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PubMed2002

Exploiting EST databases for the development and characterization of gene-derived SSR-markers in barley (Hordeum vulgare L.).

A software tool was developed for the identification of simple sequence repeats (SSRs) in a barley ( Hordeum vulgare L.) EST (expressed sequence tag) database comprising 24,595 sequences. In total, 1,856 SSR-containing sequences were identified. Trimeric SSR repeat motifs appeared to be the most abundant type. A subset of 311 primer pairs flanking SSR loci have been used for screening polymorphisms among six barley cultivars, being parents of three mapping populations. As a result, 76 EST-derived SSR-markers were integrated into a barley genetic consensus map. A correlation between polymorphism and the number of repeats was observed for SSRs built of dimeric up to tetrameric units. 3'-ESTs yielded a higher portion of polymorphic SSRs (64%) than 5'-ESTs did. The estimated PIC (polymorphic information content) value was 0.45 +/- 0.03. Approximately 80% of the SSR-markers amplified DNA fragments in Hordeum bulbosum, followed by rye, wheat (both about 60%) and rice (40%). A subset of 38 EST-derived SSR-markers comprising 114 alleles were used to investigate genetic diversity among 54 barley cultivars. In accordance with a previous, RFLP-based, study, spring and winter cultivars, as well as two- and six-rowed barleys, formed separate clades upon PCoA analysis. The results show that: (1) with the software tool developed, EST databases can be efficiently exploited for the development of cDNA-SSRs, (2) EST-derived SSRs are significantly less polymorphic than those derived from genomic regions, (3) a considerable portion of the developed SSRs can be transferred to related species, and (4) compared to RFLP-markers, cDNA-SSRs yield similar patterns of genetic diversity.

DNA, Plant↗
PubMed2005

Comparative genetic maps reveal extreme crossover localization in the Aegilops speltoides chromosomes.

A total of 137 loci were mapped in Aegilops speltoides, the closest extant relative of the wheat B genome, using two F(2) mapping populations and a set of wheat-Ae. speltoides disomic addition (DA) lines. Comparisons of Ae. speltoides genetic maps with those of Triticum monococcum indicated that Ae. speltoides conserved the gross chromosome structure observed across the tribe Triticeae. A putative inversion involving the short arm of chromosome 2 was detected in Ae. speltoides. A translocation between chromosomes 2 and 6, present in the wheat B genome, was absent. The ligustica/aucheri spike dimorphism behaved as allelic variation at a single locus, which was mapped in the centromeric region of chromosome 3. The genetic length of each chromosome arm was about 50 cM, irrespective of its physical length. Compared to T. monococcum genetic maps, recombination was virtually eliminated from the proximal 50-100 cM and was localized in short distal regions, which were often expanded compared to the T. monococcum maps. The wheat B genome and the genome of Ae. longissima, a close relative of Ae. speltoides, do not show the extreme localization of crossovers observed in Ae. speltoides.

Chromosome Mapping↗
PubMed2006

Genetic characterization of the polycotyledon locus in tomato.

Developmental mutants serve as a useful material to unravel the mechanisms necessary for organ development. The polycotyledon (poc) mutant of tomato, with multiple cotyledons in the seedling and varied phenotypic effects in the adult plant is one such mutant. Studies using physiological and anatomical methods in our lab suggest that POC is involved in the negative regulation of polar auxin transport, which is likely the reason for the pleiotropic phenotype in the mutant. Because of the physiological significance of the polycotyledon mutant described in this paper and also being first of its kind in tomato and also other plant species, we are using a map-based cloning approach to map the polycotyledon gene. Molecular mapping of this locus using segregating interspecific F2 mapping population localized polycotyledon gene close to TG424 marker on the long arm of chromosome 9. The closest marker mapped was a PCR marker identified in this study, E8A2 at a distance of 7.4 cM from the poc locus. The absence of tightly linked RAPD markers and the non-availability of more mapped markers in this region led us to initiate chromosome walk to polycotyledon gene. Both the flanking markers TG248 and E8A2 were used to screen the BAC library and a contig was developed for TG248 marker. The BAC-end sequences were analyzed for their use as RFLP markers to enrich this region for markers. Analysis of the BAC-end sequences revealed that poc is localized in the region surrounded by copia-like retrotransposon elements explaining the absence of markers in the euchromatin region on long arm of chromosome 9. Further studies identified two BAC-end sequences which mapped around the poc locus and also indicated very low physical versus genetic distance ratio in this region. The double mutant analyses of poc with the other two known polycotyledon mutants of tomato, pct and dem revealed allelism with pct; therefore, the poc mutant was named as pct1-2, and also the original pct mutant was renamed as pct1-1.

Alleles↗
PubMed2005

Quantitative trait locus mapping in natural populations: progress, caveats and future directions.

Over the last 15 years quantitative trait locus (QTL) mapping has become a popular method for understanding the genetic basis of continuous variation in a variety of systems. For example, the technique is now an integral tool in medical genetics, livestock production, plant breeding and population genetics of model organisms. Ten years ago, it was suggested that the method could be used to understand continuous variation in natural populations. In this review I: (i) clarify what is meant by natural population in the QTL context, (ii) discuss whether evolutionary biologists have successfully mapped QTL in natural populations, (iii) highlight some of the questions that have been addressed by QTL mapping in natural populations, (iv) describe how QTL mapping can be conducted in unmanipulated natural populations, (v) highlight some of the limitations of QTL mapping and (vi) try to predict some future directions for QTL mapping in natural populations.

Biological Evolution↗
PubMed2002

QTL analysis for grain protein content using SSR markers and validation studies using NILs in bread wheat.

QTL interval mapping for grain protein content (GPC) in bread wheat was conducted for the first time, using a framework map based on a mapping population, which was available in the form of 100 recombinant inbred lines (RILs). The data on GPC for QTL mapping was recorded by growing the RILs in five different environments representing three wheat growing locations from Northern India; one of these locations was repeated for 3 years. Distribution of GPC values followed normal distributions in all the environments, which could be explained by significant g x e interactions observed through analyses of variances, which also gave significant effects due to genotypes and environments. Thirteen (13) QTLs were identified in individual environments following three methods (single-marker analysis or SMA, simple interval mapping or SIM and composite interval mapping or CIM) and using LOD scores that ranged from 2.5 to 6.5. Threshold LOD scores (ranging from 3.05 to 3.57), worked out and used in each case, however, detected only seven of the above 13 QTLs. Only four (QGpc.ccsu-2B.1; QGpc.ccsu-2D.1; QGpc.ccsu-3D.1 and QGpc.ccsu-7A.1) of these QTLs were identified either in more than one location or following one more method other than CIM; another QTL (QGpc.ccsu-3D.2), which was identified using means for all the environments, was also considered to be important. These five QTLs have been recommended for marker-assisted selection (MAS). The QTLs identified as above were also validated using ten NILs derived from three crosses. Five of the ten NILs possessed 38 introgressed segments from 16 chromosomes and carried 42 of the 173 markers that were mapped. All the seven QTLs were associated with one or more of the markers carried by the above introgressed segments, thus validating the corresponding markers. More markers associated with many more QTLs to be identified should become available in the future by effective MAS for GPC improvement.

Analysis of Variance↗
PubMed1999

A maize map standard with sequenced core markers, grass genome reference points and 932 expressed sequence tagged sites (ESTs) in a 1736-locus map.

We have constructed a 1736-locus maize genome map containing1156 loci probed by cDNAs, 545 probed by random genomic clones, 16 by simple sequence repeats (SSRs), 14 by isozymes, and 5 by anonymous clones. Sequence information is available for 56% of the loci with 66% of the sequenced loci assigned functions. A total of 596 new ESTs were mapped from a B73 library of 5-wk-old shoots. The map contains 237 loci probed by barley, oat, wheat, rice, or tripsacum clones, which serve as grass genome reference points in comparisons between maize and other grass maps. Ninety core markers selected for low copy number, high polymorphism, and even spacing along the chromosome delineate the 100 bins on the map. The average bin size is 17 cM. Use of bin assignments enables comparison among different maize mapping populations and experiments including those involving cytogenetic stocks, mutants, or quantitative trait loci. Integration of nonmaize markers in the map extends the resources available for gene discovery beyond the boundaries of maize mapping information into the expanse of map, sequence, and phenotype information from other grass species. This map provides a foundation for numerous basic and applied investigations including studies of gene organization, gene and genome evolution, targeted cloning, and dissection of complex traits.

Chromosome Mapping↗
PubMed2003

Genotype-environment interactions at quantitative trait loci affecting inflorescence development in Arabidopsis thaliana.

Phenotypic plasticity and genotype-environment interactions (GEI) play a prominent role in plant morphological diversity and in the potential functional capacities of plant life-history traits. The genetic basis of plasticity and GEI, however, is poorly understood in most organisms. In this report, inflorescence development patterns in Arabidopsis thaliana were examined under different, ecologically relevant photoperiod environments for two recombinant inbred mapping populations (Ler x Col and Cvi x Ler) using a combination of quantitative genetics and quantitative trait locus (QTL) mapping. Plasticity and GEI were regularly observed for the majority of 13 inflorescence traits. These observations can be attributable (at least partly) to variable effects of specific QTL. Pooled across traits, 12/44 (27.3%) and 32/62 (51.6%) of QTL exhibited significant QTL x environment interactions in the Ler x Col and Cvi x Ler lines, respectively. These interactions were attributable to changes in magnitude of effect of QTL more often than to changes in rank order (sign) of effect. Multiple QTL x environment interactions (in Cvi x Ler) clustered in two genomic regions on chromosomes 1 and 5, indicating a disproportionate contribution of these regions to the phenotypic patterns observed. High-resolution mapping will be necessary to distinguish between the alternative explanations of pleiotropy and tight linkage among multiple genes.

Arabidopsis↗
PubMed2003

Identification and mapping of genetic loci affecting the free-threshing habit and spike compactness in wheat ( Triticum aestivum L.).

Recombinant inbred lines of the International Triticeae Mapping Initiative (ITMI) mapping population were used to localize genetic loci that affect traits related to the free-threshing habit (percent threshability, glume tenacity, and spike fragility) and to spike morphology (spike length, spikelet number, and spike compactness) of wheat ( Triticum aestivum L.). The ITMI population was planted in three environments during 1999 and 2000, and phenotypic and genotypic data were used for composite interval mapping. Two quantitative trait loci (QTL) that consistently affected threshability-associated traits were localized on chromosomes 2D and 5A. Coincident QTL on the short arm of 2D explained 44% of the variation in threshability, 17% of the variation in glume tenacity, and 42% of the variation in rachis fragility. QTL on chromosomes 2D probably represent the effect of Tg, a gene for tenacious glumes. Coincident QTL on the long arm of 5A explained 21% and 10% of the variation in glume tenacity and rachis fragility, respectively. QTL on 5A are believed to represent the effect of Q. Overall, free-threshing-related characteristics were predominantly affected by Tg and to a lesser extent by Q. Other QTL that were significantly associated with threshability-related traits in at least one environment were localized on chromosomes 2A, 2B, 6A, 6D, and 7B. Four QTL on chromosomes 1B, 4A, 6A, and 7A consistently affected spike characteristics. Coincident QTL on the short arm of chromosome 1B explained 18% and 7% of the variation in spike length and spike compactness, respectively. QTL on the long arm of 4A explained 11%, 14%, and 12% of the variation in spike length, spike compactness, and spikelet number, respectively. A QTL on the short arm of 6A explained 27% of the phenotypic variance for spike compactness, while a QTL on the long arm of 7A explained 18% of the variation in spikelet number. QTL on chromosomes 1B and 6A appear to affect spike dimensions by modulating rachis internode length, while QTL on chromosomes 4A and 7A do so by affecting the formation of spikelets. Other QTL that were significantly associated with spike morphology-related traits, in at least one environment, were localized on chromosomes 2B, 3A, 3D, 4D, and 5A.

Chromosome Mapping↗
PubMed2004

Mapping of AFLP markers linked to seed coat colour loci in Brassica juncea (L.) Czern.

Association mapping of the seed-coat colour with amplified fragment length polymorphism (AFLP) markers was carried out in 39 Brassica juncea lines. The lines had genetically diverse parentages and varied for seed-coat colour and other morphological characters. Eleven AFLP primer combinations were used to screen the 39 B. juncea lines, and a total of 335 polymorphic bands were detected. The bands were analysed for association with seed-coat colour using multiple regression analysis. This analysis revealed 15 markers associated with seed-coat colour, obtained with eight AFLP primer combinations. The marker E-ACA/M-CTG(350 )explained 69% of the variation in seed-coat colour. This marker along with markers E-AAC/M-CTC(235 )and E-AAC/M-CTA(250) explained 89% of the total variation. The 15 associated markers were validated for linkage with the seed-coat colour loci using a recombinant inbred line (RIL) mapping population. Bands were amplified with the eight AFLP primer combinations in 54 RIL progenies. Of the 15 associated markers, 11 mapped on two linkage groups. Eight markers were placed on linkage group 1 at a marker density of 6.0 cM, while the remaining three were mapped on linkage group 2 at a marker density of 3.6 cM. Marker E-ACA/M-CTG(350 )co-segregated with Gene1 controlling seed-coat colour; it was specific for yellow seed-coat colour and mapped to linkage group 1. Marker E-AAC/M-CTC(235) (AFLP8), which had been studied previously, was present on linkage group 2; it was specific for brown seed-coat colour. Since AFLP markers are not adapted for large-scale applications in plant breeding, it is important to convert these to sequence-characterised amplified region (SCAR) markers. Marker E-AAC/M-CTC(235) (AFLP8) had been previously converted into a SCAR. Work is in progress to convert the second of the linked markers, E-ACA/M-CTG(350), to a SCAR. The two linked AFLP markers converted to SCARs will be useful for developing yellow-seeded B. juncea lines by means of marker-assisted selection.

Chromosome Mapping↗
PubMed2005

Mapping of a major QTL for pre-harvest sprouting tolerance on chromosome 3A in bread wheat.

Quantitative trait loci (QTL) analysis was conducted for pre-harvest sprouting tolerance (PHST) in bread wheat for a solitary chromosome 3A, which was shown to be important for this trait in earlier studies. An inter-varietal mapping population in the form of recombinant inbred lines (RILs) developed from a cross between SPR8198 (a PHS tolerant genotype) and HD2329 (a PHS susceptible cultivar) was used for this purpose. The parents and the RIL population were grown in six different environments and the data on PHS were collected in each case. A framework linkage map of chromosome 3A with 13 markers was prepared and used for QTL analysis. A major QTL (QPhs.ccsu-3A.1) was detected on 3AL at a genetic distance of approximately 183 cM from centromere, the length of the map being 279.1 cM. The QTL explained 24.68% to 35.21% variation in individual environments and 78.03% of the variation across the environments (pooled data). The results of the present study are significant on two counts. Firstly, the detected QTL is a major QTL, explaining up to 78.03% of the variation and, secondly, the QTL showed up in all the six environments and also with the pooled data, which is rather rare in QTL analysis. The positive additive effects in the present study suggest that a superior allele of the QTL is available in the superior parent (SPR8198), which can be used for marker-aided selection for the transfer of this QTL allele to obtain PHS-tolerant progeny. It has also been shown that the red-coloured grain of PHS tolerant parent is not associated with the QTL for PHST identified during the present study, suggesting that PHS tolerant white-grained cultivars can be developed.

Chromosome Mapping↗
PubMed2006

The first gene-based map of Lupinus angustifolius L.-location of domestication genes and conserved synteny with Medicago truncatula.

We report the first gene-based linkage map of Lupinus angustifolius (narrow-leafed lupin) and its comparison to the partially sequenced genome of Medicago truncatula. The map comprises 382 loci in 20 major linkage groups, two triplets, three pairs and 11 unlinked loci and is 1,846 cM in length. The map was generated from the segregation of 163 RFLP markers, 135 gene-based PCR markers, 75 AFLP and 4 AFLP-derived SCAR markers in a mapping population of 93 recombinant inbred lines, derived from a cross between domesticated and wild-type parents. This enabled the mapping of five major genes controlling key domestication traits in L. angustifolius. Using marker sequence data, the L. angustifolius genetic map was compared to the partially completed M. truncatula genome sequence. We found evidence of conserved synteny in some regions of the genome despite the wide evolutionary distance between these legume species. We also found new evidence of widespread duplication within the L. angustifolius genome.

Alleles↗
PubMed2001

Rice ESTs with disease-resistance gene- or defense-response gene-like sequences mapped to regions containing major resistance genes or QTLs.

The chromosomal locations of 109 rice expressed sequence tags (ESTs) in the rice genome were determined using a doubled haploid mapping population. These ESTs show high similarity to disease resistance genes or to defense response genes. Nine of the ESTs were mapped to three regions that contain genetically defined resistance genes on chromosomes 6 and 11. Clustering of the ESTs in the rice genome was observed at several chromosomal regions. Some of the clusters were located in regions where quantitative trait loci (QTL) associated with partial resistance to rice blast, bacterial blight and sheath blight are known to lie. Three ESTs that were mapped to the regions containing blast resistance genes Pi2 and Pia were chosen for Northern analysis after inoculation of plants with the blast fungus. Two of them, which code for a receptor-like kinase and a putative membrane channel protein, respectively, and were mapped to the Pi2 locus, were induced by rice blast infection as early as 4 h after inoculation. Transcription of another EST, which codes for a homolog of a putative human tumor suppressor and was mapped to the region containing Pia, was repressed after blast infection. These findings demonstrate that the candidate-gene approach is an efficient way of mapping resistance genes or resistance QTLs in rice.

Chromosome Mapping↗
PubMed1999

The Ha locus of wheat: identification of a polymorphic region for tracing grain hardness in crosses.

The grain softness proteins or friabilins are known to be composed of three main components: puroindoline a, puroindoline b, and GSP-1. cDNAs for GSP-1 have previously been mapped to group-5 chromosomes and their location on chromosome 5D is closely linked to the grain hardness (Ha) locus of hexaploid wheat. A genomic DNA clone containing the GSP-1 gene (wGSP1-A1) from hexaploid wheat has been identified by fluorescent in situ hybridization as having originated from the distal end of the short arm of chromosome 5A. A genomic clone containing the gene (wGSP1-D1) was also isolated from Aegilops tauschii, the donor of the D genome to bread wheat. There are no introns in the GSP-1 genes, and there is high sequence identity between wGSP1-A1 and wGSP1-D1 up to 1 kb 5' and 300 bp 3' to wGSP1-D1. However, regions further upstream and downstream of wGSP1-D1 share no significant sequence identity to corresponding sequences in wGSP1-A1. These regions therefore identified potentially valuable sequences for tracing the Ha locus through assaying polymorphic DNA sequences. The sequence from 300 to 500 bp 3' to wGSP1-D1 (wGSP1-D13) was mapped to the Ha locus in a mapping population. wGSP1-D13 was also tightly linked to genes for puroindoline a and puroindoline b which have been previously mapped to be at the Ha locus. In addition wGSP1-D13 was used to detect RFLPs between near isogenic soft and hard Falcon lines and in a random selection of soft and hard wheats.

Base Sequence↗
PubMed1999

Construction of an AFLP genetic map with nearly complete genome coverage in Pinus taeda.

De novo construction of complete genetic linkage maps requires large mapping populations, large numbers of genetic markers, and efficient algorithms for ordering markers and evaluating order confidence. We constructed a complete genetic map of an individual loblolly pine (Pinus taeda L.) using amplified fragment length polymorphism (AFLP) markers segregating in haploid megagametophytes and PGRI mapping software. We generated 521 polymorphic fragments from 21 AFLP primer pairs. A total of 508 fragments mapped to 12 linkage groups, which is equal to the Pinus haploid chromosome number. Bootstrap locus order matrices and recombination matrices generated by PGRI were used to select 184 framework markers that could be ordered confidently. Order support was also evaluated using log likelihood criteria in MAPMAKER. Optimal marker orders from PGRI and MAPMAKER were identical, but the implied reliability of orders differed greatly. The framework map provides nearly complete coverage of the genome, estimated at approximately 1700 cM in length using a modified estimator. This map should provide a useful framework for merging existing loblolly pine maps and adding multiallelic markers as they become available. Map coverage with dominant markers in both linkage phases will make the map useful for subsequent quantitative trait locus mapping in families derived by self-pollination.

Chromosome Mapping↗
PubMed2001

Structural analysis of a Lotus japonicus genome. I. Sequence features and mapping of fifty-six TAC clones which cover the 5.4 mb regions of the genome.

A total of 56 TAC clones with an average insert size of 100 kb were isolated from a TAC library of the Lotus japonicus genome based on the expressed sequences tags (ESTs), cDNA and gene information, and their nucleotide sequences were determined according to the shot-gun based strategy. The total length of the sequenced regions is 5,473,195 bp. By comparison with the sequences in protein and EST databases and analysis with computer programs for gene modeling, a total of 605 potential protein-encoding genes with known or predicted functions, 69 gene segments, and 172 pseudogenes were identified. The average density of the genes assigned so far is 1 gene/8120 bp. Introns were identified in approximately 78% of the potential genes. There was an average of 3.8 introns per gene and the average length of the introns was 375 bp. DNA markers were generated based on the nucleotide sequences obtained, and each clone was mapped onto the linkage map using the F2 mapping population derived from a cross of L. japonicus Gifu B-129 and Miyakojima MG-20. The sequence data, gene information and mapping information are available through the World Wide Web at http://www.kazusa.or.jp/lotus/.

Base Sequence↗
PubMed1997

A chromosome-specific microdissected library increases marker density on bovine chromosome 1.

Genetic resolution of bovine chromosome 1 (BTA1) linkage group was significantly increased by screening for microsatellite clones a microdissected library constructed from a bovine cell line carrying a t(1;29) translocation. Eighty-five percent of the microsatellites (ms) (46/54) identified were informative in the USDA/MARC mapping population, and 96% of these ms (44/46) linked to BTA1 (LOD > 3.0). When merged with 40 existing BTA1 markers the genetic map spanned 153.8 cM (sex-averaged interval, 1.9 cM). The fourfold improvement in marker density of BTA1 provides a genetic map that enhances mapping of quantitative trait loci and implementation of marker assisted selection.

Animals↗
PubMed2006

A novel form of resistance in rice to the angiosperm parasite Striga hermonthica.

The root hemiparasitic weed Striga hermonthica is a serious constraint to grain production of economically important cereals in sub-Saharan Africa. Breeding for parasite resistance in cereals is widely recognized as the most sustainable form of long-term control; however, advances have been limited owing to a lack of cereal germplasm demonstrating postattachment resistance to Striga. Here, we identify a cultivar of rice (Nipponbare) that exhibits strong postattachment resistance to S. hermonthica; the parasite penetrates the host root cortex but does not form parasite-host xylem-xylem connections. In order to identify the genomic regions contributing to this resistance, a mapping population of backcross inbred lines between the resistant (Nipponbare) and susceptible (Kasalath) parents were evaluated for resistance to S. hermonthica. Composite interval mapping located seven putative quantitative trait loci (QTL) explaining 31% of the overall phenotypic variance; a second, independent, screen confirmed four of these QTL. Relative to the parental lines, allelic substitutions at these QTL altered the phenotype by at least 0.5 of a phenotypic standard deviation. Thus, they should be regarded as major genes and are likely to be useful in breeding programmes to enhance host resistance.

Chromosome Mapping↗
PubMed2003

Mapping QTLs for seed dormancy and the Vp1 homologue on chromosome 3A in wheat.

A major component of the observed genetic variation for pre-harvest sprouting in wheat ( Triticum aestivum L.) appears to be the level of seed dormancy. Group 3 chromosomes have received attention as carrying the R genes for seed-coat color and the taVp1 genes that are orthologous to the maize Vp1 gene which encode a dormancy-related transcription factor. The objectives of the present study were to map quantitative trait loci (QTLs) for seed dormancy on chromosome 3A and to investigate an association between taVp1 or R-A1 and the QTLs detected. A mapping population in the form of recombinant inbred lines developed from the cross between the highly dormant Zenkoujikomugi (Zen) and Chinese Spring (CS) was utilized. Nineteen marker loci, including taVp1, were mapped on chromosome 3A. The taVp1 locus was located in the middle of the long arm, about 85 cM from the centromere. The population was evaluated in duplicate by growing them under controlled environment conditions. Two QTLs for seed dormancy, designated as QPhs.ocs-3A.1 and QPhs.ocs-3A.2, were identified on the short and long arms, respectively. QPhs.ocs-1 explained 23-38% of the phenotypic variation and the Zen allele had a striking effect on maintaining dormancy. QPhs.ocs-2, with a minor effect, was detectable only at the dormancy-breaking stage. Although QPhs.ocs-2 was loosely linked to taVp1 by around 50 cM, they are clearly distinct genes. Zen and CS carry the white R-A1a allele, and no QTL effect was detected in the vicinity region of R-A1. Hence it was concluded that the high dormancy associated with chromosome 3A of Zen is ascribable to QPhs.ocs-1 on the short arm but is not due to the direct contribution of either the taVp1 or R-A1 locus.

Chromosomes, Plant↗