Genetic variability and correlation analysis in hybrids of mulberry silkworm, <i>Bombyx mori</i> L. for egg characters

Abstract

Abstract:The genotypic variability and correlation coefficients were studied in thirty five hybrid populations for five egg characters. Variations among genotypes were highly significant (P<0.001). Phenotypic coefficient of variation was higher than genotypic coefficient of variation for all the characters. Of them unfertilized and dead egg percentage showed highest difference between genotypic and phenotypic coefficient of variation suggesting most influence of environment on these characters. Majority of the characters showed high heritability except hatching percentage. Furthermore total number of egg laying per female showed high genetic advance together with high heritability, which indicates the importance of additive gene effect of this character. The genotypic correlations were higher than phenotypic correlation for majority of the characters under study except DEP Vs TEL and DEP Vs UEP. These low phenotypic correlations could be due to a modifying effect of environment and the association of characters at genotypic level. Hatching percentage, blue egg percentage and unfertilized egg percentage showed both positive and negative significant correlation to each other. Therefore, proper attention should be given to these characters specially total number of egg laid by female and hatching percentage in selection programme for genetic gain in Bombyx. mori.

Selection strategies considering varietal differences with respect to egg characters of mulberry silkworm, Bombyx mori L.

“…reported high heritability together with high phenotypic and genotypic coefficient of variability of filament length and estimated cocoon yield per 100 dfls. The results of Ahsan & Rahman (2008) is similar with the present findings who reported a high heritability coupled with high phenotypic and genotypic coefficient of variability for total eggs laid by female.…”

“…Chatterjee & Pradeep (2003) investigated the relationship between yield potential and molecular markers in silkworm. Similar results on different characters of silkworm were also reported by Mistri and Jayaswal (1992), Singh et al (1994), Ahsan & Rahman (2008), and .…”

“…Ahsan et al (2000) reported that varietal differences with respect to egg, larval and cocoon characters were found in B. mori. Similar results on varietal diversity have also been substantiated by the findings of Reza & Rahman (1996) and Ahsan & Rahman (2008 The genetic parameters, phenotypic (CV p ), genotypic (CV g ) and environmental (CV e ) coefficient of variability, heritability (H), genetic advance (GA) and genetic advance as percentage of mean (GA%) were estimated and presented in Table 2. The highest phenotypic and genotypic coefficient of variation was observed in UEP and the lowest in HP whereas the highest environmental co-efficient of variation was recorded in DEP and the lowest in EW.…”

“…It suggested limited scope for manipulation of these characters. These could be due to non-additive gene action which includes dominance and epitasis (Ahsan & Rahman, 2008). In such situations, progeny testing and recurrent selection might be helpful to improve these traits (Rahman, 1984;Rao, 1997;Hasan et al, 2011).…”

“…Reproductive traits are considered important by egg producers. These traits jointly or singly influence the egg production (Reza & Rahman, 2005;Zhao et al, 2007;Ahsan & Rahman, 2008). A great diversity of polyvoltine silkworm Bombyx mori L. must exist globally, by considering the fact that a large number of silkworm breeds are already evolved by selection or cross breeding and also some of the tropical countries allowed individual farmers to produce silkworm eggs (Kumaresan et al, 2007).…”