Evaluation of the Gossypium gene pool for foliar terpenoid aldehydes

Terpenoid aldehydes (TAs) accumulate in the lysigenous glands of Gossypium L. (cotton genus) and related genera and are toxic to many insect pests. Knowledge of the diversity of TAs available in the Gossypium germplasm pool could be useful in developing cultivars with enhanced expression of specific compounds to improve host-plant resistance (HPR). Qualitative and quantitative foliar analyses for seven TAs were performed by means of high performance liquid chromatography (HPLC) on Thespesia thespesioides (Brown ex Benth.) Fryxell and on 40 Gossypium genotypes comprising 30 species. Gossypium mustelinum Miers ex Watt had the highest leaf concentration of the heliocides H-1 and H-4 and total TAs, while heliocides H-2 and H-3, and hemigossypolone were highest in G. capitis-viridis Mauer, G. lobatum Gentry, and G. nobile Fryxell, Craven & Stewart, respectively. Gossypol was highest in T. thespesioides and an secession of G. laxum Phillips, although the former contained 60% more than the latter. Gossypium raimondii Ulbrich contained principally the unique TA, raimondal. Gossypol was the principal foliar TA in most of the D genome species, whereas, species in the B, C, F, G, and K genomic groups had very low concentrations of foliar gossypol compared with other TAs. In the AD genome, with minor exceptions, all six TAs occurred. Three distinct TA patterns were observed among seven G. laxum accessions. The diversity in biosynthesis and accumulation of TAs among Gossypium species should provide useful germplasm for modifying the TA quality and quantity of cotton. Resource material is also identified to study the metabolic pathways and regulatory mechanisms controlling the synthesis of these compounds.