The use of biotechnological tools and other techniques to improve crops has given rise to a significant increase in the patenting of plant components and plants. At the same time, the exclusionary rights conferred by patents have generated concerns about their implications for a sustainable agriculture and food security. As a result of these trends, it becomes critical to examine the intersection between plant breeding and patent rights. This book makes an original and important contribution to this still relatively unexplored area of research. A few countries grant patent rights on plants as well as plant varieties as such. While most jurisdictions exclude plant varieties from patentable subject matter, they allow for the patent protection of genetic constructs, including in some cases isolated genes, used to modify plants. The protection of different biological materials contained in plants may lead to the control over the plant varieties themselves, even if the law does not permit their patenting. Plant breeding proceeds through the continuous improvement on existing plant varieties. Ensuring access to such varieties as a source for further research and breeding is crucial for farming systems. This has been recognized under plant variety protections regimes, which provide for a ‘breeder’s exception’ allowing third parties to use protected varieties to develop new ones. However, patents rights can normally be exercised to restrict such use, thereby raising questions about the continuous improvement of crops, the impact of such rights on the plant breeding industry and the adequate supply of seeds to farmers at affordable prices. Such questions become particularly relevant in a context of high concentration of patent ownership in a small group of large biotechnology-based companies. An outstanding issue is, hence, the extent to which the patent law can be framed so as to allow for a kind of ‘breeder’s exception’ for further breeding when patented elements exist. This book addresses in detail this issue, particularly what could be the scope of an exception for that purpose admissible under the Agreement on Trade Related Aspects of Intellectual Property Rights (TRIPS Agreement) of the World Trade Organization (WTO).