Molecular mapping of three male-sterile, female-fertile mutants and generation of a comprehensive map of all known male sterility genes in soybean

In soybean, an environmentally stable male sterility system is vital for making hybrid seed production commercially viable. Eleven male-sterile, female-fertile mutants (ms1, ms2, ms3, ms4, ms5, ms6, ms7, ms8, ms9, msMOS, and msp) have been identified in soybean. Of these, eight (ms2, ms3, ms5, ms7, ms8, ms9, msMOS, and msp) have been mapped to soybean chromosomes. The objectives of this study were to (i) locate the ms1, ms4, and ms6 genes to soybean chromosomes; (ii) generate genetic linkage maps of the regions containing these genes; and (iii) develop a comprehensive map of all known male-sterile, female-fertile genes in soybean. The bulked segregant analysis technique was used to locate genes to soybean chromosomes. Microsatellite markers from the corresponding chromosomes were used on F2 populations to generate genetic linkage maps. The ms1 and ms6 genes were located on chromosome 13 (molecular linkage group F) and ms4 was present on chromosome 2 (molecular linkage group D1b). Molecular analyses revealed markers Satt516, BARCSOYSSR_02_1539, and AW186493 were located closest to ms1, ms4, and ms6, respectively. The ms1 and ms6 genes, although present on the same chromosome, were independently assorting with a genetic distance of 73.7 cM. Using information from this study and compiled information from previously published male sterility genes in soybean, a comprehensive genetic linkage map was generated. Eleven male sterility genes were present on seven soybean chromosomes. Four genes were present in two regions on chromosome 2 (molecular linkage group D1b) and two genes were present on chromosome 13 (molecular linkage group F).

Duplicate chlorophyll-deficient loci in soybean

Three lethal-yellow mutants have been identified in soybean (Glycine max (L.) Merr.), and assigned genetic type collection numbers T218H, T225H, and T362H. Previous genetic evaluation of T362H indicated allelism with T218H and T225H and duplicate-factor inheritance. Our objectives were to confirm the inheritance and allelism of T218H and T225H and to molecularly map the locus and (or) loci conditioning the lethal-yellow phenotype. The inheritance of T218H and T225H was 3 green : 1 lethal yellow in their original parental source germplasm of Glycine max 'Illini' and Glycine max 'Lincoln', respectively. In crosses to unrelated germplasm, a 15 green : 1 lethal yellow was observed. Allelism tests indicated that T218H and T225H were allelic. The molecular mapping population was Glycine max 'Minsoy' × T225H and simple sequence repeat (SSR) markers were used. The first locus, designated y18_1, was located on soybean molecular linkage group B2, between SSR markers Satt474 and Satt534, and linked to each by 4.4 and 13.4 cM, respectively. The second locus, designated y18_2, was located on soybean molecular linkage group D2, between SSR markers Satt543 and Sat_001, and linked to each by 2.2 and 4.4 cM, respectively.Key words: duplicate gene, Glycine max, homoeologous genomic segment, genome evolution, lethal-yellow mutant.

Comparative genomic analysis of sequences sampled from a small region on soybean (Glycine max) molecular linkage group G

Eight DNA markers spanning an interval of approximately 10 centimorgans (cM) on soybean (Glycine max) molecular linkage group G (MLG-G) were used to identify bacterial artificial chromosome (BAC) clones. Twenty-eight BAC clones in eight distinct contiguous groups (contigs) were isolated from this genome region, along with 59 BAC clones on 17 contigs homoeologous to those on MLG-G. BAC clones in four of the MLG-G contigs were also digested to produce subclones and detailed physical maps. All of the BAC-ends were sequenced, as were the subclones, to estimate proportions in different sequence categories, compare similarities among homoeologs, and explore microsynteny with Arabidopsis. Homoeologous BAC contigs were enriched in repetitive sequences compared with those on MLG-G or the soybean genome as a whole. Fingerprint and cross-hybridization comparisons between MLG-G and homoeologous contigs revealed cases of highly similar physical organization between soybean duplicates, as did DNA sequence comparisons. Twenty-seven out of 78 total sequences on soybean MLG-G showed significant similarity to Arabidopsis. The homologs mapped to six compact genome segments in Arabidopsis, with the longest containing seven homologs spanning two million base pairs. These results extend previous observations of large-scale duplication and selective gene loss in Arabidopsis, suggesting that networks of conserved synteny between Arabidopsis and other angiosperm families can stretch over long physical distances.Key words: Arabidopsis thaliana, bacterial artificial chromosomes, Glycine max, microsynteny.

Integration of a molecular linkage group containing the broomrape resistance gene Or5 into an RFLP map in sunflower

A linkage group containing the Or5 gene conferring resistance to Orobanche cumana race E, as well as 5 SCAR markers and 1 RAPD marker has been recently identified in sunflower. A SCAR marker RTS05, mapped 5.6 cM proximal to the Or5 locus, was analysed in an F2 population for which the segregation data of 80 RFLP markers (GIE cartisol - Phase II, France) were available. An association was found between the SCAR marker RTS05 and an RFLP marker S009 (32.1 cM, LOD = 4.7) that had been mapped to the linkage group 17 of the GIE Cartisol RFLP map. Another RFLP marker S010, tightly linked to S009 (0.0 cM) in the same linkage group, was screened in the F2 population that had been previously used for the Or5 linkage map identification. S010 was found to be significantly linked to all 5 SCAR markers as well as to the single RAPD marker with a LOD > 3.0 in each case. This RFLP marker was mapped between two SCAR markers and was situated at 35.1 cM from the resistance gene with a LOD = 2.7. These results showed that the Or5 linkage group could be integrated with the linkage group 17 of the GIE Cartisol RFLP map.Key words: Helianthus, Orobanche, RFLP, SCAR, linkage map.