METHOD: ELISA METHOD NARR: Five viruliferous aphids were confined on each plant for 5-6 days. Plants were assayed at 4-5 weeks and 8-9 weeks for PLRV using ELISA (PLRV test kit, Agdia, Inc.). Background ELISA readings are 0.01-0Tbr was susceptible while Brd was resistant. Somatic hybrids between these two parents were largely resistant as well.