|Weyhrich, Roger - IOWA STATE UNIVERSITY|
|Hallauer, Arnel - IOWA STATE UNIVERSITY|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 4, 1997
Publication Date: N/A
Interpretive Summary: The broadening of corn genetic diversity is considered imperative to maintain current rates of genetic gain and to minimize the risk of problems associated with genetic vulnerability. The most efficient way of broadening corn genetic diversity is to improve corn populations via recurrent selection. Enhanced germplasm developed via recurrent selection can then be used to develop improved inbred lines and hybrids that are unrelated to those currently being used commercially. Although recurrent selection methods are well known among breeders, there are many methods to choose among, and little in the way of critical data on which to base decisions among methods. A study was conducted to critically compare seven recurrent selection methods by initiating the methods in a common base population and holding other protocols associated with conducting a selection program constant. In this way, the only differences among the performance of a given selection method was the method itself. The most effective method was S2-progeny recurrent selection. This was somewhat surprising because this method has not performed well when used in other base populations. This result suggests that there is something intrinsic in the genetic architecture of a population that determines how a population responds to selection. Further studies are planned to ascertain what components of the genetic architecture of a population contributes to the success of a given selection method. These results are critical, because continued selection response is dependant on understanding selection response. The results of this study are of interest to breeders of all crop species and quantitative geneticists designing selection experiments.
Technical Abstract: Recurrent selection methods have been effectively used by maize (Zea mays L.) breeders to improve the performance of maize populations for quantitatively inherited traits. Although theoretical comparisons of such methods can be easily made, direct comparisons of the efficiencies of methods are quite time consuming and laborious. Because of these limitations, empirical data comparing multiple recurrent selection methods in the same base population are lacking for maize. Our study was designed to compare the response to selection for seven different (six intra- and one inter-population) methods in the BS11 maize population. A minimum of four cycles of selection were conducted for each of the following methods: mass, modified ear-to-row, half-sib with inbred tester, full-sib, S1-progeny, S2-progeny, and full-sib reciprocal selection. Selections for all programs except mass and full-sib reciprocal were based on an index composed of grain yield, grain moisture, stalk lodging, and root lodging. The populations per se, populations selfed, and testcrosses of the populations to the Cycle 0 population and to inbred B79 were evaluated in our study. Response to selection was measured for grain yield, grain moisture, stalk lodging, and root lodging along with other agronomic traits. All selection methods were successful in significantly improving the population per se performance for grain yield. S2-progeny selection had the greatest response for grain yield of 4.5% cycle-1 and mass selection had the lowest response (0.6 % cycle-1). All selection programs in which index selection was practiced except for modified ear-to-row were successful in improving the populations per se for all four traits simultaneously.