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ARS Home » Midwest Area » Ames, Iowa » Corn Insects and Crop Genetics Research » Research » Publications at this Location » Publication #86580
Title: EFFECTIVE POPULATION SIZE AND RESPONSE TO S1-PROGENY SELECTION IN THE BS11 MAIZE POPULATION

Author
item WEYHRICH, ROGER - IOWA STATE UNIVERSITY
item LAMKEY, KENDALL
item HALLAUER, ARNEL - IOWA STATE UNIVERSITY

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/20/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: Genetic variation is the raw material of selection. Without genetic variation germplasm will not respond to selection. Many forces affect the amount of genetic variation in a population including selection, mutation, migrations, and random genetic drift. Random genetic drift is random changes in allele frequencies due to choosing a small number of individuals sto represent a population. The smaller the sample, the less likely that the sample is representative of the original population. When conducting selection programs to improve populations, the number of individuals kept must be chosen carefully, because too few will decrease genetic variance and too many will decrease selection response. There is little empirical evidence in corn to use as a guide in choosing population size. In this study, several generations of selection were conducted in a corn population by choosing 5, 10, 20, and 30 individuals to represent the population. The eresults suggest that 10 may be the optimum number of individuals to choose to maximize short term selection response. There seemed to be little advantage to choosing more individuals and choosing fewer individuals resulted in a decrease in performance. The results of this research will benefit public and private maize breeders by defining the optimum number of individual plants needed in a breeding program.

Technical Abstract: The number of lines recombined in a recurrent selection program affects genetic variation remaining after selection as well as the selection intensity. Both of these variables are important in establishing and maintaining the rate of progress from recurrent selection. Little empirical evidence is available in maize (Zea mays L.) to establish the appropriate effective population size of recurrent selection programs. Th objective of this study was to compare the response to S1-progeny selection after intermating four (5-S1, 10-S1, 20-S1, and 30-S1) different numbers of individuals with a common selection intensity of 20%. Four cycles of selection were completed for the 5-S1, 10-S1, and 30-S1 programs and five cycles of selection were completed for the 20-S1 program. Grain yield increased significantly for the 10-S1, 20-S1, and 30-S1 programs and there was no significant difference in rate of response among programs. The 5-S1 1program decreased significantly in grain yield. All four programs improve significantly for grain yield in testcrosses with BS11C0 and the inbred B79. These results suggest that drift becomes a stronger force in altering allele frequencies than selection when fewer than 10 lines are recombined. There does not seem to be an advantage, at least in the short term, of recombining more that 10 lines.