Setting goals and identifying target environments Planning breeding programs for impact.
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Transcript of Setting goals and identifying target environments Planning breeding programs for impact.
Setting goals and
identifying target environments
Planning breeding programs for impact
IRRI: Planning breeding Programs for Impact
• Generally, to produce a cultivar that is superior to farmers’ varieties in a particular target population of environments
• Specific objectives– Replace a specific cultivar– Develop a new product– Change a single trait
What is the general objective of a breeding program?
IRRI: Planning breeding Programs for Impact
• Higher yields– Under high-inputs?– Under lower inputs (farmer management)?– Under favorable climate?– Over all possible climates?
• Quality
• Experiment station vs. on-farm performance
When is a cultivar superior”?
IRRI: Planning breeding Programs for Impact
• Will be grown by the farmer because it performs better (or obtains a better price) than the existing cultivar
• Under management practices currently used or available to the farmer
Economic benefit
A superior cultivar is one that:
IRRI: Planning breeding Programs for Impact
• Be in close touch with the farmers
• Know the contraints in the target environment
• Know the market requirements
• Know the plant traits considered important by the farmers
What makes a successful breeder?
IRRI: Planning breeding Programs for Impact
• TPE = variable set of future production environments (Cooper and Byth, 1996)
– Variability among fields/farms– Variability over seasons
• Results in genotype by environment interaction (GEI)
• Objective should be to develop a cultivar superior to the farmers’ cultivar in most seasons and most fields
Target population of environments: definition
IRRI: Planning breeding Programs for Impact
40 %
Favorable Early drought
20%
Late drought
30%
Sub.
10%
Example of predicted frequencies of stress environments within a TPE
IRRI: Planning breeding Programs for Impact
• Geographical region
• Ecosystem
• Subdivide if necessary based on– Environmental parameters– Currently used cultivars– Analyses of multi-environment trials– Breeder and farmer knowledge
Defining the target environment
IRRI: Planning breeding Programs for Impact
Exercise: Criteria for group environments into TPE
Name 2 examples for each column:
Agro-ecological factors Socio-economic factorskind of soil
irrigated vs. drought
biotic problems
water source (rainfall or irrigation)
…
market price
presence of seed producers
rich/poor farmer
etnic groups that prefer different kinds of rice
…
IRRI: Planning breeding Programs for Impact
• Cluster or principal components analysis on genotype means or genotype x environment interaction effects, also known as pattern analysis
• Tests of fixed environmental effects
• Examination of correlations of cultivar means across sites
Statistical analyses of multi-environment trials to define the TPE
IRRI: Planning breeding Programs for Impact
Pusa Patna Gerua Bhaw Chin Cutt Mott Nlak Tita Shallow
Maso 0.36 0.51 0.31 0.21 -0.08 -0.10 0.24 0.64 0.35 0.84
Pusa 0.41 0.19 0.21 0.01 0.18 0.29 0.26 0.46 0.67
Patna 0.24 0.06 0.10 0.14 0.41 0.34 0.37 0.73
Gerua 0.15 -0.31 -0.05 0.12 0.33 0.18 0.57
Bhaw 0.01 0.06 -0.01 0.27 0.17 0.24
Chin 0.42 0.18 -0.25 0.32 -0.10
Cutt 0.29 -0.14 0.35 0.03
Nlak 0.12 0.38 0.36
Deep 0.48
Correlations among line means in Eastern Indian OYT - 2002
IRRI: Planning breeding Programs for Impact
Pusa Patna Gerua Bhaw Chin Cutt Mott Nlak Tita Shallow
Maso 0.36 0.51 0.31 0.21 -0.08 -0.10 0.24 0.64 0.35 0.84
Pusa 0.41 0.19 0.21 0.01 0.18 0.29 0.26 0.46 0.67
Patna 0.24 0.06 0.10 0.14 0.41 0.34 0.37 0.73
Gerua 0.15 -0.31 -0.05 0.12 0.33 0.18 0.57
Bhaw 0.01 0.06 -0.01 0.27 0.17 0.24
Chin 0.42 0.18 -0.25 0.32 -0.10
Cutt 0.29 -0.14 0.35 0.03
Nlak 0.12 0.38 0.36
Deep 0.48
Correlations among line means in Eastern Indian OYT - 2002
IRRI: Planning breeding Programs for Impact
• Shallow sites tend to be correlated
• Deeper sites (Cuttack and Chinsurah) are correlated
• Correlation between shallow and deep sites is poor
What can we conclude from inspection of correlations?
IRRI: Planning breeding Programs for Impact
Determining the selection environment (SE)
• The chosen SE should maximize the power of the nursery to predict performance in the TE
• May need more than one SE if TE is highly variable
• SE is not equal to TE, so the relationship must be monitored
IRRI: Planning breeding Programs for Impact
1. The SE must predict performance in at least some seasons and locations within the TPE - genetic correlation (rG) between TPE and SE must be high.
2. The SE must clearly and repeatably differentiate among genotypes under evaluation - heritability (H) for screening in the SE must be high.
3. The SE must permit relatively large numbers of genotypes to be screened at low cost - the SE must permit a high selection intensity (i) to be achieved.
Requirements for the SE
IRRI: Planning breeding Programs for Impact
• Easy, well-known:– Submergence tolerance– Bacterial blight resistance
• Difficult, not well understood– Drought tolerance
Examples of SE for specific requirements
IRRI: Planning breeding Programs for Impact
Can anyone briefly summarize this unit?
IRRI: Planning breeding Programs for Impact
• Focus group discussions: Farmers are asked about positive and negative features of present cultivars
• Preference analysis: Farmers are asked to rate experimental lines in a trial
• In some cases, future farmer preferences must be predicted (i.e., they may not be aware of new options/technologies)
Breeding goals: 1. Farmers preferences
IRRI: Planning breeding Programs for Impact
• Deficiencies of currently grown varieties
• List of required traits with parents that are sources of these traits
• Ranking of traits in terms of importance and ease of improvement
• Strategy for selecting for generating populations and selection for the desired traits
Breeding goals: 2. Specific traits and strategies