Sess11 2 amele integrative breeding strategy for making climate-smart potato varieties for ssa
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Transcript of Sess11 2 amele integrative breeding strategy for making climate-smart potato varieties for ssa
Integrative Breeding Strategy for Making Climate-Smart Potato Varieties for SSA
9th APA Conference 30th June –o4 July, 2013
Outline
IntroductionUnderstanding downstream adoption challengesGermplasm appraisalExploring mechanisms and allelesStrategies Conclusion
Outline
IntroductionUnderstanding downstream adoption challengesGermplasm appraisalExploring mechanisms and allelesStrategies Conclusion
Introduction
Major African Field Crops Area Growth1994-2005 (source www.faostat.org)
80
100
120
140
160
180
200
220
1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Years
Sweet potatoesPotatoesBeans, dryYamsWheatCassavaRice, paddyMaize
Introduction
Cropping area expansion could come from
Replacing other crop
Double cropping with irrigation or bimodal RF
New areas including to non-optimal cultivation areas (warmers zones)
could be negatively affected by global warming linked to climate change
Rainfall is becoming more erratic, with longer and hotter dry spells and more intense rainstorms
Introduction
Climate change Modify or create new environments
Expose the crop to heat stress
Drought stress
Drought and heat stresses have drastic effects on potato
Tissue-specific Whole plant effects
Major environmental determinant crop facing now and in future
Introduction
Drought stress causes (cf. Monneveux et al. 2013)Decreased plant growthReduce light use efficiencyShorten crop growth cycleReduce number and size of tuber
Introduction
High temperature (Levy and Veilleux 2007)
Accelerates haulm growthPartitioning assimilates towards the haulmReducing photosynthesis and increase respirationInhibit tuber initiation and growthCauses tuber disordersShortening or abolishing tuber dormancyReduce tuber dry matterRaise level of tuber glycoalkaloid
Introduction
Climate model predicts changing climate conditions
A global yield reduction b/n 19-32 % estimated to occur due to climate change in first three decades of this century (Hijmans 2003)
Projected yield loss would be REDUCED BY 50% with adaptation measures such of USE OF TOLERANCE VARIETIES
This highlights the need to improve adaptation to climate variability in potato breeding efforts
Introduction
Options for breeders to deal with climate variability
Select directly tuber yield Select indirectly for physiological traits that improve yield under climate variabilityGenomics-based breeding to combine different genes or sets of genes that adapt crop growth to climate variability
But growers/farmers need varieties that Adapt well to climate variability at their specific conditions Together with an enhanced level of other desirable traits like consumer and commercial preferences, yield, and resistance to biotic stress
Introduction
To combine different option complexity of breeding challenges for each option need to be addressed
Drought and heat stresses seldom occur as sole stress factor at farmer fieldNot yearly eventPlants use different physiological mechanisms to adapt Market and consumption preference variation
This needs a breeding strategy that integrates knowledge from different disciplines
Social science, Plant breeding, Genomics, Physiology, Soil Science, Agronomy, Crop modeling
Objective To discuss the design of a breeding strategy that incorporates adaptation traits with the commercial and home use characteristics preferred by potato farmers
Outline
IntroductionUnderstanding downstream adoption challenges Germplasm appraisal Exploring mechanisms and alleles Strategies Conclusion
Understanding downstream adoption challenges
Breeding programs should be informed of dynamics of adoption challenges for heat or drought toleranceWhat drives the dynamics?Key processes in farmers variety and seed management and changes that are related to climate in variety use, perception and adaptation strategies Variation in trait preference and their modifications
Survey Trait elicitation through exposure to diversity
This understanding would help for client-oriented product development in a breeding program
Outline
IntroductionUnderstanding downstream adoption challenges Germplasm appraisal Exploring mechanisms and alleles Strategies Conclusion
Germplasm appraisal
Level and structure of diversity in available germplasm resource is imperative for harnessing variationRange of tools for a breeding program to uncover diversity
Farmer qualitative assessmentWhich variety grown by whom, where and why and their respective desirable and undesirable characteristics
Morphological phenotyping
Molecular genotypingSSR marker types proven effective in detecting variabilities in potato (Ghislan et al., 2004, 2009; Lung’aho et al., 2011)
Allows designing strategic crossing to mine transgressive segregants based on adapted and preferred germplasm at country or region & to harness the power of heterosis
Outline
IntroductionUnderstanding downstream adoption challenges for breeding climate-smart potatoesGermplasm appraisal for breeding climate-smart potatoesExploring mechanisms and alleles for breeding climate-smart potatoesStrategies for climate-smart potato breedingConclusion
Mechanisms and alleles
Adaptation to climate variability is not a single trait rather overall manifestation of the sum of different mechanisms operating in the plant
Trait/allele discovery
Which tolerance mechanism exist in the available germplasm?
Diploid speciesS. chacoenseS. bertheultiiS. microdontum
Tetraploid speciesAndean potatoes adapted to short day conditions possess DT
Heat tolerance
Mechanisms and alleles
Which tolerance mechanism would farmers prefer in their varieties? Which trait to use as selection objective?How, when and where to measure?
Traits need to be measured Managed stress environments (control and stressed)
Green housesField condition with
Standardized phenotyping protocols Multi-replication and multi-environment trials
Mechanism and alleles
Correlating phenotypic assessment with molecular markers
McCord et al. (2010) in tetraploid potato for internal heat necrosisAnuthakumari et al. (2012) in diploid potato for drought tolerance
Identified QTL
MAB by identifying markers tracking responsible genes
Outline
IntroductionUnderstanding downstream adoption challenges Germplasm appraisal Exploring mechanisms and alleles Strategies Conclusion
Integrative breeding design adapted from Asfaw (2011)
Strategies
Firm understanding the complexities of targetingHow diverse and dynamic are farmer environment and preferences and how to address them?Farmers preference for other traits to integrate with drought or heat toleranceListening to farmers and considering them as potential partners in variety development
Stakeholder participation Knowledge of climate and soil based targeting
Use of models that incorporate local climatic conditions and crop management for informed decision
Strategies
Defining expectations and goals within each target
If yield is 5 tons ha-1 under DT and HT stressShould not worry of “yield potential” of 30 or 40 tons ha-1
Instead think of how to get 10 tons ha-1 under real world condtion as “target yield’’Look for selection traits contributing to attain “target yield”
Strategies
To attain “target yield” Defining genetic structure of varieties
Intra-genotypic diversityIncrease frequency of genes for DT and HT
Intra-varietal Increasing choice for growers
Strategies
To determine genetic structure of varieties
Smart crossing plan
Suitable selection method
Strategies
Smart crossing plan Since autotetraploid potato breeding is complex due to
its tetrasomic inheritancehigh heterozygosis and asexual propagation,medium to low h2 estimates for DT and HT traits
Need for multiple traits simultaneous selection
traditional breeding methods (complementing parental traits or back cross) may not be effective.
RECURRENT SELECTION with PROGENY TESTING toidentify SUPERIOR PROGENITORS is most effectiveand practical to manage the complex potato genetic features.
Strategies
Smart crossing plan Narrow vs wideNarrow cross
Elite x elite cultivar crossIn crossing scheme,
first identify SUPERIOR CLONESPROGENY TEST to identify those with a high GCA, i.e., GOOD BREEDING VALUE and then, use them as progenitors to cross with several female clones
Wide crossWild/cultivated diploid speciesSexual polyploidization
Screening for 2n pollens and cross back with tetraploids
Strategies
Selection methodsGenerate series of clones and evaluate under target environment to know what works where to attain the “target yield”
Multiple environment testing and farmer participatory breedingGenomic selection
Use of high molecular DNA marker information to predict performance
Outline
IntroductionUnderstanding downstream adoption challenges for breeding climate-smart potatoesGermplasm appraisal for breeding climate-smart potatoesExploring mechanisms and alleles for breeding climate-smart potatoesStrategies for climate-smart potato breedingConclusion
Conclusion
Breeding strategy for climate-smart potatoes
Understand different aspects of production and productivity and should integrate at different stages of the cycle of breeding
Firm understanding of target environment Biophysical and socio-economic
Define expectations and goals within each target Smart crossing to combine physiological traits with consumption and market preference traitsGenerate and introduce diversity to farmers to choose from
Acknowledgment
CIPAPA
A. Asfaw, M. Bonierbale M.A. Khan
International Potato Center