Genetic analyses of micropropagated and regenerated plantlets of banana as assessed by RAPD and ISSR markers.

A cultivar of dessert banana, namely, Nanjanagudu
Rasabale (NR), classified under group “silk” (of genotype
AAB), is seriously under the threat of extinction due to its
susceptibility to bacterial wilt and bunchy-top virus disease.
A regeneration protocol using tissue culture method was
developed (Venkatachalam et al. 2006), where a large
number of plantlets were regenerated from leaf base
explants. Simultaneously, a micropropagation protocol was
also developed where high levels of up to 53.28 μM of
benzylamino purine (BAP) and 55.80 μM of kinetin (Kn)
were used. The progressive increase of cytokinins levels
resulted in concomitant increase in shoot number, with a
maximum of 80 shoot buds per segment in BAP (31.08 μM).
The plantlets were analyzed for their genetic stability using
randomly amplified polymorphic DNA (RAPD) and inter
simple sequence repeats (ISSR) markers. A total of 50 RAPD
and 12 ISSR primers resulted in 625 distinct and reproducible
bands showing homogeneous RAPD and ISSR patterns. Band
intensity histogram of each gel confirmed their monomorphic
nature with no genetic variation among the plantlets analyzed.
The present study has established for the first time that the
regeneration and rapid micropropagation protocol developed
through the present study will be of great use in conserving the
endangered cultivar – NR – without risk of genetic instability.