Glandular hairs providing resistance to aphids in certain wild potato species

SUMMARY Glandular hairs occur abundantly on Solanum polyadenium, S. tarijense and S. berthaultii. An exudate is discharged from the glandular hair when an aphid mechanically ruptures the cell walls. On contact with atmospheric oxygen, a chemical reaction is initiated in which the clear, water‐soluble material contained in the hair changes to a black insoluble material which is precipitated on the aphid's limbs. This initially impedes its movements and further accumulations eventually stick the aphids to the plant so that they are immobilized and starve to death. In experiments described, about 30 % of infesting aphids were completely immobilized within 24 h. The potential value of this source of resistance to aphids, if incorporated into the cultivated potato, is discussed, especially with reference to the advantages of its being combined with other forms of resistance and to its effectiveness against virus vectors.