An integrated genetic linkage map for silkworms with three parental combinations and its application to the mapping of single genes and QTL.
BACKGROUND
Bombyx mori, the domesticated silkworm, is a well-studied model insect with great economic and scientific significance. Although more than 400 mutations have been described in silkworms, most have not been identified, especially those affecting economically-important traits. Simple sequence repeats (SSRs) are effective and economical tools for mapping traits and genetic improvement. The current SSR linkage map is of low density and contains few polymorphisms. The purpose of this work was to develop a dense and informative linkage map that would assist in the preliminary mapping and dissection of quantitative trait loci (QTL) in a variety of silkworm strains.


RESULTS
Through an analysis of > 50,000 genotypes across new mapping populations, we constructed two new linkage maps covering 27 assigned chromosomes and merged the data with previously reported data sets. The integrated consensus map contains 692 unique SSR sites, improving the density from 6.3 cM in the previous map to 4.8 cM. We also developed 497 confirmed neighboring markers for corresponding low-polymorphism sites, with 244 having polymorphisms. Large-scale statistics on the SSR type were suggestive of highly efficient markers, based upon which we searched 16,462 available genomic scaffolds for SSR loci. With the newly constructed map, we mapped single-gene traits, the QTL of filaments, and a number of ribosomal protein genes.


CONCLUSIONS
The integrated map produced in this study is a highly efficient genetic tool for the high-throughput mapping of single genes and QTL. Compared to previous maps, the current map offers a greater number of markers and polymorphisms; thus, it may be used as a resource for marker-assisted breeding.
Zhan
Shuai
S
Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, PR China. szhan@sibs.ac.cn
Huang
Jianhua
J
Guo
Qiuhong
Q
Zhao
Yunpo
Y
Li
Weihua
W
Miao
Xuexia
X
Goldsmith
Marian R
MR
Li
Muwang
M
Huang
Yongping
Y
D000818:Animals; D012831:Bombyx / Q000235:genetics*; D002874:Chromosome Mapping; D005260:Female; D017344:Genes, Insect; D008040:Genetic Linkage; D005819:Genetic Markers; D049750:Genome, Insect; D005838:Genotype; D008297:Male; D018895:Microsatellite Repeats; D040641:Quantitative Trait Loci; D017422:Sequence Analysis, DNA
D005819:Genetic Markers
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