Well, in Argentina there are not patents for plants at all (genetically modified or not) if they can reproduce themselves. And for what its worth, Software Patents do not exist in Argentina either.
Intelectual Property is protected by copyright. I leave here a translation of an extract for that law. It only allows "inventions" as something that can have a patent. And in its 6th article, it explicitly excludes the following:
Article 6 - They are not considered inventions for the purposes of this law:
a) Discoveries, scientific theories and mathematical methods;
b) Literary or artistic works or any other aesthetic creation and scientific works;
c) Plans, rules and methods for performing intelectual activities,
playing games or for economic and business activities as well as computer programs;
d) Ways of presenting information,
e) Surgical, diagnostics or therapeutic treatment methods, applicable to the human body and animals;
f) The juxtaposition of known inventions or mixtures of known products, variations in their form, dimensions or materials, except in the case of combination or merger so that they can not function separately or that the qualities or functions thereof are modified to obtain an industrial result not obvious to a person skilled in the art;
g) All kinds of living matter and substances preexisting in nature.
Art. 7 - Are not patentable:
a) Inventions whose exploitation in the territory of Argentina must be prevented to protect public order or morality, health or life of people or animals or to preserve plants or avoid serious damage to the environment
b) All existing biological and genetic material in nature or a replica thereof, in the biological processes implicit in animal, plant and human reproduction, including genetic processes involving material capable of conducting its own duplication in normal and free conditions as it happens in the nature.