Relationship between resistance to blue-green aphid and to pea aphid in lucerne

Abstract

Seedling tests were conducted to investigate the possibility of a relationship between resistance to blue-green aphid (BGA) and resistance to pea aphid (PA) in lucerne. The Australian- bred lines tested generally had a higher level of resistance to BGA than to PA, but the reverse was true in lines from the U.S.A. Within the 23 lines tested, levels of BGA and PA resistance were highly correlated (r = 0.92, P< 0.001). While it was evident that BGA resistance and PA resistance were related, further work is required to determine the exact nature of the relationship. Possible genetic explanations discussed are close linkage and pleiotropy. The possibility of a metabolite conferring PA resistance being produced at an earlier step in the pathway leading to the production of the compound controlling BGA resistance is also discussed.