From forest to field: Perennial fruit crop domestication

Authors: MILLER, ALLISON - St Louis University; Gross, Briana

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2011
Publication Date: 8/24/2011
Citation: Miller, A., Gross, B.L. 2011. From forest to field: Perennial fruit crop domestication. American Journal of Botany. 98:1389-1414.

Interpretive Summary: Problem: Although our understanding of plant domestication is now very advanced for annual crops, our knowledge of perennial crop domestication is still nascent. Accomplishment: This manuscript represents a summary of the current state of perennial fruit crop domestication processes, including morphological and genetic changes, and places these in the context of what is known about wild perennial plants and domesticated annual plants. Impact: We suggest that perennial plants evolve much like annual plants under domestication pressures in terms of morphology. The genetic basis of domestication appears to be less extreme in perennial plants, in that the genes controlling the traits have smaller effects. Overall, it is likely that the high genetic variation and the diverse modes of mating and reproduction in domesticated perennial plants dictate a different genetic basis for domestication. This work provides a much-needed synthesis of existing studies, and lays the groundwork for promising research focused on perennial domestication genetics. At an applied level, these findings will be used for research and development in two main areas: 1) breeding and improvement of perennial fruit crops, and 2) understanding how long-lived plants respond to strong, short-term selective pressures, such as climate change.

Technical Abstract: • Premise of the study. Understanding of plant domestication and evolution are enhanced by archaeological and genetic analyses of seed-propagated annual crops. Domestication of perennial plants may reveal how genes and genomes evolve in long-lived species and how perennial plants respond to selection pressures operating on a relatively short time scale. Here, we focus on long-lived perennial crops (mainly trees and other woody plants) grown for their fruits. • Methods. We review 1) basic biology of forest trees, setting the stage for perennial domestication by considering how these species evolve in nature; 2) the suite of morphological features associated with perennial fruit crops undergoing domestication; 3) the origins and evolution of domesticated perennials grown for their fruits; and 4) the genetic basis of domestication in perennial fruit crops. • Conclusions. Long-lived perennials exhibit lengthy juvenile phases, extensive outcrossing, widespread hybridization, and limited population structure. Under domestication, these features, combined with clonal propagation, multiple geographic origins, and ongoing crop-wild gene flow contribute to mild domestication bottlenecks in perennial fruit crops. Morphological changes under domestication have many parallels to annual crops, but with key differences for mating system evolution and mode of reproduction. QTLs associated with domestication traits in perennials are mainly of minor effect, and may not be stable across years. Future studies that take advantage of genomic approaches and consider demographic history will elucidate the genetics of agriculturally and ecologically important traits in perennial fruit crops and their wild relatives.