Setting goals and

1
Planning breeding programs for impact

• Setting goals and
• identifying target environments

2
What is the general objective of a breeding
program?

• 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

3
When is a cultivar superior?

• Higher yields
• Under high-inputs?
• Under lower inputs (farmer management)?
• Under favorable climate?
• Over all possible climates?
• Quality
• Experiment station vs. on-farm performance

4
A superior cultivar is one that

• 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
5
What makes a successful breeder?

• 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

6
Target population of environments definition

• 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

7
Example of predicted frequencies of stress
environments within a TPE
Favorable
Early drought
Late drought
Sub.
40
20
30
10
8
Defining the target environment

• Geographical region
• Ecosystem
• Subdivide if necessary based on
• Environmental parameters
• Currently used cultivars
• Analyses of multi-environment trials
• Breeder and farmer knowledge

9
Exercise Criteria for group environments into
TPE

• ?Name 2 examples for each column

10
Statistical analyses of multi-environment trials
to define the TPE

• 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

11
Correlations among line means in Eastern Indian
OYT - 2002
12
Correlations among line means in Eastern Indian
OYT - 2002
13
What can we conclude from inspection of
correlations?

• Shallow sites tend to be correlated
• Deeper sites (Cuttack and Chinsurah) are
  correlated
• Correlation between shallow and deep sites is
  poor

14
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

15
Requirements for the SE

• 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.
• The SE must clearly and repeatably differentiate
  among genotypes under evaluation - heritability
  (H) for screening in the SE must be high.
• 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.

16
Examples of SE for specific requirements

• Easy, well-known
• Submergence tolerance
• Bacterial blight resistance
• Difficult, not well understood
• Drought tolerance

17
Can anyone briefly summarize this unit?
18
Breeding goals 1. Farmers preferences

• 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)

19
Breeding goals 2. Specific traits and
strategies

• 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