DISTINCTNESS, UNIFORMITY and STABILITY TEST (DUST)

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DISTINCTNESS, UNIFORMITY and STABILITY TEST (DUST)

• Renato A. Reaño
• Associate Scientist
• TTC-GRC, IRRI

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What is DUS Testing

• A test done before a protection is granted in
  respect of a new variety based on Article 7 of
  the UPOV Convention.
• The Variety must be
• Distinct
• Uniform
• Stable

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Why DUS Testing

• To generate basic description of the candidate
  variety using relevant characteristics
• To compare the candidate variety with the
  reference or Example variety
• To differentiate the candidate variety from
  Varieties of Common Knowledge

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Requirements for Conducting DUS Tests
Before Performing the DUS Test there should be

• A Test Guidelines prepared by leading crop
  experts as a basis for testing and should include
  the following
• Subject of the Guidelines
• Plant materials required for Testing
• Methods of Examination
• Assessment of Distinctness, Uniformity and
  Stability

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Requirements for Conducting DUS Tests

• 5. Grouping of Varieties and Organization of the
  Growing Cycle
• 6. Introduction to the Table of Characteristics
• 7. Table of characteristics
• 8. Explanation to the Table of Characteristics
• 9. Literatures and other references
• 10. Technical Questionnaire

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The Table of Characters in the Guidelines

• The Table of Characteristics includes
• Set of Characters to be observed
• States of Expression of these characters
• Types of Expression
• Special Characteristics
• New Types of Characteristics
• Functional Categories of Characteristics

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The Table of Characters in the Guidelines

• The Expression of a characteristic should
• Result from a given genotype or combinations of
  genotypes
• Be sufficiently consistent and repeatable in a
  particular environment
• Exhibit sufficient variation between varieties to
  be able to establish distinctness
• Be capable of precise definition and recognition
• Allow uniformity requirements to be fulfilled
• Allow stability requirement to be fulfilled

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The Table of Characters in the Guidelines

• Types of Expression of such Characters
• Qualitative- characters that are visually
  observed
• Ex. Male sterility (present or absent)
• Quantitative- characters that are measured
• Ex. Culm length Leaf length
• Pseudo-Qualitative-the range of expression is at
  least partly continuous but may vary in one
  dimension.
• Ex. Leaf Color (1) green (2) yellow green (3)
  yellow
• The expression of such depends on the genetic
  control of the characteristics

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The Table of Characters in the Guidelines

• Economic value of characters
• No requirement for a characteristic to have any
  intrinsic commercial value or merit, but such
  characteristic can be use if and when appropriate
• Characteristics of economic value like yield
  quality those important for breeding objectives
  may not always appropriate for DUS

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The Technical Questionnaire in the Guidelines

• Content of the Technical Questionnaire
• Subject
• Applicant
• Proposed Denomination and Breeders Reference
• Characteristics of the variety to be indicated
• Similar varieties and variation from these
  varieties
• Additional Information etc.

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Functional Categorization of Characteristics

• Standard Test Guidelines
• Asterisked Characteristics- suggested by UPOV for
  Harmonization
• Grouping Characteristics- by characters to
  facilitate comparison with reference varieties
• Additional Characteristics- Special traits that
  may be added to those listed in the TG

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Grouping Characteristics

• Function
• Characteristics in which the documented state of
  expression even when produced at different
  location can be used to
• To select varieties of common knowledge to be
  included in the test for distinctness
• To organize the growing trial so that similar
  varieties are grouped together

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EXAMINING DISTINCTNESS

• Requirements
• Varieties of Common Knowledge
• Clearly Distinguishing as New Variety
• Interpretation of Observation for the Assessment
  of Distinctness (with or without Statistical
  Methods)

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EXAMINING DISTINCTNESS

• A Variety must be clearly distinguishable from
  any variety whose existence is a matter of
  Common Knowledge
• To establish Common Knowledge one should consider
  specific aspects such as
• commercialization of propagation or harvesting
  material of a variety or publishing a detailed
  description
• Filing of an application for grant of breeders
  right for entering in an official register of
  varieties
• Existence of living plant material in publicly
  accessible plant collection

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EXAMINING DISTINCTNESS

• Criteria for Distinctness using Characteristics
• A Variety is considered to be clearly
  distinguishable if the difference in
  characteristics is
• Consistent if repeatable e.g. planting in two
  different season
• Clear differences on characteristics as observed
  or measured

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EXAMINING UNIFORMITY

• Determination of Off-types by Visual Assessment
• Determination of Off-types Using Measurements
• Statistical Basis for Setting Number of Off-types
• Unrelated and Very Atypical Plants

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EXAMINING UNIFORMITY

• UPOV Convention
• Article 6 of the 1961/72 and 1978 Acts A Variety
  is deemed uniform if it is sufficiently
  homogenous, having regard to the particular
  features of its sexual reproduction or vegetative
  propagation
• Article 8 of the 1991 Act A variety is uniform
  if subject to the variation that may be expected
  from the particular features of its propagation,
  it is sufficiently uniform in its relevant
  characteristics
• Relevant Characteristics at least those used in
  the examination of DUS or included in the variety
  description established et the date of the grant
  of protection of that variety.

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EXAMINING UNIFORMITY

• The uniformity requirement for a variety will be
  different for
• Vegetatively propagated variety
• Truly self pollinated variety
• Mainly self-pollinated variety
• Inbred line of hybrid variety
• Cross pollinated variety
• Hybrid varieties

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EXAMINING UNIFORMITY

• Self-Pollinated and vegetatively propagated
  Varieties
• As all the plants of the variety are very similar
  uniformity is assessed by the number of
  dissimilar plants (off-types) that occur.
• A plant is considered off-type if it can be
  clearly distinguished from the variety of
  expression of any characteristic that is used in
  testing of distinctness.
• Off-type can be determined by
• Visual assessment
• Using measurement

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EXAMINING UNIFORMITY

• Statistical Basis for Setting number of Off-types
• The individual Test Guidelines fix for each crop
• Population standard (percentage of off types to
  be accepted if all individuals of the variety
  could be examined)
• The acceptance probability (probability of
  correctly accepting that a variety is uniform)
• According to the size of the sample examined,
  Statistical Tables give the maximum number of off
  types tolerated.
• Ex. 300 plants 6 off-types is acceptable
• 500 plants 9 off-types is acceptable
• 1,500 plants 15 off-types is acceptable

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EXAMINING UNIFORMITY

• Statistical Basis for Setting number of Off-types
• For mainly self-pollinated varieties and inbred
  lines of hybrid varieties are generally treated
  as self-pollinated for testing. In such case, the
  same approach (the off-types determination) is
  applied but a higher tolerance of off-types is
  accepted.
• For cross-pollinated varieties which exhibits
  wider variation within variety it is more
  difficult to determine off-types. Relative
  tolerance limit are set by comparison with
  comparable varieties or types already known but
  should not be significantly less uniform than the
  comparable variety.
• Very atypical plants are not considered off-types
  and may be disregarded

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EXAMINING STABILITY

• UPOV requires that a variety must be stable in
  its essential characteristics, and must remain
  true to its description after repeated
  reproduction or propagation or where the breeder
  has defined a particular cycle of reproduction or
  multiplication at the end of each cycle
• A variety shall be deemed stable if its relevant
  or Essential Characteristics remained unchanged
  after repeated propagation or in the case of a
  particular cycle of propagation, at the end of
  each cycle.
• Relevant characteristics include at least all
  characteristics used for examination or included
  in the variety description established at the
  date of the grant
• All obvious characteristics may be considered
  irrespective of whether they appear or not in the
  Test Guidelines

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EXAMINING STABILITY

• In General
• Special Test of Stability are not performed
• Where appropriate, stability may be tested by
  growing a further generation from new stock to
  ensure that it exhibits the same characteristics
  as those shown in the previous materials
• When a submitted sample has been shown to be
  uniform, the material can also be considered
  stable
• If a variety is not stable, material produced
  will not conform the characteristics of the
  variety and the breeders right may be cancelled

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THANK YOU