The exiensive basic work on the in vitro propagation of bananas' (Kirkorian & Cronauer, 1984, Cronauer & Kirkorian 1986, Banetjee & De Langle, 1985, Jarret et aI, 1985, Wong. 1986 and Novak et al., 1989) has led to the technological development of physical form of the in vitro mass propagation of different cultivars throughout the various tropical and subtropical zones. However, the emphasis on the physical form of the culture medium has not received much attention. Recently, Alvatd et al. (1993) compared performance of" Cavendish shoots in liquid medium with.that on gelled medium and found that intermittent 'submergence in liqud medium was best for shoot muhiplication and dry weight was also increased. This method involved specialised culture vessels with a highly controlled mechanism for periodic submergence of cultures This study was aimed to assess a method for economic and consistent shoot muhiplication in different cultivars of banana grown commercially.
MATERIALS AND METHODS
Banana suckers of the five clones viz. Basrai, Shrimanti, Ardhapuri, Kolhapur clone and Williams which had average weight of 750 gm and basal diameter approximately of 10 cm were collected and trirmmed to 4-5 square cm so as to assess meristematic portion. Soaking it in 1000 ppmBavistin and 100 ppm streptomycin for 30-40 minutes did surface sterilizatiol} of explants. Meristematic parts of size 3 to 4 cm along with several sheath leaf primordia enclosing the adjacent tissues were excised. The shoot-tips were soaked in 500 ppm cetrimide for 30 min. and freshly prepared chlorine Water for 20 min. The meristematic tips of 5 cultivars of dwarf Cavendish (AAA) banana viz. Basrai, Shrimanti, Kolhapur clone, Ardhapuri and Williams were established on establishment media M.S. + 0.5 mg/l BAP + 5 mg/1 adenine sulphate +100 mg/I Meso-inositol + 0.8 % Agar + 3%sucrose (Jarret et al. 1985) and maintained on multiplication media, MS + 6 mg/1 BAP + 1 mg/IlBA +60 mg/1 adenine sulphate +100 mg/1 Meso-inositol +0.8 % Agar +3% sucrose ( Murashige and Skoog. 1962). Multiple shoots emerged after 6-8 weeks having 1cm length were transferred and cultured on media prepared with and without agar. The experinlent conducted in 250 mI. capacity Erlenmeyer flask with 20-30 ml media in each and plugged with cotton bunks as fIrst treatment and in second treatment 40 to 50 ml agar gelled media were filled in jam bottle.
Cultures were incubated at 25 +2 °C. for a 16 hrs photoperiods for 6 weeks. The agitated liquid cultures were maintained on three-tier illuminated shaker machine at 90 rpm. The shoots from liquid medium were sub cultured three times in 5 weeks interval. Data were scored on 10 randomly selected flasks after 5 weeks. The experiment was conducted in Factorial Complete Randomized Design and repeated thrice. Analysis of variance was done . The data on number of shoots/bottle multiplied and length of individual shoot was recorded by separating each shoot. The shoots multiplied on solid medium were'transferred on rooting medium (1/2MS + 1.0 mg/1 IAA) for induction of roots, rooted plant lets were transferred to polyhouse for hardening. The plantlets multiplied on liquid
medium were rooted on solid medium with same rooting harmones within three weeks period. The rooted Plantlets were transferred to small poly bags (4x6 cm) fIlled with sterile sand to which 1/2MS(1m1lplantlet) liquid was given weekly. The survival percentages were recorded four - weeks after planting in green house.
RESULTS AND DISCUSSION
Analysis of variance (Table 1) of the data revealed significant differences for multiple shoot formation for varieties and solid medium was desirable for rapid multiplication ( Montgomery, 1976). Interaction of variety x medium was found to be significant. 'TIle data on shoot number, shoot length & hardening survival revealed that, banana clone, Basrai (18.5) gave maximum number of shoots per bottle after 5 weeks of incubation followed by Ardhapuri (14.6), Shrimanti (13.O), Williams (12.7) and Kolllapur clones (10.5) on solid medium, while it was 27.3 shoots per bottle for Williams followed by Kolhapur clone (22.3) Basrai (21.4), Shrimanti (20.4) and Ardhapuri (20.0) in liquid media devoid of solidifying agent with same medium viz. MS+6 mg/l BAP +1 mg/l IBA +60 mg/l adenine sulphate +100mg/lMeso-inositol + 0.8% Agar +3% sucrose. The length of shoots was also more on liquid medium and was maximum in Basrai (6.3 cm ) followed by Ardhapllri (5.1), Shrinlantj (4.3cm), Kolhapur clone (3.17) cm. ) and Williams (2.24 cm) as against on solid medium, height was maximum in Shrimanti (4.3 cm) followed by Kolhapur clone (2.91 cm), Basrai (1.6 cm), Ardhapuri (1.52 cm,) and Williams (1.47 em). Liquid media with shaking may had increased absorption of nutrients resulted in promotion of growth. The hardening of rooted plantlets multiplied on solid medium was excellent in the case of all the five clones. The maximum hardening per centage were in Basrai and Ardhapuri (95%), followed by Kolhapur clone (93%), Shrimanti (90%), and Williams (89%), Survival percentage in green house during hardening of rooted plantlets multiplied on liquid medium was significantly less. The range of survival percentage was 56 to 73 . Maximum 73 % was in Shrimanti and Ardhapuri varieties.Mortality upto 25-40 percent is not economically viable. However it can be minimised if hardened in precisely controlled environmental conditions. An additional step for rooting was performed. The shoot cultures multiplied on liquid medium briefly rooted on agar gelled medium for two weeks and subjected to hardening resulted into increased survival in green house. The maximum survival was in Ardhapuri (86%), followed by Basari (83%), Shrinlanti (81%), and Williams (80%).
It is revealed that, liquid media were also better for rapid multiplication of shoots and solid medium for ex -vitro survival for all the clones under experiment. The survival percentage was relatively less in case of plant!ets produced on liquid medium. This may be due to faster growth of seedlings and less turgidity of plant cells as compared to slow grown seedlings.
Therefore, it is imperative to establish the compromise in cost of inputs and the number of plants produced for the development of cost etfective technology. To obtain maxinmm number of multiple shoots as well as maximum hardening survival ex-vitro,. liquid medium coupled with judicious selection of shoot cultures and brief cuhure of the same on gelled medium would minimise the cost of production. This can be. directly adopted for mass propagation of different cultivars of banana. (Bhagyalaxmi and Narendra Singh, 1995).
About Author / Additional Info:
Assistant Professor of Agril. Botany, State Level Biotechnology Centre,MPKV, Rahuri (MS) India