Definitions and Explanations

For purposes of this database, heterotic groups have been classified into 5 categories:

1. BSSS – Stiff Stalk and stiff stalk related germplasm or germplasm that acts similar to BSSS
2. Lancaster – Wide range of germplasm including C103, C123, Mo17, Oh43, Oh07, and more.
3. Iodent
4. W153R – Primarily LH82-derived and similar types of germplasm.
5. Unrelated – Including germplasm that is largely unrelated to or heterotically responsive in patterns unlike the four categories listed above.

Heterotic groups are often somewhat subjective and prone to exceptions, not unlike higher order botanical species classifications.  For this reason, more extensive and detailed classification of families and/or sub-families has not been provided in this database.  The classification listed for individual maize inbreds is based upon analysis and interpretation of data obtained from published patent and PVP documents.  Analysis and interpretation of published data were performed solely by the authors of this database, and to the best of their abilities.  No warranty or guarantee of the absolute accuracy of these interpretations is provided or implied.

Some corn inbreds may have multiple classifications listed for heterotic background, eg. – Iodent-Lancaster, or Lancaster-Iodent.  In these cases, the genetic background of the inbred is more like the first-listed heterotic group than the second-listed heterotic group.  Again, this is subject to the limitations and interpretation of available data.

Patent expiration dates
US patent expiration dates have been determined based upon laws and protocols prevalent at the time of each patent issue.  The current rules determining expiration date are rather long and complicated.  However, in general, US patent protection is in force for 20 years following the APPLICATION date of the patent in most cases.  Occasionally, if the time transpired between the patent application date and the patent approval date is longer than three years (1096 days), the duration of US patent protection may be extended.  In such cases, the US patent expiration date is determined to be 17 years following the APPROVAL date of the patent.

Prior to June 8, 1995, US patent protection was in force for 17 years following the application date of the patent, or 14 years following the approval date of the patent, whichever is later.

Patent maintenance fee neglect
On October 4, 2016, the entire database was updated to identify hybrid, inbred, and synthetic varieties for which patent maintenance fee payments had been neglected by the patent holder.  The US patent office requires a maintenance fee to be paid by 4 years, 8 years, and 12 years (including 6-month grace periods) following the issue date of the patent.  If these fees are not paid by the end of any grace period, the patent is deemed to be expired.  The CPIS database now reflects all fee neglect patent expirations as they occur.

Plant variety protection (PVP) expiration dates
PVP certification is currently in force for 20 years from the date of issuance of the PVP certificate.  Prior to 1980 PVP certification was in force for 17 years from the date of PVP certificate issuance.  From 1980 to 31 March 1995 PVP certification was in force for 18 years from the date of PVP certificate issuance.

Variety names
Occasionally, the same corn inbred variety has been assigned different names by the inventor/developer for PVP certification vs. patent protection.  Where identifiable, these variety names have been consolidated as one variety entry in the database.

Some inbred varieties have been patented two or sometimes three times by the patent owner.  Such inbred varieties are identified by a (n) suffix immediately following the name of the variety.  A (1) designates the first patent; a (2) designates a second patent application and issue at a later date; a (3) designates a third patent application and issue at yet a later date.  If the patent of an inbred variety possessing a (1) suffix has expired, the inbred may still be under protection via a second or third patent.  If no (n) suffix is present, the inbred variety has been patented only once, though it may still be under protection of a PVP certification.

Parental pedigree nomenclature
Parental pedigrees of corn inbreds are listed (whenever known) with the female parent listed first followed by the male parent listed last.  Where more than two parents are identified in the development of the maize inbred, parenthesis () are used to enclose the varieties used as one parent of the final cross.  For example, in the development of inbred X, the parental pedigree A / (B / C) indicates that the progeny of the cross B / C was used as the pollinator (male parent) to pollinate A (female parent) in the development of the population from which X was developed.  In this theoretical example, X is expected to possess a nuclear genetic background consisting ½ A, ¼ B, and ¼ C, and a cytoplasmic background of A.

Where backcrossing was identified in the development of the corn inbred, > or < are used to identify which parent was used multiple times (recurrent parent) in the crossing scheme.  Again, the female parent (of the final backcross) is listed first.  The male parent (of the final backcross) is listed last.  The symbols >n> or <n< are used to indicate the direction and recurrence of one parent in the backcross scheme.  For example in the development of inbred Y, D<3<E indicates that E is the recurrent parent used a total of three times (including the original cross) to develop the backcross population from which Y was developed, and D was the female of the final backcross.  In this theoretical example, Y is expected to possess a nuclear genetic background consisting 7/8 E and 1/8 D, and a cytoplasmic background of D.

Publication inclusion

Please note that patent and PVP information is available only for germplasm for which patents or PVP certificates have been issued.  If a variety patent application was submitted but is still pending, or was later withdrawn or abandoned before the patent was approved and published, the variety is not included as an entry in the database.  If PVP applications are still pending, they also do not contribute to this database.  Also, note that some information for some varieties was not possible to derive from the published literature, nor from subsequent data analysis.