Research Project: Genetic Enhancement of Sunflower Yield and Tolerance to Biotic Stress

Location: Sunflower and Plant Biology Research

2022 Annual Report

Objectives
OBJECTIVE 1: Develop and release sunflower germplasm and inbred lines with enhanced yield potential, desirable oil traits, or resistance to crop pests (insects and pathogens), along with effective molecular markers. Subobjective 1A: Develop genetic markers for Phomopsis, rust, and downy mildew resistance. Subobjective 1B: Characterize genetic and pathogenic variation in Phomopsis populations in North Central sunflower growing regions. Subobjective 1C: Evaluate diverse interspecific germplasm for resistance to Phomopsis, rust, and downy mildew. Subobjective 1D: Develop pre-breeding and advanced germplasm with novel traits or combinations of agronomically important traits. OBJECTIVE 2: Identify and characterize traits associated with resistance to insect pests and improved sunflower-pollinator interactions, and evaluate their effectiveness in insect management systems. Subobjective 2A: Evaluate susceptibility of sunflowers to insect pests and develop genetic markers for host plant resistance traits. Subobjective 2B: Assess variation and develop genetic markers for traits associated with pollinator visitation.

Approach
The economic impact of sunflower production in the United States is at least $1.5 billion per year. In the primary sunflower production areas, sunflower must compete with genetically-modified crops like corn and soybean that can be easier to produce or have more consistent yields. To maintain its position as a valuable rotational crop and ensure a consistent supply of heart-healthy oil, both maximum yield and consistency of yield must be improved. Losses from diseases and insect pests, along with related costs of management, are primary challenges for improving sunflower yields. Proposed research aims to improve resistance to diseases and insect pests and combine these traits with herbicide resistance, improved oil content and quality to create a more competitive crop. Specific objectives are to: (1) develop genetic markers for resistance to three major sunflower pathogens, (2) understand genetic and pathogenic variation for a disease that has recently increased in incidence and severity, (3) search for new sources of disease resistance from crop wild relatives of cultivated sunflower, (4) identify and characterize traits that will provide resistance to insect pests or improve sunflower-pollinator interactions (which positively contribute to yields), and (5) combine desired traits for pest resistance with other important agronomic traits to create superior germplasm. Success in these objectives will allow higher, more consistent yields and reduce costs of production, contributing to a stable supply of oil and non-oil sunflowers that supports profitable farming.

Progress Report
Subobjective 1A: Develop genetic markers for Phomopsis, rust, and downy mildew resistance. A population including 200 F5-derived recombinant inbred lines (RILs) derived from Phomopsis-susceptible (HA 89) and resistant (HA 378) parents was grown for seed increase that will permit mapping of Phomopsis resistance. A new downy mildew (DM) resistance gene, Pl37, derived from sunflower wild species H. annuus (PI 435417) was mapped to sunflower chromosome 4. This gene exhibited broad-spectrum resistance to all tested DM races including the most prevalent and virulent races. Germplasms carrying Pl37 were developed in both oil and confection sunflowers by backcross and marker-assisted selection. Subobjective 1B: Characterize population structure and genetic variation within and among populations of Phomopsis helianthi in the Northern Great Plains. Genotyping-by-sequencing reads were mapped to the Diaporthe helianthi draft genome and variants were called, resulting in a dataset of 2362 single nucleotide polymorphisms across 280 samples. Analysis of population structure revealed a single, panmictic population across the three North Central sunflower growing states of Minnesota, North Dakota, and South Dakota. A final replication of stem lesion virulence tests was completed for 20 Diaporthe helianthi isolates on a panel of 15 sunflower lines with varying resistance responses. Consistent results were observed across three replications of the greenhouse stem lesion evaluation. Analyses of stem lesion responses to the 20 isolates revealed instances of isolate-specific resistance while five sunflower lines were identified that exhibited broad-spectrum resistance to all tested isolates. These results indicate that it will be necessary to evaluate resistance to multiple isolates of this fungal pathogen and identify useful sources of broad-spectrum resistance. Subobjective 1C: Evaluate diverse interspecific germplasm for resistance to Phomopsis, rust, and downy mildew. The fifth year of field screening of 120 interspecific germplasms for resistance to Phomopsis stem canker was completed, with three interspecific pre-breeding lines identified. Replicated greenhouse screening for new sources of rust resistance identified eight promising amphiploid lines derived from six different perennial species showing high levels of resistance in segregating progeny (85 to 100% resistance). Replicated greenhouse screening also identified eight promising amphiploid lines as new sources of resistance to the most virulent race of downy mildew, allowing for further selection, gene identification, and development of mapping populations for marker-assisted breeding. Subobjective 1D: Develop pre-breeding and advanced germplasm with novel traits or combinations of agronomically important traits. Over 3,500 nursery rows of high yield, high oil, disease, insect, and herbicide-resistant sunflower experimental lines were grown in nurseries in Fargo, North Dakota, and Chile, with yield trials of experimental hybrids from these lines also grown at several locations throughout the sunflower growing region, including North Dakota, South Dakota, Minnesota, and Kansas. Of these, release dockets have been prepared for several Sclerotinia- and Phomopsis-resistant sunflower lines of both heterotic groups, downy mildew resistant lines, and early-maturing lines suitable for double cropping in the southern and central plains, and late planting in the northern plains. We are working with National Programs Staff to update our release plans, considering sunflower stakeholder needs and issues. Subobjective 2A: Evaluate susceptibility of sunflowers to insect pests and develop genetic markers for host plant resistance traits. Single-cross sunflower hybrids using either a weevil-resistant female parent (cytoplasmic male sterile [cms] HA 488) or a susceptible parent (cms HA 412HO) and several male inbred lines were artificially infested with high numbers of red sunflower seed weevils (30 adult weevils per plant) in the field. Hybrids with cms HA 488 as a parent averaged >35% fewer damaged seeds, indicating that cms HA 488 (and subsequent lines with the same resistance) is beneficial as a parent in single-cross hybrids. The germplasm has potentially high value as part of integrated pest management of the red sunflower seed weevil. The same hybrids are being evaluated for a second year to further assess the value of resistance under field conditions. Subobjective 2B: Assess variation and develop genetic markers for traits associated with pollinator visitation. Floret size explains much of the variation in wild bee preference among cultivated sunflowers. Field observations of honey bees foraging on sunflowers in Arizona suggest they share the same preference for short florets with wild bees that pollinate sunflower in the northern Great Plains. This preference means that shorter florets can increase profitability of hybrid seed production. Among sunflower lines with similar floret size but varied nectar sucrose concentrations, a first year of observations in North Dakota suggests that wild bees had no preference for nectar sugar type. Though the effect of sucrose on honey bee foraging in sunflowers has not been evaluated yet, sunflowers with more sucrose may be useful even without any bee preference because more sucrose (= less glucose) reduces crystallization in honey.

Accomplishments
1. Double-cropping oilseed sunflower after winter camelina shows benefits of double crop rotations with sunflower. Growing two crops in the same location and season (double-cropping) can increase farm revenues, increase crop production, and also reduce erosion and water loss. To evaluate yields of winter camelina (cultivar Joelle) followed by sunflower against a single crop of sunflower, ARS scientists in Fargo, North Dakota, and Morris, Minnesota, conducted field tests over two years in west-central Minnesota. The tests included an early-maturing semidwarf oil sunflower hybrid (Honeycomb NS) and three common commercial full-season oil hybrids. Although later planting associated with double-cropping generally reduced sunflower seed yield, oil content, and the oleic/linoleic acid ratio compared to a single sunflower planting, these decreases were less for the early-maturing hybrid Honeycomb NS. In one of two years, total oil yield of the double crop treatment with Honeycomb NS was 1.5 times greater than the single crop of sunflower. This demonstrates the potential of incorporating double crop rotations in environments as far north as Minnesota.

2. Identification of new rust resistance genes in sunflower. Rust is a serious fungal disease in the sunflower growing areas worldwide with an increasing importance in North America in recent years due to the frequent evolution of new pathogen races. Resistance against rust in sunflower is commonly regulated by single dominant genes. ARS scientists in Fargo, North Dakota, and colleagues at North Dakota State University developed two rust-resistant sunflower lines using new resistance genes that protect against the most common and serious types of rust. The locations of the new rust resistance genes were discovered and associated with markers so that public and private breeding programs can efficiently create sunflower hybrids that include these new sources of resistance.

3. Identification of downy mildew resistance from crop wild relatives. Downy mildew (DM) is one of the most destructive sunflower diseases worldwide, limiting yield and reducing seed quality. New DM races are continually overcoming the resistance in sunflower hybrids, requiring a search for new genes, which provides an economical strategy for disease management. ARS scientists in Fargo, North Dakota, and colleagues at North Dakota State University developed germplasms from the crop wild relatives with resistance to all known races of DM identified in North America and Europe. Genetic markers for the new DM resistance genes were developed to use in marker assisted breeding. The new germplasms provide a broad spectrum of useful sources of DM resistance genes for sunflower breeders to use, ensuring the protection from yield and seed quality losses.

Review Publications
Qi, L., Ma, G., Seiler, G.J. 2021. Registration of HA-R14, HA-R15, HA-R16, and HA-R17 oilseed sunflower germplasms with broad resistance to rust and downy mildew. Journal of Plant Registrations. 16:137–146. https://doi.org/10.1002/plr2.20187.
Bailey, D.W., Attia, Z., Reinert, S., Hulke, B.S., Kane, N.C. 2022. Effective strategies for isolating DNA from members of Asteraceae with high concentrations of secondary metabolites. Biotechniques. 72:85-89. https://doi.org/10.2144/btn-2021-0050.
Feng, J., Jan, C., Seiler, G.J. 2022. Breeding, production, and supply chain of confection sunflower in China. OCL - Oilseeds & fats, Crops and Lipids. 29. Article 13. https://doi.org/10.1051/ocl/2022004.
Innes, P., Gossweiler, A., Jensen, S., Tilley, D., St. John, L., Jones, T.A., Kitchen, S.G., Hulke, B.S. 2022. Assessment of biogeographic variation in traits of Lewis flax (Linum lewisii) for use in restoration and agriculture. AoBP (Annals of Botany PLANTS). 14(2). Article plac005. https://doi.org/10.1093/aobpla/plac005.
Ma, G., Seiler, G.J., Qi, L. 2022. Registration of two oilseed sunflower germplasms, HA-DM7 and HA-DM8, resistant to sunflower downy mildew. Journal of Plant Registrations. https://doi.org/10.1002/plr2.20206.
Qi, L., Cai, X. 2022. Characterization and mapping of a downy mildew resistance gene, Pl36, in sunflower (Helianthus annuus L.). Molecular Breeding. 42. Article 8. https://doi.org/10.1007/s11032-022-01280-1.
Gesch, R.W., Mohammed, Y.A., Walia, M.K., Hulke, B.S., Anderson, J.V. 2022. Double-cropping oilseed sunflower after winter camelina. Industrial Crops and Products. 181. Article 114811. https://doi.org/10.1016/j.indcrop.2022.114811.
Langridge, P., Braun, H., Hulke, B.S., Ober, E., Prasanna, B.M. 2021. Editorial: Special Issue: Breeding crops for climate resilience. Theoretical and Applied Genetics. 134:1607-1611. https://doi.org/10.1007/s00122-021-03854-7.
Underwood, W., Gilley, M., Misar, C.G., Gulya, T.J., Seiler, G.J., Markell, S.G. 2022. Multiple species of Asteraceae plants are susceptible to root infection by the necrotrophic fungal pathogen Sclerotinia sclerotiorum. Plant Disease. 106:1366-1373. https://doi.org/10.1094/PDIS-06-21-1314-RE.
Talukder, Z., Underwood, W., Misar, C.G., Seiler, G.J., Li, X., Cai, X., Qi, L. 2022. Genomic insights into Sclerotinia basal stalk rot resistance introgressed from wild Helianthus praecox into cultivated sunflower (Helianthus annuus L.). Frontiers in Plant Science. 13. Article 840954. https://doi.org/10.3389/fpls.2022.840954.
Talukder, M.I., Underwood, W., Misar, C., Seiler, G.J., Cai, X., Li, X., Qi, L. 2022. A quantitative genetic study of Sclerotinia head rot resistance introgressed from the wild perennial Helianthus maximiliani into cultivated sunflower (Helianthus annuus L.). International Journal of Molecular Sciences. 23(14). https://doi.org/10.3390/ijms23147727.
Yoshimura Ferguson, M.E., Mallinger, R., Prasifka, J.R. 2021. Bee community composition, but not diversity, is influenced by floret size in cultivated sunflowers. Apidologie. 52:1210-1222. https://doi.org/10.1007/s13592-021-00897-z.
Braasch, J.E., Di Santo, L.N., Tarble, Z., Prasifka, J.R., Hamilton, J.A. 2021. Testing for evolutionary change in restoration: a genomic comparison between ex situ, native and commercial seed sources of Helianthus maximiliani. Evolutionary Applications. 14:2206-2220. http://dx.doi.org/10.1111/eva.13275.
Underwood, W. 2022. Arabidopsis GOLD36/MVP1/ERMO3 is required for powdery mildew penetration resistance and proper targeting of the PEN3 transporter. Molecular Plant-Microbe Interactions. 35:393-400. https://doi.org/10.1094/MPMI-09-21-0240-R.
Prasifka, J.R., Peterson, K., Mallinger, R.E., Van Tassel, D. 2022. Changes to architecture of Silphium integrifolium Michx. during domestication reveal new trade-offs for yield. Crop Science. 62:1060-1068. https://doi.org/10.1002/csc2.20737.
Seiler, G.J. 2022. Germination and viability of wild sunflower species seeds stored at room temperature and low humidity for 38 years. Seed Science and Technology. 50(3):307-315. https://doi.org/10.15258/sst.2022.50.3.01.
Ma, G., Song, Q., Li, X., Qi, L. 2022. Genetic insight into disease resistance gene clusters by using sequencing-based fine mapping in sunflower (Helianthus annuus L.). International Journal of Molecular Sciences. 23(17):9516. https://doi.org/10.3390/ijms23179516.