Super domestication
- From Crop Domestication to Super-domestication

We are entering a new era in relation to human understandingof and influence on the genetics of crop domestication. Currentresearch on genes related to crop domestication is providingpieces in the complex jigsaw of gene evolution (see also Hancock, 2005),networking, regulation and expression in our most importantplants. Introduction of alien genes through transgenic technologymay be difficult (King et al., 2004), but continued advancesin crop improvement will depend on understanding the genomeand its genes.

Super-domesticates can be constructed with knowledge-led approachesusing the range of current technologies. Here, we use the termsuper-domestication to refer to the processes that lead to adomesticate with dramatically increased yield that could notbe selected in natural environments from naturally occurringvariation without recourse to new technologies. The array ofgenome manipulations that have been developed, mainly sincethe 1980s, enable barriers to gene exchange to be overcome andhave lead to super-domesticates with dramatically increasedyields, resistances to biotic and abiotic stresses, and withnew characters for the marketplace. Hybrid rice (see Cheng et al., 2007,in this Special Issue) can be considered a super-domesticate.

The teams of scientists that support plant breeders are planningand conducting research to change crops radically. For example,changing crops from C3 photosynthesis to C4 photosynthesis isbeing proposed because it is now known that plants with C3 photosynthesishave enzymes for C4 photosynthesis, and even well-developedC4 pathways can be found at certain locations in C3 plants.In addition, C4-enzyme genes have been inserted into and successfullyexpressed in rice (Mitchell and Sheehy, 2006). Conversion ofa crop from C3 to C4 photosynthesis would certainly be a super-domesticate.

It was with this background of rapid progress being made instudies of crop domestication that a meeting was organized inTsukuba, Japan, in October 2006, by the National Institute ofAgrobiological Sciences (NIAS) and the Organisation for EconomicCooperation and Development (OECD) and supported by Annals ofBotany. While the Tsukuba meeting was being planned, a differentmeeting, entitled Plants, People and Evolution, sponsored bythe Linnean Society of London, the Systematics Association andAnnals of Botany was in preparation. This meeting was held inLondon in August 2006. Selected papers from these meetings appearin this Special Issue of Annals of Botany.

Progress in understanding crop domestication, and further advancesthat lead to greater quantities and improved quality of foodcrops, depend increasingly on multidisciplinary team approaches(Zeder et al., 2006; Wuchty et al., 2007). Scientists representinga diversity of botanical and crop-science backgrounds, archaeobotanists,crop evolutionary biologists, geneticists, ethnobotanists, plantbreeders, statisticians and biotechnology specialists contributepapers in this present volume. The papers include both reviewsof topics related to crop domestication and original researcharticles. Two key papers discuss domestication in the New World(Pickersgill, 2007) and the Old World (Fuller, 2007), whilethe papers that follow relate to particular crops or groupsof crops. Included are papers on crops that have been intensivelystudied by molecular methods, e.g. maize (Yamasaki et al., 2007),barley (Azhaguvel and Komatsuda, 2007; Pourkheirandish and Komatsuda, 2007),tomato (Bai and Lindhout, 2007), wheat (Waines and Ehdaie, 2007);some whose genomes have been completely sequenced, e.g. rice(Cheng et al., 2007; Sweeney and McCouch, 2007) and sorghum(Dillon et al., 2007), or where sequencing projects are proceedingactively, e.g. soybean (Liu et al., 2007) and common bean (Phaseolusvulgaris; Papa et al., 2007), and some where domestication isstill at an early stage, e.g. giant cacti (Casas et al., 2007),artichoke (Sonnante et al., 2007) or banana (Heslop-Harrison and Schwarzacher, 2007).Scientists working on minor crops envy the amount of informationbeing rapidly accumulated on model crops, but by extrapolationinformation from model species and model crops is already hasteningadvances in minor crops. This will be particularly true forcurrent genomic initiatives in closely related crops such asthe legumes (Weeden, 2007), where data from common bean andsoybean will benefit the closely related African and Asian Vigna(Isemura et al., 2007). Knowledge of the sorghum genome canbe tapped to make progress in understanding the complex genomeof sugarcane (Dillon et al., 2007) and that of the rice genomefor banana (Heslop-Harrison and Schwarzacher, 2007). Minor crops,by the very fact that less is known about them, provide thepotential of rapidly finding new insights into crop domestication(e.g. Fukunaga et al., 2006).

The papers in this Special Issue are appearing in an area wherethere is currently much scientific progress. It is hoped thatthe papers here will stimulate ideas to help sciences associatedwith crop domestication achieve needed future super-domesticates.

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