Abstract: Polymerase chain reaction and PCR products directly sequencing method (a few samples sequenced by cloning) were used to analyze the genetic diversity of the wild mulberry silkworm, Bombyx mandarina in China and the phylogeny of the domesticated silkworm, B. mori. A total of 715 bp nucleotides of partial amylase gene amy were sequenced in thirty-four samples from three groups of B. mandarina and four types of B. mori. Fifty-six polymorphic sites, including 28 singleton variable sites and 28 parsimony informative sites, defined 28 haplotypes. The nucleotides diversity (π) was 0.01390±0.00103 and the haplotype diversity (Hd) was 0.988±0.011. Mismatch analysis and Fu’s Fs test revealed the population expansion of B. mori in the past. Analysis of molecular variance (AMOVA) suggested that genetic variance mostly existed within populations and accounted for 82.63% of total variation. Variance between population and population-groups was not significant. The phylogenetic analysis indicated that three clusters were formed by the thirty-four samples analyzed. Cluster A consisted of B. mandarina from different regions and B. mori from different types, which was further divided into three sub-clusters. Cluster B consisted of three B. mori and one B. mandarina, while cluster C consisted of B. mandarina from different regions only. There is no ancestor haplotype and dominant haplotype in the median-joining network. The results suggest that: (1) the amy gene is a molecular marker with rich diversity in silkworms; (2) there is great genetic diversity within B. mandarina population in China; and (3) the domesticated silkworm may be domesticated from multi-typed B. mandarina, which supports the theory of multiple origins from a variety of B. mandarina.

Key words: Domesticated silkworm (Bombyx mori), wild mulberry silkworm (B. mandarina), genetic diversity, phylogeny, amylase gene (amy)