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Wild Helianthus species are an important genetic resource for sunflower improvement, but sometimes there are adverse interactions between the wild and cultivated sunflowers. This study reports the inheritance of reduced vigor and its restoration resulting from an interaction of perennial Helianthus cytoplasms with nuclear genes of cultivated sunflower lines. The large number of vigor restoration (V) genes identified in cultivated lines are all located at the same locus, designated V1, suggesting a common origin of these genes. Additional V genes derived from the wild perennial species H. giganteus L. and H. hirsutus Raf. are located at a different locus than V1, designated V2. A major difference between the wild annual Helianthus cytoplasms and perennial cytoplasms is the lack of the vigor-reducing cytoplasms, but surprisingly V genes were observed in wild annual H. annuus L. and H. petiolaris Nutt. which were at the same locus as V1. A common vigor-reducing cytoplasmic effect of the perennial Helianthus species and the existence of a common vigor restoration V gene in most perennial Helianthus species could be explained as a result of vigor selection during Helianthus speciation. V1 was mapped on linkage group (LG) 7 of the sunflower genome, using an F2 population derived from MOLRV/HA 821. V1 co-segregated with an InDel marker ZVG31, with three single-nucleotide polymorphism (SNP) markers, SFW01024, SFW07230, and SFW00604, located above it on the map at a genetic distance of 0.8 cM, and another SNP marker, SFW08671, below it at a distance of 0.4 cM. The physical distance between the two closest flanking SNP markers corresponds to 0.56 and 1.37 Mb on the HA 412-HO and XRQ assemblies, respectively. The tightly linked markers will help select normal vigor progenies when using perennial Helianthus cytoplasms in a breeding program, which will also provide a basis for studying the mechanism of the cytonuclear interaction, and the speciation of annual and perennial Helianthus species. [ABSTRACT FROM AUTHOR]

Cultivated hybrid sunflower (Helianthus annuus L.) production depends on a single male-sterile cytoplasm, PET1, derived from H. petiolaris Nutt. and a few fertility restoration genes. This study was conducted to locate new restoration genes for the PET1 cytoplasm from the wild species of the genus Helianthus. Ten wild species populations from the USA were grown in a field nursery and crossed with cytoplasmic male-sterile inbred line cmsHA 89 to determine the presence and inheritance of restoration genes in wild annual and perennial species. Standard sunflower breeding techniques were used to obtain [F.sub.1] and [B.sub.1]C[F.sub.1] seed, whereas [F.sub.2] seed was produced by sibbing [F.sub.1] plants instead of selfing due to the low self-compatibility. All H. annuus L., H. argophyllus T. & G., H. praecox ssp. runyonii Heiser, and H. tuberosus L. populations possessed dominant fertility restoration genes at high frequencies, varying from 57 to 100%. Segregation ratios of male-fertile to male-sterile plants in the B[C.sub.1] (1:1) and [F.sub.2] (3:1) generations of nine crosses suggested a single dominant gene for fertility restoration. Other segregation ratios suggested that three genes were involved in one cross of H. argophyllus and that fertility was restored when at least two dominant alleles were present at any of the three loci. The new sources of fertility restoration genes from wild sunflowers will be valuable for sunflower breeding and selection programs by providing additional genetic diversity.

The present trend in human diets is to decrease the consumption of the saturated fatty acids, palmitic and stearic fatty acids. Studies have shown that consumption of high levels of saturated fats increases the risk of cardiovascular diseases. Vegetable oils are the principal source of fats in many diets. Sunflower oil, which is fourth in production among vegetable oils in the world, contains 6.5% palmitic and 4.5% stearic acids. In an effort to reduce saturated fats in sunflower oil, a survey of wild annual H. annuus populations was undertaken to identify potentially useful populations with low palmitic and stearic fatty acids (less than 7% combined). Achene oil of one population of wild H. annuus from Holmquist, SD had a palmitic acid level that averaged 3.9% with a range of 2.8 to 4.3%, while stearic acid averaged 1.9% with a range of 1.5 to 2.2%. The combined 5.8% palmitic and stearic acids is almost 50% lower than the present level of these fats in sunflower oil. The level of saturated fatty acids observed in the population remained low when plants were grown in the greenhouse under uniform conditions. In the greenhouse, palmitic acid averaged 4.0%, while stearic acid averaged 1.9%. This would indicate that palmitic and stearic acids have a genetic base with the potential for selection and incorporation into cultivated sunflower to lower the present level of saturated fats in sunflower oil.

Abstract: Crop‐wild hybridization occurs in numerous plant species and could alter the genetic structure and evolutionary dynamics of wild populations. Studying crop‐derived alleles in wild populations is also relevant to assessing/mitigating the risks associated with transgene escape. To date, crop‐wild hybridization has generally been examined via short‐term studies, typically within a single generation, focusing on few traits or genetic markers. Little is known about patterns of selection on crop‐derived alleles over multiple generations, particularly at a genome‐wide scale. Here, we documented patterns of natural selection in an experimental crop × wild sunflower population that was allowed to evolve under natural conditions for two generations at two locations. Allele frequencies at a genome‐wide collection of SNPs were tracked across generations, and a common garden experiment was conducted to compare trait means between generations. These data allowed us to identify instances of selection on crop‐derived alleles/traits and, in concert with QTL mapping results, test for congruence between our genotypic and phenotypic results. We found that natural selection overwhelmingly favours wild alleles and phenotypes. However, crop alleles in certain genomic regions can be favoured, and these changes often occurred in parallel across locations. We did not, however, consistently observe close agreement between our genotypic and phenotypic results. For example, when a trait evolved towards the wild phenotype, wild QTL alleles associated with that trait did not consistently increase in frequency. We discuss these results in the context of crop allele introgression into wild populations and implications for the management of GM crops. [ABSTRACT FROM AUTHOR]

Somatic embryogenesis in vitro provides an efficient means of plant multiplication, facilitating sunflower improvement and germplasm innovation. In the present study, using interspecific amphiploids (2n = 4x = 68) between cultivated sunflower and wild perennial Helianthus species as explant donors, somatic embryos were induced directly from the surface of corolla tubes at the late uninucleate or binucleate microspore development stage. Primary somatic embryos (PSEs) were obtained in amphiploids G08/2280 (H. pumilus × P21) and G08/2260 (NMSHA89 × H. maximiliani). The PSE induction frequency of G08/2280 on synthesized Medium A and B was 30.27% and 42.42 %, respectively, while that of G08/ 2260 was 5.89% and 12.16%, respectively. The difference of PSE induction frequency was significant between G08/2280 and G08/2260 (P = 0.0058), but was nonsignificant between induction Medium A and B (P = 0.1997). Secondary somatic embryos (SSEs) were rapidly produced from PSEs on subculture Medium 1 with the induction frequency of 100 %. The mean number of SSEs produced from each PSE was 19.2 and 12.2 in G08/2280 and G08/2260 within 30 d of subculture, respectively. Mature SSEs were gradually converted into young shoots on hormone-free subculture Medium 2, with the mean number of small green shoots produced from each PSE of 22.0 and 18.7 in G08/2280 and G08/2260, respectively. Through the additional process of rooting for some shoots without roots on half-strength of MS medium adding 0.25-0.5mg/l NAA, 0.5mg-1.0/l IBA, SE-derived shoots without roots gained about 40%rooting frequency. Regenerated plants acclimated successfully and displayed similar morphological and chromosome number to the amphiploid donors. [ABSTRACT FROM AUTHOR]

Wild Helianthus species are a valuable genetic resource for the improvement of cultivated sunflower. We report the discovery and characterization of a unique high frequency production of triploids when cultivated sunflower was pollinated by specific accessions of diploid Helianthus nuttallii T. & G. and H. maximiliani Schr. Genomic in situ hybridization (GISH) analyses indicated that the triploid F1s had two genomes from the wild pollen sources and one from the cultivated line. Mitotic chromosome analyses indicated that the frequency of triploid progenies from the crosses of cultivated lines × H. nuttallii accession 102 (N102) was significantly higher than those of unexpected polyploid progenies from the crosses of wild perennial species × N102, and no unexpected polyploids were obtained from the reverse crosses. Pollen stainability analysis suggested the existence of a low percentage of unreduced (2n) male gametes in some accessions, especially N102 and H. maximiliani accession 1113 (M1113), which were generated at the telophase II and tetrad stages of meiosis. The triploid F1s could be the results of preferred fertilization of the low frequency of 2n male gametes with the female gametes of the cultivated sunflower, due to the dosage factors related to recognition and rejection of foreign pollen during fertilization. The triploids have been used to produce amphiploids and aneuploids. Future studies of the male gametes' fate from pollination through fertilization will further uncover the mechanism of this whole genome transmission. Studies of the genetic control of this trait will facilitate research on sunflower polyploidy speciation and evolution, and the utilization of this trait in sunflower breeding. [ABSTRACT FROM AUTHOR]

Basal stalk rot (BSR), caused by Sclerotinia sclerotiorum, is a devastating disease in sunflower worldwide. The progress of breeding for Sclerotinia BSR resistance has been hampered due to the lack of effective sources of resistance for cultivated sunflower . Our objective was to transfer BSR resistance from wild annual Helianthus species into cultivated sunflower and identify the introgressed alien segments associated with BSR resistance using a genotyping-by-sequencing (GBS) approach. The initial crosses were made between the nuclear male sterile HA 89 with the BSR resistant plants selected from wild Helianthus argophyllus and H. petiolaris populations in 2009. The selected resistant F1 plants were backcrossed to HA 458 and HA 89, respectively. Early generation evaluations of BSR resistance were conducted in the greenhouse, while the BC2 F3 and subsequent generations were evaluated in the inoculated field nurseries. Eight introgression lines; six from H. argophyllus (H.arg 1 to H.arg 6), and two from H. petiolaris (H.pet 1 and H.pet 2), were selected. These lines consistently showed high levels of BSR resistance across seven environments from 2012 to 2015 in North Dakota and Minnesota, USA. The mean BSR disease incidence (DI) for H.arg 1 to H.arg 6, H.pet 1, and H.pet 2 was 3.0, 3.2, 0.8, 7.2, 7.7, 1.9, 2.5, and 4.4%, compared to a mean DI of 36.1% for Cargill 270 (susceptible hybrid), 31.0% for HA 89 (recurrent parent), 19.5% for HA 441 (resistant inbred), and 11.6% for Croplan 305 (resistant hybrid). Genotyping of the highly BSR resistant introgression lines using GBS revealed the presence of the H. argophyllus segments in linkage groups (LGs) 3, 8, 9, 10, and 11 of the sunflower genome, and the H. petiolaris segments only in LG8. The shared polymorphic SNP loci in the introgression lines were detected in LGs 8, 9, 10, and 11, indicating the common introgression regions potentially associated with BSR resistance. Additionally, a downy mildew resistance gene, Pl17, derived from one of the parents, HA 458, was integrated into five introgression lines. Germplasms combining resistance to Sclerotinia BSR and downy mildew represent a valuable genetic source for sunflower breeding to combat these two destructive diseases. [ABSTRACT FROM AUTHOR]

Biodiversity in Trust: Conservation and Use of Plant Genetic Resources in CGIAR Centres. Edited by D. FUCCILLO, L. SEARS, AND P. STAPLETON. Cambridge University Press, The Pitt Building, Trumpington St., [...]

Monitoring and protecting germplasm in genebanks using in situ collections while preserving its original genetic integrity is a priority of germplasm curation. Many germplasm accessions need to be regenerated due to their demand and/or seed condition. The regeneration of wild Helianthus (sunflower) species poses several challenges due to the diversity of 53 wild species. Fatty acid composition of sunflower oil is an important quality factor for the crop. Since oil quality is environmentally influenced, and evaluation of this trait is usually performed on oil from achenes from the original accessions of wild sunflower species, we conducted a study on 72 accessions of eight annual and four perennial taxa of wild sunflower species to compare the oil quality of the original accessions and those regenerated for genebank maintenance. The results showed that the fatty acid composition profiles of achenes from the original and regenerated accessions are not the same. It seems that selection for specific fatty acids in several species will require the analysis of both populations to identify germplasm accessions for use in breeding programmes. It should be borne in mind that accessions of wild species are open-pollinated segregating populations, so one would expect some variability in each succeeding generation. While there may be differences between the original and regenerated accessions, the interrelationships of fatty acids are generally similar in wild and cultivated sunflower species, so there should be no detrimental effects on oil quality when using the wild species for other traits. As more regenerated accessions become available, a more precise relationship between the original and regenerated accessions should emerge. [ABSTRACT FROM PUBLISHER]