Useful insights from evolutionary biology for developing perennial grain crops¹

Abstract

Perennial grain crops have been proposed as an elegant solution to numerous problems confronted in modern agriculture. Perennial grains are expected to increase water quality, reduce soil erosion, increase soil carbon, and improve habitat for wildlife ( Cox et al., 2006 ). Furthermore, perennials are predicted to be more resilient to abiotic stress resulting from climate change ( Cox et al., 2006 ). Initiating and expanding perennial grain breeding programs has been proposed as a strategy to address the looming challenges of land degradation, food security, energy supply, and climate change ( Glover et al., 2010 ).Strategies proposed for developing a wide array of new perennial grain crops ( Wagoner and Schaeffer, 1990 ;Cox et al., 2002 ) typically are separated into two groups: wide hybridization and de novo domestication. In de novo domestication, repeated cycles of selection are performed out of a wild perennial population to achieve a high-yielding domestic type. In wide hybridization, an existing grain crop is crossed with a wild perennial relative, and then either the hybrid population is improved, or repeated rounds of backcrossing are performed to introgress genes for perennial growth until the phenotype in other ways resembles the annual crop parent. Here, we will not address the array of genetic effects that are derived from wide hybridizations, but will rather focus our attention on the mechanisms specifi c to early stages of selection from wild populations.The breeding strategies required for selecting out of wild material vs. improving yield of domesticated species are sure to differ. Whereas the fi rst stages of domestication in cereal crops involve dramatic changes that facilitate uniform planting and effi cient harvesting, crop improvement (of existing domestic species) involves improvements in yield and palatability or diversifi cation based on regional adaptation or harvested product qualities ( Olsen and Wendel, 2013 ). Although the early steps toward domestication will include yield gains, the primary objective is to transform the phenotype in ways that make a plant useful to meet human food needs. Subsequent crop improvement is associated with relatively modest incremental morphological changes.Since few grain species have been recently domesticated ( Meyer et al., 2012 ), most plant breeding theory and practice is based on improvement of previously domesticated species. With over a decade of experience domesticating new grain crops (described by Cox et al., 2010 ), we have been searching for genetic insights that are specifi c to taking wild species through the early stages of domestication. We have found strategies for the wholesale remodeling of plants (as is required to develop perennial grains) to be rare in the plant breeding literature. Therefore, we have turned to fi ndings in other fi elds to develop more complete and effi cient strategies for our own programs and, we hope, for the benefi t of colleagues considering the domestication of other wild species.Here we review literature i...

What Agriculture Can Learn from Native Ecosystems in Building Soil Organic Matter: A Review

“…The reasons why early agriculturalists originally domesticated annual grain crops reflect the tools, energetic constraints and understanding of biological processes that humans had in the Neolithic era, 5000-10,000 years BP [83]. In the last century, the sciences of evolutionary biology, genetics and plant breeding have expanded tremendously, and many researchers believe it is now possible to breed perennial cereal, legume, fiber and oilseed crops that would yield sufficiently to eventually occupy large areas currently planted to annual species [80,84,85].When considering steps towards greater agricultural sustainability, the prospect of increasing ecological function through perennial crops is very significant, but so are discussions of land tenure, scale of production, energy return on investment and diversity of crops at both farm and regional scales [86][87][88]. Research undertaken to quantify rates of SOM accumulation under perennial grain proto-crops that are being currently bred is lacking.…”

Accelerating Silphium Domestication: An Opportunity to Develop New Crop Ideotypes and Breeding Strategies Informed by Multiple Disciplines

“…Opportunities to accelerate domestication using next-generation sequencing (NGS)-based techniques and insights from decades of advances in evolutionary biology have been reviewed elsewhere (Harfouche et al, 2012;Henry, 2012;Shapter et al, 2013;DeHaan and Van Tassel, 2014). If Silphium represents a new opportunity to do better than our ancient ancestors, we suggest that rational, intentional domestication requires us to consider not just why to use perennials or how to do it faster, that is, how to efficiently increase yields and make the crop easier to harvest, use, and propagate, but how a newly domesticated crop might be intentionally developed anticipating the stages of crop research and use after domestication.…”

Perennial Grain Legume Domestication Phase I: Criteria for Candidate Species Selection

“…Therefore, perennial legume species exhibiting free-germination or that can be quickly and easily selected to become free germinating will be strong candidates for later phases of the pipeline. Additionally, seedling establishment of perennial forage legumes is slow compared to annuals possibly because they carry high genetic load or they invest in a substantial root system prior to developing above ground foliage [7,33]; however, selection for perennial legumes with divergent root/shoot ratios has been previously accomplished [37]. We expect that increased seedling vigor and effective establishment can be improved via selection in candidates with poor establishment rates.…”

“…Past efforts to breed and domesticate other perennial grains have generated hypotheses about why annual grains were historically domesticated instead of perennial grains [32] and provided evidence suggesting how current knowledge about the ecology of perennial plants and ecosystems, combined with modern breeding approaches, makes domestication of perennial grains now possible [16,26,33]. Researchers from The Land Institute (Salina, KS, USA) and elsewhere have outlined a pipeline strategy as a guide for grain crop domestication which is composed of three phases (Phase I: Evaluating candidate species; Phase II: Wild species to new crop; and Phase III: From new crop to commodity crop) [34].…”