A GENETIC STUDY OF EGG LAYING OF TRIBOLIUM IN OPTIMAL AND STRESS ENVIRONMENTS

Abstract

As a potential biological model of non-additive gene effects, the polygenic trait egg lay was studied in the unselected heterogenous Consejo Base Population of Tribolium castaneum in three environments: optimum (33 °C), mild stress (38 °C), and severe stress (28 °C). The measured variable was number of eggs laid by virgin females during the peak period of 7-11 days after adult emergence.Egg lay was highest in 33° (18.5 ± 0.1), followed in order by 38° (14.8 ± 0.1) and 28° (12.9 ± 0.1). Similar phenotypic variances in the optimum and mild stress environments were twice those observed in severe stress. Estimates for additive gene effects were larger than those for non-additive effects, but their relative amounts varied with environments. Heritability of egg lay was highest in the optimum environment (0.36 ± 0.03), followed by mild stress (0.30 ± 0.03) and severe stress (0.25 ± 0.03). The reverse was true for estimates of non-additive gene effects where 28° > 38° > 33° with values of 0.15, 0.09 and 0.04, respectively. All genetic correlations for egg lay in different environments were positive and large (0.69 ± 0.04 to 0.86 ± 0.02).The results suggest that egg lay in Tribolium, when observed in both optimum and stress environments, could provide an appropriate biological model for evaluating mating or selection schemes whose theoretical efficiencies vary with the relative importance of non-additive gene effects.