Construction of a high-density genetic linkage map and QTL mapping of oleic acid content and three agronomic traits in sunflower (Helianthus annuus L.) using specific-locus amplified fragment sequencing (SLAF-seq).

High-density genetic linkage maps are particularly important for quantitative trait loci (QTL) mapping, genome assembly, and marker-assisted selection (MAS) in plants. In this study, a high-density genetic linkage map of sunflower (Helianthus annuus L.) was constructed using an F2 population generated from a cross between Helianthus annuus L. '86-1' and 'L-1-OL-1' via specific-locus amplified fragment sequencing (SLAF-seq). After sequence preprocessing, 530.50 M reads (105.60 Gb) were obtained that contained a total of 343,197 SLAFs, of which 39,589 were polymorphic. Of the polymorphic SLAFs, 6,136 were organized into a linkage map consisting of 17 linkage groups (LGs) spanning 2,221.86 cM, with an average genetic distance of 0.36 cM between SLAFs. Based on this high-density genetic map, QTL analysis was performed that focused on four sunflower phenotypic traits: oleic acid content (OAC), plant height (PH), head diameter (HD), and stem diameter (SD). Subsequently, for these four traits eight QTLs were detected that will likely be useful for increasing our understanding of genetic factors underlying these traits and for use in marker-assisted selection (MAS) for future sunflower breeding.

Rhodococcus gannanensis sp. nov., a novel endophytic actinobacterium isolated from root of sunflower (Helianthus annuus L.).

A novel Gram-positive, aerobic, non-motile strain, designated strain M1T, was isolated from sunflower root (Helianthus annuus L.) and characterised using a polyphasic taxonomic approach. The morphological and chemotaxonomic properties of the isolate were typical of those of members of the genus Rhodococcus. Phylogenetic analyses based on 16S rRNA gene sequence showed that strain M1T belongs to the genus Rhodococcus and clustered with Rhodococcus canchipurensis MBRL 353T (99.1%, sequence similarity) and Rhodococcus pedocola UC12T (98.7%). However, the DNA-DNA hybridizations between strain M1T and R. canchipurensis MBRL 353T and R. pedocola UC12T were found to be 52.8 ± 0.7 and 41.8 ± 0.2%, respectively. The optimal growth temperature and pH for strain M1T was found to be at 28 °C and at pH 7.0. The peptidoglycan was found to contain meso-diaminopimelic acid; galactose, glucose and arabinose were detected as diagnostic sugars. The main polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and phosphatidylinositol mannoside; MK-8(H2) was found to be the dominant menaquinone. The major fatty acids were identified as C16:0, 10-methyl C18:0 and C18:1 ω9c. Mycolic acids were found to be present. The G+C content of the genomic DNA was determined to be 69.5 mol%. Based on a comparative analysis of phenotypic and genotypic characteristics, in combination with DNA-DNA hybridization results, the isolate is concluded to represent a novel species of the genus Rhodococcus, for which the name Rhodococcus gannanensis sp. nov. is proposed. The type strain is M1T (=CGMCC 1.15992T = DSM 104003T).

Identification of differentially expressed genes in sunflower (Helianthus annuus) leaves and roots under drought stress by RNA sequencing.

BACKGROUND: Sunflower is recognized as one of the most important oil plants with strong tolerance to drought in the world. In order to study the response mechanisms of sunflower plants to drought stress, gene expression profiling using high throughput sequencing was performed for seedling leaves and roots (sunflower inbred line R5) after 24 h of drought stress (15% PEG 6000). The transcriptome assembled using sequences of 12 samples was used as a reference. RESULTS: 805 and 198 genes were identified that were differentially expressed in leaves and roots, respectively. Another 71 genes were differentially expressed in both organs, in which more genes were up-regulated than down-regulated. In agreement with results obtained for other crops or from previous sunflower studies, we also observed that nine genes may be associated with the response of sunflower to drought. CONCLUSIONS: The results of this study may provide new information regarding the sunflower drought response, as well as add to the number of known genes associated with drought tolerance.