Abstract
The mulberry silkworm, Bombyx mori L., 1758 (Lepidoptera: Bombycidae) is classified as univoltine, bivoltine, and polyvoltine based on the annual brood frequency. Voltinism in B. mori is characterized by the occurrence of embryonic diapause (facultative and obligatory diapause). Univoltine silkworms suited to cold and temperate regions lay diapausing eggs and polyvoltine silkworms suited to tropical regions lay non-diapausing eggs. In contrast, the occurrence of diapause in bivoltine silkworms is influenced by the environment. In addition to the difference in the occurrence of embryonic diapause, larval duration, and cocoon characters show distinct variations. In the present correspondence, we are presenting an interesting observation from two silkworm races Barapath and Barapolu originating from the North-East region of India that display divergence in voltinism. The unique characteristic features of univoltine, bivoltine, and polyvoltine observed in the races are discussed explaining the occurrence.
Highlights
The silkworm, Bombyx mori L., 1758 (Lepidoptera: Bombycidae), originating from its wild ancestor, Bombyx mandarina Moore, 1852 (Lepidoptera: Bombycidae) is the only invertebrate species entirely domesticated due to its economic importance
Voltinism is determined in diapause or non-diapause eggs where the univoltine eggs enter diapause every generation, the bivoltine eggs diapause expression is determined by environmental cues and the polyvoltine eggs never enter diapause (Yamashita & Yaginuma 1991; Nurakami & Yoshiki 1989; Muniraju & Mundkur 2018)
The dominance in larval duration and cocoon characters among three voltines are recognised in the order of univoltine>bivoltine>polyvoltine (Otsuki & Sato 1997; Muniraju & Mundkur 2018)
Summary
The silkworm, Bombyx mori L., 1758 (Lepidoptera: Bombycidae), originating from its wild ancestor, Bombyx mandarina Moore, 1852 (Lepidoptera: Bombycidae) is the only invertebrate species entirely domesticated due to its economic importance. The dominance in larval duration and cocoon characters among three voltines are recognised in the order of univoltine>bivoltine>polyvoltine (Otsuki & Sato 1997; Muniraju & Mundkur 2018). Barapat and Barapolu races preserved in Central Sericultural Research and Training Institute, Pampore under germplasm breeding programme as genetic resources under temperate conditions have shown atypical voltinism.
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