4.5 Inoculation techniques of plants

Blog entry week 16-20/2015

 Somaclonal variation could not be reported within different samples of callus derived from one plant of origin. Why is that an important fact considering a clonal mass propagation of neem?

 Tissue culture-induced genetic variations i.e., somaclonal variations have been reported to occur frequently in clonally propagated plants (Larkin and Scowcroft, 1981).

Although neem produces a large number of seeds per tree, it is difficult to store the seeds for extended periods of time (Sacandé and Hoekstra, 2003). Moreover, there are another studies, that proves that vegetative propagation of neem using conventional methods is not possible (Narayan et al., 1985). This gives more scope for potential applications of in vitro culture techniques towards neem improvement.

 There are also studies, that demonstrated the possibility for mass clonal propagation of a 50-year-old neem tree by nodal segment cultures. MS medium supplemented with BAP (1 M) and CH (250 mg l⁻¹) medium was used for recurrent shoot multiplication at a rate of 7–8-fold every 5 week and this rate of shoot multiplication was maintained for almost 5 years. The shoots could be readily rooted with a frequency as high as 82%. Transplantation survival of these plants was more than 87% (Chaturvedi et al., 2004).

 Why was callus used to perform this investigation?

 Simple Sequence Repeat (SSR) markers in that research were used to confirm the genetic stability of callus. These studies focuses on standardizing conditions for establishing callus cultures using novel explants from a mature neem tree and test genetic stability of the calli using molecular markers (Ramamurthy et al., 2012).

Which conclusions are possible based on the fact, that callus derived from one stock plant remains genetically stable but compared with two other neem plants shows some polymorphism?

 PCR amplifications carried out using highly polymorphic microsatellite markers have revealed that the genomic DNA at specific loci (Ai_4, Ai_11, Ai_13 and Ai_34) from various explant derived calli do not exhibit any significant polymorphism in comparison to the mother plant, confirming their genetic stability (Ramamurthy et al., 2012).

Literature:

1. Larkin, P.J. and Scowcroft, W.R. (1981). Somaclonal variations - a novel source of variability from cell cultures for plant improvement. Theor. Appl. Genet. 60:197-214.

2. Sacandé, M. and Hoekstra, F.A. (2003). Optimising conditions for neem (Azadirachta indica) seed longevity. p.761-773 In: R.D. Smith, J.B. Dickie, S.H. Linington, H.W. Pritchard and R.J. Probert (eds.), Seed Conservation: Turning Science into Practice. Kew: Royal Botanic Gardens, Kew.

3. Narayan, P. and Jaiswal, V.S. (1985). Plantlet regeneration from leaflet callus of Azadirachta indica A. Juss, J. Tree Sciences 4:65-68.

4. Chaturvedi, R., Razdan, M.K. and Bhojwani, S.S. (2004). In vitro clonal propagation of an adult tree of neem (Azadirachta indica A. Juss.) by forced axillary branching. Plant Science 166:501-506.

5. Ramamurthy A., Kag B., Hegde V., Malarini Loganathan R., Saiyed T., Sathyanarayana B.N.,  Gowda M. (2012) Studies on In Vitro Regeneration from Various Explants of a Mature Neem (Azadirachta indica) Tree. ISHS Acta Horticulturae 961: VII International Symposium on In Vitro Culture and Horticultural Breeding. p. 449-456.