Genetic Characterization of Maximilian Sunflower for the Development of a Locally Adapted Perennial Grain Oilseed

Abstract

Maximilian sunflower (Helianthus maximiliani Schrad.), a crop wild relative of sunflower (Helianthus annuus L.), has been identified as a species of interest for the development of a perennial oilseed crop. Knowledge of the diversity, the potential for crop development, and genomic resources of this crop wild relative is limited. To facilitate its use in breeding programs, a baseline characterization of locally adapted germplasm is required to develop informed breeding strategies. Individuals were collected from nine sites in southern Manitoba, Canada, and characterized for phenotypic and genotypic divergence to estimate traits of interest for the implementation of a breeding program in Maximilian sunflower. Genotype‐by‐sequencing was used to characterize population genetic parameters and identify candidate single nucleotide polymorphisms (SNPs) associated with phenotypic divergence and environmental differences between collection sites. Candidate SNPs associated with frost‐free period, temperature during the primary vegetative growth period, elevation, soil CaCO3 equivalent, days to anthesis and capitulum size were identified and may be useful for the improvement of H. maximiliani and crop species related to cultivated sunflower. Associations between temperature, population structure, and overall plant size were also identified, suggesting phenotypic divergence across a local temperature gradient. The sampled Maximilian sunflower populations exhibited a high degree of polymorphism, low levels of inbreeding, and a highly heterozygous genome at the local scale, traits that favor the establishment of locally adapted germplasm pools. There appears to be sufficient variation to make selections for agronomic traits in local germplasm of Maximilian sunflower to support its development as a perennial oilseed.

Genetic Analysis of Domestication Parallels in Annual and Perennial Sunflowers (Helianthus spp.): Routes to Crop Development

“…The Manitoba parents consisted of wild plants collected from roadside sites across southern Manitoba. Manitoban populations, previously described under growth chamber conditions in Asselin et al (2018), exhibit extensive branching (∼11-15 branches), an early flowering genetic background and a large number (∼12-20) of small capitula which are ∼7-21 mm in diameter. A series of crosses were produced and F 1 seed derived from a cross between an individual from the TLI population "o/i" and a wild Manitoban accession collected near Brunkild, Manitoba (49.49 • N, 97.57W) were grown for sib-mating.…”

“…Fragments were sequenced via eight runs on an Ion Proton TM sequencer (Thermo Fisher Scientific, Waltham, MA, United States). The conservative three selective base approach was chosen as H. maximiliani is an obligate outcrossing species and exhibit a high degree of heterozygosity (Asselin et al, 2018). Trimmed reads were aligned to the cultivated H. annuus reference genome, HA412.v.1.1.bronze.20142015, 1 using GSNAP (Wu and Nacu, 2010) with polymorphisms within the first and last 3 bp for the read being ignored (Ott et al, 2017).…”

“…Maximilian sunflower produces an oil rich seed safe for human consumption primarily composed of linoleic and oleic acids and surveys of wild populations have shown an oil content of 31.1% (Dorrell and Whelan, 1978;Seiler, 1994;Seiler and Brothers, 1999). The natural range of Maximilian sunflower, along with its phenotypic divergence (Kawakami et al, 2011;Asselin et al, 2018), high seed production potential, and documented resistance to known common pathogens of annual sunflower (H. annuus L.) such as Sclerotinia rot [Sclerotinia sclerotiorum (Lib. ) de Bary] (Taski-Ajdukovic et al, 2006;Liu et al, 2011), has attracted attention to the species for the development of a perennial oilseed.…”

“…) de Bary] (Taski-Ajdukovic et al, 2006;Liu et al, 2011), has attracted attention to the species for the development of a perennial oilseed. Maximilian sunflower is a candidate species for the development of dual-use perennial crop for edible oil, forage and bioenergy applications and is targeted for domestication and improvement (Cox et al, 2002;Van Tassel et al, 2014;Asselin et al, 2018).…”

“…Genotype-by-sequencing (GBS) has successfully been utilized for species in which heterologous reference genomes are available for single nucleotide polymorphism (SNP) discovery, such as for wild crop relatives of soybean (Chang et al, 2014), wheat (Edae et al, 2016), and sunflower (Baute et al, 2016;Asselin et al, 2018). The goals of this research were to examine parallels between the domestication of cultivated sunflower and the development of Maximilian sunflower as a perennial oilseed crop.…”