Identification, uniformity, and stability testing is one of the key criteria for testing the identity, uniformity, and stability of breeds. This is required under the PPV & FR Act 2001 to grant breeder, researcher, and farmer rights. It must be clearly distinguishable from all collections of reference breeds. It must be consistent if a typical plants do not exceed the minimum allowed and traits are maintained in different environments and over time.
They should be stable as long as all properties are preserved during replication. Species-specific descriptors are used to characterize, distinguish, and protect breeds. Descriptors must meet three technical requirements for identity. Consistency, stability, and distinctiveness are the abilities of descriptors to show distinct differences in variation between breeds.
Homogeneity is uniformity within a breed, and stability is the absence of temporal or spatial variation. Examination of the identity, uniformity, and stability of a breed is one of the breeder's rights requirements and is conducted in accordance with national guidelines developed under the UPOV guidelines.
Plant morphological characteristics are widely accepted as undisputed descriptors of plant species for DUS testing and cultivar characterization. Consecutive use of morphological descriptors is useful for distinguishing different breeds.
The best way to determine whether a descriptor meets the above requirements is to evaluate the trait in field trials in which different cultivars are grown under the same conditions.
DUS Testing
According to the "Plant Protection and Farmers' Rights Act," new plant varieties can be registered and protected for a certain period of time. Annuals are 15 years old, and vines are 18 years old. Registration and protection are granted to varieties only if they meet the criteria of distinctiveness, uniformity, and stability. This requires testing to determine whether the breed meets the DUS test criteria.
Testing of Distinctiveness
Distinctiveness is necessary to describe breeds with a set of characteristics and to distinguish new breeds from all other known breeds. The PPV & Farmer Rights Act stipulates that a breed to be registered must exhibit distinctiveness for each essential characteristic in comparison with other morphologically similar breeds.
One or more essential characteristics must make the breed clearly distinguishable from other breeds generally known to exist at the time protection is sought. For example: cultivation or marketing already underway, registration of a variety already created or underway in an official variety register, listing in a comparative collection, or an accurate description in a publication
A lack of uniformity in breeds indicates a lack of expression or distinction of specific characteristic states in specific breeds. In other words, whether it is possible to distinguish between candidate cultivars using non-uniform characteristics
The presence of multiple characteristic morphologies or states in a particular breed can occur due to the complex nature of the trait and the breed's genetic background or pedigree, its breeding history, and breeding methods.
While this is highly unexpected for purely self-pollinated plants and single hybrids, it is possible for hybrids involving two or more parents of open-pollinated and cross-pollinated species.
Figure ;1 Show DUS morphological trait and DUS genomic marker
Testing of Uniformity
Breeds should exhibit as little variation as possible in order to be able to accurately describe and assess varietal differences. In order to be considered uniform and ensure stability, it is also necessary that the cultivar exhibit some tolerance to variations that differ according to the cultivar's reproductive system.
This means that varieties of vegetatively propagated, self-pollinated, often cross-pollinated, inbred, synthetic varieties, and hybrid cultivars require different levels of uniformity.
For self-pollinated and vegetatively propagated cultivars, where all individual plants of the cultivar are expected to be fairly similar, it is possible to assess uniformity by counting the number of off-type plants.
Intra-varietal character uniformity assessment is necessary to avoid impurities and contamination from other cultivars. Defining the characteristic phenotypic state of a breed is very important, as the uniformity of the breed depends on the defined description. A breed's DUS test loses its power in the absence of a clear signature condition.
Stability
If the relevant traits do not change after repeated breeding, the breed is considered stable. Generally, stability testing cannot be performed over a period of 2 or 3 years. In general, if the submitted samples are found to be consistent, the material can also be considered stable.
Special attention should be paid to stability when examining identity and uniformity. If necessary, further generations are grown from new seeds provided by the applicant to test stability and ensure that they have the same properties as the previously provided material.
Planting Material for Distinctiveness Uniformity and Stability Testing
The amount of planting material required is specified in the individual test guidelines for each crop. Materials submitted for DUS testing must be representative of the candidate cultivar. For seed-propagated cultivars, especially cross-pollinated cultivars, the material to be tested should belong to the same generation as the marketed material.
This is especially relevant for hybrids and synthetic cultivars where the tested plant material should cover the final stages of the breeding cycle. Planting material should be visibly healthy and not lack vigour or be affected by major pests or diseases.
Some traits of a cultivar can be affected by external factors such as pests and diseases, chemical treatments, exposure to tissue culture, and scions from different stages of growth of the tree, so the authorities recommend planting It is necessary to make sure that the material does not have such factors.
Seeds must have sufficient germination capacity. If the seed is to be stored, it is desirable that the germination capacity be higher than the minimum seed certification standard for the crop.
Conclusion
In summary, there is sufficient scope to understand the various components involved in assessing the distinctiveness of plant cultivars obtained and propagated by various methods. Areas tested for homogeneity are equally important given that they are critical for cultivar purity.
Statistical analysis of property-related data should be considered to clarify the homogeneity testing procedure. Exemplary breed issues in each DUS test guideline should be understood in a practical sense, e.g., breeds are not required for all traits.
References
Chakrabarty, S. K., & Choudhury, D. R. (2019). DUS testing for plant variety protection: Some researchable issues. INDIAN JOURNAL OF GENETICS AND PLANT BREEDING, 79(Sup-01), 320-325.
Gupta, A., Amrapali, S., Kumar, M., Khati, P., Lal, B., Agrawal, P. K., ... & Bhatt, J. C. (2016). Distinctness, uniformity and stability testing in maize inbreds. National Academy Science Letters, 39(1), 5-9.
Selvan, R. T., Parthiban, K. T., & Palanikumaran, B. (2019). Distinctness, uniformity and stability (DUS) characterization of Neolamarckiacadamba genetic resources. Curr. Agric. Res. J, 7, 268-275.
Singh, P. K. Principles and Procedures of Distinctiveness, Uniformity, and Stability (DUS) Testing in Tomato. Chief Editor Dr. RK Naresh, 69.
Authors:
Abhay Kumar Pandey*, Dharmendra Kumar, Shivanshu Shekhar
Dept. of Genetics and Plant Breeding,
Acharya Narendra Deva University of Agriculture and Technology,
Kumarganj, Ayodhya, Uttar Pradesh (224 229) India
*email: