Cyst Nematode Resistance Gene Research Articles

Dissecting nematode resistance regions in soybean revealed pleiotropic effect of soybean cyst and reniform nematode resistance genes.

Reniform nematode (RN, Rotylenchulus reniformis Linford & Oliveira) has emerged as one of the most important plant parasitic nematodes of soybean [Glycine max (L.) Merr.]. Planting resistant varieties is the most effective strategy for nematode management. The objective of this study was to identify quantitative trait loci (QTL) for RN resistance in an exotic soybean line, PI 438489B, using two linkage maps constructed from the Universal Soybean Linkage Panel (USLP 1.0) and next-generation whole-genome resequencing (WGRS) technology. Two QTL controlling RN resistance were identified-the soybean cyst nematode (SCN, Heterodera glycines) resistance gene GmSNAP18 at the rhg1 locus and its paralog GmSNAP11. Strong association between resistant phenotype and haplotypes of the GmSNAP11 and GmSNAP18 was observed. The results indicated that GmSNAP11 possibly could have epistatic effect on GmSNAP18, or vice versa, with the presence of a significant correlation in RN resistance of rhg1-a GmSNAP18 vs. rhg1-b GmSNAP18. Most importantly, our preliminary data suggested that GmSNAP18 and GmSNAP11 proteins physically interact in planta, suggesting that they belong to the same pathway for resistance. Unlike GmSNAP18, no indication of GmSNAP11 copy number variation was found. Moreover, gene-based single nucleotide polymorphism (SNP) markers were developed for rapid detection of RN or SCN resistance at these loci. Our analysis substantiates synergic interaction between GmSNAP11 and GmSNAP18 genes and confirms their roles in RN as well as SCN resistance. These results could contribute to a better understanding of evolution and subfunctionalization of genes conferring resistance to multiple nematode species and provide a framework for further investigations.

Identification of novel haplotype of a cyst nematode resistance gene, GmSNAP18 in soybean [Glycine max (L.) Merr.

Soybean cyst nematode (SCN) is one of the most damaging pest of soybean. Discovery and characterization of the genes involved in SCN resistance are important in soybean breeding. Soluble NSF attachment protein (SNAP) genes are related to SCN resistance in soybean. SNAP genes include five gene families, and 2 haplotypes of exons 6 and 9 of SNAP18 are considered resistant to the SCN. In present study the haplotypes of GmSNAP18 were surveyed and chacterized in a total of 60 diverse soybean genotypes including Korean cultivars, landraces, and wild-types. The target region of exons 6 and 9 in GmSNAP18 region was amplified and sequenced to examine nucleotide variation. Characterization of 5 haplotypes identified in present study for the GmSNAP18 gene revealed two haplotypes as resistant, 1 as susceptible and two as novel. A total of twelve genotypes showed resistant haplotypes, and 45 cultivars were found susceptible. Interestingly, the two novel haplotypes were present in 3 soybean lines. The information provided here about the haplotypic variation of GmSNAP18 gene can be further explored for soybean breeding to develop resistant varieties.

Cereal cyst nematode resistance gene CreV effective against Heterodera filipjevi transferred from chromosome 6VL of Dasypyrum villosum to bread wheat

Cereal cyst nematodes (CCN) are a global economic problem for cereal production. Heterodera filipjevi is one of the most commonly identified and widespread CCN species found in many wheat production regions of the world. Transferring novel genes for resistance to H. filipjevi from wild relatives of wheat is a promising strategy for protection of wheat crops. A set of wheat–Dasypyrum villosum chromosome addition lines, T6V#4S·6AL translocation lines and their donor parental lines were tested for their response to the nematode. D. villosum and wheat–D. villosum disomic addition line DA6V#4 were resistant. As T6V#4S·6AL translocation lines were susceptible, resistance was presumed to be located on chromosome 6V#4L. The objective of this study was to produce and characterize wheat–6V#4L translocations and confirm the chromosome location of the resistance. Introgression lines T6V#4L·6AS, T6V#4L-4BL·4BS and DT6V#4L were developed and subjected to molecular cytogenetic analysis. These and four additional wheat–6V#4 introgression lines were tested for response to H. filipjevi in the greenhouse. The results indicated that introgression lines DA6V#4, T6V#4L·6AS, T6V#4L-4BL·4BS, T6V#4L·6V#4S-7BS and DT6VL#4 had higher levels of H. filipjevi resistance than their recurrent parent. However, Del6V#4L-1 and translocation line T6V#4S·6AL were equally susceptible to wheat cv. Chinese Spring. The CCN resistance gene, temporarily named CreV, was therefore physically mapped to chromosome arm 6V#4L FL 0.80–1.00. Translocation chromosomes T6V#4L·6AS transferred to a modern wheat cv. Aikang 58 with its co-dominant molecular markers could be utilized as a novel germplasm for CCN resistance breeding in wheat.

PCR-RFLP 法による国内のトマト品種からのジャガイモシストセンチュウ抵抗性遺伝子<i>Hero A</i> の検出

We developed polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) markers for the potato cyst nematode (PCN) resistance gene Hero A in tomato. Using these PCR-RFLP markers, we evaluated the presence of Hero A in 22 tomato cultivars. All cultivars displayed complete concordance between their PCN phenotype and the genotype as determined by PCR-RFLP. We confirmed that PCN-resistant tomato cultivars in Japan contained the Hero A gene, whereas susceptible cultivars did not. PCN is a highly important quarantine pest, and the PCR-RFLP markers for Hero A provide a means of testing for resistance without the need to use live nematodes.

A soybean cyst nematode resistance gene points to a new mechanism of plant resistance to pathogens

Soybean (Glycine max (L.) Merr.) is an important crop that provides a sustainable source of protein and oil worldwide. Soybean cyst nematode (Heterodera glycines Ichinohe) is a microscopic roundworm that feeds on the roots of soybean and is a major constraint to soybean production. This nematode causes more than US$1 billion in yield losses annually in the United States alone, making it the most economically important pathogen on soybean. Although planting of resistant cultivars forms the core management strategy for this pathogen, nothing is known about the nature of resistance. Moreover, the increase in virulent populations of this parasite on most known resistance sources necessitates the development of novel approaches for control. Here we report the map-based cloning of a gene at the Rhg4 (for resistance to Heterodera glycines 4) locus, a major quantitative trait locus contributing to resistance to this pathogen. Mutation analysis, gene silencing and transgenic complementation confirm that the gene confers resistance. The gene encodes a serine hydroxymethyltransferase, an enzyme that is ubiquitous in nature and structurally conserved across kingdoms. The enzyme is responsible for interconversion of serine and glycine and is essential for cellular one-carbon metabolism. Alleles of Rhg4 conferring resistance or susceptibility differ by two genetic polymorphisms that alter a key regulatory property of the enzyme. Our discovery reveals an unprecedented plant resistance mechanism against a pathogen. The mechanistic knowledge of the resistance gene can be readily exploited to improve nematode resistance of soybean, an increasingly important global crop.

Comparison of the Effects in Field Tests of Soybean Cyst Nematode Resistance Genes from Different Resistance Sources

The soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) continues to be the most damaging soybean [Glycine max (L.) Merr.] pathogen in the United States. Many quantitative trait loci (QTL) that confer SCN resistance have been mapped. These QTL include rhg1, which was mapped in several sources of SCN resistance, and two resistance QTL mapped from Glycine soja Siebold & Zucc. The objective of this study was to test the effects of different QTL on SCN reproduction in the field, as well as their associated effects on agronomic traits. Three populations of near isogenic lines (NILs) that segregated for major SCN resistance QTL were developed and planted in field plots in 2006 and 2007. Plant introduction (PI) 88788, PI 437654, and G. soja PI 468916 were the sources of the SCN resistance QTL. Soybean cyst nematode field population densities were estimated from soil samples taken shortly after emergence [initial population density (Pi)] and again close to maturity [final population density (Pf)]. A lower SCN reproductive factor (Rf = Pi/Pf) was found on NILs with the SCN resistance alleles from PI 88788 and PI 468916 (p < 0.05) than those with the susceptibility alleles. The rhg1 allele from PI 88788 was also associated with greater yields in multiple environments than those lines with the susceptibility allele. The results indicate that the rhg1 allele from PI 88788 remains as an effective source of resistance to SCN, and with further research, the SCN resistance QTL alleles from G. soja may serve as a novel source of SCN resistance.

Tahıl kist nematodu, Heterodera filipjevi (Madzhidov, 1981) Stelter’nin patotipinin belirlenmesi ve buğday genotiplerinin, H. filipjevi populasyonlarına karşı dayanıklılıklarının araştırılması

*Summary Determination of the pathotype group of Heterodera filipjevi (Madzhidov, 1981) population and resistance of H. populations against wheat genotypes The international pathotype differential lines were used to determine the pathotype group of Heterodera filipjevi (Madzhidov, 1981) Stelter population collected from Yozgat province, Turkey. The reaction of H. filipjevi Yozgat population on the differential lines indicated they were different than the other 5 known H. filipjevi pathotypes. Futherwork was conducted with these H. filipjevi populations to assess the usabilitiy of known published Cereal Cyst Nematode (CCN) resistance genes against a closely related species and pathotypes of Heterodera avenae Wollenweber, 1924. Several of these wheat lines known to possess resistance against H. avenae pathotypes and also the Haymana H. filipjevi populations did not exhibit resistance against H. filipjevi Yozgat populations.

Characterization and expression profiling of a novel cereal cyst nematode resistance gene analog in wheat

Based on the conserved regions of known resistance genes, a NBS-LRR type CCN resistance gene analog was isolated from the CCN resistant E-10 near isogenic lines (NILs) of wheat, designated as CreZ (GenBank Acc. N: EU327996). It contained a complete ORF that was 2775 bp in length and encoded 924 amino acids. Sequence comparison indicated that it shared 92% nucleotide and 87% amino acid identity with those of the known CCN-resistance gene Cre3 and had similar characteristic conserved motifs as those in other established NBS-LRR disease resistance genes. The expression profiling of CreZ indicated that it was specifically expressed in the roots of resistant plants and real-time PCR analysis demonstrated that expression levels drastically increased when the plants were inoculated with cereal cyst nematodes. It could be inferred, then, that CreZ belongs to the NBS-LRR resistance gene family and is a candidate gene for potential resistance to the cereal cyst nematode.

Cloning and sequence diversity analysis of GmHs1 pro-1 in Chinese domesticated and wild soybeans

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is the most important pathogen in soybean production worldwide and causes substantial yield losses. An apparent narrow genetic base of SCN resistance was observed in current elite soybean cultivars, and searching for novel SCN resistance genes as well as novel resistance sources rather than focusing on the two important genes rhg1 and Rhg4 has become another major objective in soybean research. In the present paper we report a 1,477 bp Hs1pro-1 homolog, named GmHs1pro-1. This gene was cloned from soybean variety Wenfeng 7 based on information for Hs1pro-1, a beet cyst nematode resistance gene in sugar beet. It has two domains, Hs1pro-1_N and Hs1pro-1_C, both of which are believed to confer resistance to nematodes. Of the 1,477 bp sequence in GmHs1pro-1, an open reading frame of 1,314 bp, encoding a protein with 437 amino acids, was flanked by a 5′-untranslated region of 27 bp and a 3′-untranslated region of 135 bp. Fourteen single-nucleotide polymorphisms (SNPs) were observed in 44 soybean accessions including 23 wild soybeans, 8 landraces, and 13 soybean varieties (or lines), among which 5 in wild soybeans and 3 in landrace accessions were unique. Sequence diversity analysis on the 44 soybean accessions showed π = 0.00168 and θ = 0.00218 for GmHs1pro-1; landraces had the highest diversity, followed by wild soybeans, with varieties (or lines) having the lowest. Although we did not detect a significant effect of selection on GmHs1pro-1 in the three populations, sequence diversity, unique SNPs, and phylogenetic analysis indicated a slight domestication bottleneck and an intensive selection bottleneck. High sequence diversity, more unique SNPs, and broader representation across the phylogenetic tree in wild soybeans and landraces indicated that wild collections and landrace accessions are invaluable germplasm for broadening the genetic base of elite soybean varieties resistant to SCN.

Marker-assisted pyramiding of two cereal cyst nematode resistance genes from Aegilops variabilis in wheat

The cereal cyst nematode (CCN) Heterodera avenae, is a significant pathogen of wheat. The wild grass Aegilops variabilis Accession No.1 has been found to be resistant to pathotypes of CCN; at least two genes transferred to wheat, designated as CreX and CreY, are involved in the resistance response. The CreY gene may be the same as Rkn-mn1, which confers resistance to root knot nematode (RKN) Meloidogyne naasi. The objective of this work was to pyramid the two CCN resistance genes in a wheat background through marker-assisted selection. As a first step, molecular markers flanking CreX were identified. The completely linked RAPD marker of Rkn-mn1 (CreY), OpY16-1065, previously obtained, was converted into a SCAR. All these dominant markers were used to incorporate in the same genotype the two Ae. variabilis chromosome segments carrying the two genes for resistance. CCN bioassays with the Ha12 pathotype showed that the level of resistance of the pyramided line was significantly higher than that of CreX and CreY single introgression lines, but lower than that of Ae. variabilis. This study thus illustrates the utilization of molecular markers in breeding for host resistance.

Cloning and sequence analysis of the leucine-rich repeats region of cereal cyst nematode resistance gene

AbstractAccording to the sequence of Rccn4, which is highly similar to the nucleotide-binding site (NBS) coding region of the cereal cyst nematode resistance gene, Cre3, three 3′ nested primers were designed to amplify its 3′ flanking region through single oligonucleotide nested polymerase chain reaction (SON-PCR). One 1264 bp band, Rccn-L, was amplified from E-10, a wheat–Aegilops variabilis translocation line containing the cereal cyst nematode resistance gene from Ae. variabilis. Sequence analysis showed that Rccn-L possesses the 3′ flanking sequence of Rccn4 and contains a 55 bp-sized consensus sequence with Rccn4. The coding region was 1026 bp, consisting of an incomplete open reading frame, a terminator codon and no initiation codon and intron; it encoded a peptide of 342 amino acid residues and shared 86% nucleotide sequence identity with Cre3. The peptide had a conserved leucine-rich repeat (LRR) domain, containing the imperfect repeats, XXLXXLXXL, comprising 17% leucine residues, and shares, respectively, 89% nucleotide sequence and 78% amino acid sequence identity with the LRR sequence of the Cre3 locus. In the present study, SON-PCR was used successfully, for the first time, in plant genome research and proved to be a valuable method in plant gene cloning. The acquirement of Rccn-L established the foundation for obtaining the complete Rccn gene and further structural and functional investigations.

Construction of a BAC Library Covering a Common Region between Two Sugar Beet Translocation Lines with Two Cyst Nematode Resistance Genes

Resistance against the beet cyst nematode (BCN) has been introduced into cultivated sugar beet from wild beet by conventional breeding. The first gene effective against the BCN, Hs1pro-1, was isolated from the sugar beet translocation line A906001. It is assumed that a second nematode resistance gene, Hs1pro-1, is present in the translocation line PRO3, which does not carry Hs1pro-1 but still imparts complete resistance against the nematode and resides in the overlapping region between the two lines. The overall goal of this study was to construct a bacterial artificial chromosome (BAC) library to facilitate the cloning of Hs1pro-1. A BAC library from PRO3 was constructed containing 45,041 clones with an average insert size of 108.36 kb. Screening of the library with organelle specific probes indicated less than 1% mitochondrial and 4% chloroplast DNA content. The library covers 6.17 genome equivalents which provides a 99.76% probability of recovering any specific sequence present in the genome.

Near Isogenic Lines Confirm a Soybean Cyst Nematode Resistance Gene from PI 88788 on Linkage Group J

Near Isogenic Lines Confirm a Soybean Cyst Nematode Resistance Gene from PI 88788 on Linkage Group J

Near Isogenic Lines Confirm a Soybean Cyst Nematode Resistance Gene from PI 88788 on Linkage Group J

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is one of the most destructive soybean [Glycine max (L.) Merr.] pests worldwide. The most common source of SCN resistance used in soybean breeding in the northern USA is PI 88788. Previous research has shown that PI 88788 carries a major quantitative trait locus (QTL) conferring SCN resistance on linkage group (LG) G, which is believed to be rhg1 The objective of our research was to map and confirm additional SCN resistance QTL in Bell, a cultivar with resistance from PI 88788. One hundred four F4–derived lines (F4 population) developed from crossing the cultivars Bell and Colfax were tested for associations between 54 molecular markers and resistance to SCN populations PA3 (HG type 7, race 3) and PA14 (HG type 1.3.5.6.7, race 14). Three populations of near isogenic lines (NILs) were developed from F4 plants heterozygous for a region on LG J where a significant QTL was identified in the F4 population. The NIL populations were tested with genetic markers and also for resistance to both SCN populations. In the F4 population, SCN resistance QTL were identified at both rhg1 and on LG J. The LG J QTL was confirmed in NIL populations and was given the confirmed QTL designation cqSCN‐003. The effect of cqSCN‐003 was diminished in the NIL populations compared to the F4 population. This was at least partially the result of segregation distortion in the F4 population between the region containing rhg1 and the region containing cqSCN‐003. These results show the importance of verifying QTL in confirmation populations to estimate accurately their effects.

Identification of microsatellite markers associated with the cereal cyst nematode resistance gene Cre3 in wheat

Cereal cyst nematode (CCN) is a root disease caused by the pathogen Heterodera avenae Woll. that significantly reduces wheat (Triticum aestivum L.) grain yields in temperate countries. The Cre3 gene, located on chromosome 2DL, provides high levels of resistance to the Australian pathotype and isolates from Syria and Algeria, and has become available to wheat breeders. Selection for lines carrying the Cre3 gene in Australian wheat breeding programs is currently based on a dominant PCR marker (Cre3spf/r) diagnostic for the Cre3 gene. However, this marker has limitations that increase the cost and reduce selection efficiency in screening early-generation breeding lines. Such limitations would be minimised by the identification of a microsatellite marker linked to the Cre3 gene. We have constructed 2 genetic linkage maps of wheat chromosome 2DL and identified microsatellite markers mapping closely to the diagnostic Cre3spf/r marker. These closely linked markers were validated in a diverse range of germplasm, and one microsatellite marker, Xgwm301, which mapped 4 cM from Cre3spf/r, was shown to be highly associated with the presence of the Cre3 gene. Amplification conditions for the Xgwm301 locus were optimised, and its use in marker-assisted selection to identify Cre3 CCN-resistant wheat in the Australian Grain Technologies breeding program is demonstrated.

Near Isogenic Lines Confirm a Soybean Cyst Nematode Resistance Gene from PI 88788 on Linkage Group J

Soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) is one of the most destructive soybean [Glycine max (L.) Merr.] pests worldwide. The most common source of SCN resistance used in soybean breeding in the northern USA is PI 88788. Previous research has shown that PI 88788 carries a major quantitative trait locus (QTL) conferring SCN resistance on linkage group (LG) G, which is believed to be rhg1 The objective of our research was to map and confirm additional SCN resistance QTL in Bell, a cultivar with resistance from PI 88788. One hundred four F4–derived lines (F4 population) developed from crossing the cultivars Bell and Colfax were tested for associations between 54 molecular markers and resistance to SCN populations PA3 (HG type 7, race 3) and PA14 (HG type 1.3.5.6.7, race 14). Three populations of near isogenic lines (NILs) were developed from F4 plants heterozygous for a region on LG J where a significant QTL was identified in the F4 population. The NIL populations were tested with genetic markers and also for resistance to both SCN populations. In the F4 population, SCN resistance QTL were identified at both rhg1 and on LG J. The LG J QTL was confirmed in NIL populations and was given the confirmed QTL designation cqSCN-003. The effect of cqSCN-003 was diminished in the NIL populations compared to the F4 population. This was at least partially the result of segregation distortion in the F4 population between the region containing rhg1 and the region containing cqSCN-003. These results show the importance of verifying QTL in confirmation populations to estimate accurately their effects.

The cre1 and cre3 nematode resistance genes are located at homeologous loci in the wheat genome.

Differential responses in host-nematode pathotype interactions occur in wheat lines carrying different cereal cyst nematode resistance (Cre) genes. Cre1, located on chromosome 2B, confers resistance to most European nematodes and the sole Australian pathotype, while Cre3, present on chromosome 2D, is highly resistant to the Australian pathotype and susceptible to a number of European pathotypes. Genes encoding nucleotide binding site-leucine rich repeat (NBS-LRR) proteins that cosegregate with the Cre3 locus cross hybridize to homologues whose restriction fragment length polymorphism (RFLP) patterns distinguish near-isogenic Cre1 nematode-resistant wheat lines. Genetic mapping showed that the NBS-LRR gene members that distinguished the Cre1 near-isogenic lines were located on chromosome 2BL at a locus, designated Xcsl107, that cosegregates with the Cre1 locus. A haplotype of NBS-LRR genes from the Xcsl107 locus provides a diagnostic marker for the presence of Cre1 nematode resistance in a wide collection of wheat lines and segregating families. Genetic analysis of NBS-LRR haplotypes that cosegregate with Cre1 and Cre3 resistance, together with flanking cDNA markers and other markers from homoeologous group 2 chromosomes, revealed a conserved gene order that suggests Cre1 and Cre3 are homeoloci.

Identification of a putative cation transporter gene from sugar beet ( Beta vulgaris L.) by DDRT-PCR closely linked to the beet cyst nematode resistance gene Hs1pro-1

The beet cyst nematode ( Heterodera schachtii Schm.) is a widespread pest that causes agronomic losses in sugar beet cultivation. Since no nematode resistance genes have been found in Beta vulgaris L. cultivars, a chromosomal fragment from Beta procumbens has been bred into cultivated sugar beet in order to provide resistance to Heterodera schachtii. The introgressed translocation carries the nematode resistance gene Hs1 pro-1 and may also contain genes that are linked to the defense response and/or signal transduction. A novel cDNA designated Bp23 was isolated from the translocation in this work by comparing resistant and susceptible sugar beets of a segregating F 2 population by differential display. Bp23 shows similarity to Arabidopsis thaliana BAC clones and to diverse plant ESTs with similarity to the Escherichia coli cation transporter ChaC. The open reading frame could encode a hydrophilic protein of 25 kDa that is similar to cation transporters and has a presumptive K + selective motif at the N-terminus.

Genetic and physical mapping of homologues of the virus resistance gene Rx1 and the cyst nematode resistance gene Gpa2 in potato.

Nine resistance gene homologues (RGHs) were identified in two diploid potato clones (SH and RH), with a specific primer pair based on conserved motifs in the LRR domain of the potato cyst nematode resistance gene Gpa2 and the potato virus X resistance gene Rx1. A modified AFLP method was used to facilitate the genetic mapping of the RGHs in the four haplotypes under investigation. All nine RGHs appeared to be located in the Gpa2/ Rx1 cluster on chromosome XII. Construction of a physical map using bacterial artificial chromosome (BAC) clones for both the Solanum tuberosum ssp. tuberosum and the S. tuberosum ssp. andigena haplotype of SH showed that the RGHs are located within a stretch of less than 200 kb. Sequence analysis of the RGHs revealed that they are highly similar (93 to 95%) to Gpa2 and Rx1. The sequence identities among all RGHs range from 85 to 100%. Two pairs of RGHs are identical, or nearly so (100 and 99.9%), with each member located in a different genotype. Southern-blot analysis on genomic DNA revealed no evidence for additional homologues outside the Gpa2/ Rx1 cluster on chromosome XII.

The broad-spectrum potato cyst nematode resistance gene (Hero) from tomato is the only member of a large gene family of NBS-LRR genes with an unusual amino acid repeat in the LRR region.

The Hero gene of tomato is a broad spectrum resistance gene that confers a high level of resistance to all pathotypes of the potato cyst nematodes Globodera rostochiensis and partial resistance to G. pallida. The gene was identified by map-based cloning, sequencing and complementation analysis of two susceptible tomato lines with an array of 13 overlapping cosmids spanning a total distance of 135 kb. Hero encodes a protein with a nucleotide-binding site (NBS) and a leucine-rich-repeat (LRR) domain and is a member of a gene family of 14 highly homologous genes, which are clustered within a continuous 118-kb region. The isolated Hero gene displayed resistance to various G. rostochiensis pathotypes and partial resistance to G. pallida pathotype Pa2/3 in transgenic tomato lines. None of the Hero homologues conferred resistance to G. rostochiensis pathotypes. Hero can be distinguished from its homologues by the length of a compound hexanucleotide microsatellite, which codes for a charged and repetitive amino acid domain within the LRR. We propose that the expansion of this microsatellite may be involved in the evolution of the Hero resistance gene.