LEAF SURFACE WETNESS IN SORGHUM AND RESISTANCE TO SHOOT FLY, ATHERIGONA-SOCCATA - ROLE OF SOIL AND PLANT WATER POTENTIALS

In experiments with potted plants, the relationships between soil matr ic potential, plant water potential and production of water droplets ( leaf surface wetness) on the folded central whorl leaf of seedlings of sorghum genotypes that are either resistant or susceptible to shoot f ly (Atherigona soccata) damage were investigated. Differences in soil matric potentials in the pots affected the plant water status, which i n turn had profound effects on the production of water droplets on the central whorl leaf of the sorghum genotype susceptible to shoot fly. There was no consistent variation in the relationship between plant wa ter potential and soil matric potential of resistant and susceptible s orghum genotypes. However, there was very little or practically no wat er droplets on the central whorl leaf of the resistant genotypes, indi cating that the production of water droplets is not solely the result of internal water status of the plant. It is suggested that leaf surfa ce wetness is genetically controlled and that an understanding of the mechanism by which water is transferred to the leaf surface will enhan ce breeding for resistance to shoot fly.