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