Submitted to: Theoretical and Applied Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/4/2004
Publication Date: 1/16/2005
Citation: Ipek, M., Ipek, A., Almquist, S.G., Simon, P.W. 2005. Demonstration of linkage and development of the first low-density genetic map of garlic based on aflptm markers. Theoretical and Applied Genetics. 110:228-236. Interpretive Summary: Genetic analysis of garlic has only been possible with the recent development of methods to routinely produce seed. Genetic linkage maps of chromosomes are prepared for detailed genetic analysis to determine the location of the genes. This research reports the first genetic linkage map for garlic. This information is of interest to garlic growers and researchers since it establishes a foundation for future garlic genetic analysis.
Technical Abstract: Garlic (Allium sativum L.) is a long-cultivated clonally propagated diploid plant (2n=2x=16). With routine seed production now underway we used populations (MP1 and MP2) generated by self pollination of unrelated plants to generate two low-density genetic maps of garlic consisting of AFLP and gene-specific markers. We did not observe any two plants with identical marker patterns in either population indicating that they were the result of amphimixis rather than apomixis. This is an important finding since several Alliums are facultative apomicts. A total of 360 markers segregated in MP1 (12.8 AFLP markers per primer combination) and 321 markers segregated in MP2 (13.9 per primer combination) to indicate a fairly high level of genetic heterozygosity in the garlic nuclear genome. Of these markers, 15.3% in MP1 and 24.3% in MP2 had segregation ratios distorted from the expected 3:1. Interestingly, 94.7% of those distorted segregations fit a 15:1 segregation ratio for duplicated loci suggesting extensive levels of duplication in the garlic genome and supporting similar observations for onion. The genetic map for the MP1 family with 216 markers spanned 1166 cM of the garlic genome (5.4 cM average) while 143 markers of MP2 spanned 862 cM (6.0 cM average). Gene-specific markers for alliinase, chitinase, sucrose 1-fructosyltransferase (SST-1) and chalcone synthase (CHS) were mapped demonstrating the immediate utility of the garlic genetic map. These two garlic families had relatively few segregating AFLP markers in common, which supports their relatively distant relationship based on diversity analysis. Of those markers that were conserved, linkages were also conserved.