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1985 United States Farm Maize Germplasm Base and Commercial Breeding Strategies¹

Six surveys have been conducted, beginning in 1956, to determine the breadth of the U. S. maize (Zea mays L.) germplasm being commercially utilized and whether it is changing over time. The present survey was based on seed produced in 1984 available for planting in 1985. Twenty-one public inbred lines were used as parents in hybrids in an amount that exceeded 0.1% of the total need each. Inbred B73 was used for 11.3% of the total 1985 seed requirements followed by A632 with 1.9%, W117 with 1.5%, Mo17 with 1.5%, and CM174 with 1.3%. All other lines occurred in less than 1% of the total requirement. Substantial decreases in public line usage were found in comparison with the 1979 survey. Hybrids using only private lines accounted for 62% of the total production. One or more public lines were included in 38% of the total production and one or more private lines were in 92% of the total production. The predominant source of new inbred line development was single crosses (20%), but 53% of the effort was identified as being from sources other than those specified in the survey questionnaire. Recycling of old elite inbred line families as sources of new lines declined from 1979. Significant effort, however, involved recycling within the B73, Oh43, and A632 inbred line families. Lines from 'Reid' germplasm were included as 44% of the total production in 1984, followed by ‘Iodent’ (24%) and ‘Lancaster’ (12%). Eighty-eight percent of the seed produced included Reid germplasm because the reporting split production by parental component. Normal cytoplasm was used in 87% of the total production. The C-type male-sterile cytoplasm was used in 8% and the S-type was used in 3% of the total production.

Key Words: Zea mays L. • Cytoplasmic sterility • Hybrid production • Line development

² Research geneticist, USDA-ARS, and emeritus professor of agronomy, Univ. of Missouri, Columbia, MO 65211.

Received for publication March 14, 1986.