Part 4. Test Growing

• Examining DUS
• Choice of comparators
• Examining distinctness
• Examining uniformity
• Examining stability

Section 37(1)(a) of the PBR Act sets out the situations in which test growing of a new variety is necessary.  This requires the new variety to be examined for Distinctness, Uniformity and Stability (DUS) against its most similar variety or varieties of common knowledge. Where a test growing trial is conducted in Australia it must conform to the usual scientific standards and follow the UPOV Test Guidelines (TG) where they are available. Test Guidelines for most plant genera are available at http://www.upov.int/test_guidelines/en/.

Examining DUS

The purpose of test growing is to establish that the new plant variety is distinct from all other varieties of common knowledge (VCK), is sufficiently uniform in its relevant characteristics, and that these characteristics remain stable after repeated propagation or, in the case of a particular cycle of propagation, at the end of each such cycle.

The broad aims, intent and principles of DUS examinations are explained by TG/1 - General Introduction to DUS

The remaining TGs set out the expected test growing requirements of DUS testing for particular genera. Strict adherence in all aspects of the TGs is not always required. For example, it is open for the examiner to decide that strict adherence is not required where the general requirements of the TG are outside those used in the Australian breeder testing system (e.g. supply of planting material; number of growing cycles, etc) or where the requirements do not appropriately apply to the particular circumstances of the application.

Where UPOV TGs don’t exist, National Descriptors (NDs) must be used by QPs. Examiners can allow considerable flexibility to amend and improve NDs using information and experience gained from the trialling of the candidate varieties concerned.

When no TG or ND exists, the QP will work with the PBR office to develop a draft ND. NDs are developed according to the UPOV’s guidance in relation to characteristics, states of expression etc.

A physical examination of the comparative growing trial will be conducted by the PBR Office (unless notified otherwise) at a time when the trial displays the major differences between the candidate variety and the most similar VCK.

Further information is provided in UPOV TGP/8 (Trial Design and Techniques used in DUS test)

Choice of comparators

It is the role of the QP to choose the comparator varieties to be grown with the candidate variety in the comparative growing trial. As a minimum the comparator varieties must include the most similar VCK to the candidate. However, other varieties may also be included. Such as parental lines or example varieties that may be useful references during the examination.  For a candidate variety to be distinct it is necessary to establish that it is clearly distinguishable from any other variety whose existence is a matter of common knowledge at the time of filing of the application.

There is no comprehensive definition for VCK. However, VCK include:

• a variety cultivated and marketed
• an application for PBR or entering on an official register in any country
• a published description of a variety
• existence of living plant material in publicly accessible plant collections

A variety of common knowledge is not limited by national or geographical borders, it is a worldwide test.

Whilst it is necessary to consider distinctness in relation to all VCK, a systematic individual comparison is not required. Where a candidate variety is clearly distinguishable from a group of varieties (for example by being in a different flower colour group) it is not necessary for a systematic individual comparison with the varieties in that other group (or groups). The QP uses appropriate grouping characteristics to narrow down the choice of comparators so the growing trial includes at least the most similar VCK.

Therefore, where a candidate variety can be distinguished in a reliable way from groups of varieties of common knowledge, it is not necessary to include those groups in the growing trial with the respective candidate variety. However, where there is little possibility of clearly distinguishing them from the candidate variety, then these varieties should be compared with the candidate variety in a growing trial. This emphasises the importance of harmonization of variety descriptions in minimising the workload of the DUS examiner. Once a candidate variety is clearly distinguished from the most similar VCK, logic dictates that it is also distinct from all other VCK.

It is the sole responsibility of the QP to choose the comparators for inclusion in the test growing trial (or when an overseas test report is used to prepare the detailed description, to choose and include relevant comparator varieties in that description).  The QP uses a process of elimination to identify the most similar VCK for the comparative trial using a range of factors including, but not limited to:

• UPOV grouping characteristics;
• Parental/source material;
• List of PBR varieties;
• List of other existing varieties;
• Variety information from the PBR office (eg extracted from the IVDS  or the Plant Varieties Journal);
• Personal experience with the species;
• Other published information.

If there are no other varieties in cultivation, QPs should compare their new varieties with the parental/source material and/or similar ecotypes.

The QP is then required to justify their selection of most similar VCK by publishing the relevant information in the Grouping Characteristics and/or the Varieties Subsequently Excluded section(s) of the Detailed Description.  

The PBR examiner ensures that the detailed description (of the candidate and VCK) is consistent with the states of expression cited in the Choice of Comparators section.  Any inconsistencies/deficiencies are identified, marked and returned to the QP for consideration and rectification before publication. Where it is necessary, the PBR examiner can require a further test growing which includes specified comparators.

Examining distinctness

When examining a variety for distinctness the QP and applicant must nominate one or more characteristics that clearly differentiate it from the most similar VCK.  In other words clear differences must be present between the new variety and all varieties whose existence is a matter of common knowledge at the priority date.

Two methods are used to observe distinctness of plant varieties:

1. Visual Observation (V) and,
2. Measurement (M).

The type of expression of the relevant characteristic will help determine the observation method used to differentiate a variety from its comparators. These can be broken down into three types:

i. Qualitative (QL) characteristics: qualitative characteristics are, in general, observed visually;

ii. Quantitative (QN) characteristics: quantitative characteristics can be measured or visually observed; and

iii. Pseudo-qualitative (PQ) characteristics: pseudo-qualitative characteristics are, in general, observed visually.

Further information is provided in UPOV TGP/9 (Examining Distinctness)

Examining uniformity

The level of variation in the expression of relevant characteristics within varieties is the basis for the assessment of uniformity. This variation has both genetic components and environmental components (e.g. temperature, light, soil etc.). The level of variation due to the environment depends on the interaction between individual plants and the environment and is influenced by the type of expression of the characteristic. The genetic component is mainly influenced by the features of propagation.

As a general rule, the states of expression of qualitative characteristics are not influenced by the environment. As opposed to quantitative and pseudo-qualitative characteristics, the level of variation due to the environment can differ from species to species and from characteristic to characteristic.

Two methods are used to determine uniformity they are:

1. “Off type” count method (QL), and visually assessed
2. Relative variance method (QN+MS); Candidate should not be significantly less uniform than the comparators

Further information is provided in TGP/10 (Examining Uniformity).

Examining stability

Examining a variety for Stability is a necessary requirement in the process of establishing a varieties eligibility for PBR.  A variety shall be deemed to be stable if its relevant characteristics remain unchanged after repeated propagation or, in the case of a particular cycle of propagation, at the end of each such cycle.

There are two methods used for examining stability;

1. Indirect - Inferred from uniformity: this applies to asexually propagated varieties taken as stable if they are uniform, and
2. Direct – comparison between two generations: This is used for sexually (seed) propagated varieties taken as stable if two generations are not different

Further information is provided at TGP/11 (Examining Stability)