Relationship between gossypol gland density on cotton squares and resistance to tobacco budworm (Lepidoptera: Noctuidae) larvae

Young tobacco budworm, Heliothis virescens (F.), larvae prefer to feed along the margin area of the calyx crown of cotton ( Gossypium hirsute L.) squares. This area is devoid of gossypol glands. On resistant cotton lines, which contain glands in the calyx crown, the larvae feed sporadically on the tissue and avoid the gossypol glands. The numbers of gossypol glands on bracts of small squares, calyx crown, bract mid-rib, and the entire calyx differed significantly between a susceptible and three resistant cotton lines. When young larvae were placed on squares for 12 d, the lines with >80 glands per small square bract or 30 glands per calyx crown produced larvae significantly smaller than did lines with fewer glands.