Gossypium hirsutum L. Texas race stocks numbers 254, 277, 695, 810, 953, 1055, 1122, and 1123 show resistance to pests, and numbers 2077, 2079, 2083, 2103, 2105, 2154, 2190, and 2193 are used for treatment of asthma in Mexico and the Caribbean. These stocks and the cultivars 'TAMCOT CAMD-E' and 'Stoneville 213' were grown to the ten-leaf stage in the greenhouse at College Station, Texas. One-half of each of the top three leaves from each of nine plants per race stock or cultivar was collected, and concentrations of volatile terpenes extracted by ethyl ether were determined by capillary gas chromatography. The cultivars contained slightly more than 1000 ppm of total volatile terpenes per gram of fresh weight. All race stocks, except 695, contained significantly (P = 0.05) higher concentrations of the volatile terpenes than the cultivars. The pest resistant race stocks average 209% and the medicinal stocks 227% as much volatile terpene as 'TAMCOT CAMD-E'. Race stocks 254, 277, 1055, 1123, 2154, and 2193 contained more than 250% of the concentration in 'TAMCOT CAMD-E'. Seven different qualitative variations were found in the composition of volatile terpenes in the race stocks compared to the cultivars. In some cases the variations occurred in only part of the plants of a stock. Stocks 254, 277, 2077, 2079 and 2105 did not contain limonene, -pinene and -pinene, which made up about 15% of the total volatile terpenes in the cultivars. Stocks 254, 277, 695, 810, 953, 1055, 2083, 2154, 2190, and 2193 did not contain Y-bisabolene and -bisabolol which made up over 20% of the total volatile terpenes in cultivars. -Caryaphyllene and -humulene made up only 2.6 and 1.1% of the total volatile terpenes in stock 953 compared to 27.7 and 8.1% in 'TAMCOT CAMD-E'. Copaene which makes up about 1% of the total volatile terpene in the cultivars was absent from stock 2193, but occurred in excess of 4% in stocks 2083 and 2103. Compounds that were not detected in the cultivars but made up more than 5% of the total volatile terpenes in race stocks included: Y-terpinene in stocks 695 and 2083; unknown 17.65 (unknown numbers refer to the retention times in minutes) in stocks 254, 810, 2077, 2079, 2103, 2105, 2154, 2190, and 2193; and unknown 17.75 in stocks 695, 953, and 1055. Unknown 17.65 (12.7%) in stock 810 is probably different from unknown 17.65 in the other race stocks because its concentration was consistently associated with that of another unknown 17.50 (9.9%), whereas in other stocks 17.50 was missing and unknown 17.65 was consistently associated with the minor unknown 18.00. All the medicinal race stocks, except 2083, contained more than 7% of the unknown 17.65, which was missing from cultivars and occurred only sporadically at low concentrations in the pest-resistant race stocks. Thus, this compound may be associated with the medicinal properties of these race stocks.

The inheritability of quantitative differences in volatile terpenes were examined by crossing appropriate race stocks with 'TAMCOT CAMD-E' and determining the volatile terpene content of five Fl and five selfed progeny for each parent of each of the crosses. Both increased concentration of total volatile terpenes and the occurrence of various specific volatile terpenes were partially dominant; there was no evidence for regulatory genes being involved in the control of concentrations. Thus, it should be possible to construct genetically at least 128 different compositions of volatile terpenes in Upland cotton.