PLANTING DATE AND PLANT-DENSITY EFFECTS ON CONDENSED TANNIN CONCENTRATION OF COTTON

Condensed tannins are feeding deterrents to cotton bollworm [Helicoverpa zea (Boddie); syn. Heliothis zea], tobacco budworm [Helicoverpa virescens (F.); syn. Heliothis virescens], and spider mite (Tetranychus urticae Koch) in cotton (Gossypium hirsutum L.). This study was conducted to determine the effects of planting date and plant density on the condensed tannin concentrations of six plant parts of cotton sampled at two growth stages at College Station, TX, in 1988 and 1989. Cotton was sown every 2 wk to provide three planting dates beginning on 25 April in both years. Genotypes evaluated were 'Tamcot CD3H', 'Arkot 518', and four high-tannin lines (TAM 8611124, TAM 86E3, TAM 86E8, and 86CC2) selected for spider mite resistance. The topmost unfolded leaf, a fourth mainstem leaf from the terminal, a 6-d-old bract, a 10-d-old sepal, and a bract and a sepal from a white bloom were sampled at first bloom and at 2 wk post first bloom from plants spaced 8 and 30 cm within rows spaced 1.02 m apart. Younger tissue consistently had a higher condensed tannin concentration than mature tissue. Condensed tannin concentrations were highest in TAM 8611124 and lowest in the two commercial cultivars, Arkot 518 and Tamcot CD3H. TAM 86E8, TAM 86E3, and 86CC2 were intermediate in tannins. Breeding cotton for high tannin concentration would require consideration of the tissue sampled because of the interaction of genotype with this factor.