Abstract
This study was undertaken to evaluate the discriminating power of gamete selection in the Sq generation and to determine the extent to which combining ability of So genotypes of corn, estimated by the gamete selection method using an inbred tester, might be altered by test-controlled selection in subsequent generations of inbreeding. The extent of variability within and among S₁ progenies would be expected to show whether or not So testing provides an accurate prediction of lines derived by gamete selection. Another objective was to proceed with a breeding program designed to improve an inbred line by gamete selection. The inbred line being improved was Tx403. Selfed or backcrossed seed of So plants from a complex hybrid population, classified in the first cycle of gamete selection as low, medium or high in combining ability, were chosen as the basis for this work. Twenty eight of the S₁ families were derived by selfing and 24 by backcrossing So plants to the elite line Tx403. Among the selfs, there were 8 low, 12 medium and 8 high combiners. The backcrossed group was comprised of 5 low, 13 medium and 6 high combining families. In 1968, five visually selected plants, within each family, were selfed and simultaneously test-crossed onto five plants of the tester Tx508. In addition, a bulk sample of pollen, representative of each family, was used to fertilize five ears of the inbred tester. Test-crosses were grown in 1969 in a restricted randomized block design with four replications. The single cross (Tx403 x Tx508) was used as check and it was entered each 20th plot. Since selections were to be made on the basis of combining ability, grain yield was the most important factor. However, data were also recorded on maturity, ear height, breakage and number of plants exhibiting symptoms of maize dwarf mosaic virus infection..
Rosario, Theodore Nieves (1970). An evaluation of second cycle gametic selections with a monogametic tester for improving an inbred line of corn. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -179536.