Phenotypic selection among maize (Zea mays L.) doubled haploid (DH) lines may be conducted in a single year (one-stage selection) or in two years at more locations (two-stage selection). Furthermore, estimates of quantitative trait locus (QTL) effects among DH lines may be used in marker-assisted recurrent selection (MARS). Our objective was to determine the usefulness of one- and two-stage phenotypic selection among DH testcrosses versus MARS that exploits QTL estimates from DH lines. We evaluated testcrosses of 430 DH lines in multienvironment trials in 2006 and identified marker-trait associations for grain yield, moisture, plant integrity, and stay green. We then conducted three cycles of MARS from the F 2 of the original cross and intercrossed the best DH lines in the original mapping population. We also selected, based on testcross phenotypic values, the best DH lines in 2006 (Phen-1) and in 2006 and 2007 (Phen-2). In field evaluations in 2008, the means for each of the four traits and for a multiple-trait index were generally comparable between the MARS cycles and Phen-2, and were superior to those in Phen-1. Frequencies of favorable marker alleles increased with MARS. While MARS led to favorable selection responses, the responses to each cycle of MARS were inconsistent. This result suggested that progenies from all cycles of MARS should be sampled and tested for their performance to capture variation in the response. We concluded that multiple cycles of MARS based on QTL mapping in a DH population lead to the same amount of genetic gain as two-stage DH testcross selection but at a much lower cost.
|Original language||English (US)|
|Number of pages||10|
|State||Published - Dec 1 2009|
- Doubled haploids
- Marker-assisted recurrent selection
- Molecular markers