RFLP Linkage Map of an Alfalfa Meiotic Mutant Based on an F1 Population

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Abstract
RFLP linkage maps of two diploid alfalfa genotypes, a mutant producing 2n eggs at high frequency (PG-F9; 50 RFLP loci) and a genotype of cultivated alfalfa at the diploid level (W2x-1; 55 RFLP loci), were produced using a pseudo-testcross strategy. Codominant markers with no more than one RFLP allele in common between the two parents and dominant markers segregating 1:1 were scored in an F1 population and used for linkage analysis. Bridge loci segregating in both parents were used to align the two maps, resulting in the detection of eight major linkage groups with at least one bridge locus. Thirty-five RFLP loci detected by a set of DNA clones used previously for mapping in diploid alfalfa allowed a comparison with previously published alfalfa linkage maps. Only a few discrepancies were observed, and these were mainly due to DNA probes detecting multiple RFLP loci, suggesting the presence of unlinked duplicated regions in the alfalfa genome A low level of segregation distortion (8.8%) was observed compared to previously published alfalfa maps obtained using F2 or back-cross mapping populations. Our results indicate that noninbred F1 mapping populations could be used to overcome the possible effects of inbreeding depression on segregation distortion for generating genetic linkage maps in diploid alfalfa.

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