Effect of Extra Water and Space on Selection Efficiency of Plus Trees in Eucalyptus tereticornis

The effect of extra water and space enjoyed by the parents were studied on their progenies. To study the water effect, four plantations were selected wherein the water channels were passing through. Five parents on water channel and five away from the water channel were selected randomly in each plantation. Similarly, in other four plantations, five parents in external row and five in internal rows per plantation were selected to study the space effect. The parents on water channel and in external row had significantly more height and diameter than those of away from water channel and in internal rows respectively. However, the mean values for height and collar diameter between the progenies of these contrasting parents had no significant differences. These results show that the parents having superior phenotype due to extra water or extra space facilities did not contain superior gene combinations for these traits indicating that such parents should not be selected as plus trees for a breeding programme. In plantations, selection of superior phenotypes having no extra advantage of water or space were expected to increase the selection efficiency. The results have been discussed in the light of improving the selection efficiency for plus trees.