The genus Amorphophallus: Cyto-histo-molecular genesis and commercial prospects

The genus Amorphophallus with 90 to 170 species primarily occurs in Tropical Asia and Africa; 10 species are endemic to India. The edible species are A. paeoniifolius. A. Konjac K. Koch, A. mulleri Bl, and A. variabilis. Amorphophallus can be divided into two groups relating to the climatic conditions. Amorphophallus species from deep equatorial that does not have a true dry period can be classified as group-2 Amorphophallus. A. paeoniifolius is a “classic” Group-1 Amorphophallus and tubers should be stored dry when dormant. Habitat destruction of Amorphophallus especially in the tropical forests of Western Ghats (India), Java, Madura, Bali, Sumatra and Indonesia has lead to the disappearance of many of the species. In situ conservation of genus can be effectively done through formation of biological reserves and sanctuaries in the ‘hot spots’ of India and Indo Malayan region. Ex situ conservation of germplasm of root and tuber crops requires special attention due to vegetative propagation. True seeds are produced by artificial pollination and appropriate breeding methods in some species. In vitro technology can be utilized at various stages in conservation, utilization and genetic improvement. Recalcitrancy in Amorphophallus can be tackled in vivo and in vitro under axenic conditions. Sprouting can be induced in vivo in dormant apical and axillary buds within 30–40 days under ambient conditions of temperature (30 ± 2°C) and moisture (60–80%). Accordingly a 100 g tuber can produce 10–30 sprouts in vivo and 100–200 sprouts in vitro. Various tools viz. biochemical, cytological, histological and molecular markers are used to study its phylogeny. Cytological variations with 26, 28 and 39(2n) numbers in Amorphophallus paeoniifolius indicate the presence of triploids and hyperploids. Molecular markers, DNA sequencing and protein characterization indicate an evolutionary trend of increasing spacer size. Insertion/deletion events are found to be common in the evolution of this spacer. Konjac glucamannan extracted from the tubers of A. konjac, being a water resistant gel forming substance found its use in drug delivery, medicine and material technology. The medicinal properties of A.paeonifolius and A.konjac are also known in ancient times. It is being used for medicinal purposes in ancient China, Japan and India. On-farm conservation of agro-biodiversity of Amorphophallus, which is based on traditional/indigenous knowledge, needs prior attention. The medicinal properties of these nutrition rich high energy food crop species needs to be reassessed and refined with biotechnological tools to meet the global challenge of food, health care and nutrition.