Abstract
Rapid and uniform seed germination is a crucial prerequisite for crop establishment and high yield levels in crop production. A disclosure of genetic factors contributing to adequate seed vigor would help to further increase yield potential and stability. Here we carried out a genome-wide association study in order to define genomic regions influencing seed germination and early seedling growth in oilseed rape (Brassica napus L.). A population of 248 genetically diverse winter-type B. napus accessions was genotyped with the Brassica 60k SNP Illumina genotyping array. Automated high-throughput in vitro phenotyping provided extensive data for multiple traits related to germination and early vigor, such as germination speed, absolute germination rate and radicle elongation. The data obtained indicate that seed germination and radicle growth are strongly environmentally dependent, but could nevertheless be substantially improved by genomic-based breeding. Conditions during seed production and storage were shown to have a profound effect on seed vigor, and a variable manifestation of seed dormancy appears to contribute to differences in germination performance in B. napus. Several promising positional and functional candidate genes could be identified within the genomic regions associated with germination speed, absolute germination rate, radicle growth and thousand seed weight. These include B. napus orthologs of the Arabidopsis thaliana genes SNOWY COTYLEDON 1 (SCO1), ARABIDOPSIS TWO-COMPONENT RESPONSE REGULATOR (ARR4), and ARGINYL-t-RNA PROTEIN TRANSFERASE 1 (ATE1), which have been shown previously to play a role in seed germination and seedling growth in A. thaliana.
Highlights
Selection bottlenecks have a large impact on the diversity available for breeders to sustain selection gains for important traits, in crop species like modern oilseed rape (Brassica napus L.) with relatively small gene pools
Abbreviations of traits are explained in Materials and Methods
Narrow-sense heritability revealed that germination performance is influenced by both genetic as well as environmental factors
Summary
Selection bottlenecks have a large impact on the diversity available for breeders to sustain selection gains for important traits, in crop species like modern oilseed rape (Brassica napus L.) with relatively small gene pools. A main focus in genetics and breeding of oilseed rape has been on analysis and improvement of general breeding targets, such as abiotic and biotic stress resistances (e.g., Obermeier et al, 2013; Hatzig et al, 2014) or flowering time optimization (Schiessl et al, 2014). Enhancement of such traits can contribute directly to an increase and stabilization of yield levels. Different studies dealing with drought (Bettey et al, 2000), salt or cold stress (Foolad et al, 1999) strengthen such correlations
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