Maize Phenotyping under the Seeds of Discovery Initiative

The Seeds of Discovery Initiative for Maize is the most comprehensive genome–wide association mapping study undertaken. The genetic material evaluated is based on the “Breeder’s Core Collection” of the CIMMYT Maize Germplasm Bank which consists  of 4471 accessions selected for acceptable agronomic performance under the Latin American Maize Project (LAMP). A single plant per accession was sampled for genotyping, and the same plant was used as pollen parent in crosses with 10 plants of a CIMMYT hybrid of the same environmental adaptation as the accession (ie., highland accessions were crossed to highland hybrids and tropical accessions to tropical hybrids). This produced a series of modified topcrosses which were evaluated in phenotypic trials. A total of 4110 accessions were successfully topcrossed, and more than 3900 of these have been evaluated for one or more traits.

Over three planting seasons, a total of 36 phenotypic trials were planted in 14 different locations in 10 different states of Mexico.  Thirty-four trials were successfully harvested, with data taken on a total of 34,606 plots.  The trial design was augmented row-column with commercial hybrids used as checks for spatial adjustment. Trials were conducted on abiotic and biotic stresses, agronomic traits, yield, and grain quality. Traits were chosen based on their importance in Latin America and worldwide.  Segregation within the accession topcrosses, due to heterozygosity of the landrace parent, necessitated adjustments to existing protocols, mainly in the number of plants measured per row, to account for the variation within row.