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Banana (Musa spp.) is an important fruit crop cultivated worldwide. Tissue culture
banana plants are now widely used as planting materials for commercial banana
cultivation. High cost of production, poor multiplication rate and less survival of
plantlets during acclimatization are some of the problems experienced in conventional
micropropagation of banana. As there is high demand for tissue culture banana plants,
the conventional tissue culture techniques need to be modified to increase the
multiplication rate and to reduce the unit cost of production of plantlets. Use of
temporary immersion bioreactor (TIB) is a very good option to increase multiplication
rate and reduce cost of production.
The investigations on ‘Commercial micropropagation of banana (Musa spp.) using
a temporary immersion bioreactor system’ was hence taken up at Centre for Plant
Biotechnology and Molecular Biology (CPBMB), College of Horticulture from 2018-
2020. The aim of the investigations was to develop an efficient commercial
micropropagation protocol in banana using a temporary immersion bioreactor system.
Established cultures of the cultivar Nedunendran (AAB) received from the
commercial micropropagation unit of CPBMB at the 5
th subculture cycle were utilized
for the study. The micropropagation protocol standardized at CPBMB for the cultivar
Nedunendran was followed for production of plantlets. The protocol was optimized for
bioreactor micropropagation and at each stage of propagation, it was compared with
conventional micropropagation system. Number of clumps/ 500 ml. of medium to
initiate shoot multiplication, media for multiplication and rooting were standardized
for TIB and compared with conventional micropropagation system. Immersion
duration of one minute at three hourly intervals were fixed for all the experiments. The
root and shoot characters, survival of plantlets after hardening and growth of plants
after hardening were also compared for plants from both the culture systems. The
clonal fidelity analysis standardized at CPBMB for banana using specific ISSR
marker was used to analyze the fidelity of rooted plants from the two culture systems
after 8th subculture passage.
Higher clump size (20 clumps/ 500 ml media) was found good to initiate shoot
multiplication in TIB with multiplication of 6.2 shoots/clump while in conventional
system 15 and 20 clumps/ 500 ml of medium were found on par and recorded
multiplication of 6.7 and 6.2 shoots/ clump respectively. Temporary immersion
bioreactor system exhibited significantly higher shoot proliferation (13.00 shoots/clump)
than the conventional system (7.67 shoots/ clump). Murashige and Skoog (MS)
multiplication medium supplemented with 5mg L-1 BA recorded highest shoot
proliferation in the both culture systems, recording 14.71 shoots/ clump in TIB and 8.35
shoots/ clump in conventional system. In both the culture systems, in the three different
rooting media tried (MS + 2mg L-1 IBA+ 2% Sucrose, MS + 2mg L-1 IBA+ 3%
Sucrose, MS + 1mg L-1 IBA+ 2% Sucrose), 99-100 per cent rooting was observed.
Plantlets from TIB recorded significantly higher number of roots (10.29) than the
conventional system (4.70). The root length of plantlets was more in conventional system
(8.82 cm) as compared to TIB system (7.93 cm). Plantlets from bioreactor recorded
significantly higher shoot length (10.88 cm) and more number of leaves (4.84) while
plantlets from conventional system recorded less shoot length (8.94 cm) and less number
of leaves (4.39). Survival of the plantlets after hardening was 90-91 per cent in both the
culture systems.
After sixty days of secondary hardening, plants from TIB exhibited better growth
recording more plant height and more number of leaves than the conventional system.
Plants from the rooting medium MS + 2mg L-1 IBA+ 2 per cent sucrose recorded plant
height of 36.05 cm in TIB while plants from conventional system recorded plant height
of 29.80 cm and the number of leaves was 6.3 in bioreactor plants and 5.7 in
conventional system.
Clonal fidelity analyzed using specific ISSR marker, UBC857 revealed that there
was no polymorphism in the ISSR amplification profiles of rooted plants after the 8th
subculture cycle when compared with the amplification profile of source mother plant in
both the culture systems and the plants produced are true to type.
An efficient commercial micropropagation protocol for banana using a TIB was
thus developed in the present study. Temporary immersion bioreactor system exhibited
high shoot multiplication, better shoot and root characters for plantlets and better growth
of plants after hardening. Due to the high rate of multiplication
in TIB, there is more production of plantlets and use of liquid media considerably
reduced the media cost. Clonal fidelity analysis revealed that the plantlets produced after
8th subculture stage were true to type. Field evaluation of plants from both the culture
systems and comparison of yield and quality of plants have to be taken up further.