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Use of the EM algorithm to detect QTL affecting multiple-traits in an across half-sib family analysis.

QTL detection experiments in livestock species commonly use the half-sib design. Each male is mated to a number of females, each female producing a limited number of progeny. Analysis consists of attempting to detect associations between phenotype and genotype measured on the progeny. When family sizes are limiting experimenters may wish to incorporate as much information as possible into a single analysis. However, combining information across sires is problematic because of incomplete linkage disequilibrium between the markers and the QTL in the population. This study describes formulae for obtaining MLEs via the expectation maximization (EM) algorithm for use in a multiple-trait, multiple-family analysis. A model specifying a QTL with only two alleles, and a common within sire error variance is assumed. Compared to single-family analyses, power can be improved up to fourfold with multi-family analyses. The accuracy and precision of QTL location estimates are also substantially improved. With small family sizes, the multi-family, multi-trait analyses reduce substantially, but not totally remove, biases in QTL effect estimates. In situations where multiple QTL alleles are segregating the multi-family analysis will average out the effects of the different QTL alleles.

Algorithms↗

PubMed2001

Identification of causal relationships among traits related to drought resistance in Stylosanthes scabra using QTL analysis.

Previous studies have shown that a negative relationship exists between transpiration efficiency (TE) and carbon isotope discrimination (Delta) and between TE and specific leaf area (SLA) in Stylosanthes scabra. A glasshouse experiment was conducted to confirm these relationships in an F(2) population and to study the causal nature of these relationships through quantitative trait loci (QTL) analysis. One hundred and twenty F(2) genotypes from a cross between two genotypes within S. scabra were used. Three replications for each genotype were maintained through vegetative propagation. Water stress was imposed by maintaining plants at 40% of field capacity for about 45 d. To facilitate QTL analysis, a genetic linkage map consisting of 151 RAPD markers was developed. Results from this study show that Delta was significantly and negatively correlated with TE and biomass production. Similarly, SLA showed significant negative correlation with TE and biomass production. Most of the QTL for TE and Delta were present on linkage groups 5 and 11. Similarly, QTL for SLA, transpiration and biomass productivity traits were clustered on linkage groups 13 and 24. One unlinked marker was also associated with these traits. There were several markers coincident between different traits. At all the coincident QTL, the direction of QTL effects was consistent with phenotypic data. At the coincident markers between TE and Delta, high alleles of TE were associated with low alleles of Delta. Similarly, low alleles of SLA were associated with high alleles of biomass productivity traits and transpiration. At the coincident markers between trans-4-hydroxy-N:-methyl proline (MHP) and relative water content (RWC), low alleles of MHP were associated with high alleles of RWC. This study suggests the causal nature of the relationship between TE and Delta. Phenotypic data and QTL data show that SLA was more closely associated with biomass production than with TE. This study also shows that a cause-effect relationship may exist between SLA and biomass production.

Alleles↗

PubMed2005

[QTL mapping of five agronomic traits in maize].

Agronomic traits have significant influence on stability and adaptability in maize production. In this investigation, using a population with 266 F2:3 families from Yuyu22 (Zong3 x 87-1), two-location field tests were conducted in Wuhan and Xiangfan in 2001, with a randomized complete block design, to characterize five agronomic traits: ear height, tassel branch number, stalk diameter, days to pollen, and days to silk. Correlation analysis of field performance indicated that ear height, tassel branch number and stalk diameter were significantly positive correlative with single-plant yield, days to pollen and days to silk were highly positive correlative with each other, and tassel branch number was significantly positive correlative with stalk diameter too. Utilizing data of field tests and molecular markers, Composite Interval Mapping (CIM) method was used to localize the quantitative trait loci of these traits and 500 times permutation test was conducted to have proper LOD threshold value. As the results, total seven QTL of ear height, nine QTL of tassel branch number, eight QTL of stalk diameter, nine QTL of days to pollen, and seven QTL of days to silk were mapped on 10 chromosomes of maize; all of these QTL distributed unevenly on chromosomes and trended to cluster together. According to analysis of this investigation, the phenotype correlations of quantitative traits may result from the correlations of QTL controlling those traits. Those will be helpful to further understand genetic basis of agronomic traits in maize.

Chromosome Mapping↗

PubMed1996

Comparative genetic and QTL mapping in sorghum and maize.

DNA markers and genetic maps will be important tools for direct investigations of several facets of crop improvement and will provide vital links between plant breeding and basic plant biology. The markers and maps will become more important for increased crop production because plant genetics will be required to extend or replace extant management practices such as chemical fertilizers, pesticides, and irrigation (Lee, 1995). Despite the importance of the sorghum crop, comprehensive genetic characterization has been limited. Therefore, the primary goal of this research program was to develop basic genetic tools to facilitate research in the genetics and breeding of sorghum. The first phase of this project consisted of constructing a genetic map based on restriction fragment length polymorphisms (RFLPs). The ISU sorghum map was created through linkage analysis of 78 F2 plants of an intraspecific cross between inbred CK60 and accession P1229828 (Pereira et al., 1994). The map consists of 201 loci distributed among 10 linkage groups covering 1,299 cM. Comparison of sorghum and maize RFLP maps on the basis of common sets of DNA probes revealed a high degree of conservation as reflected by homology, copy number, and collinearity. Examples of conserved and rearranged locus orders were observed. The same sorghum population was used to map genetic factors (mutants and QTL) for several traits including vegetative and reproductive morphology, maturity, insect, and disease resistance. This presentation will emphasize analysis of genetic factors affecting plant height, an important character for sorghum adaptation in temperate latitudes for grain production. Four QTL for plant height were identified in a sample of 152 F2 plants (Pereira and Lee, 1995) whereas 6 QTL were detected among their F3 progeny. These observations and assessments of other traits at 4 QTL common to F2 plants and their F3 progeny indicate some of these regions correspond to loci (dw) previously identified on the basis of alleles with highly qualitative effects. Four of the six sorghum plant height QTL seem to be orthologous to plant height QTL in maize. Other possible instances of orthologous QTL included regions for maturity and tillering. These observations suggest that the conservation of the maize and sorghum genomes encompasses sequence homology, collinearity, and function. The genetic information and technology developed on the basis of DNA markers could be used in several facets of breeding, genetics, and other basic biological investigations. In addition, DNA markers have been used to survey large collections of elite sorghum germ plasm to determine the degree of genetic relationships and genetic diversity (Ahnert et al., 1996). RFLP data seem to portray genetic relationships more accurately than the methods based exclusively on the coancestry coefficient. This information provides the basis for more accurate perceptions of genetic relationships and diversity.

Adaptation, Physiological↗

PubMed1993

Quantitative trait loci (QTL) analyses and alcohol-related behaviors.

Recombinant inbred (RI) strains can make an important contribution toward the merger of molecular genetics and quantitative genetics in the quest for quantitative trait loci (QTL). We present preliminary analyses of alcohol-related processes from our ongoing research using the BXD RI series. Issues concerning reliability, genetic correlations, and RI QTL analysis are discussed. Several strategies for replication and extension of QTL candidate regions are considered: F1 crosses between RI strains, F2 crosses, heterogeneous stock, interspecific backcrosses, QTL selection, and the use of murine QTL in chromosomal regions syntenic to human chromosomes as candidate chromosomal regions for human QTL.

Alcohol Drinking↗

PubMed2002

Identification of genetic factors controlling the efficiency of Agrobacterium rhizogenes-mediated transformation in Brassica oleracea by QTL analysis.

We have identified quantitative trait loci (QTL) for transgenic and adventitious root production using an Agrobacterium rhizogenes-mediated co-transformation system in conjunction with a Brassica oleracea double haploid (DH) mapping population. Three QTL for green fluorescent protein (GFP)-fluorescent root production and four QTL for adventitious root production were identified as accounting for 26% and 32% of the genetic variation in the population, respectively. Two of the QTL regions identified were common to both transgenic and adventitious root production. Two different methods of QTL analysis were employed (marker regression and interval mapping) and with the exception of one region on linkage group O7 for transgenic root production, both techniques detected the same regions of the genome. The regions we identified to be associated with the control of transgenic root production following A. rhizogenes-mediated transformation are the first to be detected using a QTL mapping approach. In addition, this is the first study to identify genetic regions that co-regulate both transgenic and adventitious root production within the constraints of an A. rhizogenes-mediated transformation process. We have identified plant genotypes that do not produce any transgenic roots that may be deficient for T-DNA integration via illegitimate recombination and that may also be potentially important for the development of homologous recombination protocols. Conversely, we have also identified plant genotypes with high rates of transgenic root production that will be critical in the development of high throughput transformation systems.

Journal Article↗

PubMed2003

Construction of a linkage map and QTL analysis of horticultural traits for watermelon [Citrullus lanatus (THUNB.) MATSUM & NAKAI] using RAPD, RFLP and ISSR markers.

We have been constructing linkage maps for watermelon ( Citrullus lanatus) on the basis of random amplified polymorphic DNA (RAPD), restriction fragment length polymorphism (RFLP), inter-simple sequence repeats (ISSRs) and isozymes using an F(2) population derived from a crossing between a cultivated inbred line (H-7; C. lanatus) and an African wild form (SA-1; C. lanatus). A total of 120 F(2) plants was used for construction of a linkage map using 477 RAPDs, 53 RFLPs, 23 ISSRs and one isozyme markers. Linkage analysis revealed that 554 loci could be mapped to 11 linkage groups that extended for 2,384 centimorgans (cM). While a BC(1) population [(H-7 x SA-1) x H-7] consisting of 60 individuals was grown and scored for quantitative traits. Another linkage map with a total length of 1,729 cM was constructed in the BC(1) using genetic markers found to segregate in the F(2) population. A QTL analysis was applied by means of interval mapping for locating such agronomic traits as hardness of rind, Brix of flesh juice, flesh color (red and yellow) and rind color. The relative order of markers in the BC(1) map was essentially the same as that on the linkage map in the F(2). A total of five QTLs for four agronomic traits was detected. The QTL for hardness of rind was mapped on group 4. The linkage group 8 contained the QTL for sugar content of the flesh as expressed in Brix of the juice. The QTL for red flesh color was detected on groups 2 and 8. The QTL for rind color mapped on the group 3. The present map and QTL analysis may provide a useful tool for breeders by introducing valuable wild watermelon genes to cultivars.

Chromosome Mapping↗

PubMed2003

QTL analysis for ascochyta blight resistance in an intraspecific population of chickpea (Cicer arietinum L.).

In both controlled environment and the field, six QTLs for ascochyta blight resistance were identified in three regions of the genome of an intraspecific population of chickpea using the IDS and AUDPC disease scoring systems. One QTL-region was detected from both environments, whereas the other two regions were detected from each environment. All the QTL-regions were significantly associated with ascochyta blight resistance using either of the disease scoring systems. The QTLs were verified by multiple interval mapping, and a two-QTL genetic model with considerable epistasis was established for both environments. The major QTLs generally showed additive gene action, as well as dominance inter-locus interaction in the multiple genetic model. All the QTLs were mapped near a RGA marker. The major QTLs were located on LG III, which was mapped with five different types of RGA markers. A CLRR-RGA marker and a STMS marker flanked QTL 6 for controlled environment resistance at 0.06 and 0.04 cM, respectively. Other STMS markers flanked QTL 1 for field resistance at a 5.6 cM interval. After validation, these flanking markers may be used in marker-assisted selection to breed for elite chickpea cultivars with durable resistance to ascochyta blight. The tight linkage of RGA markers to the major QTL on LG III will allow map-based cloning of the underlying resistance genes.

Alleles↗

PubMed2004

Comparative AB-QTL analysis in barley using a single exotic donor of Hordeum vulgare ssp. spontaneum.

This paper reports on the first comparative advanced backcross quantitative trait locus (AB-QTL) study in barley. The BC(2)F(2) population Hx101 was generated from crossing var. Harry [H; Hordeum vulgare ssp. vulgare ( Hv)] with ISR101-23 [101; H. v. ssp. spontaneum ( Hsp)]. The results of the AB-QTL analysis for 13 quantitative traits are presented and, subsequently, compared with the AB-QTL study of the barley cross Apex x ISR101-23 (Ax101; Pillen et al., Theor Appl Genet 107:340-352). Both AB populations share the exotic Hsp donor accession ISR101-23. In Hx101, 108 putative QTLs (17%) were identified among the 650 markerxtrait combinations tested. Altogether 52 (48 %) favorable effects were identified from the exotic parent. At these marker loci, the homozygous Hsp genotype was associated with an improvement in the trait compared to the homozygous Hv genotype. The percentage of QTLs detected in Hx101 was comparable to that in Ax101 (17% vs. 15%), however more favorable exotic QTL alleles were located in Hx101 than in Ax101 (48% vs. 34%). In Hx101, the Hsp QTL allele at EBmac0679([4H]) was associated with a yield increase of 5.9% averaged across the six environments tested. A comparison of putative QTLs between Hx101 and Ax101 was based on 26 shared SSR markers. In total, 26% of the putative QTLs could be detected simultaneously in both AB populations. This finding indicates that only a portion of the QTL effects of the donor allele can be transferred from one elite recipient to the next.

Alleles↗

PubMed2004

Comparative genetic analysis of quantitative traits in sunflower (Helianthus annuus L.) 3. Characterisation of QTL involved in resistance to Sclerotinia sclerotiorum and Phoma macdonaldi.

One hundred and fifty F(2)-F(3) families from a cross between two inbred sunflower lines FU and PAZ2 were used to map quantitative trait loci (QTL) for resistance to white rot (Sclerotinia sclerotiorum) attacks of terminal buds and capitula, and black stem ( Phoma macdonaldii). A genetic linkage map of 18 linkage groups with 216 molecular markers spanning 1,937 cM was constructed. Disease resistances were measured in field experiments for S. sclerotiorum and under controlled conditions for P. macdonaldii. For resistance to S. sclerotiorum terminal bud attack, seven QTL were identified, each explaining less than 10% of phenotypic variance. For capitulum attack by this parasite, there were four QTL (each explaining up to 20% of variation) and for P. macdonaldii resistance, four QTL were identified, each having effects of up to 16%. The S. sclerotiorum capitulum resistance QTL were compared with those reported previously and it was concluded that resistance to this disease is governed by a considerable number of QTL, located on almost all the sunflower linkage groups.

Ascomycota↗

PubMed2004

A major QTL conditioning salt tolerance in S-100 soybean and descendent cultivars.

Deployment of salt tolerant cultivars is an effective approach to minimize yield loss in a saline soil. In soybean, Glycine max (L.) Merr., substantial genetic variation exists for salt response. However, breeding for salt tolerance is hampered because no economically viable screening method has been developed for practical breeding. To facilitate the development of an effective screening method for salt tolerance in soybean, the present study was conducted to determine the heritability of salt tolerance and to identify associated quantitative trait loci (QTL). F2:5 lines from the cross of 'S-100' (salt tolerant) x 'Tokyo' (salt sensitive) were evaluated in a saline field in Hyde County, N.C., USA, in 1999 and in a greenhouse located in Raleigh, N.C., USA, in 2001. S-100 and Tokyo are ancestors of popular soybean cultivars released for the southern USA. The visual salt tolerance ratings of the F2:5 lines ranged from 0 (complete death) to 5 (normal healthy appearance). The entry-mean heritability for salt tolerance was 0.85, 0.48, and 0.57 in the field (four replications), greenhouse (two replications), and combined environments, respectively. The genotypic correlation between field and greenhouse ratings was 0.55, indicating reasonably good agreement between the two screening environments. To identify QTL associated with salt tolerance, each line was characterized with RFLP markers and an initial QTL single-factor analysis was completed. These results were used to identify genomic regions associated with the trait and to saturate the selected genomic regions with SSR markers to improve mapping precision. Subsequently, a major QTL for salt tolerance was discovered near the Sat_091 SSR marker on linkage group (LG) N, accounting for 41, 60, and 79% of the total genetic variation for salt tolerance in the field, greenhouse, and combined environments, respectively. The QTL allele associated with tolerance was derived from S-100. Pedigree tracking was used to examine the association between the salt tolerance QTL and flanking SSR marker alleles in U.S. cultivars descended from S-100 or Tokyo through 60 years of breeding. The presence of alleles from S-100 at the Sat_091 and Satt237 marker loci was always associated with salt tolerance in descendants. Alleles from Tokyo for these same markers were generally associated with salt sensitivity in descendent cultivars. The strong relationship between the SSR marker alleles and salt tolerance suggests that these markers could be used for marker-assisted selection in commercial breeding.

Adaptation, Physiological↗

PubMed2005

Mapping of a spontaneous mutation for early flowering time in maize highlights contrasting allelic series at two-linked QTL on chromosome 8.

Only a few mutations affecting flowering time have been detected in maize. We analyzed a spontaneous early mutation, vgt-f7p, which appeared during production of the inbred line F7. This mutation shortens the time from planting to flowering by about 100 growing degree days (GDD), and reduces the number of nodes. It therefore seems to affect the timing of meristem differentiation from a vegetative to a reproductive state. It was mapped to a 6 cM confidence interval on chromosome 8, using a QTL mapping approach. QTL analysis of a mapping population generated by crossing the mutant F7 line (F7p) and the Gaspé flint population showed that vgt-f7p is probably allelic to vgt1, a QTL described in previous studies, and affects earliness more strongly than the Gaspé allele at vgt1. Global analysis of the QTL in the region suggested that there may be two consensus QTL, vgt1 and vgt2. These two QTL have contrasting allelic effects: rare alleles conferring extremely early flowering at vgt1 vs. greater diversity and milder effects at locus vgt2. Finally, detailed syntenic analysis showed that the vgt1 region displays a highly conserved duplicated region on chromosome 6, which also plays an important role in maize flowering time variation. The cloning of vgt1 should, therefore, also facilitate the analysis of the molecular basis of variation due to this second region.

Alleles↗

PubMed2005

QTLs mapping for fruit size and shape in chromosomes 2 and 4 in pepper and a comparison of the pepper QTL map with that of tomato.

Quantitative trait locus (QTL) mapping for fruit weight and shape in pepper (Capsicum spp.) was performed using C. chinense and C. frutescens introgression lines of chromosomes 2 and 4. In chromosome 2, a single major fruit-weight QTL, fw2.1, was detected in both populations that explained 62% of the trait variation. This QTL, as well as a fruit-shape QTL, fs2.1, which had a more minor effect, were localized to the tomato fruit-shape gene ovate. The cloned tomato fruit-weight QTL, fw2.2, did not play a major role in controlling fruit size variations in pepper. In chromosome 4, two fruit-weight QTLs, fw4.1 and fw4.2, were detected in the same genomic regions in both mapping populations. In addition, a single fruit-shape QTL was detected in each of the mapping populations that co-localized with one of the fruit-weight QTLs, suggesting pleiotropy or close linkage of the genes controlling size and shape. fw2.1 and fw4.2 represent major fruit-weight QTLs that are conserved in the three Capsicum species analyzed to date for fruit-size variations. Co-localization of the pepper QTLs with QTLs identified for similar traits in tomato suggests that the pepper and tomato QTLs are orthologous. Compared to fruit-shape QTLs, fruit-weight QTLs were more often conserved between pepper and tomato. This implies that different modes of selection were employed for these traits during domestication of the two Solanaceae species.

Capsicum↗

PubMed2005

AB-QTL analysis in spring barley. I. Detection of resistance genes against powdery mildew, leaf rust and scald introgressed from wild barley.

The objective of this study was to map new resistance genes against powdery mildew (Blumeria graminis f. sp. hordei L.), leaf rust (Puccinia hordei L.) and scald [Rhynchosporium secalis (Oud.) J. Davis] in the advanced backcross doubled haploid (BC2DH) population S42 derived from a cross between the spring barley cultivar 'Scarlett' and the wild barley accession ISR42-8 (Hordeum vulgare ssp. spontaneum). Using field data of disease severity recorded in eight environments under natural infestation and genotype data of 98 SSR loci, we detected nine QTL for powdery mildew, six QTL for leaf rust resistance and three QTL for scald resistance. The presence of the exotic QTL alleles reduced disease symptoms by a maximum of 51.5, 37.6 and 16.5% for powdery mildew, leaf rust and scald, respectively. Some of the detected QTL may correspond to previously identified qualitative (i.e. Mla) and to quantitative resistance genes. Others may be newly identified resistance genes. For the majority of resistance QTL (61.0%) the wild barley contributed the favourable allele demonstrating the usefulness of wild barley in the quest for resistant cultivars.

Ascomycota↗

PubMed2006

An updated 'Essex' by 'Forrest' linkage map and first composite interval map of QTL underlying six soybean traits.

DNA marker maps based on single populations are the basis for gene, loci and genomic analyses. Individual maps can be integrated to produce composite maps with higher marker densities if shared marker orders are consistent. However, estimates of marker order in composite maps must include sets of markers that were not polymorphic in multiple populations. Often some of the pooled markers were not codominant, or were not correctly scored. The soybean composite map was composed of data from five separate populations based on northern US germplasm but does not yet include 'Essex' by 'Forrest' recombinant inbred line (RIL) population (E x F) or any southern US soybean cultivars. The objectives were, to update the E x F map with codominant markers, to compare marker orders among this map, the Forrest physical map and the composite soybean map and to compare QTL identified by composite interval maps to the earlier interval maps. Two hundred and thirty seven markers were used to construct the core of the E x F map. The majority of marker orders were consistent between the maps. However, 19 putative marker inversions were detected on 12 of 20 linkage groups (LG). Eleven marker distance compressions were also found. The number of inverted markers ranged from 1 to 2 per LG. Thus, marker order inversions may be common in southern compared to northern US germplasm. A total of 61 QTL among 37 measures of six traits were detected by composite interval maps, interval maps and single point analysis. Seventeen of the QTL found in composite intervals had previously been detected among the 29 QTL found in simple interval maps. The genomic locations of the known QTL were more closely delimited. A genome sequencing project to compare Southern and Northern US soybean cultivars would catalog and delimit inverted regions and the associated QTL. Gene introgression in cultivar development programs would be accelerated.

Chromosome Mapping↗

PubMed2006

Mapping QTL for dollar spot resistance in creeping bentgrass (Agrostis stolonifera L.).

Dollar spot caused by Sclerotinia homoeocarpa F. T. Bennett is the most economically important turf disease on golf courses in North America. Dollar spot resistance in a creeping bentgrass cultivar would greatly reduce the frequency, costs, and environmental impacts of fungicide application. Little work has been done to understand the genetics of resistance to dollar spot in creeping bentgrass. Therefore, QTL analysis was used to determine the location, number and effects of genomic regions associated with dollar spot resistance in the field. To meet this objective, field inoculations using a single isolate were performed over 2 years and multiple locations using progeny of a full sib mapping population '549 x 372'. Dollar spot resistance seems to be inherited quantitatively and broad sense heritability for resistance was estimated to be 0.88. We have detected one QTL with large effect on linkage group 7.1 with LOD values ranging from 3.4 to 8.6 and explaining 14-36% of the phenotypic variance. Several smaller effect QTL specific to rating dates, locations and years were also detected. The association of the tightly linked markers with the LG 7.1 QTL based on 106 progeny was further examined by single marker analysis on all 697 progeny. The high significance of the QTL on LG 7.1 at a sample size of 697 (P < 0.0001), along with its consistency across locations, years and ratings dates, indicated that it was stable over environments. Markers tightly linked to the QTL can be utilized for marker-assisted selection in future bentgrass breeding programs.

Agrostis↗

PubMed2006

Most significant genome regions involved in the control of earliness traits in bread wheat, as revealed by QTL meta-analysis.

Earliness is one of the most important adaptation traits in plant breeding. Our purpose was to identify the genome regions of bread wheat involved in the control of earliness and its three components: photoperiod sensitivity (PS), vernalization requirement (VR) and intrinsic earliness (IE). A QTL meta-analysis was carried out to examine the replicability of QTL across 13 independent studies and to propose meta-QTL (MQTL). Initial QTL were projected on a recent consensus map (2004). Quality criteria were proposed to assess the reliability of this projection. These criteria were based on the distances between markers in the QTL regions. Chromosomes of groups 2 and 5 had a greater incidence on earliness control as they carry the known, major genes Ppd and Vrn. Other chromosome regions played an intermediate role in earliness control: 4A [heading date (HD) Meta-QTL], 4B (HD MQTL), 2B (VR MQTL) and 5B (IE MQTL). Markers at this four MQTL should prove helpful in marker-assisted selection, to better control earliness.

Bread↗

PubMed2005

Marker-assisted introgression of trypanotolerance QTL in mice.

A marker-assisted introgression (MAI) experiment was conducted to use genetic markers to transfer each of the three trypanotolerance QTL from a donor mouse strain, C57BL/6, into a recipient mouse strain, A/J. We used a backcross strategy that consisted of selecting two lines, each carrying two of the donor QTL alleles through the backcross (BC) phase. At the fourth BC generation, single-carrier animals were selected for the production of homozygous animal in the intercross phase. The QTL regions (QTLR) were located on chromosomes MMU1, MMU5, and MMU17. Groups of mice with different genotypes and the parental lines were subjected to a challenge with Trypanosoma congolense. The results show that trypanotolerance QTL was successfully moved into the recipient background genotype, yielding a longer survival time. The mean estimated survival time was 57.9, 49.5, and 46.8 days for groups of mice carrying the donor QTL on MMU1, MMU5, and MMU17 on A/J background. The mean estimated survival time was 29.7 days for the susceptible A/J line and 68.8 days for the resistant C57BL/6 line. The estimated QTLR effects are close to 30% smaller than those in the original mapping population which was likely caused by the difference in the background on which the effects of QTLR are tested. This is the first report of successful marker-assisted introgression of QTL in animals. It is experimental proof of the use of genetic markers for marker-assisted introgression in animal breeding.

Animals↗