De-domestication: An extension of crop evolution

  

 Domestication has been an area of intense interest and study ever since Darwin, and useful as a model for evolution and the effects of strong directional selection. Feralization refers to the process by which formerly domesticated population transit to life outside of cultivation or husbandry and escape a regime of artificial selection2.

Feralization, like domestication, is a process not an event, accompanied by incomplete transitions, admixture, and introgression. De-domesticates originate from one of the three pathways. Endoferal origin due to spontaneous mutations in ancestral crop population, exo-endoferal origin by natural hybridization within landraces or varieties with divergent genotypes and exoferal origin by genomic introgression from wild relatives or by crop - wild hybridization. Under loosening artificial selection due to wide application of non-intensive farming practices, crops, especially diploid ones, tend to be more likely to initiate de-domestication. De-domesticates have multiple roles in both wild and agricultural ecosystems. Some of the key loci involved in de-domestication events are seed shattering in rice, barley and wheat, and red pericarp in rice2.

De-domestication plays a key role in origin of weedy rice (WD) and the novel mutations further promote continued evolution and genetic diversity of WD. Analysis of DNA sequence polymorphism of the seed shattering genes (sh4 and qsh1) in weedy, wild and cultivated rice indicates the multiple origin of WD with most samples having evolved from their cultivated progenitor4.

The Tibetan semi-wild wheat is a feral form of Tibetan landrace, and two associated loci, including a 0.8 Mb deletion region containing Btr1/2 homologs and a genomic region with TaQ-5A gene was found to be responsible for rachis brittleness (seed persistent phenotype) during the de-domestication episode1.

Tibetan weedy barley was evolved from de-domestication of cultivated barley with two different genotypes controlling brittle rachis was reported while studying the origin of qingke barley. It was found that the novel haplotype with both Btr1Btr2 observed in weedy barleys was probably generated via hybridization between qingke or eastern barleys with the haplotypes btr1Btr2 and Btr1btr2 followed by local recombination3.

Domestication has been the focus of huge amount of research, the potential for feralization to expand our knowledge is relatively untapped. Feral animal and plant populations offer exciting new avenues for research as well as potential sources to make cultivated plants and animals more locally adapted. The wealth of associated genomic data due to the relationships to domesticated populations, combined with thorough sampling, should prove feral populations to be powerful datasets to understand complex biological systems.

References: 

1. GUO, W., XIN, M., WANG, Z., YAO, Y., HU, Z., SONG, W. AND SUN, Q., 2020, Origin and adaptation to high altitude of Tibetan semi-wild wheat. Nature communications., 11(1): 1-12. 

2. WU, D., LAO, S. AND FAN, L., 2021, De-domestication: an extension of crop evolution. Trends in Plant Science., 26(6): 560-574. 

3. ZENG, X., GUO, Y., MASCHER, M., GUO, G., LI, S., MAO, L., XIA, Z., ZHOU, J. AND YUAN, H., 2018, Origin and evolution of qingke barley in Tibet. Nature Communications., 9(1): 5433. 

4. ZHU, Y. Q., FANG, J., WANG, Y., PANG, L. H. AND LU, B. R., 2021, Key roles of de-domestication and novel mutation in origin and diversification of global weedy rice. Biology., 10(9): 828.