RESISTANCE OF COMMON BEAN LINES TO THE POTATO LEAFHOPPER (HOMOPTERA, CICADELLIDAE)

In 1993, seed from the EMP series reportedly resistant to leafhoppers (Empoasca kraemeri Ross & Moore), was obtained from Centro Internacion al de Agricultura Tropical (CIAT), South America and planted at Ridget own, ON. Under severe potato leafhopper, Empoasca fabae (Harris), pres sure the selections exhibited varying degrees of leafhopper injury. Th e majority of the EMP lines displayed lower hopperburn scores than 'Ex Rico 23' white navy bean. In 1994 and 1995 the selected EMP lines wer e planted in small field plots at Ridgetown along with locally adapted bean cultivars of high susceptibility, moderate susceptibility, and m oderate resistance. Numbers of nymphs varied among genotypes with some EMP lines sustaining concomitant low nymphal populations and low hopp erburn scores, suggesting an antixenosis effect. However, several EMP lines exhibiting low hopperburn scores sustained high numbers of nymph s suggesting a tolerant mode of resistance. Uniformity of adult leafho pper populations among plots suggests that the mechanism of resistance has no effect on adult populations. The data from these experiments d emonstrate that there is a high level of resistance to potato leafhopp ers in several of the breeding lines obtained from CIAT, such as EMP 4 23 and EMP 419, and that many of these lines are adapted to the growin g conditions of southern Ontario.