In vitro conservation, regeneration and evaluation of genetic fidelity of threatened Banana cv. Nanjanagud Rasabale (AAB)

Banana cv. Nanjanagud Rasabale (AAB, Silk subgroup) is one of the unique cultivars of Karnataka, India is now failed to revive its GI (Geographical Indication) tag, the major bane of the cultivar is high susceptibility to Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc). Hence, there is a need for the conservation of this elite cultivar from the threat of extinction. Plant germplasm can be conserved by different approaches one of the valuable biotechnological approaches is in vitro conservation. Laboratory studies were undertaken to come out with an effective protocol for conserving plantlets through a slow growth process by media manipulation, viz., by adding different growth retardants. Growth retardants such as ancymidol, paclobutrazol, abscisic acid, and DMSO at three different concentrations each were supplemented to MS medium. Among different treatment combinations, MS medium supplemented with DMSO 2.25 ml/l was found to be most effective by prolonging the period of successive sub-culture (154.53 days) and enabling mid to long- term conservation of shoot tips. The conserved cultures were regenerated using a standardized medium comprising MS Basal + 4 mg/l BAP + 0.5 mg/l NAA + 3% sucrose + 0.6% agar-agar. Growth was retrieved successfully with parameters evaluated. Assessment of genetic stability was performed by using Inter Simple Sequence Repeat amplification (ISSR) markers. All the 15 ISSR primers amplified unambiguous indicating monomorphic bands with 100 % monomorphism. Overall, the cultures were conserved by extending the sub- culture period and prolonged storage life without any genetic variation by using growth retardants.