The expert consultation on the use of crop wild relatives for pre-breeding in potato was a workshop organized by the Global Crop Diversity Trust in collaboration with CIP and took place from the 22nd – 24th of February 2012.
Transcript of "Elsa Camadro's presentation in the framework of the expert consultation on the use of crop wild relatives for pre-breeding in potato"
Reproductive behavior and germplasm classification of wild potato populations: relevance in germplasm conservation and breeding Elsa L. Camadro Laboratorio de Genética Instituto Nacional de Tecnología Agropecuaria Universidad Nacional de Mar del Plata Consejo Nacional de Investigaciones Científicas y Técnicas Argentina
Premises of the presentationThe knowledge of the reproductive biology of wild potatoes and its consequences in the functioning of natural populations is of utmost importance to understand the morphological and molecular variability encountered in the groupThe choice of genetic materials and methodological approches used to classify wild germplasm has direct consequences in:population samplingex situ conservation of germplasm (gene frequencies)breeding
Plant classifications in the XXth and XXIth centuries Artificial binomial system developed by von Linneus in the XVIIIth based in the use of “holotypes” (single physical examples or illustrations of organisms known to have been used when the species or lower-ranked taxon were formally described)with the more recent aid of biochemical and molecular tools
Species Concept based on reproductive relations morphological phenotypes and morphological discontinuities (uni- and biparental organisms) (biparental organisms) Biological species Taxonomic speciesThe Biological species can coincide (or not) with the Taxonomic species If the two uses of the term are not distinguished, the confusion is perpetuated
Genus Solanum ~1,000-2,000 species (herbs or shrubs) ≥110 ≤235 wild and cultivated tuber- bearing speciesSection Petota (Tuberarium)Subsection Potatoe (Hyperbasarthrum) Spooner y Hijmans 2001
Species concept in subsection Hyperbasarthrum (actually Potatoe) Early XXth centuryNarrow taxonomic unit, with little phenotypic variability (Bitter, Juzepczuk, Bukasov) Mid XXth century Profound revision of tuber-bearing species due to great phenotypic variability encountered (Hawkes 1963) Late XXth and early XXIth centuries New revisions (Hawkes 1990; Spooner´s group)
Taxonomic revisions (last 20 years) Mainly based on: Herbarium materials and samples of living plantas, with more recent application of molecular tools toaccessions with previously assigned specific categories No. of tuber-bearing species: Hawkes (1990): 227 Spooner and Hijmans (2001): 203 Spooner and Salas (2006): 189 Spooner (2009): converging around 110
Main features of wild and cultivated potatoesForm polyploid series (2n=2x, 3x, 4x, 5x, 6x; x=12)Can reproduce: •sexually (by seeds) •asexually (by stolons and tubers)
Posses one multiallelic S-locus conferring gametophytic SI diploids obligate outcrossers polyploids -allogamous (can self-pollinate by competitive S-alleles interaction) -autogamous (self-pollinate) S7 S1 S2 S4 1st Third S1 S2 S1 S2Self-compatible Self-incompatible
-continues- Present scarce genome differentiation All species share a common genome (A), and four derived genomes (B, C, D, E) Under genetic control, can produce: •2n pollen and/or 2n eggs Gametophytes with sporophytic chromosome numbers •Haploids Sporophytes with gametophytic chromosome numbers In nature, are isolated by external and/or internal hybridization barriers The internal barriers are genetically controlled and can be incomplete Camadro et al. 2004
General ObservationsThe breeding system provides for: maintenance of superior genotypes in stable environments evolution of new genotypic combinations in changing environments overlapping of generations (parental, hybrids, BCs) The morphological phenotypic differences among taxa are not of great magnitudeHybridization and gene flow within and between ploidy levels and generations produce very complex patterns of morphological variation
Potato accessions Samples of natural populations ex situ conserved as:original collections or multiplications of original collections Purposes Conservation of samples of natural variability of a species and of genes for breeding and other applied purposes P1 P2 P3 xxxx xx x x x x x x xxxx xx x x x x x x xxxx x x x x x x x x x x x x x Passport information for potato accessions:Collection date, locality, latitude, longitude and altitude a.s.l.
Information unavaible or lackingIn situ samplingNo. and spatial distribution of sampled plants at collection siteNo. harvested fruits or tubers/sampled plantNo. sampled plants/populationHow the seed sample (accession) is formedIf seedlings are sampled, their spatial distribution Are accessions representative samples of the natural genetic variability at the sampling site?Ex situ seed/tuber multiplicationEffective no. of parental plantsNo. harvested fruits or tubers/plantNo. harvested seeds/fruitHow the seed sample (accession) is formed Discarding unwanted contamination/crossing Has genetic drift being avoided?
Current classification approaches are based on the Taxonomic species conceptnot taken into consideration:Natural populations of sexual reproducing allogamous plants are expected to exhibit morphological and genetic variation (one plant=one genotype)Morphological and genetic variation can occur within and between populations of the same taxonomic speciesNatural populations can consist of uni- and biparental plants, with overlapping of generationsBreeding relations within and among spontaneous populations provide for hybridization and introgression among ploidy levels and generations, creating complex patterns of variation
Prevention of fertilization due to abnormalities in Pollen tube growth Pollen germination Estigma 1/31st Third 1er Tercio 2do2/3 Tercio 3 3/3 er Tercio ovary Gametophytic SI Cross Incompatibility Bilateral (CI) Unilateral or Bilateral Camadro y Peloquin 1981
Inviability of embryo and/or endosperm in the F1 hybrid seed due to abnormal embryo and/or endosperm development/abortionHybrid sterility (principally male sterility)Inviability or weakness of F2 and advanced segregating generations Camadro et al. 2004
Inviability of F1 hybrid seed endosperm Genetic causes (EBN)Abortion Endosperm abortion embryo Genetic causes (cannot be circumvented)
2x 1NBE cmm x 2x 1NBE cmm, 15 DDP 4x 2NBE acl x 2x 1NBE cmm, 9 DDP 2x 2NBE grl x 4x 4NBE grl, 9 DDP 4x 2NBE acl x 2x 2NBE grl, 11DDP Masuelli y Camadro (1997)
Male sterility and cytological abnormalities Interspecific artificial hybrids Diploids: S. tuberosum (tbr) x S. chacoense (chc), tbr x S.gourlayi (grl), tbr x S. spegazzinii (spg) (Santini et al. 2000) Tetraploids: grl x tbr and tbr x grl (Larrosa et al. 2005) Spontaneous hybrids grl-S. infundibuliforme (Larrosa et al. 2005)
Species of hybrid origin S. ruiz-lealli(Raimondi et al. 2000; Marfil et al. 2009) “Species” S. okadae(Camadro et al. 2007; Bottini et al. 2008) S. chacoense(Bottini et al. 2009; Larrosa et al. 2010; Poulsen et al. 2011)
“tetrad” type sterilitytbr x grl tbr x chc Interspecific 2x (artificial) F1 hybrids Santini et al. (2000)
N S. x ruiz-lealli2x species of hybrid origin) E E Raimondi et al. 2005
polenFertile and sterile pollen in spontaneous and artificial hybrids and populations with specific category Larrosa et al. 2010
Tetrad stage in spontaneous and artificial hybrids and populations with specific category Larrosa et al. 2010
P MI MII AIMII AI AII MIIAII AII TI TII Meiosis in spontaneous and artificial hybrids and populations with specific category Larrosa et al. 2010
Bolivia Argentina a ba S. okadae (2x) Accessions from Germplasm Potato Bank, INTA, Argentina Argentina Camadro et al. 2007
S. kurtzianum (2x)OKA 872 OKA 5026 OKA 6003OKA 6144 OKA 4505 OKA 6125 Accessions from Germplasm Potato Bank, INTA, Argentina Bedogni & Camadro 2009
Evaluation of morphological characters(quanti- and qualitative) and molecular markers (SSR) Accessions from: S. kurtzianum, Catamarca, La Rioja and Mendoza Sympatric “species”: •S. chacoense (chc), •S. spegazzinii (spg) “outliers” •S. oplocense (opl) y S. maglia (mag) Genetic distances among sympatric accessions with different specific statuts was smaller than among allopatric accessions with the same specific status Bedogni & Camadro 2009
Accessions of S. kurtzianum (ktz) S. chacoense (chc), S. spegazzinii (spg), S. maglia (mag) and S. oplocense (opl)oplC OKA 6147C OL 4943C OKA 6144M SCl 4505R OKA 6003R OKA 6125M ClM 872C OKA 6141C OKA 5026M magR OKA 6113C OKA 6107 0.00 0.22 0.45 0.67 0.90 SM Coefficient = chc = ktz = spg C=Catamarca, M=Mendoza, R=La Rioja Nuclear SSR markers Bedogni & Camadro 2009
UPGMA phenogram of accessions of S. kurtzianum (ktz),S. chacoense (chc), S. spegazzinii (spg), S. maglia (mag) and S. tuberosum ssp. tuberosum (tbr) M ClM 872 M mag M SCl 4505 R OKA 6125 C OKA 6144 R OKA 6003 R OKA 6113 tbr C OKA 6147 C OKA 6107 C OKA 6141 C OL 4943 C OKA 5026 0.00 1.60 3.21 4.81 6.42 Euclidean Distance Coefficient = chc = ktz = spg C=Catamarca , M= Mendoza, R= La Rioja Morphological Qualitative Traits Bedogni & Camadro 2009
UPGMA phenogram of accesssions of S. kurtzianum (ktz),S. chacoense (chc), S. spegazzinii (spg), S. maglia (mag) and S. tuberosum ssp. tuberosum (tbr) tbr C OKA 6107 C OKA 6147 M mag R OKA 6003 C OKA 5026 C OL 4943 M SCl 4505 C OKA 6144 R OKA 6113 R OKA 6125 M ClM 872 C OKA 6141 0.00 2.02 4.05 6.07 8.09 Euclidian Distance Coefficient Morphological Quantitative Traits Caracteres Morfológicos Cuantitativos Bedogni & Camadro 2009
To fully exploit in breeding the genetic variability of the wild potato germplasmScreen various accessions (if available),(particularly if the “species” has wide geographic or environmental distribution)Take into consideration: macro- and micro-environments of the originally sampled sites type of original samples (botanical seed, seedlings, tubers)Screen 15-25 plants/accession for allogamous “species” (one plant= one genotype) and ≥10 plants for autogamous “species” (there could be homozygosity for different gene combinations)Use incomplete diallele crossing designs (keeping tract of individual genotypic combinations. Breeding barriers can be incomplete, hybrids are very frequent and there are nuclear-cytoplasmic interactions)Conclude with respect to a given accession, not a species (do not extrapolate results).