| Maize (Zea maysL.) inbred lines and hybrids are protected by U.S. Patent and/or Plant Variety Protection Act (PVPA). Protection lasts 20 years and it affects breeding access in a highly confidential and competitive market. This research assessed the usefulness of patent expired short-season maize inbred lines. The study was conducted i) to understand the nature of gene action of a short- season maize breeding sample for agronomy and grain quality traits ii) to identify ex-PVP inbred lines and hybrids as potential breeding sources for short-season maize breeding programs for agronomic, grain quality, and nutritional traits iii) to identify and validate heterotic groups of ex-PVP inbreds and NDSU lines, and iv) to identify desirable top heterotic patterns among ex-PVP, industry testers, and NDSU lines. Three North Carolina Mating Design II (NCII) crosses were made, including NDSU lines, ex-PVP lines, and top industry testers in the 2010 North Dakota State University (NDSU) Fargo summer nursery and in the 2010-2011 NDSU New Zealand winter nursery. Hybrids were planted across six different ND environments in 2011 and 2012 following partially balanced lattice experimental designs. Combining ability analyses were performed following NCII design. Additive and non-additive genetic variances were important for regulating the expression of most traits with the preponderance of additive genetic variance. Our research identified ex-PVP inbred lines PH207, Q381, PHP02, S8324, PHK76, CR1Ht, PHT77, LH205, LH54, and PHJ40 that could be used as breeding sources to increase mostly grain yield. Most of the inbred lines belong to Stiff Stalk (SS), non-SS, or Lancaster backgrounds, although some belong to both SS/non-SS genetic backgrounds. The top heterotic patterns, from our trials, were represented in the following combinations: SS x non-SS, Iodent x SS, SS x Lancaster, Iodent x Lancaster, and SS/non-SS x SS. Our trials suggest most ex-PVP lines are not useful directly in immediate hybrid production for agronomic and grain quality traits. In such a context, improvements in intellectual property and re-thinking of breeding rights access are encouraged to explore more suitable hybrids for short-season maize breeding programs. |
