Fig. 1. Striga development at the vicinity of sorghum roots. (a) Three days after infection to detect germination stimulant production; (b) Two days after ethylene treatment to detect haustorial initiation activity. (1) Wild accession PQ-434, (2) cv. CK60 (high germination stimulant sorghum). Bar = 1 mm. Arrows in b2 point to haustoria.