Agronomy and Horticulture Department


Date of this Version



Published in CROP SCIENCE, VOL. 19, MARCH·APRIL 1979.


Most red clover (Trifolium pratense L.) cultivars are susceptible to attack by the yellow clover aphid (Therioaphis trifolii Monell) and the pea aphid (Acyrthosiphon pisum Harris). Starting with 27 yellow clover aphid-resistant plants selected from a wide diversity of germplasm, phenotypic recurrent selection was used to improve resistance to the two aphids. Through five cycles of testing and selection for yellow clover aphid resistance and three such cycles for pea aphid resistance, a synthetic, 'N-2', was developed that had a high level of resistance to both aphids.