**1. Introduction**

The developments of precise genetic engineering tools, such as sequencing platforms, *in planta* gene editing, and molecular marker-assisted breeding, have made possible the recent rapid advances in agricultural biotechnology. These are all exciting accomplishments as plant breeders are racing worldwide to meet the needs of the increasing human population against the backdrop of industrialization, climate change, and water scarcity. Improved understanding of the genetic make-up underpinning the phenotype, variability, and adaptability of desirable crops and ornamentals offers unprecedented opportunities for highly targeted genetic engineering approaches.

Traditional plant breeding can be an arduous and long process. However, highly related, similar, and/or identical plant varieties can subsequently easily be produced. Accordingly, plant breeders need protection to recover their investments. Plant breeding has conventionally offered challenges for intellectual property (IP) protection

due to a number of technical and legal factors, which include the definition and the verification of whether the breeding of a new(er) plant variety constitutes a new innovation—or not. Just a few countries (e.g., USA and Japan) issue utility patents for plant varieties, thus this type of IP rights protection is not a feasible option for developing countries.

The International Union for the Protection of New Varieties of Plants (UPOV) was established as an international organization by the 1961 International Convention for the Protection of New Varieties of Plants [1]. UPOV strives to recognize the rights of plant breeders on an international basis and to provide and promote an effective system of plant variety protection, with the aim of encouraging the development of new varieties of plants. Through periodic revisions, the UPOV system has been gradually strengthening breeders' rights by adding crop species, restricting farmsaving of seed, and extending the scope of protection. Seventy-eight countries are UPOV member states as of November 2021. UPOV defines a "plant variety" as a more precisely defined group of plants, selected from within a species, with a common set of characteristics [1].

In a globalized economy, the problem of plant variety derivation and the need for an appropriate protection system was identified decades ago. A plant variety should be declared distinct only if it differs in important characteristics from all other known varieties. The concept of "essentially derived varieties" (EDVs) [of plants] was introduced by UPOV to refine the scope of plant breeders' rights. The goal was to prevent fraudulent practices and the exploitation of minor changes in relation to the initial plant variety (IV), for example by genetic engineering or mutagenesis, without the holder of the initial variety right being able to share in the revenues. According to the UPOV's definition in Article 14(5)(b), which describes the scope of the breeders' rights, "a variety shall be deemed to be essentially derived from another variety ("the initial variety") when (i) it is predominantly derived from the initial variety, or from a variety that is itself predominantly derived from the initial variety, while retaining the expression of the essential characteristics that result from the genotype or combination of genotypes of the initial variety, (ii) it is clearly distinguishable from the initial variety and (iii) except for the differences which result from the act of derivation, it conforms to the initial variety in the expression of the essential characteristics that result from the genotype or combination of genotypes of the initial variety" [1]. This definition was in 2017 further clarified with the issuance of explanatory notes on essentially-derived varieties under the 1991 Act of the UPOV Convention [1]. To honor the IV breeder's rights, the breeder of the EDV must reach an agreement with the holder of the IV before exploitation. Where derivation occurs, it is important to be able to distinguish between subsequent (second, third, etc.) plant varieties that have been "derived" from an existing variety, which are allowed; and those that have been "essentially derived," which are not allowed [2]. The EDV concept aims to ensure a fair return on investment to the breeder of the IV.

Molecular genetic markers are increasingly becoming a powerful scientific tool that can be used to characterize plant genetic resources and to provide comparison(s) of genetic similarities between various plant varieties. In particular, genetic distance estimates based on molecular markers are gradually becoming a preferred approach to estimating genetic conformity between putative EDVs and their IVs.

This chapter reviews the use of molecular markers for the determination of "EDV" as used by UPOV. It summarizes recent publications that demonstrate the advantages afforded by the use of molecular markers, their high throughput, high map resolution, and high repeatability for the determination of EDVs. The overarching goal of these efforts is to help provide a predictable business environment that will allow a greater breadth of genetic diversity to be surveyed with ever-increasing effectiveness to continually improve abilities to select new genotypes that are optimally able to perform in target agricultural environments. It also highlights criticisms that address the use of molecular markers for determination of EDVs.
