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Roullier
Caroline
Avril 2011
Thesis supervisors: Vincent Lebot & Doyle MC Key
Elucidating sweet potato evolutionnary history with molecular markers
Sweet potato Ipomoea batatas
Convolvulaceae family, Ipomoea gender (from 600 to 700 species), series Batatas
Just one cultivated species: Ipomoea batatas
(L.)
Tuberous roots only in I. batatas (some wild species have thickening roots)
Cultivated form hexaploid (6x=90) ; Wild / Weedy form (4X, 6X?)
Sporophytic incompatibility / clonal propagation
Sweet potato domestication history in America: Which
botanical origin?
Serie Batatas :
*
13 wild species ; one cultivated / wild‐weedy
*
All endemics from America (exepted I. littoralis)
* 2 types of genomes « A and B*
», cross incompatible
• Various ploidy level (from 2x to 6x)
• Taxonomic debate (I. trifida, I. batatas, a single taxon?)
• Ipomoea trifida is a probable ancestor*
*
*
*?
Ipomoea species Ploidy 2n x=15
Geographical origin
I. cyanchifolia 2x South AmericaI. lacunosa 2x North AmericaI. leucantha 2x North AmericaI. littoralis 2x Pacific and Indian OceansI. ramosissima 2x Central and south AmericaI. tenuissima 2x Greater Antilles, south
Florida and CaribbeanI. triloba 2x Caribbean and circum-
CaribbeanI. umbraticola 2x Central and north AmericaI. tiliacea 4x Caribbean and circum-
CaribbeanI. tabascana 4x Central America (Mexico)I. cordotriloba (I. trichocarpa) 2x, 4x North America
I. grandifolia 2x South AmericaI. trifida 2x, 3x,
4x, 6xCentral and south America
I. batatas 6x, 4x, Central and / or south America ?
•
Which ancestors species contributed to cultivated I. Batatas genome?
•
How many genomes are implicated ? allo‐polyploid, auto‐ polyploid or auto/allo polyploid origin?
Sweet potato domestication history in Amerca: Which botanical origin?
I. trifida 2X / 4X is implicated
Morphological , taxonomical : I. trifida distribution range Austin,1987
Molecular data (Zhang, 2000)
Higher level of genetic diversity in Central America / No regional specific patterns
Sweet potato domestication history in America: A single origin: the most parsimonious hypothesis
* A primary center of diversity in central‐ caribbean America
* Early diffusion to Peru
* The Peru‐Ecuador region is a secondary center of diversity
Archeological data
:
Oldest archaeological remains are in the Andean valleys of Pacific coasts
* Canyon Chilca Peru : 8000 ans BP (Engel, 1970; Woolfe, 1992).
•Casma Valley, cost of
Peru
: 1785 et 1120 BC (Ugent et al., 1981).
Molecular data :
(Gichuki, 2003)Two genetic genepool in primary center of
diversity
Geographical arguments
(Diamond, 1997)
Ethnobotanical arguments (Roots crops domestication) (Lebot, 2009)
Sweet potato domestication history in America: Multiple domestication centres?
«
Population structure
»
and genetic diversity of New World sweet potatoes with both
chloroplast and nuclear SSRs markers
Are there different sweet potato genepools in America? How many?
What do we lean from population structure and genetic diversity about domestication scenari and sweet potato diffusion on the continent?
Single domestication event following by early diffusion and diversification
Multiple independant domestication events?
Which diversification processes? Clonality/reproduction
Sweet potato domestication history in America
Plant material
The CIP collection (Dr Tay, Dr Rossel)
NWSA
CSA
CI
CA
CI+CSA+CA= CCAGeographic area Country
Number of acc. cpSSRs
Number of acc. SSR
ND Argentina 3 1 ND Bolivia 8 2 ND Brazil 6 ND Paraguay 2 Total ND 19 3 NWSA Ecuador 33 17 NWSA Peru 66 23 NWSA South Columbia 19 9 Total NWSA 85 49 CSA North Columbia 24 7 CSA Venezuela 31 20 Total CSA 55 27 CA Costa Rica 2 1 CA Guatemala 30 9 CA Honduras 5 CA Mexico 25 10 CA Nicaragua 3 CA Panama 22 10 Total CA 87 30 CI Cuba 10 4 CI Dominican Republic 22 9 CI Jamaica 13 5 CI Puerto Rico 2 CI St Vincent 3 1 Total CI 50 19 Total 329 130
Molecular markers
Locus TM Forward Primer Name Reverse Primer Name SSR MotifJ263 57 CTCTGCTTCTCCTGCTGCTT GTGCGGCACTTGTCTTTGATA AAC(6)J315E 57 TAGGTGTGTTTATGGGAGATT GGGACTTGACTTTCATTATTAC (TCAG)5J522A 57 ACCCGCATAGACACTCACCT TGACCGAAGTGTATCTAGTGG (CAC)7Ib297 58 GCAATTTCACACACAAACACG CCCTTCTTCCACCACTTTCA (CT)13J10A 58 TCAACCACTTTCATTCACTCC GTAATTCCACCTTGCGAAGC (AAG)6J206A 58 ATCAGGGAGAGAGGACAGTAA TAGGCAAACCATAAACAGAGA (GAT)6J116a 58 TCTTTTGCATCAAAGAAATCCA CCTCAGCTTCTGGGAAACAG (CCT)7J130 60 CCAGTTGTGGCGGAGAAAG GGATTCTTGTGAGGGACAACA (GAA)8J1809E 60 CTTCTCTTGCTCGCCTGTTC GATAGTCGGAGGCATCTCCA (CCT)6IbR16 60 GACTTCCTTGGTGTAGTTGC AGGGTTAAGCGGGAGACT (GATA)4IbC5 60 CCACAAAAATCCCAGTCAACA AGTGGTCGTCGACGTAGGTT (AAG)8J544b 60 AGCAGTTGAGGAAAGCAAGG CAGGATTTACAGCCCCAGAA (TCT)6IbS11 60 CCCTGCGAAATCGAAATCT GGACTTCCTCTGCCTTGTTG (TTC)10IbR12 60 GATCGAGGAGAAGCTCCACA GCCGGCAAATTAAGTCCATC (CAG)5A
Markers Primers (5'-3') Expected
size T (°C)
F: GATCCCGGACGTAATCCTGR: ATCGTACCGAGGGTTCGAATF: CTGTTCTTTCCATGACCCCTCR: CCACCTAGCCAAGCCAGAF: TCCAATGGCTTTGGCTAR: AGAAACGAAGGAACCCACF: GCAATTGCAATGGCTTCTTTAR: TTTATGTTCGGTGGAAATCACAF: GCTCTCACGCTCAATTACTTAR: ATGCTTAATTGACGACCTGTF: AATAAGTACTTGGCCGTGAAR: CGATTCAAGTAGGCAAAGAGF: ATATAAGGGGCCATTTTAGGR: ACGATAGAGGAGAAGGTTCC
ccmp2 199-202 60
ntcp18 194-198 60
ntcp28 178-183 58
ntcp26 175-178 60
IBcp5 242-246 55
IBcp8 195-197 55
IBcp10 199-201 55
7 chloroplast SSRs :
4 universal primers (Weising & Gardner, 1998
; Bryan, 1999)
3 specific primers developped at CIRAD / CEFE (Montpellier)
13 nuclear SSRs:
All developped at CIP
Results : chloroplastic SSRs
Geographical haplotypes distribution
H2
H3
H4
H6
H8
H13
H14
H23
H16
H1, H5, H7, H9, H10, H11, H12, H15, H17, H18, H19, H20, H21, H22, H24
MECU DO
PU
VC
BR
VECO
PE
EC
PANI
HN
GT
BO
PR
AR
JA
Results : chloroplastic SSRs
Geographical haplotypes distribution
H2
H3
H4
H6
H8
H13
H14
H23
H16
H1, H5, H7, H9, H10, H11, H12, H15, H17, H18, H19, H20, H21, H22, H24
MECU DO
PU
VC
BR
VECO
PE
EC
PA
CR
NI
HN
GT
BO
PR
AR
JA
Two distinct haplotypes groups separated by numerous mutation events
Each group with 2 or 3 major haplotypes from which derive the minor ones by one‐step mutation
Genetic structure and geographical distribution of haplotypes are highly correlated
Minimum spanning tree
Results : chloroplastic SSRs
Chloroplastic diversity structure
Results : nulcear SSRs
Nuclear diversity structure of new world sweet potatoes
K means clustering : this technique assigns individuals to a defined number of
genetic groups (hereafter K) in order to maximize the intergroup
variance (Arrigo,
2010).
No population genetic models!
101 individuals; 100 000 independent runs ; K from 1 to 10; Geographic composition of clusters
K=2Cluster 1: 40 NSWA / 5 CCACluster 2: 60 CCA / 6 NWSA
Results : nulcear SSRs
Nuclear diversity structure of new world sweet potatoes
K means clustering : this technique assigns individuals to a defined number of
genetic groups (hereafter K) in order to maximize the intergroup
variance (Arrigo,
2010).
No population genetic models!
101 individuals; 100 000 independent runs ; K from 1 to 10; Geographic composition of clusters
K>3
Cluster 1 : two regional groupsCluster 2 : different groups non- regional
Methode d’assignation?
Both phylogeographical signals are globally congruentPlant transfers and local recombination Few misidentifications
ASA CCAA
Cp group1 Cp group2
Results : nulcear SSRs
Comparison of cpSSRs and nuclear SSRs phylogeographical signals
Results : nulcear SSRs
MLGs and clonal lineages
115 samples without missing data
6 groups of 2 or 3 clones (14 accessions) / 101 MLGs
7 clonal lineages (17 accessions)
All geographically restricted
Higher diversity in CCAA region but not significant (p value =0.5) CA>CSA>ASA>CAI
Locus name
Allele number Private alleles Global ASA (49) CCAA (49) ASA CCAA
J315E 9 9 9 (8.61) 3
J522A 10 6 7 (6.51) 1J263 7 4 5 (4.65) 2Ib297 23 18 21 (19.11) 2 3J10A 10 9 9 (8.3) 1 2J206A 9 5 5 (5) 4J116A 15 14 15 (14.42) 2IbC5 12 10 11 (10.63) 1IbR16 8 7 8 (7.8) 3J130 4 4 4 (4)J1809E 8 6 7 (6.67) 1 1IbS11 12 10 11 (10.56) 1 2J544b 8 7 7 (6.96) 1total 135 109 119 13 17Mean 10.384 8.385 9.153 (8.654)
Locus nameAllele number ASA (49) CA(30) CAI(19) CSA(26)
total 109 109 83 98Mean per locus 8.385 8.385 6.385 7.538total (19) 89.22 100.86 83 92.4Mean per locus (19) 6.86 7.76 6.38 7.1
Genetic diversity and differentiation of the two groups
Results : nuclear SSRs
Indice de diversité?
Summary : results
Identication of two genepools corresponding to regional groups : the NWSA and the CCA genepools
Ancient divergence between the two genetic groups with chloroplast SSRs, predated domestication time
No significant difference in diversity between NWSA and CCA genepools
Incongruence betwwen cpSSRs structure, nuclear SSrs structure and geographical region : transfers of clones between the two groups and local recombination
Discussion
Scenario 1 : a single domestication
Divergence chloroplastic
predated domestication time
*Hybridisation with local wild pool* Early in diffusion process
(redomestication?)
No significant difference in diversity between NWSA and CCA genepools
*Opposite scenario?*Wild/cultivated geneflow?
Scenario 2 : Multiple domestication events in time and space
Discussion
Divergence chloroplastic
predated domesticaiton time :
At least two domestication events from* a single widely distributed,
geographically differentiated species*
different wild Ipomoea species
Numerous haplotypes in each group* multiple domestication events
in each region* wild/cultivated geneflow
(redomestication?)
Diffusion and diversifying processes
Discussion
Diversification processes
Clonal diversification (17%)Recombination / Sexual propagation (83%)
mixed clonal/sexual reproduction
DiffusionIsolation by distance patterns in both NWSA and CCA areas
Slow diffusion?Differences in pollen flows, social exchanges in both
regions?Geneflows between two genepools
Conclusion
Multiple domestication events, once in the lowlands of north‐ western South America, and once in the lowlands of Central
America
Importance of wild/cultivated geneflows. Re‐domestication?Protracted domestication?
High number of American landraces : social exchange of clones, somatic mutation, local recombination, and gene flow between wild
and cultivated forms
Usefull tools for rationalizing the conservation and use of germplasm
Necessity to study the genetic relationships between cultivated samples and wild relatives ancestors populations
Plant material
Wild relatives samples from various geograpahical area
The CIP collection (Dr Tay, Dr Rossel)2X I. trifida; wild and weedy I. batatas, I. triloba, I. tiliacea, I. leucantha, I. tabascana)
The Konarc collection (Dr Yakata)(4X / 6X I. trifida and 4X I. tiliacea )
The USDA collection (Dr Jarret)4X wild I. batatas, I. batatas var apiculataWild tetraploid I. batatas from Ecuador
Chloroplastic sequence IGSNuclear sequence ITS / Nuclear SSRs
Pays Nbre pop Effecti total
Colombie 5 38
Costa Rica 4 24
Cuba 2 4
Guatemala 9 40
Mexique 7 36Nicaragua 18 96
Venezuela 2 8
Total 47 246
?
Two distinct haplotypes groups separated by numerous mutation events
Each group with 2 or 3 major haplotypes from which derive the minor ones by one‐step mutation
Genetic structure and geographical distribution of haplotypes are highly correlated
Minimum spanning tree
Results : chloroplastic SSRs
Chloroplastic diversity structure
Roullier
Caroline
Thesis supervisor: Vincent Lebot ; Co‐supervisor: Doyle MC Key
Thanks for your attention