Last updated: 
18 November 2021

All applications for plant breeder's rights (PBR) must satisfy three essential criteria:

  • distinctness

  • uniformity

  • stability.


Distinctness is shown by a comparison of the variety with the most similar variety or varieties of common knowledge. Quantitative and qualitative differences between the new and existing varieties must be established and recorded.

Morphological characteristics are preferred, especially those least affected by environmental factors. However, tests such as comparative DNA or protein profiles are acceptable as supporting evidence. Clear and repeatable varietal differences must be demonstrated.

Performance attributes can also be included as distinguishing characteristics if they are clear and consistent.

Additional test of distinctness for Australian native species

As part of your application for a variety of an Australian native species, you must submit a satisfactory specimen to the Australian Cultivar Registration Authority (ACRA).

You should do this before you start your comparative growing trial, as ACRA may suggest comparators to use in your trial. If you don't use these, you will have to repeat the trial or justify your reasoning for not using them. Information on how to submit specimens and the fees are available on the ACRA website.

Once you have submitted your specimen complete the Confirmation of submission of a satisfactory specimen to the herbarium form.

PBR examination will only be finalised once any issues raised by the ACRA have been resolved.


The required standard of uniformity for each type of propagation is set out below. Exceptions and guidelines for uniformity testing for particular species are given in the technical guidelines of the International Union for the Protection of New Varieties of Plants (UPOV).

Visual characteristics

For characteristics that are assessed visually, and not by measured characteristics, uniformity is usually assessed using the off-type method. A plant is an off-type when it does not conform to the distinctive characteristics of the variety under consideration.

In vegetatively propagated or fully self-pollinated varieties, the number of off-types must not exceed a certain amount (see the table below). For example, in a comparative tomato growing trial containing between six and 35 plants of the new variety only one plant can be an off-type specimen. If more than one plant did not conform to the distinctive characteristics, the variety would be considered as lacking uniformity and therefore could not be registered under PBR.

Maximum number of off-types allowed

Number of plants or plant parts assessed

Maximum number of off-types









For partially self-pollinated varieties, the allowable number of off-types is doubled.

Uniformity in cross-pollinated varieties is usually assessed using the relative variance method (see measured characteristics below).

Where a characteristic is visually assessed, the new variety is considered uniform if the number of off-types is no more than the number found in other known varieties.

Measured characteristics

For measured characteristics, where it can be difficult to determine what is or is not an off-type, uniformity can be assessed using a statistical technique called the 'relative variance method'.

Variance is a statistical term that describes the dispersion of a population. It is the square of the standard deviation.

The variance of a measured distinctive characteristic of the new variety is compared with the average variance of the comparator varieties for the same characteristic. Measured characteristics are considered uniform if their variance is less than 1.4 times the average variance of the varieties used for comparison.

The plant height variance example below demonstrates.

Plant Height Variance


Plant height (cm)

Variance of new variety


Variance of comparator variety 1


Variance of comparator variety 2


Variance of comparator variety 3


Average variance of comparator varieties


Ratio of new variety to average of comparator varieties



The variance of the new variety is 5.1. We divide this by 5.43, which is the average variance of the competitor varieties. The result is 0.939.

As 0.939 is less than the allowed limit of 1.4, the new variety is uniform for the plant height characteristic.


A variety is stable if it remains true to description after repeated propagation or reproduction.

Breeders of varieties propagated from seed need to demonstrate stability by including two generations in the comparative trial. If necessary, stability can be demonstrated in a separate trial.

If the variety is to be vegetatively propagated and is uniform, a demonstration of stability is usually not required.

More information

The Report of the Expert Panel on ‘Clarification of Plant Breeding Issues under the Plant Breeder’s Rights Act 1994’ is a very useful guide for applicants. It includes a number of scenarios of various types of breeding activities and clarifies whether they would meet the PBR requirements.

Report of the Expert Panel on Breeding - December 2002.pdf