Quantitative trait locus analysis of the early domestication of sunflower

Genetic analyses of the domestication syndrome have revealed that domestication-related traits typically have a very similar genetic architecture across most crops, being conditioned by a small number of quantitative trait loci (QTL), each with a relatively large effect on the phenotype. To date, the domestication of sunflower (Helianthus annuus L.) stands as the only counterexample to this pattern. In previous work involving a cross between wild sunflower (also H. annuus) and a highly improved oilseed cultivar, we found that domestication-related traits in sunflower are controlled by numerous QTL, typically of small effect. To provide insight into the minimum genetic changes required to transform the weedy common sunflower into a useful crop plant, we mapped QTL underlying domestication-related traits in a cross between a wild sunflower and a primitive Native American landrace that has not been the target of modern breeding programs. Consistent with the results of the previous study, our data indicate that the domestication of sunflower was driven by selection on a large number of loci, most of which had small to moderate phenotypic effects. Unlike the results of the previous study, however, nearly all of the QTL identified herein had phenotypic effects in the expected direction, with the domesticated allele producing a more crop-like phenotype and the wild allele producing a more wild-like phenotype. Taken together, these results are consistent with the hypothesis that selection during the post-domestication era has resulted in the introduction of apparently maladaptive alleles into the modern sunflower gene pool.     

Genetic analysis of phytosterol content in sunflower seeds

Interest in phytosterol contents due to their potential benefits for human health has been largely documented in several crop species. Studies were focused mainly on total sterol content and their concentration or distribution in seed. This study aimed at providing new insight into the genetic control of total and individual sterol contents in sunflower seed through QTL analyses in a RIL population characterized over 2?years showing contrasted rainfall during seed filling. Results indicated that 13 regions on 9 linkage groups were involved in different phytosterol traits. Most of the QTL mapped were stable across years in spite of contrasted growing conditions. Some of them explained up to 30?% of phenotypic variation. Two QTL, located on LG10, near b1, and on LG14, were found to co-localize with QTL for oil content, indicating that likely, a part of the genetic variation for sterol content is only the result of genetic variation for oil content. However, three other QTL, stable over the 2?years, were found on LG1, LG4 and LG7 each associated with a particular class of sterols, suggesting that some enzymes known to be involved in the sterol metabolic pathway may determine the specificity of sterol profiles in sunflower seeds. These results suggest that it may be possible to introduce these traits as criteria in breeding programmes for quality in sunflower. The molecular markers linked to genetic factors controlling phytosterol contents could help selection during breeding programs.     

Molecular basis of the high-palmitic acid trait in sunflower seed oil

Sunflower (Helianthus annuus L.) seed oil with high palmitic acid content has enhanced thermo-oxidative stability, which makes it well suited to high-temperature uses. CAS-5 is a sunflower mutant line that accumulates over 25 % palmitic acid in its seed oil, compared to 5–8 % in conventional cultivars. The objective of this study was to investigate the molecular basis of the high-palmitic acid trait in CAS-5 through both candidate gene and QTL mapping approaches. An F₂ population derived from the cross between CAS-5 and the conventional line HA-89 was developed. A 3-ketoacyl-ACP synthase II (KASII) locus on a telomeric region of linkage group (LG) 9 of the sunflower genetic map was found to co-segregate with palmitic acid content in this population. The KASII locus explained the vast majority of the phenotypic variation (98 %) of the trait. Two minor QTL affecting palmitic acid content were also found on the lower half of LG 9 and on LG 17. Additionally, QTL associated with other major fatty acids (stearic, oleic, and linoleic acid) were identified on LG 1, 6, and 10. This result may reflect untapped genetic variation that could exist among sunflower cultivars for genes determining fatty acid composition. In addition to demonstrating the major role of a KASII locus in the accumulation of high levels of palmitic acid in CAS-5 seeds, this study stressed the importance of characterizing genes with minor effects on fatty acid profile in order to establish optimal breeding strategies for modifying fatty acid composition in sunflower seed oil.     

Consensus mapping of major resistance genes and independent QTL for quantitative resistance to sunflower downy mildew

Major gene resistance to sunflower downy mildew (Plasmopara halstedii) races 304 and 314 was found to segregate independently from the resistance to races 334, 307 and 304 determined by the gene Pl2, already positioned on Linkage Group (LG) 8 of sunflower molecular maps. Using a consensus SSR-SNP map constructed from the INEDI RIL population and a new RIL population FU?×?PAZ2, the positions of Pl2 and Pl5 were confirmed and the new gene, denoted Pl21, was mapped on LG13, at 8?cM from Pl5. The two RIL populations were observed for their quantitative resistance to downy mildew in the field and both indicated the existence of a QTL on LG8 at 20-40?cM from the major resistance gene cluster. In addition, for the INEDI population, a strong QTL on LG10, reported previously, was confirmed and a third QTL was mapped on LG7. A growth chamber test methodology, significantly correlated with field results, also revealed the major QTL on LG10, explaining 65?% of variability. This QTL mapped in the same area as a gene involved in stomatal opening and root growth, which may be suggested as a possible candidate to explain the control of this character. These results indicate that it should be possible to combine major genes and other resistance mechanisms, a strategy that could help to improve durability of sunflower resistance to downy mildew.     

Stearoyl-ACP and oleoyl-PC desaturase genes cosegregate with quantitative trait loci underlying high stearic and high oleic acid mutant phenotypes in sunflower

The genetic control of the synthesis of stearic acid (C18:0) and oleic acid (C18:1) in the seed oil of sunflower was studied through candidate-gene and QTL analysis. Two F₂ mapping populations were developed using the high C18:0 mutant CAS-3 crossed to either HA-89 (standard, high linoleic fatty acid profile), or HAOL-9 (high C18:1 version of HA-89). A stearoyl-ACP desaturase locus (SAD17A), and an oleoyl-PC de-saturase locus (OLD7) were found to cosegregate with the previously described Es1 and Ol genes controlling the high C18:0 and the high C18:1 traits, respectively. Using linkage maps constructed from AFLP and RFLP markers, these loci mapped to LG1 (SAD17A) and to LG14 (OLD7) and were found to underlie the major QTLs affecting the concentrations of C18:0 and C18:1, explaining around 80% and 56% of the phenotypic variance of these fatty acids, respectively. These QTLs pleiotropically affected the levels of other primary fatty acids in the seed storage lipids. A minor QTL affecting both C18:0 and C18:1 levels was identified on LG8 in the HAOL-9×CAS-3 F₂. This QTL showed a significant epistatic interaction for C18:1 with the QTL at the OLD7 locus, and was hypothesized to be a modifier of Ol. Two additional minor C18:0 QTLs were also detected on LG7 and LG3 in the HA-89×CAS-3 and the HAOL-9×CAS-3 F₂ populations, respectively. No association between a mapped FatB thioesterase locus and fatty acid concentration was found. These results provide strong support about the role of fatty acid desaturase genes in determining fatty acid composition in the seed oil of sunflower. Received: 7 December 2000 / Accepted: 21 May 2001     

Mapping minor QTL for increased stearic acid content in sunflower seed oil

Increased stearic acid (C18:0) content in the seed oil of sunflower would improve the oil quality for some edible uses. The sunflower line CAS-20 (C18:0 genotype Es1Es1es2es2), developed from the high C18:0 mutant line CAS-3 (C18:0 genotype es1es1es2es2; 25% C18:0), shows increased C18:0 levels in its seed oil (8.6%). The objective of this research was to map quantitative trait loci (QTL) conferring increased C18:0 content in CAS-20 in an F₂ mapping population developed from crosses between HA-89 (wild type Es1Es1Es2Es2; low C18:0) and CAS-20, which segregates independently of the macromutation Es1 controlling high C18:0 content in CAS-3. Seed oil fatty acid composition was measured in the F₂ population by gas-liquid chromatography. A genetic linkage map of 17 linkage groups (LGs) comprising 80 RFLP and 19 SSR marker loci from this population was used to identify QTL controlling fatty acid composition. Three QTL affecting C18:0 content were identified on LG3, LG11, and LG13, with all alleles for increased C18:0 content inherited from CAS-20. In total, these QTL explained 43.6% of the C18:0 phenotypic variation. Additionally, four candidate genes (two stearate desaturase genes, SAD6 and SAD17, and a FatA and a FatB thioesterase gene) were placed on the QTL map. On the basis of positional information, QTL on LG11 was suggested to be a SAD6 locus. The results presented show that increased C18:0 content in sunflower seed oil is not a simple trait, and the markers flanking these QTL constitute a powerful tool for plant breeding programs.     

Seed and agronomic QTL in low linolenic acid, lipoxygenase-free soybean (Glycine max (L.) Merrill) germplasm.

Linolenic acid and seed lipoxygenases are associated with off flavours in soybean products. F5 recombinant inbred lines (RILs) from a cross between a low linolenic acid line (RG10) and a seed lipoxygenase-free line (OX948) were genotyped for simple sequence repeats (SSR), random amplified polymorphic DNA (RAPD), sequence-tagged sites (STS), and cleaved amplified polymorphic sequence (CAPS) markers and evaluated for seed and agronomic traits at 3 Ontario locations in 2 years. One hundred twenty markers covering 1247.5 cM were mapped to 18 linkage groups (LGs) in the soybean composite genetic map. Seed lipoxygenases L-1 and L-2 mapped as single major genes to the same location on LG G13-F. L-3 mapped to LG G11-E. This is the first report of a map position for L-3. A major quantitative trait locus (QTL) associated with reduced linolenic acid content was identified on LG G3-B2. QTLs for 12 additional seed and agronomic traits were detected. Linolenic acid content, linoleic acid content, yield, seed mass, protein content, and plant height QTL were present in at least 4 of 6 environments. Three to 8 QTLs per trait were detected that accounted for up to 78% of total variation. Linolenic acid and lipoxygenase loci did not overlap yield QTL, suggesting that it should be possible to develop high-yielding lines resistant to oxidative degradation by marker-assisted selection (MAS).     

Genetic Control of Water Use Efficiency and Leaf Carbon Isotope Discrimination in Sunflower (Helianthus annuus L.) Subjected to Two Drought Scenarios

High water use efficiency (WUE) can be achieved by coordination of biomass accumulation and water consumption. WUE is physiologically and genetically linked to carbon isotope discrimination (CID) in leaves of plants. A population of 148 recombinant inbred lines (RILs) of sunflower derived from a cross between XRQ and PSC8 lines was studied to identify quantitative trait loci (QTL) controlling WUE and CID, and to compare QTL associated with these traits in different drought scenarios. We conducted greenhouse experiments in 2011 and 2012 by using 100 balances which provided a daily measurement of water transpired, and we determined WUE, CID, biomass and cumulative water transpired by plants. Wide phenotypic variability, significant genotypic effects, and significant negative correlations between WUE and CID were observed in both experiments. A total of nine QTL controlling WUE and eight controlling CID were identified across the two experiments. A QTL for phenotypic response controlling WUE and CID was also significantly identified. The QTL for WUE were specific to the drought scenarios, whereas the QTL for CID were independent of the drought scenarios and could be found in all the experiments. Our results showed that the stable genomic regions controlling CID were located on the linkage groups 06 and 13 (LG06 and LG13). Three QTL for CID were co-localized with the QTL for WUE, biomass and cumulative water transpired. We found that CID and WUE are highly correlated and have common genetic control. Interestingly, the genetic control of these traits showed an interaction with the environment (between the two drought scenarios and control conditions). Our results open a way for breeding higher WUE by using CID and marker-assisted approaches and therefore help to maintain the stability of sunflower crop production.     

Molecular analysis of the high stearic acid content in sunflower mutant CAS-14

Increasing the stearic acid content to improve sunflower (Helianthus annuus L.) oil quality is a desirable breeding objective for food-processing applications. CAS-14 is a sunflower mutant line with a high stearic acid content in its seed oil (>35% vs. <6% in currently grown sunflower hybrids), which is controlled by the Es3 gene. However, the expression of the high stearic acid character in CAS-14 is strongly influenced by temperature during seed maturation and it is not uniform along the seed. The objectives of this study were (1) to identify PCR-based molecular markers linked to the Es3 gene from CAS-14, (2) to map this gene on the sunflower genetic map, and (3) to characterize the interaction between CAS-14 and CAS-3, a sunflower high stearic acid (about 26%) mutant line with the Es1 and Es2 genes determining this trait. Two F₂ mapping populations were developed from crosses between CAS-14 and P21, a nuclear male sterile line with the Ms₁₁ gene controlling this character, and between CAS-14 and CAS-3. One hundred and thirty-three individuals from P21×CAS-14, and 164 individuals from CAS-3×CAS-14 were phenotyped in F₂ and F₃ seed generations for fatty acid composition using gas–liquid chromatography, and they were then genotyped with microsatellite [simple sequence repeat (SSR)] and insertion–deletion (INDEL) markers. Bulk segregant analysis in the P21×CAS-14 population identified two markers on LG 8 putatively linked to Es3. A large linkage group was identified using additional markers mapping to LG 8. Es3 mapped to the distal half of LG 8 and was flanked by the SSR markers ORS243 and ORS1161 at genetic distances of 0.5, and 3.9 cM, respectively. The Ms₁₁ gene was also mapped to LG 8 and genetic distance between this gene and Es3 was found to be 7.4 cM. In the CAS-3×CAS-14 population, two QTLs were identified on LG 1 and LG 8, which underlie the Es1 gene from CAS-3 and the Es3 gene from CAS-14, respectively. A significant epistatic interaction between these two QTLs was found. Results from this study provided a basis for determining CAS-14 efficient breeding strategies.     

Ecological patterns and genetic analysis of post‐dispersal seed predation in sunflower (Helianthus annuus) crop‐wild hybrids

Crop‐wild hybridization has been documented in many cultivated species, but the ecological and genetic factors that influence the likelihood or rate that cultivar alleles will introgress into wild populations are poorly understood. Seed predation is one factor that could mitigate the spread of otherwise advantageous cultivar alleles into the wild by reducing seedling recruitment of crop‐like individuals in hybrid populations. Seed predation has previously been linked to several seed characters that differ between cultivated and wild sunflower, such as seed size and oil content. In this study, seed morphological and nutritional characters were measured in a segregating population of sunflower crop‐wild hybrids and wild and cultivated lines. Seed predation rates among lines were then assessed in the field. The relationship between seed predation and seed characters was investigated and quantitative trait loci (QTL) were mapped for all traits. There was no effect of seed type (hybrid vs. parents) on seed predation, although a trend toward more early predation of wild seeds was observed. Within the hybrids, seed predators preferred seeds that contained more oil and energy but were lower in fibre. The relationship between seed predation and oil content was supported by co‐localized QTL for these traits on one linkage group. These results suggest that oil content may be a more important determinant of seed predation than seed size and provide molecular genetic evidence for this relationship. The cultivar allele was also found to increase predation at all QTL, indicating that post‐dispersal seed predation may mitigate the spread of cultivar alleles into wild populations.     

Habitat-specific natural selection at a flowering-time QTL is a main driver of local adaptation in two wild barley populations

Understanding the genetic basis of local adaptation requires insight in the fitness effects of individual loci under natural field conditions. While rapid progress is made in the search for genes that control differences between plant populations, it is typically unknown whether the genes under study are in fact key targets of habitat-specific natural selection. Using a quantitative trait loci (QTL) approach, we show that a QTL associated with flowering-time variation between two locally adapted wild barley populations is an important determinant of fitness in one, but not in the other population's native habitat. The QTL mapped to the same position as a habitat-specific QTL for field fitness that affected plant reproductive output in only one of the parental habitats, indicating that the genomic region is under differential selection between the native habitats. Consistent with the QTL results, phenotypic selection of flowering time differed between the two environments, whereas other traits (growth rate and seed weight) were under selection but experienced no habitat-specific differential selection. This implies the flowering-time QTL as a driver of adaptive population divergence. Our results from phenotypic selection and QTL analysis are consistent with local adaptation without genetic trade-offs in performance across environments, i.e. without alleles or traits having opposing fitness effects in contrasting environments.     

Genetic mapping of seed shape in three populations of recombinant inbred lines of soybean (Glycine max L. Merr.)

Round soybean seeds are sought-after for food-type soybean. Also the genetic control of seed geometry is of scientific interest. The objectives of this study were to estimate heritability and map quantitative trait loci (QTLs) responsible for seed shape traits. Three densely mapped recombinant inbred populations each with 192 segregants were used, Minsoy × Archer, Minsoy × Noir1, and Noir1 × Archer. A two rep two location experiment was conducted in Los Andes, Chile, and East Lansing, MI, USA. Seed height (SH), width (SW), length (SL), and seed volume (SV) as width × height × length were measured to determine seed shape. Heritability was estimated by variance component analysis. A total of 19 significant QTLs (LOD ≥ 3.7) in ten linkage groups (LG) were detected for all the traits. Only one QTL was stable across populations and environments and six were stable in at least two populations in both environments. The amount of phenotypic variation explained by a single QTL varied from 7.5% for SH, to 18.5% for SW and at least 30% of the genetic variation for the traits is controlled by four QTL or less. All traits were highly correlated with each other in all populations with values ranging from 0.5 to 0.9, except for SL and SW that were not significantly correlated or had a low correlation in all populations. Narrow sense heritabilities for all traits ranged from 0.42 to 0.88. We note that LG u9, u11, and u14 are hot points of the genome for QTLs for various traits. The number and genomic distribution of the QTLs confirms the complex genetic control of seed shape. Transgressive segregation was observed for all traits suggesting that careful selection of parents with similar phenotypes but different genotypes using molecular markers can result in desirable transgressive segregants.     

Identifying genetic components controlling fertility in the outcrossing grass species perennial ryegrass (Lolium perenne) by quantitative trait loci analysis and comparative genetics

Mutational load and resource allocation factors and their effects on limiting seed set were investigated in ryegrass by comparative mapping genomics and quantitative trait loci (QTL) analysis in two perennial ryegrass (Lolium perenne) mapping families sharing common genetic markers. Quantitative trait loci for seed-set were identified on chromosome (LG) 7 in both families and on LG4 of the F2/WSC family. On LG7, seed-set and heading date QTLs colocalized in both families and cannot be unequivocally resolved. Comparative genomics suggests that the LG7 region is syntenous to a region of rice LG6 which contains both fertility (S5(n)) and heading date (Hd1, Hd3a) candidate genes. The LG4 region is syntenous to a region of rice LG3 which contains a fertility (S33) candidate gene. QTL maxima for seed-set and heading date on LG4 in the F2/WSC family are separated by c. 8 cm, indicating distinct genetic control. Low seed set is under the control of recessive genes at both LG4 and LG7 locations. The identification of QTLs associated with seed set, a major component of seed yield in perennial ryegrass, indicates that mutational load associated with these genomic regions can be mitigated through marker-assisted selection.     

Genetic mapping of EST-derived simple sequence repeats (EST-SSRs) to identify QTL for leaf morphological characters in a Quercus robur full-sib family

The availability of genomic resources such as expressed sequence tag-derived simple sequence repeat (EST-SSR) markers in adaptive genes with high transferability across related species allows the construction of genetic maps and the comparison of genome structure and quantitative trait loci (QTL) positions. In the present study, genetic linkage maps were constructed for both parents of a Quercus robur × Q. robur ssp. slavonica full-sib pedigree. A total of 182 markers (61 AFLPs, 23 nuclear SSRs, 98 EST-SSRs) and 172 markers (49 AFLPs, 21 nSSRs, 101 EST-SSRs, 1 isozyme) were mapped on the female and male linkage maps, respectively. The total map length and average marker spacing were 1,038 and 5.7 cM for the female map and 998.5 and 5.8 cM for the male map. A total of 68 nuclear SSRs and EST-SSRs segregating in both parents allowed to define homologous linkage groups (LG) between both parental maps. QTL for leaf morphological traits were mapped on all 12 LG at a chromosome-wide level and on 6 LG at a genome-wide level. The phenotypic effects explained by each single QTL ranged from 4.0 % for leaf area to 15.8 % for the number of intercalary veins. QTL clusters for leaf characters that discriminate between Q. robur and Quercus petraea were mapped reproducibly on three LG, and some putative candidate genes among potentially many others were identified on LG3 and LG5. Genetic linkage maps based on EST-SSRs can be valuable tools for the identification of genes involved in adaptive trait variation and for comparative mapping.     

甘蓝型油菜种子发芽率QTL定位及相关生理性状

利用GH06×P174组合衍生的183个重组自交系进行种子发芽率遗传分析及种子发芽期间种子生理性状分析。用复合区间作图法对在室温下保存两年的种子(STY)、保存1年的种子(SOY)与新收获种子(FS)发芽率进行QTL定位。另外对保存两年的种子及新收获的种子萌发期间脂肪酶活性、电导率、还原糖含量、总糖含量及根系活力进行了测定, 并对结果进行分析。结果表明3批种子的发芽率QTL位点各不相同, 保存两年的种子在第9、14、17条连锁群上分别检测到1个位点, 保存1年的种子在第5、9条连锁群上各检测到1个位点, 新收获的种子在第4、18条连锁群上分别测检到1个位点。研究发现, 3批种子的发芽率相关性不显著, 发芽率差异达到极显著水平, 同时保存不同年份种子的发芽率QTL各不相同, 这表明甘蓝型油菜发芽率受很多不同因素所控制。保存两年及新收获种子的发芽率与电导率之间的相关性均达到极显著负相关, 表明可以通过电导率的测定估测发芽率, 电导率的研究对种子发芽率的研究具有重要意义。     

Comparative genetic analysis of quantitative traits in sunflower (Helianthus annuus L.). 2. Characterisation of QTL involved in developmental and agronomic traits

Seed weight and oil content are important properties of cultivated sunflower under complex genetic and environmental control, and associated with morphological and developmental characteristics such as plant height or flowering dates. Using a genetic map with 290 markers for a cross between two inbred sunflower lines and 2 years of observations on F3 families, QTL controlling seed weight, oil content, plant height, plant lodging, flowering dates, maturity dates and delay from flowering to maturity were detected. QTL detected were compared between the F2 and F3 generations and between the 2 years of testing for the F3 families in 1997 and 1999. Some of the QTL controlling seed weight overlapped with those controlling oil content. Several other co-localisations of QTL controlling developmental or morphological characteristics were observed and the relationships between the traits were also shown by correlation analyses. The relationships between all these traits and with resistance to Sclerotinia sclerotiorum and Diaporthe helianthi are discussed.     

Effects of floral traits and plant genetic composition on pollinator behavior

Pollinator-mediated selection plays a major role in floral evolution and speciation. Floral traits that influence animal pollinator behavior are the target of pollinator-mediated selection, but can only evolve if floral phenotypes have underlying genetic variation. Thus, understanding the genetic basis of a floral trait is a crucial step in studying pollinator-mediated selection. In this study I tested the effect of quantitative trait loci (QTL) underlying floral traits on pollinator behavior in recombinant inbred lines (RILs) in the common sunflower, Helianthus annuus L. and its crop relative. The indirect effects of QTL on pollinator behavior, mediated by floral phenotypes, were analyzed for six insect visitor types using structural equation modeling (SEM) and path analysis. For three of the six visitor types (large and small bees and non-bee insects) valid models were revealed when all three levels (QTL, floral traits, and pollinator behavior) were incorporated. Nested model without genetics were validated for five of the six visitor types. The results suggest that insect behavior as a reaction to floral phenotypes is affected by the genetic architecture of floral traits. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: Heikki Hokkanen     

Analysis of an intraspecific RIL population uncovers genomic segments harbouring multiple QTL for seed relevant traits in lentil (<Emphasis Type="Italic">Lens culinaris</Emphasis> L.)

Improving seed related traits remains key objective in lentil breeding. In recent years, genomic resources have shown great promise to accelerate crop improvement. However, limited genomic resources in lentil greatly restrict the use of genomics assisted breeding. The present investigation aims to build an intraspecific genetic linkage map and identify the QTL associated with important seed relevant traits using 94 recombinant inbreds (WA 8649090 × Precoz). A total of 288 polymorphic DNA markers including simple sequence repeat (SSR), inter simple sequence repeat (ISSR) and random amplified polymorphic DNA (RAPD) were assayed on mapping population. The resultant genetic linkage map comprised 220 loci spanning 604.2 cM of the lentil genome, with average inter-marker distance of 2.74 cM. QTL mapping in this RIL population uncovered a total of 18 QTL encompassing nine major and nine minor QTL. All major QTL were detected for seed related traits viz., seed diameter (SD), seed thickness (ST), seed weight (SW) and seed plumpness (SP) across two locations. A considerable proportion of the phenotypic variation (PV) was accounted to these QTL. For instance, one major QTL on LG5 controlling SW (QTL 15) explained 50% PV in one location, while the same QTL accounted for 34.18% PV in other location. Importantly, the genomic region containing multiple QTL for different seed traits was mapped to a 17-cM region on LG5. The genomic region harbouring QTL for multiple traits opens up exciting opportunities for genomics assisted improvement of lentil.     

Construction of a cucumber genetic linkage map with SRAP markers and location of the genes for lateral branch traits

Cucumber (Cucumis sativus L. 2n = 2x = 14), thatbelongs to Cucurbitaceae family, is one of majorvegetables with a planting area second to that of to-mato in the world[1]. Due to its economical importanceplant breeders and geneticists have paid much atten-tion to the genetic study on this important vegetablecrop, but the research progress in cucumber is muchless than that in tomato. In 1990, Pierce[2] reviewed allthe reported genes of cucumber that had been geneti-cally analyzed since the 1930…     

Pleiotropy of the branching locus (B) masks linked and unlinked quantitative trait loci affecting seed traits in sunflower

The discovery of unbranched, monocephalic natural variants was pivotal for the domestication of sunflower (Helianthus annuus L.). The branching locus (B), one of several loci apparently targeted by aboriginal selection for monocephaly, pleiotropically affects plant, seed and capitula morphology and, when segregating, confounds the discovery of favorable alleles for seed yield and other traits. The present study was undertaken to gain deeper insights into the genetics of branching and seed traits affected by branching. We produced an unbranched hybrid testcross recombinant inbred line (TC-RIL) population by crossing branched (bb) and unbranched (BB) RILs to an unbranched (BB) tester. The elimination of branching concomitantly eliminated a cluster of B-linked seed trait quantitative trait loci (QTL) identified by RIL per se testing. We identified a seed oil content QTL linked in repulsion and a 100-seed weight QTL linked in coupling to the B locus and additional unlinked QTL, previously masked by B-locus pleiotropy. Genomic segments flanking the B locus harbor multiple loci for domestication and post-domestication traits, the effects of which are masked by B-locus pleiotropy in populations segregating for branching and can only be disentangled by genetic analyses in unbranched populations. QTL analyses of NILs carrying wild B alleles substantiated the pleiotropic effects of the B locus. The effect of the B locus on branching was masked by the effects of wild alleles at independent branching loci in hybrids between monocephalic domesticated lines and polycephalic wild ecotypes; hence, the B locus appears to be necessary, but not sufficient, for monocephaly in domesticated sunflower.