Terpenoid Aldehydes in Upland Cottons. II. Genotype-Environment Interactions

Cotton (Gossypium hirsutum L.) has unique secondary natural products, sesqui- and sesterterpenoid aldehydes, that have the potential to control phytophagous insect pests, but information on their inheritance has been limited to only one compound, gossypol (G). The objective of this study was to determine genetic and environmental variances and interactions, heritability, and genotypic stability for the major nonvolatile terpenoids in foliar pigment glands. A genotype-by-environment experiment, which included 14 genotypes having from normal to very elevated terpenoid content, was conducted at five diverse Texas locations over 2 yr. Flower buds at the third-grown square stage and first nonglossy terminal leaves were sampled 3 wk after first bloom and analyzed by high performance liquid chromatography (HPLC) for G, p-hemigossypol quinone (HGQ), and the heliocides H₁, H₂, H₃, and H₄. Aniline-reaction measurements were made for total flower bud terpenoids. The HPLC data for location means showed differences between the high and low values ranging from eightfold for leaf HGQ to less than twofold for flower bud H₂. Genetic ✕ environment variance components were less than genetic variance components in all instances and were generally very small. Error variance exceeded genetic variance only for HGQ, G, and H₄ in leaves and for H₄ in flower buds. Broad-sense heritabilities averaged 0.46, 0.94,0.61, and 0.93 for leaves on a plotbasis, leaves on an entry mean-basis, flower buds on a plot-basis, and flower buds on an entry mean-basis, respectively. Stability analyses gave regression coefficients from 0.06 to 2.11 (1.00 defined a stable genotype.) for high-terpenoid lines, whereas commercial cultivars had values from 0.11 to 1.05. Our results indicated that plant breeders and geneticists can select for higher terpenoid levels if this goal is considered desirable in the broad context of increasing cotton host-plant resistance. Texas Agric. Exp. Stn. manuscript TA-24413.