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Soybean [Glycine max (L.) Merr.] oil typically contains 2-4% stearic acid. Seed oil with 20% stearic acid would be useful for solid fat applications, both for its cooking properties and health benefits. Breeding lines with high stearic acid have been developed, but many suffer from agronomic problems. This study identifies a new source of high stearic acid, determines its relationship with another high stearic locus and presents molecular markers for it is use in breeding. TCJWB03-806-7-19, a 'Holladay' mutant with high stearic acid, was crossed to two FAM94-41-derived lines that contained a point mutation in a seed-specific isoform of a Δ9-stearoyl-acyl carrier protein-desaturase (SACPD-C). Fatty acid analysis was performed over two growing seasons with F(2)-derived lines and transgressive segregation for stearic acid content was observed. Sequencing of SACPD isoforms in TCJWB03-806-7-19 revealed the deletion of an 'A' nucleotide in exon 3 of SACPD-B, which results in a protein whose final 28 amino acids are predicted to differ from Williams 82 SACPD-B. Sorting intolerant from tolerant (SIFT) analysis revealed that this frameshift mutation may affect SACPD-B protein function. Allele-specific genotyping for the SACPD-C point mutation and SACPD-B nucleotide deletion was performed in both populations. Additive effects and R(2) for stearic acid were +3.3 and 0.55 for SACPD-C and +1.9 and 0.19 for SACPD-B. Average stearic acid in lines homozygous for both mutations was 14.6%. This SACPD-B mutation represents a novel high stearic allele.

Key message fap1 mutation is caused by a G174A change in GmKASIIIA that disrupts a donor splice site recognition and creates a GATCTG motif that enhanced its expression. Abstract Soybean oil with reduced palmitic acid content is desirable to reduce the health risks associated with consumption of this fatty acid. The objectives of this study were: to identify the genomic location of the reduced palmitate fap1 mutation, determine its molecular basis, estimate the amount of phenotypic variation in fatty acid composition explained by this locus, determine if there are epistatic interactions between the fap1 and fap nc loci and, determine if the fap1 mutation has pleiotropic effects on seed yield, oil and protein content in three soybean populations. This study detected two major QTL for 16:0 content located in chromosome 5 (GmFATB1a, fap nc ) and chromosome 9 near BARCSOYSSR_09_1707 that explained, with their interaction, 66-94 % of the variation in 16:0 content in the three populations. Sequencing results of a putative candidate gene, GmKASIIIA, revealed a single unique polymorphism in the germplasm line C1726, which was predicted to disrupt the donor splice site recognition between exon one and intron one and produce a truncated KASIIIA protein. This G to A change also created the GATCTG motif that enhanced gene expression of the mutated GmKASIIIA gene. Lines homozygous for the GmKASIIIA mutation (fap1) had a significant reduction in 16:0, 18:0, and oil content; and an increase in unsaturated fatty acids content. There were significant epistatic interactions between GmKASIIIA (fap1) and fap nc for 16:0 and oil contents, and seed yield in two populations. In conclusion, the fap1 phenotype is caused by a single unique SNP in the GmKASIIIA gene.

Aegilops markgrafii (Greuter) Hammer is an important source of genes for resistance to abiotic stresses and diseases in wheat (Triticum aestivum L.). A series of six wheat ‘Alcedo’-Ae. markgrafii chromosome disomic addition lines, designated as AI(B), AII(C), AIII(D), AV(E), AIV(F), and AVIII(G) carrying the Ae. markgrafii chromosomes B, C, D, E, F, and G, respectively, were tested with SSR markers to establish homoeologous relationships to wheat and identify markers useful in chromosome engineering. The addition lines were evaluated for resistance to rust and powdery mildew diseases. The parents Alcedo and Ae. markgrafii accession ‘S740-69’ were tested with 1500 SSR primer pairs and 935 polymorphic markers were identified. After selecting for robust markers and confirming the polymorphisms on the addition lines, 132 markers were considered useful for engineering and establishing homoeologous relationships. Based on the marker analysis, we concluded that the chromosomes B, C, D, E, F, and G belong to wheat homoeologous groups 2, 5, 6, 7, 3, and 4, respectively. Also, we observed chromosomal rearrangements in several addition lines. When tested with 20 isolates of powdery mildew pathogen (Blumeria graminis f. sp. tritici) from five geographic regions of the United States, four addition lines [AIII(D), AV(E), AIV(F), and AVIII(G)] showed resistance to some isolates, with addition line AV(E) being resistant to 19 of 20 isolates. The addition lines were tested with two races (TDBJ and TNBJ) of the leaf rust pathogen (Puccinia triticina), and only addition line AI(B) exhibited resistance at a level comparable to the Ae. markgrafii parent. Addition lines AII(C) and AIII(D) had been previously identified as resistant to the Ug99 race group of the stem rust pathogen (Puccinia graminis f. sp. tritici). The addition lines were also tested for resistance to six United States races (PSTv-4, PSTv-14, PSTv-37, PSTv-40, PSTv-51, and PSTv-198) of the stripe rust pathogen (Puccinia striiformis f. sp. tritici); we found no resistance either in Alcedo or any of the addition lines. The homoeologous relationships of the chromosomes in the addition lines, molecular markers located on each chromosome, and disease resistance associated with each chromosome will allow for chromosome engineering of the resistance genes.

Two new sources of elevated seed stearic acid were identified and the feasibility of an elevated stearic acid, high oleic acid germplasm was studied. Soybean [Glycine max (L.) Merr.] oil typically contains 2-4% stearic acid. Oil with at least 20% stearic acid is desirable because of its improved baking properties and health profile. This study identifies two new sources of high stearic acid and evaluates the interaction of high stearic and oleic acid alleles. TCHM08-1087 and TCHM08-755, high stearic acid 'Holladay' mutants, were crossed to FAM94-41-3, a line containing a point mutation in a seed-specific isoform of a Δ9-stearoyl-acyl carrier protein-desaturase (SACPD-C). F2-derived lines were evaluated for fatty acid content in four field environments. Sequencing of SACPDs in TCHM08-1087 and TCHM08-755 revealed distinct deletions of at least one megabase encompassing SACPD-C in both lines. After genotyping, the additive effect for stearic acid was estimated at +1.8% for the SACPD-C point mutation and +4.1% for the SACPD-C deletions. Average stearic acid in lines homozygous for the deletions was 12.2%. A FAM94-41-3-derived line and TCHM08-1087-11, a selection from TCHM08-1087, were crossed to S09-2902-145, a line containing missense mutations in two fatty acid desaturases (FAD2-1A and FAD2-1B). F1 plants were grown in a greenhouse and individual F2 seed were genotyped and phenotyped. No interaction was observed between either FAD2-1A or FAD2-1B and any of the SACPD-C mutant alleles. Seed homozygous mutant for SACPD-C/FAD2-1A/FAD2-1B contained 12.7% stearic acid and 65.5% oleic acid while seed homozygous for the SACPD-C deletion and mutant for FAD2-1A and FAD2-1B averaged 10.4% stearic acid and 75.9% oleic acid.

Key message The heritability of genetic resistance of radiata pine against Fusarium circinatum was not clear. We demonstrated that there are at least 3 QTLs that could be involved in this resistance/susceptibility. Abstract A genetic linkage map was developed for Pinus radiata, using Amplified Fragment Length Polymorphism (AFLP), Inter-Simple Sequence Repeat (ISSR), Selective Amplification of Microsatellite Polymorphic Loci (SAMPL), and Simple Sequence Repeat (SSR) molecular markers, based on a two-way pseudo-testcross strategy, using 86 individuals of a F1 full-sib family and 787 molecular markers for genotyping. Linkage analysis generated a map of medium to high density for each parent, with 1,060 and 1,258 cM for parents XO and XP, respectively. A total of 458 markers were mapped on 12 linkage groups (LG) in XO and XP, which equals the number of haploid chromosomes present in P. radiata. Analysis of quantitative trait loci (QTL) for resistance against pitch canker disease caused by Fusarium circinatum was made using Bayesian Information Criterion (BIC). In the XO parental map, two groups (LG-1 and LG-9) showed high probabilities for one or more QTLs. Only one group in the XP parental map showed probability for one or more QTLs. The results indicate that resistance to pitch canker is inherited from both parents. These results provide the basis for further studies focused on structure, evolution, and function of the P. radiata genome.

Blumeria graminis f. sp. tritici (Bgt) is a globally important fungal pathogen of wheat that can rapidly evolve to defeat wheat powdery mildew (Pm) resistance genes. Despite periodic regional deployment of the Pm1a resistance gene in US wheat production, Bgt strains that overcome Pm1a have been notably nonpersistent in the United States, while on other continents, they are more widely established.A genome-wide association study (GWAS) was conducted to map sequence variants associated with Pm1a virulence in 216 Bgt isolates from six countries, including the United States. A virulence variant apparently unique to Bgt isolates from the United States was detected in the previously mapped gene AvrPm1a (BgtE-5612) on Bgt chromosome 6; an in vitro growth assay suggested no fitness reduction associated with this variant.A gene on Bgt chromosome 8, Bgt-51526, was shown to function as a second determinant of Pm1a virulence, and despite < 30% amino acid identity, BGT-51526 and BGTE-5612 were predicted to share > 85% of their secondary structure. A co-expression study in Nicotiana benthamiana showed that BGTE-5612 and BGT-51526 each produce a PM1A-dependent hypersensitive response.More than one member of a B. graminis effector family can be recognized by a single wheat immune receptor, and a two-gene model is necessary to explain virulence to Pm1a.

Soybeans [Glycine max (L.) Merr.] have undesirable levels of polyunsaturated fatty acids in their oil that result in oxidative instability and poor flavor. The process of hydrogénation improves the stability but creates undesirable trans fats. Lines carrying fan genes have decreased linolenic acid (18:3) content. Changes in transcription or activity of the desaturase encoded by the GmFAD3 gene cause a reduction in 18:3 content in certain lines.