RESISTANCE IN SORGHUM TO SHOOT FLY ATHERIGONA-SOCCATA - EVIDENCE FOR THE SOURCE OF LEAF SURFACE WETNESS

Leaf surface wetness (LSW) of the central whorl leaf of sorghum seedli ngs has been associated with susceptibility to shoot fly. Previous phy sical and physiological evidence suggested that LSW originates from th e plant. This was confirmed by radioactive labelling methods using tri tium and carbon-14. Tritiated water applied to the soil of potted seed lings was translocated to the surface of the whorl leaf. There were si gnificant differences in the amount of tritiated water collected from susceptible (CSH 5) and resistant (IS 18551) genotypes. Studies with c arbon-l4 labelling of sorghum seedlings indicated the presence of (sma ll amounts of) solutes in the surface water that may affect larval mov ement and survival.