Comparison on Mitochondrial DNA Fingerprint for Identification of Thai Native Silkworm Varieties

Abstract

There are many varieties of Thai native silkworms, Bombyx mori Linnaeus, showing high potential for silk product improvement. However, since they are all very closely related and basically have morphological identity especially in their adult stage, it is difficult to identify them in a breeding process. Therefore, a molecular technique, Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP), was applied to study among 5 native silkworm varieties; Nonrusee, Nanglai, Keawsakol, Nangluang and Nangnoisrisaket 1, and compared to a wild silkworm, Philosamia ricini Boisduval. The regions between cytochrome oxidase subunit I-II gene (COI-COII gene) from mitochondrial genome of all silkworms were amplified by PCR, and were digested with 9 restriction enzymes; Bfa I, Cla I, Hha I, Mbo I, Mse I, Msp I, Rsa I, Taq I, and Xnm I to generate band polymorphisms on agarose and polyacrylamide gel. Four restriction enzymes; Cla 1, Hha 1, Msp I, and Xnm I were not useful in separating the Thai native silkworm varieties and the wild silkworm. However, there were five restriction enzymes that cut the COI-Coll gene target, and four of them; Bfa 1, Mbo I, Rsa I, and Tag I generated band patterns to differentiate between Thai native silkworm varieties and the wild silkworm. Only Mse I produced band polymorphisms that is not only separated the Thai native group from the wild one, but also divided them into two groups. The first group composed of Nonrusee and Nanglai, and the second group consisted of Keawsakol, Nangluang, and Nangnoisrisaket 1