Modifications of evaluation index and subordinate function formulae to determine superiority of mulberry silkworm crosses

Characters of silkworm could be divided into positive and negative directions. Highest values were preferred for positive direction while lowest performance was preferred for negative direction traits such as mortality, duration, double cocoon, etc. Since 1993, evaluation index formula, as well as subordinate function formula was used in 1971 for determines superior silkworm varieties. It is very easy to apply these formulae on positive direction characters. But these formulae are not suitable for negative direction characters. Some researchers were applying these formulae on both positive and negative characters. Other researchers neglected calculations of evaluation index and subordinate function for negative direction characters. The present study suggested new modifications of evaluation index and subordinate function formulae for easily calculation of all characters. Thirteen single hybrids of mulberry silkworm Bombyx mori L. were used in this investigation. Results reveal that, using suggested modified formulae would change the decision of judgment of superiority of some hybrid genotypes.