GENOTYPIC AND CULTURAL-EFFECTS ON CONDENSED TANNIN CONCENTRATION OF COTTON LEAVES

Condensed tannins reportedly act as feeding deterrents to bollworm [Helicoverpa zea (Boddie)], tobacco budworm [Heliothis virescens (F.)], and twospotted spider mite [Tetranychus urticae (Koch)] in cotton [Gossypium hirsutum L.]. This study was conducted to determine the effects of planting date, plant density, growth stage, and leaf age on the condensed tannin concentration of six cotton genotypes planted at College Station, TX, in 1988 and 1989. Planting commenced on 25 April in both years and consisted of three plantings at approximately 2-wk intervals. The topmost unfolded leaf from the terminal and the fourth mainstem leaf from the terminal were sampled at five growth stages from plants spaced 8 and 30 cm, within rows spaced at 102 cm. Genotypes included two commercial checks and four high-tannin breeding lines developed in a spider mite resistance program. Condensed tannin concentration, expressed as a percentage of fresh weight, was determined spectrophotometrically following extraction with HCl-butanol. The younger leaf tissue had significantly higher levels of condensed tannins than the more mature leaf tissue. Condensed tannin concentration increased with plant age through the first-bloom growth stage. The condensed tannin concentration of plants sown on Planting Dates 1, 2, and 3 did not differ in 1988, but in 1989, plants from Planting Date 2 had higher condensed tannin concentrations than those from Planting Dates 1 or 3. Plant density did not significantly affect condensed tannin concentration. Many interactions of other factors with genotypes suggest that breeding for high tannin levels would require close attention to leaf age, growth stage, and environment.