Use and Protection of Exotic Maize Germplasm: What the Past 35 Years Have Taught Us.

New World maize is represented by the Rockefeller-NRC collections that are in better shape now than in the 80s, when they neared extinction. Most variation can’t be evaluated in the U.S. because accessions aren’t adapted. Hallauer’s observation ‘Most genetic diversity is detrimental’ remains correct; its corollary is: ‘The less elite the diversity, the more detrimental it is likely to be’.

The first temperate-adapted, all-tropical (TAAT) lines came from a tropical hybrid diallel. NC298 and NC300 have had much breeding use, while NC296 was in a wholesaled hybrid. Competitive, TAAT inbreds can be developed, but this takes 15 years. Current genomic magic is not apt to shorten that time.

At most land-grants, a program’s value is measured by overhead. Neither study of maize races nor breeding TAAT lines brings in much money, let alone much overhead. I have lobbied to endow field-breeding technician positions for a few public corn breeding programs. This would discourage closing good programs at retirements.

Diseases exist for which little or no resistance exists among US lines. Unlike the 1970s SLB, no seed packets are on the shelf to solve these problems. NC358, another TAAT line, at least provides resistance to Lethal Necrosis.

Major companies should introduce lines carrying resistance to foreign pests into their domestic breeding. Some have claimed to be doing so. But personnel changes, pressure for new hybrids now, and the time required confound such efforts. Instead, they emphasize intensive selection among elite sources, waiting for threats to arrive before reacting.

Good news: A 40 year problem of replenishing seed of tropical, highland accessions seems to have been solved, and GEM has provided access to elite 25% to 50% tropical sources around the globe. The NCPIS now holds the only complete set of typical accessions of the races of maize (~ 1200 accessions).