DIVERGENT SELECTION FOR EGG NUMBER IN TRIBOLIUM-CASTANEUM .2. CORRELATED RESPONSES IN HATCHABILITY, PUPATION TIME AND ADULT EMERGENCE TIME

Two-way family selection for 8-10 day total egg number (TEN) at 33.33 and 50.00% selection intensities for 7 generations was practised in Tribolium castaneum. Its correlated responses in unselected traits, viz. hatchability, pupation time (PT) and adult emergence time (AT), were studied with the help of a contemporaneous control line. The estimates of heritability obtained from dam components were higher than that from sire + dam components followed by sire components in all the 3 unselected traits. The base population and the control line showed almost similar trend. In general, the magnitude of heritabilities for the different traits was moderately high. The genetic and phenotypic correlations between TEN and hatchability were positive and of moderately high magnitude, whereas the values for TEN with PT and AT were negative and of high magnitude in the base population, selected and control lines. The average hatchability percentage increased by 1.61 and 1.49 in the HS1 and HS2 lines respectively. It decreased by 0.41 and 0.44 in the LS1 and LS2 lines respectively. There was a shortening of PT by 0.44 day in each of the high selected line, whereas a lengthening of the period by 0.25 and 0.26 day only observed in the low selected lines. LS1 and LS2, respectively, after 7 generations of selection. Almost similar trend was recorded in AT with respect to its shortening and lengthening. There was a poor agreement between the ratio of observed and expected correlated responses for all the traits.