Progress and Bottlenecks in the Early Domestication of the Perennial Oilseed Silphium integrifolium, a Sunflower Substitute

Abstract

Silflower (Silphium integrifolium Michx.) is in the early stages of domestication as a perennial version of oilseed sunflower, its close relative. Grain crops with deep perennial root systems will provide farmers with new alternatives for managing soil moisture and limiting or remediating soil erosion, fertilizer leaching, and loss of soil biota. Several cycles of selection for increased seed production potential following initial germplasm evaluation in 2002 have provided opportunities to document the botany and ecology of this relatively obscure species, to compare agronomic practices for improving its propagation and management, and to evaluate the differences between semi-domesticated and wild accessions that have accrued over this time through intentional and unintentional genetic processes. Key findings include: domestication has increased aboveground biomass at seedling and adult stages; seed yield has increased more, achieving modest improvement in harvest index. Harvest index decreases with nitrogen fertilization. Silflower acquires nitrogen and water from greater depth than typical crops. In agricultural silflower stands within its native range, we found that Puccinia silphii (rust) and Eucosma giganteana (moth) populations build up to unacceptable levels, but we also found genetic variation for traits contributing to resistance or tolerance. Breeding or management for reduced height and vegetative plasticity should be top priorities for future silflower research outside its native range.

Strategies, Advances, and Challenges in Breeding Perennial Grain Crops

“…In this special issue, reports on de novo domestication projects include intermediate wheatgrass (Thinopyrum intermedium), which produces a grain similar to wheat called Kernza ® [29,30], silflower (Silphium integrifolium), a member of the sunflower family under development as an oilseed crop [31,32], and perennial barley (Hordeum spp.) [33].…”

Effect of Puccinia silphii on Yield Components and Leaf Physiology in Silphium integrifolium: Lessons for the Domestication of a Perennial Oilseed Crop

“…A final possibility is that the domestication process has resulted in lower baseline but more plastic allocation to resins. Higher resin content in wild compared to selected plants has been observed in silphium [6]. Likewise, domesticated sunflowers produce fewer sesquiterpene lactone-containing trichomes than wild accessions, although investment appeared to be constitutive, not plastic [37].…”

“…Rust caused by Puccinia silphii [6] is likely to be an important disease in the development of silphium. Puccinia silphii is a microcyclic fungal pathogen producing only the hyaline basidiospore and over-wintering teliospore, and lacking the haploid pychniospore, dikaryotic aeciospore, and the long-distance dispersing urediniospore stages of macrocyclic rusts [7].…”

Patterns of genetic variation in a prairie wildflower,Silphium integrifolium, suggest a non-prairie origin and locally adaptive variation

“…Perhaps motivated by the prairie origin hypothesis, the overwhelming majority of germplasm involved in S. integrifolium breeding programs derive from collections from the western region (Vilela et al 2018). From those limited collections, significant heritable domestication improvements have been made in the accumulation of above ground biomass and seed yield (Vilela et al 2018). Our population genetic results suggest that past domestication improvements have been achieved with a limited genetic variation resource.…”

“…Accessions used in S. perfoliatum breeding have little genetic diversity from (often) unknown geographic origins (Wever et al 2019). To date, most S. integrifolium breeding progress has been made from accessions that originated within a small geographic area (Kansas, USA) (Vilela et al 2018), with a general lack of genomic resources (Van Tassel et al 2017). The extent to which breeding populations are representative of species-wide diversity has not been genetically evaluated.…”