Improvement of tuberose (Agave amica Medik) through induced mutation breeding

Tuberose (Polianthes tuberosa Linn., changed to Agave amica (Medik.) Thiede & Goverts) is a tropical bulbous flowering plant grown commercially for its sweet-scented flowers and extraction of highly valued essential oils. The major problems in conventional breeding of tuberose are lack of genetic variability, seed sterility and self- incompatibility. To achieve the rapid evolution, induced mutation was opted. It is one of the important pathway to find variability in vegetatively propagated species like tuberose. Mutation breeding is well suited to tuberose plants because it can be easily vegetatively propagated, facilitating the production of spontaneous and induced mutations. The changes in leaf variegation, plant form, flower colour, shape and fragrance, early flowering, disease, insect and nematode resistance, stress tolerance, long shelf life/vase life and high recovery of essential oils can be easily detected from its phenotypic expression as well as from cytological studies. Induction of mutation was carried out by physical mutagens like X-rays, fast neutrons, gamma rays, etc. and chemical mutagens like- EMS, DES, Sodium azide, etc. Till now two induced mutants of tuberose namely, Rajat Rekha and Svarna Rekha have been developed by gamma rays irradiation at CSIR-National Botanical Research Institute, Lucknow, Uttar Pradesh, India. More induced mutation studies were also carried out through induced mutation. This review not only provides examples of successful mutation results obtained by physical and chemical mutagens, but it also described research on mutagenesis and compares results of X-rays, fast neutrons, gamma rays, EMS, DES, Sodium azide, etc. using tuberose plants.