Phenotypic effects of allotetraploidization of wildArachisand their implications for peanut domestication.
OBJECTIVE
Several species ofArachishave been cultivated for their edible seeds, historically and to the present day. The diploid species that have a history of cultivation show relatively small signatures of domestication. In contrast, the tetraploid speciesA. hypogaeaevolved into highly domesticated forms and became a major world crop, the cultivated peanut. It seems likely that allotetraploidization (hybridity and/or tetraploidization) in some way enhanced attractiveness for cultivation. Here we investigate this using six different hybridization and tetraploidization events, from distinctArachisdiploid species, including one event derived from the same wild species that originated peanut.


METHODS
Twenty-six anatomical, morphological, and physiological traits were examined in the induced allotetraploid plants and compared with their wild diploid parents.


RESULTS
Nineteen traits were transgressive (showed strong response to hybridization and chromosome duplication): allotetraploids had larger leaves, stomata and epidermal cells than did their diploid parents. In addition, allotetraploids produced more photosynthetic pigments. These traits have the same trend across the different hybrid combinations, suggesting that the changes are more likely due to ploidy rather than hybridity. In contrast, seed dimensions and seed mass did not significantly change in response to hybridization or tetraploidization.


CONCLUSIONS
We suggest that the original allotetraploid that gave rise to cultivated peanut may have been attractive because of an increase in plant size, different transpiration characteristics, higher photosynthetic capacity, or other characteristics, but contrary to accepted knowledge, increased seed size was unlikely to have been important in the initial domestication.
Embrapa Genetic Resources and Biotechnology, PqEB, W5 Norte Final, Brasília, DF 70770-917, Brazil soraya.bertioli@embrapa.br sorayab@uga.edu.|University of Georgia, Center for Applied Genetic Technologies, 111 Riverbend Road, Athens, Georgia 30602-6810 USA.
Soraya C M
SC
Leal-Bertioli
Embrapa Genetic Resources and Biotechnology, PqEB, W5 Norte Final, Brasília, DF 70770-917, Brazil.
Márcio C
MC
Moretzsohn
University of Brasília, Institute of Biological Sciences, Campus Darcy Ribeiro, Brasília, DF 70910-900, Brazil.|Catholic University of Brasília, Biotechnology and Genomic Sciences, SGAN 916 Módulo B Avenida W5, Brasília, DF 70790-160, Brazil.
Silvio P
SP
Santos
Embrapa Genetic Resources and Biotechnology, PqEB, W5 Norte Final, Brasília, DF 70770-917, Brazil.
Ana C M
AC
Brasileiro
Embrapa Genetic Resources and Biotechnology, PqEB, W5 Norte Final, Brasília, DF 70770-917, Brazil.
Patrícia M
PM
Guimarães
University of Georgia, Center for Applied Genetic Technologies, 111 Riverbend Road, Athens, Georgia 30602-6810 USA.|University of Brasília, Institute of Biological Sciences, Campus Darcy Ribeiro, Brasília, DF 70910-900, Brazil.
David J
DJ
Bertioli
Embrapa Genetic Resources and Biotechnology, PqEB, W5 Norte Final, Brasília, DF 70770-917, Brazil.
Ana Claudia G
AC
Araujo
D010367:Arachis / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D018556:Crops, Agricultural; D004171:Diploidy; D000071278:Domestication; D018745:Genome, Plant / Q000235:genetics*; D005838:Genotype; D006824:Hybridization, Genetic; D010641:Phenotype; D010788:Photosynthesis; D018515:Plant Leaves / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D011123:Polyploidy; D012639:Seeds / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D057891:Tetraploidy
Arachis; Fabaceae; allotetraploid; domestication; hybridization; leaf morphology; leaf pigments; plant architecture; polyploidy; tetraploidization