Proline, P5CS activityand glycine betaine content in intra-hirsutum (HxH), inter-specific (HxB) and G. arboreum cultivars under water stress

Water stress created by with holding irrigation caused significant increase in free proline and glycine betaine content in the leaves of intra-hirsutum (HxH), inter-specific (HxB) and G. arboreum cultivars of cotton. The increase in the levels of proline is mainly attributed to de-novo synthesis of proline as evident from increased activity of P5CS specifically in G. arboreum cultivars. However, besides de novo synthesis of proline, loss of feed back inhibition of free proline appears to operate in regulating the levels of free proline in intra-hirsutum and inter-specific hybrids. Cotton is a natural glycine betaine accumulator and hence, a higher level of glycine betaine was recorded in control plants, which further increased on imposition of stress. A significant variation in the levels of free proline and glycine betaine was observed in all the cultivars tested. The levels of both the osmolytes increased simultaneously and can be used to select the drought tolerant segregating population involving breeding of cotton for drought tolerance.