Ethyl methane sulphonate (EMS) mediated changes in callus growth of clusterbean (Cyamopsis tetragonoloba L.) raised under saline conditions

摘要

Soil salinity is the major biotic stress, which restricts the distribution and productivity of the crops. Agricultural production in the future will increasingly rely on our ability to grow plants on salt affected and marginal lands using saline water. Ethyl methane sulphonate is the most commonly used chemical mutagen to increase genetic variability in crop plants and could be useful in increased plant tolerance to salinity. Clusterbean is one of the most important summer annual legume. In the present study, aseptically grown7-day old seedling explants of clusterbean viz. cotyledon, cotyledonary node, hypocotyl and the embryo axis (cut on radical side) were cultured on MS medium + B5 vitamins (MSB5 medium) supplemented with various growth regulators. Among various explant tried, cotyledonary node gave good response in terms of callus growth which was further selected for future experimentation. The best medium for callus growth was MSB5 with 2 mgl"1 2,4-D and 1 mgl"1 BAP. All the calli produced were compact and their color changed with increase of salt concentration from greenish to brownish green, dark brownish and finally blackish at 200 mM NaCl. Further, calli pieces dipped in sterile liquid MS medium adjuncted with aqueous filter sterilized solution of 0.5% EMS for a range of time duration (0.5, 1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 h) were raised on MSB5 medium without NaCl. These calli were subcultured on the above medium with or without 200 mM NaCl. EMS treatment of 2.5, 3.0 and 3.5h duration improved callus growth on salt amended medium; growth being maximum after 3.0h EMS treatment. It seems that exposing mutagen treated calli to salinity/ salt stress, forces these to face stress doubly-ionic toxicity and toxic effects of mutagen. The survival and regeneration of the putative variant calli is suppressed under such circumstances.