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

Condensed tannins are feeding deterrents to cotton bollworm [Helicover pa zea (Boddie); syn. Heliothis zea], tobacco budworm [Helicoverpa vir escens (F.); syn. Heliothis virescens], and spider mite (Tetranychus u rticae Koch) in cotton (Gossypium hirsutum L.). This study was conduct ed to determine the effects of planting date and plant density on the condensed tannin concentrations of six plant parts of cotton sampled a t two growth stages at College Station, TX, in 1988 and 1989. Cotton w as sown every 2 wk to provide three planting dates beginning on 25 Apr il in both years. Genotypes evaluated were 'Tamcot CD3H', 'Arkot 518', and four high-tannin lines (TAM 8611124, TAM 86E3, TAM 86E8, and 86CC 2) selected for spider mite resistance. The topmost unfolded leaf, a f ourth mainstem leaf from the terminal, a 6-d-old bract, a 10-d-old sep al, and a bract and a sepal from a white bloom were sampled at first b loom and at 2 wk post first bloom from plants spaced 8 and 30 cm withi n rows spaced 1.02 m apart. Younger tissue consistently had a higher c ondensed tannin concentration than mature tissue. Condensed tannin con centrations were highest in TAM 8611124 and lowest in the two commerci al cultivars, Arkot 518 and Tamcot CD3H. TAM 86E8, TAM 86E3, and 86CC2 were intermediate in tannins. Breeding cotton for high tannin concent ration would require consideration of the tissue sampled because of th e interaction of genotype with this factor.