Oleate content is important for the nutritional value and oxidative stability of soybean [Glycine max (L.) Merr.] seed oil. Response to selection for higher oleate content depends on its heritability in breeding populations, and correlated responses of other fatty acid and agronomic traits to selection for oleate content depend on their genetic correlations with oleate. The objective of this study was to estimate the heritability of oleate content and to determine the correlation of oleate with other fatty acid and agronomic traits in three soybean populations segregating for major and minor oleate genes grown in multiple environments. One of the populations consisted of 721 lines, providing excellent precision for estimation of the genetic parameters. The results of this study indicated that heritability for oleate content was sufficiently high that early generation selection can be effective when practiced on unreplicated lines grown at a single environment. Significant negative correlations were observed between oleate and linoleate, oleate and linolenate, as well as oleate and palmitate in all three populations. Significant positive correlations were detected between palmitate and stearate in one population segregating for oleate genes and fapnc and fap1 alleles, which reduce palmitate content. In the same population we also observed a significant negative correlation between yield and oleate content, and positive correlations between yield and linoleate, and linolenate and palmitate contents.

The microsomal ω‐6 desaturase enzymes, which catalyze the desaturation of oleic acid to linoleic acid during fatty acid biosynthesis, are encoded by the FAD2‐1 and FAD2‐2 genes in soybean [Glycine max (L.) Merr.]. Breeders aim to incorporate the high‐oleate trait into soybean germplasm in order to improve the nutritional value and oxidative stability of soybean oil. The objectives of this study were to map the isoforms of the FAD2‐1 and FAD2‐2 genes and investigate the association of these genetic loci with the oleate phenotype in three populations segregating for oleate content. The populations were grown in replicated multienvironment field trials. According to linkage analysis conducted for two of the populations, FAD2‐1A and FAD2‐1B mapped on Linkage Groups O and I, respectively, while the closely linked FAD2‐2A and FAD2‐2B isoforms mapped on Linkage Group L. Oleate quantitative trait loci with minor effects were detected in the proximity of FAD2‐1B and possibly FAD2‐2B on Linkage Groups I and L. Quantitative trait loci affecting maturity were also detected on chromosomal regions adjacent to the FAD2 genes. The genotyping assays developed for the FAD2‐1A, FAD2‐1B, and FAD2‐2B isoforms, as well as their linked simple sequence repeat markers, can be used in soybean breeding programs for the elevation of oleic acid seed content through marker‐assisted selection.

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.

Dynamic behaviours of rotor's radial rub-impact in the presence of turborotor's non-linear clearance-excitation force are analysed by numerical simulations in all the six degrees of freedom of a rotor, which represent all the three kinds of vibrations: lateral, axial, and torsional vibrations. Results are displayed by bifurcation diagrams, waveforms, frequency spectrums, orbits, Poincare maps, and frequency waterfalls. Much more complicated dynamic behaviours are represented in these results. Compared with the case of pure rub-impact that does not involve any other non-linear elements, the stable motion regime is largely reduced, correspondingly the rotating speed threshold of rub-impact is also reduced slightly, and the complicated motion patterns appear in the early stage of rub-impact. Thick superharmonics and subharmonics emerge in axial and torsional vibrations, respectively, which are the typical characteristics of a chaotic motion. This indicates that the main motion pattern of the system is chaos. In the full range of investigated speed, the lateral vibrations nearly take on a sole synchronous component, and the axial vibration shows very rich superharmonic components, which mainly scatter in three thick superharmonic bands that approach to three fixed frequency components with their amplitudes growing as the rotating speed increases. The torsional vibration demonstrates rich subharmonics near half-time-frequency components, and the amplitudes of which increase with rotating speed. These conclusions are of great significance to the rotordynamic design and fault diagnostics of turborotor systems.

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