(b) The following shall be defenses in any action charging infringement and shall be pleaded:
(1) noninfringement, absence of liability for infringement, or unenforceability;
(2) invalidity of the plant variety protection in suit on any ground specified in section
2402 of this title as a condition for protectability;
(3) invalidity of the plant variety protection in suit for failure to comply with any requirement of section
2422 of this title;
(4) that the asserted infringement was performed under an existing certificate adverse to that asserted and prior to notice of the infringement; and
(5) any other fact or act made a defense by this chapter.
