Transferability, amplification quality, and genome specificity of microsatellites in Brassica carinata and related species.

No information is available on the transferability and amplification quality of microsatellite (SSR) markers of the public domain in Brassica carinata A. Braun. The objective of the presented research was to study the amplification of a set of 73 SSRs from B. nigra (L.) Koch and B. napus L. in B. carinata, and to compare the results with those obtained in the amplification of the same markers in other Brassica species of the U triangle. This set of SSRs from B. nigra (B genome) and B. napus (AC genome) allows the identification of the 3 basic genomes of the Brassica species tested. 94.3% of the SSR markers from B. nigra and 97.4% of those from B. napus amplified SSR-specific products in B. carinata. Very high-quality amplification with a strong signal and easy scoring in B. carinata was recorded for 52.8% of the specific loci from B. nigra SSRs and 59.3% of the specific loci from B. napus SSRs, compared to 66.7% in B. nigra and 62.8% in B. napus. Genome specificity and amplification quality of B. nigra and B. napus SSR markers in the 6 species under study is reported. High-quality transferable SSR markers provide an efficient and cost-effective platform to advance in molecular research in B. carinata.

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 P21xCAS-14, and 164 individuals from CAS-3xCAS-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 P21xCAS-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-3xCAS-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.

Quantitative trait loci for broomrape (Orobanche cumana Wallr.) resistance in sunflower.

Broomrape (Orobanche cumana Wallr.) is a root parasite of sunflower that is regarded as one of the most important constraints of sunflower production in the Mediterranean region. Breeding for resistance is the most effective method of control. P-96 is a sunflower line which shows dominant resistance to broomrape race E and recessive resistance to the very new race F. The objective of this study was to map and characterize quantitative trait loci (QTL) for resistance to race E and to race F of broomrape in P-96. A population from a cross between P-96 and the susceptible line P-21 was phenotyped for broomrape resistance in four experiments, two for race E and two for race F, by measuring different resistance parameters (resistance or susceptibility, number of broomrape per plant, and proportion of resistant plants per F(3) family). This population was also genotyped with microsatellite and RFLP markers. A linkage map comprising 103 marker loci distributed on 17 linkage groups was developed, and composite interval mapping analyses were performed. In total, five QTL ( or1.1, or3.1, or7.1 or13.1 and or13.2) for resistance to race E and six QTL ( or1.1, or4.1, or5.1, or13.1, or13.2 and or16.1) for resistance to race F of broomrape were detected on 7 of the 17 linkage groups. Phenotypic variance for race E resistance was mainly explained by the major QTL or3.1 associated to the resistance or susceptibility character ( R(2)=59%), while race F resistance was explained by QTL with a small to moderate effect ( R(2) from 15.0% to 38.7%), mainly associated with the number of broomrape per plant. Or3.1 was race E-specific, while or1.1, or13.1 and or13.2 of were non-race specific. Or13.1, and or13.2 were stable across the four experiments. Or3.1, and or7.1 were stable over the two race E experiments and or1.1 and or5.1 over the two race F experiments. The results from this study suggest that resistance to broomrape in sunflower is controlled by a combination of qualitative, race-specific resistance affecting the presence or absence of broomrape and a quantitative non-race specific resistance affecting their number.

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 F(2) 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-9xCAS-3 F(2). 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-89xCAS-3 and the HAOL-9xCAS-3 F(2) 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.

Genetic control of high stearic acid content in the seed oil of the sunflower mutant CAS-3.

A sunflower mutant, CAS-3, with about 25% stearic acid (C18:0) in the seed oil was recently isolated after a chemical-mutagen treatment of RDF-1-532 seeds (8% C18:0). To study the inheritance of the high C18:0 content, CAS-3 was reciprocally crossed to RDF-1-532 and HA-89 (5% C18:0). Significant reciprocal-cross differences were found in one of the two crosses, indicating possible maternal effects. In the CAS-3 and RDF-1-532 crosses, the segregation patterns of the F(1), BC(1), and F(2) populations fitted a one-locus (designated Es1) model with two alleles (Es1, es1) and with partial dominance of low over high C18:0 content. Segregation patterns in the CAS-3 and HA-89 crosses indicated the presence of a second independent locus (designated Es2) with two alleles (Es2, es2), also with partial dominance of low over high C18:0 content. From these results, the proposed genotypes (C18:0 content) of each parent were as follows: CAS-3 (25.0% C18:0) =es1es1es2es2; RDF-1-532 (8.0% C18:0) =Es1Es1es2es2; and HA-89 (4.6% C18:0) =Es1Es1Es2Es2. The relationship between the proposed genotypes and their C18:0 content indicates that the Es1 locus has a greater effect on the C18:0 content than the Es2 locus. Apparently, the mutagenic treatment caused a mutation of Es1 to es1 in RDF-1-532.