-PCR) is a cost-effective tool for genetically differentiating distinct cultivar-specific populations or lineages with well-defined virulence patterns, because of the close correspondence between rep-PCR based clusters and pathotypes of inbred lines.     

Validation of a QTL for resistance to ascochyta blight linked to resistance to fusarium wilt race 5 in chickpea (<Emphasis Type="Italic">Cicer arietinum</Emphasis> L.)

Ascochyta blight caused by Ascochyta rabiei and fusarium wilt caused by Fusarium oxysporum. f. sp. ciceris are the two most serious diseases of chickpea (Cicer arietinum). Quantitative trait loci (QTL) or genes for ascochyta blight resistance and a cluster of resistance genes for several fusarium wilt races (foc1, foc3, foc4 and foc5) located on LG2 of the chickpea map have been reported independently. In order to validate these results and study the linkage relationship between the loci that confer resistance to blight and wilt, an intraspecific chickpea recombinant inbred lines (RIL) population that segregates for resistance to both diseases was studied. A new LG2 was established using sequence tagged microsatellite sites (STMS) markers selected from other chickpea maps. Resistance to race 5 of F. oxysporum (foc5) was inherited as a single gene and mapped to LG2, flanked by the STMS markers TA110 (6.5 cM apart) and TA59 (8.9 cM apart). A QTL for resistance to ascochyta blight (QTL_AR3) was also detected on LG2 using evaluation data obtained separately in two cropping seasons. This genomic region, where QTL_AR3 is located, was highly saturated with STMS markers. STMS TA194 appeared tightly linked to QTL_AR3 and was flanked by the STMS markers TR58 and TS82 (6.5 cM apart). The genetic distance between foc5 and QTL_AR3 peak was around 24 cM including six markers within this interval. The markers linked to both loci could facilitate the pyramiding of resistance genes for both diseases through MAS.     

Genetics of host-pathogen interactions in the <Emphasis Type="Italic">Pyrenophora teres</Emphasis> f. <Emphasis Type="Italic">teres</Emphasis> (net form) – barley (<Emphasis Type="Italic">Hordeum vulgare)</Emphasis> pathosystem

The genetics of host-pathogen interactions in the Hordeum vulgare – P. teres f. teres pathosystem was studied in twelve resistant barley accessions, i.e. CI 9825, CI 9819, Diamond, CI 4922, CI 5401, Harbin, c-8755, c-21849, c-8721 c-23874, c-19979, c-15811. F₂ analyses of crosses with susceptible genotypes employing various isolates (from Europe, USA, Canada, and Australia) revealed that resistance is mostly isolate-specific and controlled by one or two genes. Segregation in ascospore progeny from two crosses between isolates of different origin revealed that avirulence in P. teres is also determined by one or two genes. An epistatic effect of suppressor genes on avirulence genes is proposed for the genetics of virulence to Diamond, Harbin, CI 5401 and c-8721 in the fungal crosses D (181-6 × A80) and F (H-22 × 92-178/9). Segregation in F₂ of crosses of three new sources of resistance (c-23874, c-19979, c-15811) to the susceptible cv. Pirkka was studied in laboratory and greenhouse tests by using seven P. teres isolates, i.e. 181-6, d8-3, d8-4, d9-1, d9-4, F4 and F74. In addition, virulence to these barley accessions of ascospore progeny from crosses of the same isolates was studied. Based on these studies it was concluded that depending on the isolate used, resistance of c-23874 is determined at least by two genes and in c-19979 and c-15811 by three genes. The results of this parallel analyses of genetics of resistance and genetics of virulence allows the postulation of a gene–for–gene interaction in the P. teres – H. vulgare pathosystem.     

Genetic diversity and population structure of Acidovorax avenae subsp. avenae isolated from sugarcane in Argentina

A significant increase in the occurrence of red stripe (caused by Acidovorax avenae subsp. avenae) has been observed in the last decade in Argentina. Considering that no extensive sampling of the main sugarcane-producing area in the country has been conducted to characterize the diversity and population structure of A. avenae subsp. avenae, molecular markers were employed to analyse 112 isolates from Tucumán. By using repetitive element polymorphism-based polymerase chain reaction (rep-PCR) almost all isolates were differentiated and grouped into 10 clusters, revealing a high genetic diversity. Using the amplified fragment length polymorphism (AFLP) technique, five pairs of isolates were discriminated that could not be distinguished with rep-PCR. Cluster analysis showed no clear association between isolate clustering, sugarcane host genotype, crop age, type of tissue sampled, fertilization, or year of sampling. Linkage equilibrium analysis by using rep-PCR data indicated that the population has some degree of clonality. Three housekeeping genes were also sequenced: ugpB and pilT sequences were highly similar to A. avenae subsp. avenae sequences from other Argentinian isolates, whereas the lepA sequence did not reveal significant similarity. An additional four housekeeping genes could not be amplified, suggesting the existence of differences in those regions. Subsequently, virulence of 14 A. avenae subsp. avenae isolates was evaluated under controlled conditions. Results showed a differential level of aggressiveness among the isolates on a resistant sugarcane variety. This study confirmed that rep-PCR is an adequate tool for genetic analysis and population structure characterization in bacteria, and revealed both high genetic diversity and clonal population structure of A. avenae subsp. avenae in Tucumán, Argentina.     

Pathogenic and genetic diversity of Puccinia triticina from triticale in Poland between 2012 and 2015

Variation among Puccinia triticina isolates collected from triticale in Poland between 2012 and 2015 was studied based on virulence and simple sequence repeat (SSR) markers. Two hundred and forty-two single-uredinial isolates from four geographically separated locations were tested for virulence against 33 near-isogenic Thatcher lines containing known Lr resistance genes, and their molecular genotypes were characterized with 34 SSR markers. Structure and relationships of the regional and annual populations of P. triticina were analysed using an assignment-based approach for both the virulence and SSR data. The molecular marker analysis was based on two different models of SSR evolution: the stepwise mutation model with a variable mutation rate (SMMv) and the infinite alleles model (IAM). A highly significant deviation from Hardy–Weinberg equilibrium among SSR genotypes, a high proportion of heterozygotes, and a moderate association of relationships between virulence phenotypes and SSR genotypes were consistent with the occurrence of clonal lineages of related races within the population. While the results suggest that genetic drift and mutation affect variation within the pathogen population, it seems that migration has the most significant role in shaping the population structure of P. triticina occurring on triticale in Poland.     

Genetic variability within Phaeoisariopsis griseola from Central America and its implications for resistance breeding of common bean

The genetic and virulence variability of 112 isolates of Phaeoisariopsis griseola , collected from various locations in Central America, were studied using seven random amplified polymorphic DNA (RAPD) primers and 12 common-bean differential genotypes. Broad molecular diversity ( H  = 0·92) among isolates was found using RAPD markers. Fifty pathotypes were identified on 12 differential bean genotypes, 29 of which were represented by only one isolate. Only 18 pathotypes were found in two or more countries. Pathotype 63-63 was the most virulent and caused leaf spots on all 12 common-bean differential genotypes. Comparison of virulence phenotypes and RAPD profiles to known Andean P. griseola isolates confirmed that all isolates belonged to the Mesoamerican group. Pairwise comparison between individual RAPD loci showed that the majority were in gametic phase linkage disequilibrium, revealing that P. griseola maintains a genetic structure that is consistent with asexual reproduction. The molecular and virulence diversities of P. griseola isolates from Central America imply that using single resistance genes to manage angular leaf spot is inadequate and stacking resistance genes may be necessary to manage the disease effectively.     

Genetic diversity among <Emphasis Type="Italic">Brenneria nigrifluens</Emphasis> strains in Iran

To investigate the variability of Brenneria nigrifluens, the casual agent of shallow bark canker of Persian walnut (Juglans regia L.), a collection of 24 strains isolated from five geographic regions, was analyzed by means of three marker systems, repetitive polymerase chain reaction (rep-PCR), insertion sequence (IS50)-PCR and random amplified polymorphic DNA (RAPD). Cluster analysis was performed using UPGMA. Strains were differentiated into 6 groups at about 80% similarity according to geographic regions. This is possibly due to cultivation of Persian walnut being mainly based on the ecotype and/or local seedlings that have become adapted to particular environments and so have allowed selection of different B. nigrifluens populations. The results of this study showed that the four rep-PCR primers produced 75 products of which 73.3% were polymorphic, eight RAPD primers produced 146 fragments of which 74.6% were polymorphic and IS50 produced 32 fragments of which 93.75% were polymorphic. The usefulness of each system was examined in terms of polymorphism information content (PIC) and marker index (MI). The highest MI was observed for IS50-PCR (21.11) followed by RAPD (7.85), and rep-PCR (6.92). The Mantel test identified significant correlation between the similarity coefficients calculated from them. Among the molecular markers tested, IS50-PCR appears to be a more suitable marker for fingerprinting and assessing genetic relationships among B. nigrifluens strains. This is the first study on genetic diversity of B. nigrifluens. The results can have a bearing on the choice of disease management strategies.     

Genetic diversity and aggressiveness of Erwinia psidii on Eucalyptus spp. in Brazil

The genetic variability and aggressiveness of Brazilian Erwinia psidii isolates from Eucalyptus spp. was studied and compared with reference isolates from guava (Psidium guajava). Repetitive element sequence (rep)-based PCR markers of 101 isolates from Eucalyptus spp. and five from guava showed that the populations of E. psidii displayed a relatively low genetic variability. No correlation of genetic clustering based on rep-PCR analysis with geographic origin or host of origin was observed, indicating that genome rearrangements associated with adaptation to a particular host were not detected by these molecular markers. A higher genotypic richness was detected in the Mato Grosso do Sul population, probably reflecting a pathogen dissemination associated with the recent expansion in eucalypt plantations. Wilcoxon and ANOVA tests of disease severity data indicated differences in aggressiveness among isolates and an isolate × clone interaction. The area under the disease progress curve (AUDPC) and disease severity for some isolates were significantly different between two susceptible clones tested. Notably, isolate LPF681 from guava was not able to cause disease on a susceptible Eucalyptus urophylla clone, suggesting that some co-evolution between pathogen and host has taken place. The variability in aggressiveness and virulence among isolates of E. psidii observed in this study will be important for the establishment of appropriate screening approaches to select for disease resistance.     

Genetic relationships among strains of <Emphasis Type="Italic">Xanthomonas campestris</Emphasis>pv. <Emphasis Type="Italic">campestris</Emphasis>revealed by novel rep-PCR primers

Novel primers for rep-PCR were developed with the original software and based on `ancient diverged periodical sequences'. Rep-PCR with these primers was applied to study genetic relationships among 51 Xanthomonas campestris strains. The strains were collected from different countries including Russia, Japan, UK, Germany and Hungary. Reference strains of three X. campestrispathovars and five other Xanthomonas species were included. Based on qualitative differences in amplification profiles, the strains were divided into four major groups. Two subgroups recognised within X. campestrispopulation were similar to RFLP haplotypes. The third subgroup included strains of two other pathovariants and Japanese isolates of X. campestris pv. campestriswhile the fourth group comprised the other species of Xanthomonas. The analysis of the diversity within X. campestris resulted in the conclusion that isolates belong to distinct clonal populations (subgroups). The differences between the subgroups of X. campestris were only slightly smaller than between species of Xanthomonas. A PCR fragment about 600 bp amplified by primer KRPN2 was found in nearly all tested strains of X. campestris.SCAR primers designed for this marker produced a single specific band for strains of X. campestris, but not for other Xanthomonas, Pseudomonas and Erwiniastrains tested. Application of the new primer set for rep-PCR offers a rapid, simple and reproducible method for identification of bacterial strains. The X. campestris-specific SCAR primers may be used in diagnostics of this important plant pathogen.     

Characterization of the rust resistance gene present in the common bean cultivar Ouro Negro,the main rust resistance source used in Brazil

The main goal of the present work was to characterize the rust resistance (RR) gene present in the Mesoamerican common bean cultivar Ouro Negro, temporarily named Ur‐OuroNegro or Ur‐ON, which is the main RR source used in Brazil. The RR spectrum presented by cv. Ouro Negro was compared with those of other bean lines harbouring known RR genes when inoculated with nine selected races of Uromyces appendiculatus, the causal agent of bean rust. In addition, all bean lines were screened with molecular markers linked to Ur‐ON in order to identify additional evidence for the presence of alleles for this locus in the screened RR sources. The allelic relationships of Ur‐ON were tested with previously characterized RR genes from lines resistant to at least one race of the pathogen. Allelism tests were also carried out between cv. Ouro Negro and cvs CNC and CSW 643, important RR sources in Brazil harbouring unnamed RR genes. The results showed that the major dominant gene conditioning RR in cv. Ouro Negro is positioned at a locus distinct from those with which it was compared. It is proposed that this gene – or complex gene locus – is unique and be designated Ur‐14.     

Tagging and mapping a second resistance gene for <Emphasis Type="Italic">Fusarium</Emphasis> wilt race 0 in chickpea

A second gene conferring resistance to the chickpea wilt pathogen, Fusarium oxysporum f. sp ciceris race 0, has been mapped to linkage group 2 (LG2) of the chickpea genetic map. Resistance to race 0 is controlled by two genes which segregate independently; one present in accession JG62 (Foc0 ₁ /foc0 ₁ ) and mapping to LG5 and the second present in accession CA2139 (Foc0 ₂ /foc0 ₂ ) but remaining unmapped. Both genes separately confer complete resistance to race 0 of the wilt pathogen. Using a Recombinant Inbred Line (RIL) population that segregated for both genes (CA2139 × JG62) and the genotypic information provided by two markers flanking Foc0 ₁ /foc0 ₁ ten resistant lines containing the resistant allele Foc0 ₂ /foc0 ₂ were selected. Genotypic analysis using these ten resistant lines paired with ten susceptible RILs, selected in the same population, revealed that sequence tagged microsatellite sites (STMS) markers sited on LG2 were strongly associated with Foc0 ₂ /foc0 ₂ . Linkage analysis, using data from two mapping populations (CA2139/JG62 and CA2156/JG62), located Foc0 ₂ /foc0 ₂ in a region where genes for resistance to wilt races 1, 2, 3, 4 and 5 have previously been reported and which is highly saturated with tightly-linked STMS markers that could be used in marker-assisted selection (MAS).