Cultivar · Maize inbred line
B73
B73 is a public maize inbred line developed at Iowa State University and released in 1972 from the Iowa Stiff Stalk Synthetic population. It is one of the most influential lines in temperate maize breeding and was the source of the first maize reference genome.
Record
Cultivar / variety- Variety of
- Maize
- Botanical taxon
- Zea mays
- Type
- Inbred line
- Breeding method
- Recurrent selection and inbreeding from a synthetic population
- Origin
- Iowa, United States
- Released
- 1972
- Breeder / institution
- Iowa State University (developed by Wilbert A. Russell)
- Registry status
- Historical
- Registries
- USDA GRIN · United States · as of 2026-07-12B73 is maintained as a public maize inbred accession in the U.S. National Plant Germplasm System; specific record identifiers are not reproduced here.
- Adaptation
- Temperate maize adapted to U.S. Corn Belt conditions; as an inbred line it is used in breeding rather than grown for commercial grain on its own.
- Intended use
- Public inbred parent line for hybrid maize breeding, Reference genome and germplasm for maize genetics and genomics, Teaching and research material
Registry listing or variety protection is jurisdiction- and date-specific and does not by itself indicate current commercial availability, universal cultivation approval, patent status, or a recommendation.
B73 is a public inbred line of maize developed by Wilbert A. Russell at Iowa State University and released in 1972. It was derived from the Iowa Stiff Stalk Synthetic (BSSS), a breeding population of largely Reid’s Yellow Dent heritage that had undergone several cycles of recurrent selection; B73 was recovered from the fifth cycle of that program.
An inbred line is a near-homozygous, self-pollinated line used as a parent in hybrid production and as a stable reference in research rather than grown for commercial grain in its own right. B73 became a foundational member of the "Stiff Stalk" heterotic pool and, decades later, the basis of the first assembled maize reference genome.
Background and development
The Iowa Stiff Stalk Synthetic was assembled in the 1930s from sixteen inbred lines of predominantly Reid’s Yellow Dent background and improved through repeated cycles of recurrent selection at Iowa State University. Several widely used inbreds were extracted from this population over the following decades, including B14 and B37; B73 was released by Wilbert A. Russell in 1972 from the fifth selection cycle.
Because it descends from the Stiff Stalk population, B73 is treated as a defining member of the Stiff Stalk heterotic group. In temperate hybrid maize, Stiff Stalk lines are typically crossed with complementary "non-Stiff-Stalk" lines (such as those of the Lancaster group) to exploit heterosis.
Breeding and research significance
B73 has been used extensively as a public parent line and as a common reference point in maize genetics. The classic single cross of B73 with the Lancaster-group line Mo17 has been studied for decades as a model of hybrid vigour and complementary heterotic pools.
In 2009 B73 was reported as the source of the first assembled maize reference genome, and it remains a standard genetic and genomic reference for the species. This role is one reason the line continues to be maintained and distributed through public germplasm systems.
Status and availability
Scope & limitations
Geographic scope: Developed in Iowa, United States, for temperate maize breeding; used internationally in research and public breeding programs.
Climate context: Temperate maize germplasm; adaptation and performance are environment-specific and evaluated in a breeding context rather than as a stand-alone crop.
- B73 is a public inbred line and research reference, not a commercial hybrid; its per-plant grain performance is not representative of the hybrids to which it contributes.
- Heterotic-group and pedigree descriptions summarize the documented breeding literature; fine pedigree details vary between sources.
Sources
This article draws on the following authoritative sources. See our sources & methodology for how they are selected.
- [1]GRIN-Global / National Plant Germplasm System (opens in a new tab)Authoritative
USDA Agricultural Research Service (ARS)
Cited for: Maintenance of B73 as a public maize inbred accession
- Type:
- Official registry
- Jurisdiction:
- United States / Global
- Accessed:
- 2026-07-12
- [2]USDA ARS — Agricultural Research Service (opens in a new tab)Authoritative
USDA Agricultural Research Service (ARS)
Cited for: Maize germplasm history, Stiff Stalk heritage, and reference-genome research
- Type:
- Government agency
- Jurisdiction:
- United States
- Accessed:
- 2026-07-12
- High
Cited for: Zea mays taxonomic placement
- Type:
- Reference database
- Jurisdiction:
- Global
- Accessed:
- 2026-07-12