Effect of Jasmonic Acid on Growth Characteristics of Calli derived from Mature Embryos of Wheat Cultivars showing Differential Resistance to Karnal Bunt (Tilletia indica)

Effect of jasmonic acid (JA) was observed on the modulation of plant growth, differentiation and senescence under in vitro conditions. Calli raised from both Karnal bunt (KB) susceptible and resistant cultivars of wheat, were sub-cultured in MS medium containing different concentrations of JA (0, 10, 25, 50, 100 �M) and observed at different time intervals. It was found that low concentration of JA (up to 25 �M) did not hamper the growth and development of calli but at high concentrations (> 50 �M), inhibited the growth of calli. In the absence of JA, the calli proliferated to attain a maximum size; however, size of calli drastically decreased and attained minimum at 100 �M concentration of JA. It was also evident by growth doubling time (GDT) values which were increasing with the increase in JA concentration. However, GDT values remained significantly higher for susceptible callus than resistant. Similarly, the extent of inhibition of root proliferaion was more pronounced at higher concentrations of JA. At zero or very low concentration of JA (10�M), most of the calli of both the cultivars were green up to 30 days in callus maintenance medium. However, at 25 �M, few calli turned brown and extent of senescence increased at higher concentrations. The induction in protease activity differed in susceptible and resistant cultivars and calli grown in the presence of JA showed lower protease activity than the calli grown in the absence of JA at later stages of growth of calli.