Abstract
Landraces are valuable genetic resources for broadening the genetic base of elite germplasm in maize. Extensive exploitation of landraces has been hampered by their genetic heterogeneity and heavy genetic load. These limitations may be overcome by the in-vivo doubled haploid (DH) technique. A set of 132 DH lines derived from three European landraces and 106 elite flint (EF) lines were genotyped for 56,110 single nucleotide polymorphism (SNP) markers and evaluated in field trials at five locations in Germany in 2010 for several agronomic traits. In addition, the landraces were compared with synthetic populations produced by intermating DH lines derived from the respective landrace. Our objectives were to (1) evaluate the phenotypic and molecular diversity captured within DH lines derived from European landraces, (2) assess the breeding potential (usefulness) of DH lines derived from landraces to broaden the genetic base of the EF germplasm, and (3) compare the performance of each landrace with the synthetic population produced from the respective DH lines. Large genotypic variances among DH lines derived from landraces allowed the identification of DH lines with grain yields comparable to those of EF lines. Selected DH lines may thus be introgressed into elite germplasm without impairing its yield level. Large genetic distances of the DH lines to the EF lines demonstrated the potential of DH lines derived from landraces to broaden the genetic base of the EF germplasm. The comparison of landraces with their respective synthetic population showed no yield improvement and no reduction of phenotypic diversity. Owing to the low population structure and rapid decrease of linkage disequilibrium within populations of DH lines derived from landraces, these would be an ideal tool for association mapping. Altogether, the DH technology opens new opportunities for characterizing and utilizing the genetic diversity present in gene bank accessions of maize.
Highlights
According to molecular evidence, maize (Zea mays L.) was introduced into Europe over two distinct paths
The goals of this study were to (1) evaluate the phenotypic and molecular diversity captured within doubled haploid (DH) lines derived from European landraces and compare them with the diversity of elite flint (EF) lines, (2) assess the breeding potential of DH lines derived from landraces to broaden the genetic base of the EF germplasm, and (3) compare the performance of each landrace with the synthetic population produced from their respective DH lines
Owing to the large estimates of genotypic variance among the DH lines derived from landraces, individual lines with superior performance for agronomic and morphological traits can be selected and introgressed into the elite material
Summary
Maize (Zea mays L.) was introduced into Europe over two distinct paths. A first introduction of Caribbean Flint maize in Spain by Colombus in 1493 was followed by introductions of Northern Flints from North America to North-Western Europe during the 16th century [1]. This flint maize was cultivated as open-pollinated populations in different regions of Europe over centuries, resulting in a broad diversity of landraces. The value of landraces as genetic resources was recognized before their extinction. They were collected at their growing locations and are being conserved ex situ, in gene banks
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