Identifying Hybrid Genotypes of Mulberry Silkworm (Bombyx mori) Using Heterosis for Biological and Silk Yielding Traits

The Mulberry Silkworm Moth is an important economic and domesticated insect species that needs continuously new genetic combinations to avoid fractioning of genetic diversity and gene erosion. In this study ten bivoltine hybrids were screened by heterosis using 11 biological and silk yielding quantitative traits. Heterosis was measured using multiple evaluation index (MEI), mid-parent heterosis (MPH) and better-parent heterosis (BPH), and hybrids were ranked using MEI and cumulative sub-ordinate function (CSF). The hybrids produced MEI >50 with the highest in PO(206)xJ(101) (63.2). All hybrids produced evaluation index (EI) >50 for filament length, while seven hybrids produced EI >50 for fecundity, larval body weight, pupation rate, cocoon shell ratio and cocoon yield. The hybrids improved vigour of biological and silk yielding by 5.6% to 27.5% over respective mid-parents values. PO(206)xJ(101) produced the highest MPH (66.8%) for cocoon shell weight, while MKD(205)xC(102) produced a negative MPH (- 0.8%) for silk productivity. A mean heterosis of 4.2% to 23.0% was found over respective better-parents. PO(206)xJ(101) produced the highest BPH (54.8%) for cocoon shell weight. MKD(206)xC(102) produced a negative BPH for egg hatchability, larval body weight and pupation rate. The heterosis findings showed enough genetic divergence and variable combining ability of the parental strains. CSF varied between 0.5 and 0.79. PO(206)xJ(101), based on MEI and SF, was ranked 1(st), followed by PO(205)xC(102) and recommended for field rearing.