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?


• 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”?


• 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:


• 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?


• 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


40 %

Favorable Early drought

20%

Late drought

30%

Sub.

10%

Example of predicted frequencies of stress environments within a TPE


• 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


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

…


• 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


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


• 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?


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


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


• Easy, well-known:– Submergence tolerance– Bacterial blight resistance

• Difficult, not well understood– Drought tolerance

Examples of SE for specific requirements


Can anyone briefly summarize this unit?


• 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


• 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

Setting goals and identifying target environments Planning breeding programs for impact.

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