Associated Effects of Mass Selection for Soil-Insect Resistances in Sweet Potato1

Abstract

Abstract Character associations in a sweet potato [ Ipomoea batatas (L.) Lam.] population after 4 cycles of selection for resistance to soil insects and in a control population with no selection were studied by use of contingency tables of pairs of traits. Possible common factors were indicated for resistances to the sweet potato flea beetle and the wireworm- Diabrotica-Systena (WDS) complex. Selection changed the means and distributions of 6 of 13 unselected root and vine traits. None of these changes were directly associated with insect resistances, but that in root cracking was caused by the grading techniques. Two traits appeared genetically associated (cortex thickness and leaf-whorl color), and 2 appeared to be expressions of the same character change (flesh-color changes were also expressed as skin-color changes). The selected population had shorter internodes than the unselected. These changes in unselected traits were probably due to drift caused by small population sizes in the selected generations. No barriers to development of insect-resistant cultivars were detected.