Abstract
The effects of different concentrations of BAP and TDZ on somaclonal variation based on genetic and phenotypic variability among micropropagated shoot tips of banana cultivars; ‘Berangan Intan’, ‘Berangan’ and ‘Rastali’ were studied. With the highest concentrations of both BAP and TDZ up to 44.4µM and 7.5 µM, respectively, most shoots were curled and other morphological changes such as hyperhydricity and undifferentiated shoots were observed. Detectable genetic changes to reveal stable variations among 27 micropropagated variants produced by BAP and TDZ were confirmed using RAPD markers. The percentage of polymorphism among somaclones of cultivars; Berangan Intan, Berangan and Rastali regenerated by TDZ was 24.4, 27.3 and 29.5, respectively which was higher than BAP with the percentages of 16.7, 24.2 and 24.7, respectively. The number of scorable bands among the RAPD profiles obtained with 19 primers tested in this study varied from 6 for opa11 and opk03 to 18 by opc01 in somaclones derived from BAP and 4 for opk03 to 14 with opa04, opb18 and opc04 in the case of TDZ. Cluster analysis of the somaclones regenerated with each BAP and TDZ resulted in the formation of two major groups, one belonging to Berangan Intan and Berangan (AAA) and the other to Rastali (AAB). From each dendrogram caused by BAP and TDZ, it could be concluded that regenerated somaclones by higher concentrations of both BAP and TDZ accumulated much genetic variation compared to control and lower concentrations of each BAP and TDZ.
Highlights
Banana is one of the most important fruit crops as an inexpensively and produced source of energy providing a staple food for about 400 million people in developing countries from an area of approximately 10 million ha (Kotecha and Desai, 1996; INIBAP, 2000; FAO, 2002; Ray, 2002; Kulkarni et al, 2007; Pillay and Tripathi, 2007; OGTR, 2008; Roux et al, 2008; Bakry et al, 2009).Tissue culture causes a wide range of genetic variation as an option in plant improvement which can be combined into plant breeding programs (Jain, 1997; Rout et al, 2000; Hwang, 2004)
Considering tissue culture provides strange source of variability with a great potential in crop improvement, the objective of the present study was to assess the efficiency of TDZ and BAP at different concentrations to produce polymorphism among regenerated somaclones derived from proliferating shoot tips of banana cultivars: ‘Berangan Intan’, ‘Berangan’ and ‘Rastali’ using Random Amplified Polymorphic DNA (RAPD) markers
There was a significant increment in variation rate between the lowest and the highest concentrations of BAP and the results indicated that the variability index among regenerated somaclones significantly increased with increasing concentration of BAP up to 44.4 μM for all cultivars (Table 3), which is generally in agreement with the findings reported by Venkatachalam et al (2007)
Summary
Banana is one of the most important fruit crops as an inexpensively and produced source of energy providing a staple food for about 400 million people in developing countries from an area of approximately 10 million ha (Kotecha and Desai, 1996; INIBAP, 2000; FAO, 2002; Ray, 2002; Kulkarni et al, 2007; Pillay and Tripathi, 2007; OGTR, 2008; Roux et al, 2008; Bakry et al, 2009).Tissue culture causes a wide range of genetic variation as an option in plant improvement which can be combined into plant breeding programs (Jain, 1997; Rout et al, 2000; Hwang, 2004). Bairu et al (2007) studied the effect of different types and concentrations of plant growth regulators on somaclonal variation in banana cultivar ‘Cavendish’. They stated that percent of somaclonal variation increased with an increasing rate of multiplication up to 72%. Sheidai et al (2008) reported that the time – period of subculture has an increasing effect on the genetic variations induced in the regenerated banana cultivar ‘Valery’ They showed the use of RAPD molecular markers in revealing somaclonal variation in banana. Venkatachalam and Sreedhar (2007) used high levels of growth regulators during micropropagation of banana They reported that no induced somaclonal variation caused by tissue culture conditions in banana cv. ‘Nanjanagudu Rasable’ (AAB) was observed in spite of exposure to high concentrations of cytokinins during micropropagation
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