Abstract
Key messageDoubled-haploid libraries from landraces capture native genetic diversity for a multitude of quantitative traits and make it accessible for breeding and genome-based studies.Maize landraces comprise large allelic diversity. We created doubled-haploid (DH) libraries from three European flint maize landraces and characterized them with respect to their molecular diversity, population structure, trait means, variances, and trait correlations. In total, 899 DH lines were evaluated using high-quality genotypic and multi-environment phenotypic data from up to 11 environments. The DH lines covered 95% of the molecular variation present in 35 landraces of an earlier study and represent the original three landrace populations in an unbiased manner. A comprehensive analysis of the target trait plant development at early growth stages as well as other important agronomic traits revealed large genetic variation for line per se and testcross performance. The majority of the 378 DH lines evaluated as testcrosses outperformed the commercial hybrids for early development. For total biomass yield, we observed a yield gap of 15% between mean testcross yield of the commercial hybrids and mean testcross yield of the DH lines. The DH lines also exhibited genetic variation for undesirable traits like root lodging and tillering, but correlations with target traits early development and yield were low or nonsignificant. The presented diversity atlas is a valuable, publicly available resource for genome-based studies to identify novel trait variation and evaluate the prospects of genomic prediction in landrace-derived material.
Highlights
Maize (Zea mays L. ssp. mays) seed banks around the world harbor thousands of landrace accessions, representing a rich resource of currently untapped native diversity that could be harnessed for plant improvement and adaptation to environmental changes (Hoisington et al 1999; Ortiz et al 2010; McCouch et al 2013; Hellin et al 2014; Wang et al 2017)
While 95.3, 96.6, and 96.7% of the molecular variance were found within S0 and DH of KE, PE, and LL, respectively, less than 5% of the molecular variance was explained by differences between S 0 gametes and DH lines of different landraces
The contribution of rare alleles to the additive genetic variance is small and the molecular variance assessed with array data should translate directly into genetic variation observable in phenotypes
Summary
Maize (Zea mays L. ssp. mays) seed banks around the world harbor thousands of landrace accessions, representing a rich resource of currently untapped native diversity that could be harnessed for plant improvement and adaptation to environmental changes (Hoisington et al 1999; Ortiz et al 2010; McCouch et al 2013; Hellin et al 2014; Wang et al 2017). Mays) seed banks around the world harbor thousands of landrace accessions, representing a rich resource of currently untapped native diversity that could be harnessed for plant improvement and adaptation to environmental changes (Hoisington et al 1999; Ortiz et al 2010; McCouch et al 2013; Hellin et al 2014; Wang et al 2017). European flint maize went through several bottlenecks, the first of which occurred in the Americas (Doebley et al 1986), followed by the introduction to Europe (Rebourg et al 2003). In the course of maize breeding, landraces were replaced by hybrids. Subsequent selection at high intensities has led to an additional decline in genetic diversity of elite germplasm, especially within the flint heterotic pool important for European maize breeding (Messmer et al 1992; Reif et al 2005a, b; Lu et al 2009). Revisiting the vast diversity of landraces stored in seed banks is considered a promising approach
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