Activite rythmique de l'aspartate aminotransferase chez Leptosphaeria michotii (West) sacc.: approche moleculaire

SIGLEINIST T 73191 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Impact of four decades of breeding on molecular differentiation between forage and turf cultivars of [i]Lolium perenne[/i]

How much differentiated are forage and turf type cultivars within L. perenne? To estimate this, we used 10 SSR/STS markers for genotyping a collection of 7 natural populations, 50 forage and turf cultivars and 4 old cultivars of dual usage registered since 1965-2004. We showed that differentiation between usage types has steadily increased since the opening of a turf national list in France and that it has mostly involved 3 markers, among which 2 were mapped onto linkage group 1 in L. perenne. Relative to natural populations, assumed to sample genetic diversity in perennial ryegrass when breeding started, turf cultivars were found to be more distantly related than forage cultivars, especially those which were recently registered. However, genetic differentiation remained primarily between cultivars whatsoever type they were. Differentiation between cultivars has increased to be about twice higher on average than between natural populations, even of quite distant geographical origin. Loss of genetic variability after 40 years of breeding was found to be very low. All alleles present in natural populations were sampled again in the collection of cultivars we investigated. The results are briefly discussed in conclusion as respect to phenotypic differentiation and efficiency of breeding methods in the grasses

Combined linkage and association mapping of flowering time in Sunflower (Helianthus annuus L.)

International audienceAssociation mapping and linkage mapping were used to identify quantitative trait loci (QTL) and/or causative mutations involved in the control of flowering time in cultivated sunflower Helianthus annuus. A panel of 384 inbred lines was phenotyped through testcrosses with two tester inbred lines across 15 location × year combinations. A recombinant inbred line (RIL) population comprising 273 lines was phenotyped both per se and through testcrosses with one or two testers in 16 location × year combinations. In the association mapping approach, kinship estimation using 5,923 single nucleotide polymorphisms was found to be the best covariate to correct for effects of panel structure. Linkage disequilibrium decay ranged from 0.08 to 0.26 cM for a threshold of 0.20, after correcting for structure effects, depending on the linkage group (LG) and the ancestry of inbred lines. A possible hitchhiking effect is hypothesized for LG10 and LG08. A total of 11 regions across 10 LGs were found to be associated with flowering time, and QTLs were mapped on 11 LGs in the RIL population. Whereas eight regions were demonstrated to be common between the two approaches, the linkage disequilibrium approach did not detect a documented QTL that was confirmed using the linkage mapping approach

Study on essential derivation in maize: III. Selection and evaluation of a panel of single nucleotide polymorphism loci for use in European and North American germplasm

Pairwise distance data for maize (Zea mays L.) inbred lines generated using sets of single nucleotide polymorphisms (SNPs) selected from a 50k Infinium array were compared with pairwise distances generated using a set of 163 simple sequence repeat (SSR) loci previously identified to help determine essentially derived variety (EDV) status (UPOV, 1991). Final comparisons were made using 26,874 SNPs after discarding SNPs with insufficient data quality or vulnerability to ascertainment bias. Inbred lines developed in the United States or in western Europe that had been previously published to establish SSR-based thresholds provided the means to determine equivalent SNP-based protocols. Use of 3072 SNPs selected to provide even genomic coverage according to genetic and physical maps provided robust, precise, high discrimination among inbred lines with consistent zonal classification with up to 20% missing data. Comparisons of intercepts and slopes for SSR and SNP inbred pairwise distance data translated the 82% SSR green-orange similarity threshold to 91% using SNPs and the 90% SSR orange-red threshold to 95% using SNPs. Information required to conduct analyses using these 3072 SNPS is presented