Occurrence of Terpenoid Aldehydes and Lysigenous Cavities in the 'glandless' Seeds of Australian Gossypium Species

Abstract

The presence of lysigenous cavities filled with terpenoid aldehydes (generically termed 'gossypol') in most tissues of cultivated cottons and their relatives imparts natural resistance to a variety of insect, fungal, and bacterial pests. Deposition of terpenoid aldehydes in cultivated cotton seed, however, renders cottonseed oils and protein meals toxic to non-ruminant animals, including humans. Seeds of the socalled 'glandless-seeded' Australian Gossypium L. species (Gossypium subgenus Sturtia (R.Br.) Tod.) reportedly lack terpenoid aldehydes, and thus may represent an important genetic resource in the development of cottonseed oils and protein meals free of these toxins. Information supporting this assertion, however, is fragmentary and contradictory. To resolve this, seeds of all known Australian Gossypium species were surveyed chemically and anatomically. Immature lysigenous cavities were present in seeds of all 18 species. Lysigenous cavities of sect. Sturtia and sect. Hibiscoidea Tod. seeds were unpigrnented and invisible to the naked eye, while pigmented, macroscopically visible lysigenous cavities occurred in all the sect. Grandicalyx (Fryxell) Fryxell seeds. HPLC (high performance liquid chromatography) analysis revealed that sect. Sturtia and sect. Hibiscoidea seeds did not contain detectable levels of terpenoid aldehydes, but that sect. Grandicalyx seeds contained gossypol.

Expression of the “glanded-plant and glandless-seed” trait of Australian diploid cottons in different genetic backgrounds

“…In these genotypes, a decrease in the TTA content was observed despite the maintenance of a high number of pigment glands per leaf and flower bud unit area. This observation was in accordance with those of others (Altman et al 1990;Brubaker et al 1996). It indicates that separation between pigment gland morphogenesis and terpenoid synthesis mechanisms was possible in particular situations.…”

“…Pauly (1979) indicates that it is difficult to determine exactly the function of the alleles controlling the glandular character in the production and/or the storage of the terpenoid, and he stressed that more than one gene was responsible for the production of some terpenoidic compounds. Brubaker et al (1996), in a study on the presence of terpenoids and gossypol glands in seeds of the Australian species, proposed that the two mechanisms could be independent. Benedict et al (2004) discovered a somaclonal variant where a decrease in terpenoid products in seed and leaf tissues was not associated with a reduction in number or size of glands.…”

“…Among the 50 species of Gossypium, the "glandless-seed and glanded-plant" trait is found only in some Australian wild species belonging to Sturtia and Hibiscoidea sections (Brubaker et al 1996). All the Australian native diploid species belonging to these sections such as G. sturtianum and G. australe present this natural trait which means they produce seed without visible pigment glands but still possess foliar gossypol glands that endow them with a certain level of protection against herbivores.…”

Molecular systematics in Gossypium and its relatives

“…In particular, seeds of species in sect. Grandicalyx are apparently adapted for highly localized ant-dispersal (see below), and they contain terpenoid aldehydes (Brubaker et al 1996) that may be a deterrent to dispersal by many other potential dispersal agents.…”

“…All sect. Grandicalyx species have seeds containing considerable amoimts of terpenoid aldehydes (Brubaker et al 1996) that have toxicity to a broadspectrum of animals (Cherry and Leffler 1984). We have no information or direct observations on the degree to which insects, birds, or small mammals infest or harvest mature seeds of the Ktmberley species.…”