Construction and characterization of two BAC libraries representing a deep-coverage of the genome of chicory (Cichorium intybus L., Asteraceae)

<p>Abstract</p> <p>Background</p> <p>The Asteraceae represents an important plant family with respect to the numbers of species present in the wild and used by man. Nonetheless, genomic resources for Asteraceae species are relatively underdeveloped, hampering within species genetic studies as well as comparative genomics studies at the family level. So far, six BAC libraries have been described for the main crops of the family, <it>i.e</it>. lettuce and sunflower. Here we present the characterization of BAC libraries of chicory (<it>Cichorium intybus </it>L.) constructed from two genotypes differing in traits related to sexual and vegetative reproduction. Resolving the molecular mechanisms underlying traits controlling the reproductive system of chicory is a key determinant for hybrid development, and more generally will provide new insights into these traits, which are poorly investigated so far at the molecular level in Asteraceae.</p> <p>Findings</p> <p>Two bacterial artificial chromosome (BAC) libraries, CinS2S2 and CinS1S4, were constructed from <it>Hin</it>dIII-digested high molecular weight DNA of the contrasting genotypes C15 and C30.01, respectively. C15 was hermaphrodite, non-embryogenic, and <it>S</it>₂<it>S</it>₂for the <it>S</it>-locus implicated in self-incompatibility, whereas C30.01 was male sterile, embryogenic, and <it>S</it>₁<it>S</it>₄. The CinS2S2 and CinS1S4 libraries contain 89,088 and 81,408 clones. Mean insert sizes of the CinS2S2 and CinS1S4 clones are 90 and 120 kb, respectively, and provide together a coverage of 12.3 haploid genome equivalents. Contamination with mitochondrial and chloroplast DNA sequences was evaluated with four mitochondrial and four chloroplast specific probes, and was estimated to be 0.024% and 1.00% for the CinS2S2 library, and 0.028% and 2.35% for the CinS1S4 library. Using two single copy genes putatively implicated in somatic embryogenesis, screening of both libraries resulted in detection of 12 and 13 positive clones for each gene, in accordance with expected numbers.</p> <p>Conclusions</p> <p>This indicated that both BAC libraries are valuable tools for molecular studies in chicory, one goal being the positional cloning of the <it>S</it>-locus in this Asteraceae species.</p

Molecular and physical mapping of genes affecting awning in wheat

absen

High-density genetic maps for loci involved in nuclear male sterility (NMS1) and sporophytic self-incompatibility (S-locus) in chicory (Cichorium intybus L., Asteraceae)

International audienceHigh-density genetic maps were constructed for loci involved in nuclear male sterility (NMS1-locus) and sporophytic self-incompatibility (S-locus) in chicory (Cichorium intybus L.). The mapping population consisted of 389 F1' individuals derived from a cross between two plants, K28 (male-sterile) and K59 (pollen-fertile), both heterozygous at the S-locus. This F1' mapping population segregated for both male sterility (MS) and strong self-incompatibility (SI) phenotypes. Phenotyping F1' individuals for MS allowed us to map the NMS1-locus to linkage group (LG) 5, while controlled diallel and factorial crosses to identify compatible/incompatible phenotypes mapped the S-locus to LG2. To increase the density of markers around these loci, bulked segregant analysis was used. Bulks and parental plants K28 and K59 were screened using amplified fragment length polymorphism (AFLP) analysis, with a complete set of 256 primer combinations of EcoRI-ANN and MseI-CNN. A total of 31,000 fragments were generated, of which 2,350 showed polymorphism between K59 and K28. Thirteen AFLP markers were identified close to the NMS1-locus and six in the vicinity of the S-locus. From these AFLP markers, eight were transformed into sequence-characterized amplified region (SCAR) markers and of these five showed co-dominant polymorphism. The chromosomal regions containing the NMS1-locus and the S-locus were each confined to a region of 0.8 cM. In addition, we mapped genes encoding proteins similar to S-receptor kinase, the female determinant of sporophytic SI in the Brasicaceae, and also markers in the vicinity of the putative S-locus of sunflower, but none of these genes or markers mapped close to the chicory S-locus

Location of genes involved in ear compactness in wheat (Triticum aestivum) by means of molecular markers

absen

Detection of QTLs for heading time and photoperiod response in wheat using a doubled-haploid population

International audienceThe genetic basis of heading time in wheat (Triticum aestivum L.) was investigated through the study of flowering under normal autumn sown field conditions as well as photoperiod responses under a controlled environment. Quantitative trait loci (QTLs) for these traits were mapped in a doubled-haploid (DH) population derived from a cross between the wheat cultivars 'Courtot' and 'Chinese Spring'. A molecular marker linkage map of this cross that was previously constructed based on 187 DH lines and 380 markers was used for QTL mapping. The genome was well covered (85%) except for chromosomes 1D and 4D, and a set of anchor loci regularly spaced over the genome (one marker each 15.5 cM) was chosen for marker regression analysis. The presence of a QTL was declared at a significance threshold of alpha = 0.005. The population was grown under field conditions in Clermont-Ferrand, France during two years (1994-1995), in Norwich, U.K. over one year (1998), and also under controlled environments in Norwich. For each trait, between 2 and 4 QTLs were identified with individual effects ranging between 6.3% and 44.4% of the total phenotypic variation. Two QTLs were detected that simultaneously affected heading time and photoperiod response. For heading time, these two QTLs were detected in more than one year. One QTL located on chromosome arm 2BS near the locus Xfbb121-2B, co-segregated with the gene Ppd-B1 known to be involved in photoperiod response. This chromosome region explained a large part of the variation (23.4-44.4% depending on the years or the traits). Another region located on chromosome arm 7BS between the loci Xfbb324-7B and Xfbb53-7B also had a strong effect (7.3-15.3%). This region may correspond to a QTL for earliness per se.Les bases génétiques de la date d'épiaison chez le blé (Triticum aestivum L.) ont été analysées au travers de l'étude de la floraison en conditions normales de semis d'automne au champ et également de la réponse à la photopériode en environnement contrôlé. Des QTL (« quantitative trait loci ») pour ces caractères ont été cartographiés en utilisant une population de lignées haploïdes-doublées issues du croisement entre les cultivars 'Courtot' et 'Chinese Spring'. Une carte de marqueurs moléculaires de ce croisement qui avait été préalablement construite à partir de 187 lignées et 380 marqueurs a été utilisée pour la cartographie des QTL. Le génome a été bien couvert (85%) sauf les chromosomes 1D et 4D et un lot de marqueurs ancres espacés régulièrement (un marqueur tous les 15,5 cM) a été choisi pour l'analyse en régression. La présence d'un QTL a été décidée comme significative à un seuil alpha = 0,005. La population a été cultivée au champ deux années à Clermont-Ferrand, France (1994-1995) et une année à Norwich, U.K. (1998) mais aussi sous environnement contrôlé à Norwich. Pour chaque caractère, entre 2 et 4 QTL ont été identifiés, avec des effets individuels compris entre 6,3 et 44,4% de la variation phénotypique totale. Deux QTL affectant simultanément la date d'épiaison et la réponse à la photopériode ont été détectés. Pour l'épiaison, ces deux QTL ont été détectés plusieurs années. Un QTL localisé sur le bras court du chromosome 2B près du locus Xfbb121-2B, co-ségrège avec le gène Ppd-B1 impliqué dans la réponse à la photopériode. Cette région chromosomique explique une grande part de la variation (23,4-44,4% suivant les années ou les caractères). Une autre région localisée sur le bras court du chromosome 7B entre les locus Xfbb324-7B et Xfbb53-7B a aussi un effet fort (7,3-15,3%). Cette région pourrait correspondre à un QTL de précocité per se

An update of the Courtot X Chinese Spring intervarietal molecular marker linkage map for the QTL detection of agronomic traits in wheat

DOI:10.1007/s00122-002-1044-8absen

QTL analysis of bread-making quality in wheat using a doubled haploid population

absen