Comparison of conventional, modified single seed descent, and doubled haploid breeding methods for maize inbred line development using GEM breeding crosses

Choice of germplasm combined with use of efficient breeding methods and careful evaluation are essential tools for maize inbred line and hybrid development. Breeding crosses from the Germplasm Enhancement of Maize (GEM) project (www.public.iastate.edu/∼usda-gem) between exotic accessions and elite Corn Belt inbreds provide a unique opportunity for broadening US Corn Belt Maize germplasm by selecting exotic alleles in an elite genetic background. Progress in GEM could be enhanced by identifying more efficient procedures for both developing inbreds and determining which of the several hundred GEM breeding crosses have the most potential for future improvement and gene discovery.;The primary research objective was to compare four breeding methods for their effectiveness and efficiency for developing superior maize inbred lines and hybrids from GEM breeding crosses. In addition, the study also aimed at identifying breeding methods that could be useful for prioritizing GEM breeding crosses for further line development and trait identification. Furthermore, breeding methods were compared to determine the effectiveness of mass selection for producing more adapted genotypes from GEM breeding crosses. Four breeding methods; Conventional GEM (CG), Conventional Mass (CM), Modified Single Seed Descent (MSSD) and Doubled Haploid ( DH) were compared using three GEM breeding crosses ANTIG01:N16DE4, AR16035:S0209, and DKXL212:S0943b.;Results showed that more DH lines were recovered from the non-stiff stalk than from the stiff stalk breeding crosses in the DH method due to differences in chromosome doubling rather than the induction phase. Field observations showed more uniformity in the MSSD S2 lines derived from the Stiff Stalk than the non-Stiff Stalk (ANTIG01:N16DE4) breeding cross. The testcross evaluations generally showed no method effects between breeding methods, but method effects were present in the per se agronomic evaluations. The MSSD and CM methods had a higher proportion of top five lines in the second year testcross evaluations (about one third each) based on both yield and yield/moisture performance compared to the CG and DH methods. Hybrids from MSSD lines tended to have higher grain moisture than hybrids from the CG, CM and DH methods, but MSSD hybrids with high yield/moisture could be selected. The MSSD method may be an effective and efficient alternative to both pedigree and DH methods for developing high performing lines from the GEM breeding crosses.