shifting goal posts for pre-breeding: tapping the wild’ · -crossing barriers between crops and...

Shifting goal posts for pre-breeding: tapping ‘the wild’ to adapt agricultural systems to climate change

Jaime Prohens Universitat Politècnica de València, Spain [email protected]

Climate change is here... to stay with us!

And agriculture will be one of the most affected sectors

Climate change will increase abiotic and biotic stresses in many areas

A new paradigm: tapping ‘the wild’ for adapting the crops to climate change

Tanksley and McCouch (1997)


Tanksley and McCouch (1997)

Multitude of stressing environments

Environments highly modified to avoid

stress

Adaptation to modifed environments

Not only bottleneck during domestication: -Many species never participated in domestication (geographical reasons or lack of domestication-prone characteristics)


Solanum chilense (tomato CWR)

Solanum incanum (eggplant CWR)

Oryza rufipogon (rice CWR)

Many wild species are tolerant to stress

Up to now wild relatives have been used in breeding of several crops, but this has been mostly restricted to specific traits (e.g., introgression of disease resistance), especially when looking at commercial varieties One extreme example is tomato

Up to now wild relatives have been used in breeding of several crops, but this has been mostly restricted to specific traits (e.g., introgression of disease resistance), especially when looking at commercial varieties We need to shift the goal posts!

DISEASE RESISTANCE

Up to now wild relatives have been used in breeding of several crops, but this has been mostly restricted to specific traits (e.g., introgression of disease resistance), especially when looking at commercial varieties We need to shift the goal posts!

CLIMATE CHANGE ADAPTATION

DISEASE RESISTANCE


How should we proceed for tapping ‘the wild’ for adaptation to climate change? -Conventional approach: Use one wild relative for a specific trait -New approach: Introgressiomics for climate change adaptation Mass scale development of multiple plant materials carrying introgressions of genomes from (mostly wild) related species into the genetic background of crops that may allow developing new cultivars adapted to climate change (and other breeding goals) Two possible strategies: -Focused: Strategies aimed at one specific target (drought, high temperatures, climate change adaptation) -Non-focused: Strategies aimed at the massive generation of introgression materials for present and future (unforeseen) needs (climate change adaptation, quality, new challenges)


This is not an easy task: -Many undesirable traits in wild relatives (chemical and physical defence traits, low yield, small fruit size) -Many wild plants are difficult to manage under “domesticated” conditions (germination, adequate development, flowering, fruiting, etc.) -Crossing barriers between crops and wild relatives are frequently present (secondary and tertiary genepools) -Long time needed for developing pre-bred materials readily and easily usable by breeders -Protocols are needed for screening for climate change traits -Crop wild relatives accessions are much less represented than crops in collections -Access to germplasm (CWR, but also crops) collections is perceived as increasingly difficult by breeders -Information on already existing pre-bred materials is often missing or unavailable -Often few available evaluation data on crop wild relatives -The taxonomy of crop wild relatives is sometimes (not to say frequently…) confusing

Steps for introgressiomics: 1) Identifying the target wild species: -Primary, secondary and tertiary genepools Based on diversity: -Genetic -Phenotypic -Evaluation -Environments -Origins -Genepools

Genepool concept (Harlan and de Wet, 1971)

Steps for introgressiomics: 1) Identifying the target wild species: -Primary, secondary and tertiary genepools Based on diversity: -Genetic -Phenotypic -Evaluation -Environments -Origins -Genepools

3 3 3

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Eggplant pre-breeding project

Steps for introgressiomics:

GP-1

GP-2

GP-3

Steps for introgressiomics: 2) Interspecific hybridization: -Barriers to hybridization (pre-zygotic, post-zygotic) -Techniques to overcome the interspecific hybridization: -Direction of the cross -Pollen mixture -Pollen irradiation -Differences among genotypes -Embryo rescue

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Primary genepool Secondary genepool Tertiary genepool

Fru

it s

et

(%)

S. melongena ( )

MEL1

MEL2

MEL3

MEL4

MEL5

MEL6

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Primary genepool Secondary genepool Tertiary genepool

Fru

it s

et

(%)

S. melongena ( )

MEL1

MEL2

MEL3

MEL4

MEL5

MEL6

Steps for introgressiomics: 2) Interspecific hybridization: -Barriers to hybridization (pre-zygotic, post-zygotic) -Techniques to overcome the interspecific hybridization: -Direction of the cross -Pollen mixture -Pollen irradiation -Differences among genotypes -Embryo rescue

Steps for introgressiomics: 3) Hybrids fertility: -Different number of chromosomes -Irregular pairing during meiosis -Use hybrid as maternal parent -Genome duplication to restore fertility

Interspecific hybrid S. melongena x S. anguivi

Sterile hybrid (2x)

Genome

duplication

(Partially) fertile hybrid (4x)

Crossing with

tetraploid crop

(4x)

BC1(4x)

Anther or

microspore

culture

BC1(2x)

Successive

backcrosses with

diploid crop (2x)

Crop materials with introgressions

Steps for introgressiomics: 4) Backcrossing -Usually fertility is restored during the backcross process -Some parts may not present recombination -Phenotypic selection (Focused strategy) -Marker assisted selection (Focused and non-focused strategies)

Steps for introgressiomics: 5) Development of introgression materials -Introgression lines collections:

Steps for introgressiomics: 5) Development of introgression materials -Chromosome substitution lines:

Steps for introgressiomics: 6) Combination of genes from different wild species

-Intercrossing of introgression lines from different wild species -MAGIC populations

Steps for introgressiomics: 6) Combination of genes from different wild species

-Intercrossing of introgression lines from different wild species -MAGIC populations

Successive backcrosses to cultivated (SSD)

Massive introgression for tapping “the wild”: Establishing programmes for the simultaneous introgression from many wild species This will facilitate having materials readily usable by breeders against climatic change challenges and unforeseen future needs. This will allow combining genes from different wild species to get crops adapted not only to disease resistance but to the broader objective of adapting to climate change.

Shifting global goal posts From the “Drill, baby, drill” goal post…

Coined by Michael Steele in 2008 for supporting increased drilling for petroleum and gas

Shifting global goal posts To the “Introgress, baby, introgress” goal post…

Coined on Dec. 2015 at a climate change-CWR workshop in BCN for supporting increased introgression from wild relatives for adaptation of crops to climate change

The Nirvana for breeders working on adaptation to climate change breeders’

Repository of pre-bred materials with introgressions from multiple wild species

Introgression lines species A (GP1)

Introgression lines species N (GP1)

…

Introgression lines species a (GP2)

Introgression lines species n (GP2)

…

Introgression materials species

a (GP3)

… Introgression materials species

n (GP3)

Multi-wild spp. introgression

materials

… Multi-wild spp.

introgression materials

Integrated -Phenotypic Database : -Evaluation -Pedigree -Genotypic

shifting goal posts for pre-breeding: tapping the wild’ · -crossing barriers between crops and...

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