LABORATORY AND FIELD-RESISTANCE TO THE EUROPEAN CORN-BORER IN MAIZE GERMPLASM

There is a continuing need to screen maize (Zea mays L.) germplasm for sources of resistance to the European corn borer, Ostrinia nubilalis (Hubner). This study was conducted to determine the resistance characteristics to a univoltine strain of the European corn borer of six groups of maize germplasm and to examine the relationship among resistance characteristics. The groups of germplasm consisted of (i) a latitudinal series of inbred lines; (ii) a set of the indigenous landraces of Mexico; (iii) two Argentine landraces; (iv) three Canadian synthetic populations; (v) three International Maize and Wheat Improvement Center (CIMMYT) maize pools; and (vi) two inbred lines used as controls. In addition, a multiple borer resistance population was studied. All germplasm was evaluated for seedling DIMBOA [2,4-dihydroxy-7-methoxy-(2H)-1,4-benzoxazin-3(4H)-one] content, susceptibility to leaf-feeding (both laboratory and field) and to stalk tunneling by the European corn borer, susceptibility to Gibberella zeae (Schwein.) Petch (stalk rot) and Ustilago zeae (Beckm.) Unger (corn smut), and their ability to mature in the climatic conditions prevailing at Ottawa, ON. The inbred lines were characterized by high resistance to leaf feeding, but susceptibility to stalk tunneling, whereas the indigenous Mexican landraces were susceptible to leaf feeding. Many significant correlations were found among the various parameters, including validation of the relation of seedling DIMBOA levels and laboratory leaf-feeding tests with the field resistance to European corn borer. This study confirms the importance of examining broad groups of germplasm when searching for sources of resistance to the European corn borer.