Location: Sunflower and Plant Biology Research2018 Annual Report
Objective 1: Identify gaps and acquire new wild species to fill gaps or deficiencies in the sunflower germplasm collection. Objective 2: Identify insect pests and pathogens of sunflower, develop effective screening methods to optimize assessment of resistance to sunflower pathogens, determine mechanisms of plant resistance, phenotype germplasm for resistance to major insect pests and pathogens, and introgress insect and disease resistance genes from the wild species into diverse cultivated germplasm. Subobjective 2A: Identify and monitor pathogens. Subobjective 2B: Develop effective screening procedures for Phomopsis and insect damage. Subobjective 2C: Identify and assess mechanisms of insect resistance. Subobjective 2D: Transfer disease resistance, insect resistance, and other agronomic traits from wild Helianthus species into cultivated sunflower and improve methods for interspecific hybridization and release of pre-breeding germplasm. Subobjective 2E: Characterize and map resistance to pathogens and insect pests, and other agronomic traits. Objective 3: Develop sunflower germplasm with high yield, high oil content, and desirable fatty acid concentrations, as well as novel resistance genes for diseases and insects. Subobjective 3A: Develop new inbred lines with novel fatty acid compositions, such as low saturated fatty acids, and high oleic acid. Subobjective 3B: Pyramid disease and insect resistance genes with high yield and oil content in a common germplasm.
Currently, there are a number of factors that reduce sunflower yield including a host of insects and diseases that require careful and costly management practices, reducing profitability. Research is proposed to reduce the input costs by developing durable pest resistance, herbicide resistance, oil content and quality increasing the oil per acre yield of sunflower. Specifically, we will collect wild sunflower relatives to broaden the crop’s genetic base. This germplasm will be phenotyped for resistance to major insect pests and pathogens, cytoplasmic male sterility, and fertility restoration. Methods for improving interspecific hybridization will focus on techniques to detect introgressed alien chromosome segments in interspecific crosses using the genomic fluorescence in situ hybridization technique. Interspecific gene transfer will be evaluated using molecular markers for desirable agronomic traits such as resistance genes to rust and downy mildew. Interspecific germplasm with useful genes will be introgressed into cultivated sunflower and released as enhanced pre-breeding germplasm. Current diseases will be monitored for shifts in virulence and races, and for newly emerged diseases. A field test will be developed to reliably test for the newly emerged Phomopsis stem canker pathogen. An efficient non-destructive screening method will be developed for detecting damage of banded sunflower moth, sunflower moth, red sunflower seed weevil, and sunflower stem weevil. Insect resistance mechanisms will be identified and assessed for sunflower moth. Resistance genes for pathogens and insects, and other agronomic traits will be characterized and mapped. DNA markers for selected traits will be developed and used for marker-assisted breeding. Enhanced sunflower germplasm with high yield, high oil content, and desirable fatty acids concentration, as well as novel resistance genes for diseases and insects will be developed and released. Accomplishing these objectives will provide producers with improved sunflower that will provide a stable supply of high quality oil and confectionery sunflower, improving on-farm profitability and providing the consumer with a reliable domestic supply of a healthy oil, a staple in the American diet.
This is the final report for project 3060-21000-039-00D which ended in March 2018. This work is continued in project 3060-21000-043-00D, “Genetic Enhancement of Sunflower Yield and Tolerance to Biotic Stress”. Objective 1: Identify gaps and acquire new wild species to fill gaps or deficiencies in the sunflower germplasm collection. Explorations to fill gaps in the National Plant Germplasm System crop wild relatives’ collection were undertaken annually. Five explorations covered four western and southwestern, two southeastern, and parts of two upper Mid-west states covering 9,500 miles driven with the collection of 96 populations of 18 Helianthus species. Unique among these populations were the first collections of a newly discovered species, perennial H. winteri collected in California. The first of two collecting trips for 2017-2018 also is complete, and this trip added six accessions of Helianthus maximiliani from North Dakota and Minnesota. These new populations make additional unique material available as sources of useful traits for cultivated sunflower improvement. Subobjective 2A: Identify and monitor pathogens. Pathogen survey work was not conducted for three years due to a critical vacancy. However, results provide a contrast between observed long-term trends and annual variation. Over many years, Sclerotinia head rot and basal stalk rot have been slowly declining, while Phomopsis has become much more common (from <2% to 10–15% prevalence). For the 2017 field season, low precipitation led to a decrease in disease prevalence for most sunflower pathogens. Data also show Phomopsis and downy mildew have considerable species- and race-level diversity, respectively, suggesting that continued work to map resistance genes and understand pathogen virulence is needed to support genetic resistance of sunflower hybrids. Subobjective 2B: Develop effective screening procedures for Phomopsis and insect damage. Artificial infestation methods have been tested and validated for Phomopsis and may be used if locations with consistent natural infestations are unavailable in the future. The use of X-ray imaging for insect damage assessments on stems and seeds has substantially improved accuracy of insect research and survey data, and also reduced labor costs. All current and future insect damage assessments will use this method. Subobjective 2C: Identify and assess mechanisms of insect resistance. Results over five years provided two key insights on seed feeding by banded sunflower moth (BSM) larvae. First, cultivated inbred lines (from two heterotic groups and an additional biparental population) vary from moderately resistant to very susceptible to BSM, indicating crosses to wild material are not needed to produce germplasm resistant to this pest. Second, there is a moderate correlation between damage to inbred parents and hybrids, suggesting the most damaged inbred lines can be discarded if BSM susceptibility is a selective factor in advancing germplasm. Results from 2017 confirmed those from 2016; several lines from a population used to map glandular trichome abundance, a putative defense trait, were resistant to larval feeding, but the resistance was not related to glandular trichome number. Subobjective 2D: Transfer disease resistance, insect resistance, and other agronomic traits from wild Helianthus species into cultivated sunflower and improve methods for interspecific hybridization and release of pre-breeding germplasm. Over the last five years, oilseed sunflower germplasms with resistance to Sclerotinia basal stalk rot (HA-BSR1 to HA-BSR8, BSR-DIV 830, BSR STR 1623, BSR CAL 2376, BSR MAX 1018/1314/1323, BSR NUT 1008/1324) and Sclerotinia head rot (HR MAX 1018/1323 and HR NUT 1324/1008) were released. Interspecific sources of cytoplasmic male-sterility (CMS GRO1, CMS GRO1-RV, CMS MAX3-RV, CMS TUB1-HA 89) and fertility restoration (RF GIG2-MAX, RF GIG2-GRO, RF GIG2-ANG, RF GIG2-ATR, RF TUB1-ANG) were also released. Additional useful germplasms derived from wild sunflowers were developed and released, including 10 alloplasmic germplasms, 15 bulk populations, and 10 amphiploid genetic stocks. Additional work planned with alien addition lines for 2017–2018 was incomplete due to a critical vacancy. Subobjective 2E: Characterize and map resistance to pathogens and insect pests, and other agronomic traits. Genetic mapping was accomplished for rust resistance genes (R2, R14, R15, and R16), downy mildew resistance genes in already-released lines (Pl17 in HA 458 and Pl22 in Tx16R), novel downy mildew resistance genes from wild sunflowers (Pl18, Pl19, and Pl20), and a male fertility restoration gene (Rf6). Markers (SNP) were also developed to facilitate marker-assisted selection with other rust resistance genes (R4, R5, R13a, and R13b). QTL mapping for Sclerotinia basal stalk rot (BSR) resistance in an RIL population identified six QTL in an RIL population, and the two most significant QTL explain 32% and 20% of the observed phenotypic variance, respectively. Association mapping with a 260-line population found 52 significant loci associated with resistance to Sclerotinia head rot. Field trials in 2017 included the first year Sclerotinia stalk rot testing of the three AB-populations and a second year for testing a RIL population derived from the cross of HA 89 with HA-R3 for QTL analysis of Phomposis resistance. Subobjective 3A: Develop new inbred lines with novel fatty acid compositions, such as low saturated fatty acids, and high oleic acid. A half-diallel genetic population analyzed in previous years has shown plants with variation in linoleic, stearic, and palmitic acids in a high oleic background. Two lines with contrasting saturated and polyunsaturated fat compositions in a high oleic background were analyzed in three environments, and resulting quantitative loci associated with variation in these fats have been mapped. Meanwhile, the breeding program has been converted to concentrate on developing high oleic sunflower lines with diversity in genetic background and other traits. Several lines with high oleic or high oleic, low saturated fat have been released during this project period, including HOLS1, HOLS2, HOLS3, HOLS4, RHA 476, RHA 478, HA 481, HA 482, RHA 483, RHA 484, and HA 487. Subobjective 3B: Pyramid disease and insect resistance genes with high yield and oil content in a common germplasm. Over 2000 nursery rows of high yield, high oil, disease, insect, and herbicide resistant sunflower experimental lines were grown each year of the project plan in nurseries in Fargo, North Dakota, Puerto Rico, and Chile. Of particular importance are several Sclerotinia and Phomopsis resistant sunflower lines of both heterotic groups that have been released or are near release. During this period, 17 oilseed germplasms with Sclerotinia, Phomopsis, downy mildew, and imidazolinone herbicide resistance have been released. Six sunflower confection germplasms, HA-R12, HA-R13, HA-DM2, HA-DM3, HA-DM4, and HA-DM5 were developed by the backcross and pedigree breeding methods, with selection in each generation for downy mildew and/or rust resistance. These germplasms carry unique pyramids of major downy mildew and rust resistance genes. Breeding programs are ongoing and will continue to advance genetic progress on biotic stress resistance balanced with genes for crop quality and yield.
1. Release of disease-resistant sunflower germplasms with good yield potential. Sunflowers struggle with diseases caused by pathogens such as Phomopsis and Sclerotinia. Resistance to these diseases is the result of several genes working together in a sunflower variety. Sunflower producers and seed companies need new sources of resistance to these diseases in agronomically favorable, high-yielding backgrounds. Through breeding and targeted selection for disease resistance, high yield, and other favorable traits, ARS scientists in Fargo, North Dakota developed 2 new female (maintainer) and 4 male (restorer) oilseed sunflower lines that can fill this need. These lines are being used by seed companies to make new commercial hybrids, which will then be sold to farmers and grown for oil production, limiting the losses traditionally incurred by these diseases.
2. Native pollinators support consistent, high sunflower yields. Low or inconsistent yields are challenging for individual growers and the overall sunflower market. When sunflower hybrids do not effectively self-pollinate because of crop genetics or environmental conditions during flowering, pollinators are needed to ensure high yields. ARS scientists in Fargo, North Dakota grew 15 confection sunflower hybrids over two years, documenting contributions of bee pollination to crop yields. On average, 26% of yield was accounted for by bees, with lines that attracted more bees seeing higher benefits from pollinators. Virtually all bee visits to confection sunflowers were by solitary, wild bees rather than the honey bees, though honey bee colonies were located adjacent to the research plots. Because of wild bees’ demonstrated importance to yields and clear preference for certain hybrids, growers can consider bee conservation as part of crop management and breeders can use pollinator attraction as a component of inbred and hybrid development.
3. Mapping a new sunflower rust resistance gene. Rust is one of the most common diseases in sunflower production. The development of genetically resistant sunflower hybrids is economically and environmentally friendly compared to other management practices, such as fungicide application. ARS scientists in Fargo, North Dakota used an inbred line, HA-R8, to locate a gene, R15, which confers resistance to all known rust races identified in North America. This gene is independent of currently known rust resistance genes. The newly discovered rust resistance gene and its associated molecular markers provide a new tool for the management of sunflower rust and help breeders efficiently create rust-resistant sunflowers.
4. Floret size explains frequency of wild bee visits to cultivated sunflowers. By moving pollen between the hundreds of small flowers (florets) on male and female plants, wild bees and honey bees are responsible for 100% of sunflower hybrid seed production. Wild bees have additional downstream benefits when they visit those hybrids in farmers’ fields, usually adding 20–30% to yields. However, when bees choose not to visit particular sunflower varieties, the benefits are greatly reduced. ARS scientists and collaborators in Fargo, North Dakota examined floret sizes in female sunflower lines and assessed effects of floret size on pollinator visitation. Floret lengths ranged from about 7 to 10 millimeters, and the values for specific lines were consistent across years. Floret size explained most of the differences in bee visits to sunflower varieties, likely because they are unable to access nectar at the bottom of larger florets. Public and private sunflower breeders now know that selection for varieties just 1–2 millimeters shorter could more than double visits from wild bees, and development of genetic markers for floret size will eliminate the need for tedious examination of floret size to enhance bee visitation to sunflowers.
5. Mapping of genes governing a sunflower defense against insect pests. Glandular trichomes are a type of plant hair which often contains chemicals that repel or kill insects. Previous research shows larvae of the sunflower moth, a flower- and seed-feeding pest, are repelled or stunted by chemicals extracted from sunflower glandular trichomes, and lines vary greatly in the number of these glandular hairs produced. ARS scientists in Fargo, North Dakota used a population made from parents with very few or very many glandular trichomes to find the location of genes that determine glandular trichome number. Two significant markers were found, suggesting that this trait could be bred into any sunflower line. Genes near the two markers are similar to genes known to function in trichome development in other plant species. Identification of the markers provides a way for breeders to include a non-GMO insect resistance trait into their sunflower hybrids, which are used by farmers across the country.
6. Release of disease resistant germplasm from wild sunflowers. Scletotinia basal stalk rot (BSR) and downy mildew are two fungal diseases that are major yield limiting factors in global sunflower production. The use of resistant hybrids, where available, is the most efficient and environmentally friendly means of managing these diseases. ARS scientists in Fargo, North Dakota transferred resistance to BSR from three species of wild annual sunflowers into cultivated sunflower, resulting in the release of seven sunflower germplasms, HA-BSR2 to HA-BSR8. All lines except HA-BSR5 also have resistance to downy mildew derived from one of the crossing parents. These lines represent the first oilseed sunflowers with resistance to Sclerotinia BSR and downy mildew and are being used across the U.S. and internationally to breed for resistance to multiple diseases that reduce seed quality and severely impact yield.
7. Novel plant production from interspecific sunflower. Sunflower is an important crop supplying heart-healthy oil for human consumption. Though wild sunflower species have many unique genes that can be used to improve cultivated sunflower, some combinations of crosses between species result in plants that are sterile and cannot produce seed. In an effort to generate plants from crosses that have sterile offspring, ARS scientists in Fargo, North Dakota developed a tissue culture method of producing plants from the tubular flowers of an interspecific cross between cultivated sunflower and one of its wild relatives. Plants generated from tissue culture had the same chromosome number and similar appearance as their parents. This discovery provides a new method to produce large numbers of plants derived from crosses with wild species, helping scientists and breeders move useful traits from wild relatives into cultivated sunflowers
8. Wild sunflower as an alternate source of hydrocarbons. Industrial chemicals used to produce fuels, feeds and other products are often imported. To reduce dependence on foreign sources and support economic growth in the U.S., preliminary research with wild annual sunflower has shown leaves can provide useful levels of extractable hydrocarbons. In a new study, ARS scientists in Fargo, North Dakota and their collaborators sampled sunflower populations from eastern Oklahoma to North Dakota, to coastal southern California. The highest hydrocarbon yields were observed in the Texas Panhandle, while the lowest were in North Dakota and Minnesota. This study confirms that there are populations and areas where hydrocarbons are particularly high, information that is essential to public or private groups with an interest in producing sunflower-derived hydrocarbons.
Corbi, J., Baack, E.J., Dechaine, J.M., Seiler, G., Burke, J.M. 2018. Genome-wide analysis of allele frequency change in sunflower crop-wild hybrid populations evolving under natural conditions. Molecular Ecology. 27(1):233-247. https://doi.org/10.1111/mec.14202.
Mallinger, R.E., Prasifka, J.R. 2017. Benefits of insect pollination to confection sunflowers differ across plant genotypes. Crop Science. 57(6):3264-3272. https://doi.org/10.2135/cropsci2017.03.0148.
Portlas, Z.M., Tetlie, J.R., Prischmann-Voldseth, D., Hulke, B.S., Prasifka, J.R. 2018. Variation in floret size explains differences in wild bee visitation to cultivated sunflowers. Plant Genetic Resources. https://doi.org/10.1017/S1479262118000072.
Prasifka, J.R., Mallinger, R.E., Hulke, B.S., Larson, S.R., Van Tassel, D. 2017. Plant-herbivore and plant-pollinator interactions of the developing perennial oilseed crop, Silphium integrifolium. Environmental Entomology. 46(6):1339-1345. https://doi.org/10.1093/ee/nvx134.
Underwood, W., Somerville, S.C. 2017. Phosphorylation is required for the pathogen defense function of the Arabidopsis PEN3 ABC transporter. Plant Signaling and Behavior. 12(10):e1379644. https://doi.org/10.1080/15592324.2017.1379644.
Fu, X., Qi, L., Hulke, B., Seiler, G., Jan, C. 2017. Somatic embryogenesis from corolla tubes of interspecific amphiploids between cultivated sunflower (Helianthus annuus L.) and its wild species. Helia. 40(66):1-19.
Hulke, B.S., May, W.E. 2018. Registration of oilseed sunflower restorer germplasms RHA 476 and RHA 477, adapted for short season environments. Journal of Plant Registrations. 12:148-151. https://doi.org/10.3198/jpr2017.07.0048crg.
Hulke, B.S., Ma, G., Qi, L.L., Gulya, T.J. 2018. Registration of oilseed sunflower germplasms RHA 461, RHA 462, RHA 463, HA 465, HA 466, HA 467, and RHA 468 with diversity in Sclerotinia resistance, yield, and other traits. Journal of Plant Registrations. 12:142-147. https://doi.org/10.3198/jpr2017.04.0023crg.
Talukder, Z.I., Hu, J., Seiler, G.J., Qi, L.L. 2017. Registration of an oilseed sunflower germplasm line HA-BSR1 highly tolerant to Sclerotinia basal stalk rot. Journal of Plant Registrations. 11:315-319.
Royaute, R., Wilson, E.S., Helm, B.R., Mallinger, R.E., Prasifka, J.R., Greenlee, K.J., Bowsher, J.H. 2018. Phenotypic integration in an extended phenotype: among-individual variation in nest-building traits of the alfalfa leafcutting bee (Megachile rotundata). Journal of Evolutionary Biology. https://doi.org/10.1111/jeb.13259.
Gao, Q.M., Kane, N.C., Hulke, B.S., Reinert, S., Pogoda, C.S., Tittes, S., Prasifka, J.R. 2018. Genetic architecture of capitate glandular trichome density in florets of domesticated sunflower (Helianthus annuus L.). Frontiers in Plant Science. https://doi.org/10.3389/fpls.2017.02227.
Ma, G.J., Song, Q.J., Markell, S.G., Qi, L.L. 2018. High-throughput genotyping-by-sequencing facilitates molecular tagging of a novel rust resistance gene, R15, in sunflower (Helianthus annuus L.). Theoretical and Applied Genetics. https://doi.org/10.1007/s00122-018-3087-5.
Qi, L.L., Talukder, Z.I., Long, Y.M., Seiler, G.J. 2018. Registration of oilseed sunflower germplasms HA-BSR2, HA-BSR3, HA-BSR4, and HA-BSR5 with resistance to sclerotinia basal stalk rot and downy mildew. Journal of Plant Registrations. https://doi.org/10.3198/jpr2017.11.0083crg.
Seiler, G.J., Misar, C.G., Gulya, T.J., Underwood, W.R., Flett, B.C., Gilley, M.A., Markell, S.G. 2017. Identification of novel sources of resistance to Sclerotinia basal stalk rot in South African sunflower germplasm. Plant Health Progress. 18:87-90. https://doi.org/10.1094/PHP-01-17-0007-RS.